1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-1996, 1998-2012 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
11 @settitle Debugging with @value{GDBN}
12 @setchapternewpage odd
24 @c readline appendices use @vindex, @findex and @ftable,
25 @c annotate.texi and gdbmi use @findex.
29 @c !!set GDB manual's edition---not the same as GDB version!
30 @c This is updated by GNU Press.
33 @c !!set GDB edit command default editor
36 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
38 @c This is a dir.info fragment to support semi-automated addition of
39 @c manuals to an info tree.
40 @dircategory Software development
42 * Gdb: (gdb). The GNU debugger.
46 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
47 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
48 Free Software Foundation, Inc.
50 Permission is granted to copy, distribute and/or modify this document
51 under the terms of the GNU Free Documentation License, Version 1.3 or
52 any later version published by the Free Software Foundation; with the
53 Invariant Sections being ``Free Software'' and ``Free Software Needs
54 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
55 and with the Back-Cover Texts as in (a) below.
57 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
58 this GNU Manual. Buying copies from GNU Press supports the FSF in
59 developing GNU and promoting software freedom.''
63 This file documents the @sc{gnu} debugger @value{GDBN}.
65 This is the @value{EDITION} Edition, of @cite{Debugging with
66 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
67 @ifset VERSION_PACKAGE
68 @value{VERSION_PACKAGE}
70 Version @value{GDBVN}.
76 @title Debugging with @value{GDBN}
77 @subtitle The @sc{gnu} Source-Level Debugger
79 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
80 @ifset VERSION_PACKAGE
82 @subtitle @value{VERSION_PACKAGE}
84 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
88 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
89 \hfill {\it Debugging with @value{GDBN}}\par
90 \hfill \TeX{}info \texinfoversion\par
94 @vskip 0pt plus 1filll
95 Published by the Free Software Foundation @*
96 51 Franklin Street, Fifth Floor,
97 Boston, MA 02110-1301, USA@*
98 ISBN 978-0-9831592-3-0 @*
105 @node Top, Summary, (dir), (dir)
107 @top Debugging with @value{GDBN}
109 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
111 This is the @value{EDITION} Edition, for @value{GDBN}
112 @ifset VERSION_PACKAGE
113 @value{VERSION_PACKAGE}
115 Version @value{GDBVN}.
117 Copyright (C) 1988-2010 Free Software Foundation, Inc.
119 This edition of the GDB manual is dedicated to the memory of Fred
120 Fish. Fred was a long-standing contributor to GDB and to Free
121 software in general. We will miss him.
124 * Summary:: Summary of @value{GDBN}
125 * Sample Session:: A sample @value{GDBN} session
127 * Invocation:: Getting in and out of @value{GDBN}
128 * Commands:: @value{GDBN} commands
129 * Running:: Running programs under @value{GDBN}
130 * Stopping:: Stopping and continuing
131 * Reverse Execution:: Running programs backward
132 * Process Record and Replay:: Recording inferior's execution and replaying it
133 * Stack:: Examining the stack
134 * Source:: Examining source files
135 * Data:: Examining data
136 * Optimized Code:: Debugging optimized code
137 * Macros:: Preprocessor Macros
138 * Tracepoints:: Debugging remote targets non-intrusively
139 * Overlays:: Debugging programs that use overlays
141 * Languages:: Using @value{GDBN} with different languages
143 * Symbols:: Examining the symbol table
144 * Altering:: Altering execution
145 * GDB Files:: @value{GDBN} files
146 * Targets:: Specifying a debugging target
147 * Remote Debugging:: Debugging remote programs
148 * Configurations:: Configuration-specific information
149 * Controlling GDB:: Controlling @value{GDBN}
150 * Extending GDB:: Extending @value{GDBN}
151 * Interpreters:: Command Interpreters
152 * TUI:: @value{GDBN} Text User Interface
153 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
154 * GDB/MI:: @value{GDBN}'s Machine Interface.
155 * Annotations:: @value{GDBN}'s annotation interface.
156 * JIT Interface:: Using the JIT debugging interface.
157 * In-Process Agent:: In-Process Agent
159 * GDB Bugs:: Reporting bugs in @value{GDBN}
161 @ifset SYSTEM_READLINE
162 * Command Line Editing: (rluserman). Command Line Editing
163 * Using History Interactively: (history). Using History Interactively
165 @ifclear SYSTEM_READLINE
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
169 * In Memoriam:: In Memoriam
170 * Formatting Documentation:: How to format and print @value{GDBN} documentation
171 * Installing GDB:: Installing GDB
172 * Maintenance Commands:: Maintenance Commands
173 * Remote Protocol:: GDB Remote Serial Protocol
174 * Agent Expressions:: The GDB Agent Expression Mechanism
175 * Target Descriptions:: How targets can describe themselves to
177 * Operating System Information:: Getting additional information from
179 * Trace File Format:: GDB trace file format
180 * Index Section Format:: .gdb_index section format
181 * Copying:: GNU General Public License says
182 how you can copy and share GDB
183 * GNU Free Documentation License:: The license for this documentation
192 @unnumbered Summary of @value{GDBN}
194 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
195 going on ``inside'' another program while it executes---or what another
196 program was doing at the moment it crashed.
198 @value{GDBN} can do four main kinds of things (plus other things in support of
199 these) to help you catch bugs in the act:
203 Start your program, specifying anything that might affect its behavior.
206 Make your program stop on specified conditions.
209 Examine what has happened, when your program has stopped.
212 Change things in your program, so you can experiment with correcting the
213 effects of one bug and go on to learn about another.
216 You can use @value{GDBN} to debug programs written in C and C@t{++}.
217 For more information, see @ref{Supported Languages,,Supported Languages}.
218 For more information, see @ref{C,,C and C++}.
220 Support for D is partial. For information on D, see
224 Support for Modula-2 is partial. For information on Modula-2, see
225 @ref{Modula-2,,Modula-2}.
227 Support for OpenCL C is partial. For information on OpenCL C, see
228 @ref{OpenCL C,,OpenCL C}.
231 Debugging Pascal programs which use sets, subranges, file variables, or
232 nested functions does not currently work. @value{GDBN} does not support
233 entering expressions, printing values, or similar features using Pascal
237 @value{GDBN} can be used to debug programs written in Fortran, although
238 it may be necessary to refer to some variables with a trailing
241 @value{GDBN} can be used to debug programs written in Objective-C,
242 using either the Apple/NeXT or the GNU Objective-C runtime.
245 * Free Software:: Freely redistributable software
246 * Contributors:: Contributors to GDB
250 @unnumberedsec Free Software
252 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
253 General Public License
254 (GPL). The GPL gives you the freedom to copy or adapt a licensed
255 program---but every person getting a copy also gets with it the
256 freedom to modify that copy (which means that they must get access to
257 the source code), and the freedom to distribute further copies.
258 Typical software companies use copyrights to limit your freedoms; the
259 Free Software Foundation uses the GPL to preserve these freedoms.
261 Fundamentally, the General Public License is a license which says that
262 you have these freedoms and that you cannot take these freedoms away
265 @unnumberedsec Free Software Needs Free Documentation
267 The biggest deficiency in the free software community today is not in
268 the software---it is the lack of good free documentation that we can
269 include with the free software. Many of our most important
270 programs do not come with free reference manuals and free introductory
271 texts. Documentation is an essential part of any software package;
272 when an important free software package does not come with a free
273 manual and a free tutorial, that is a major gap. We have many such
276 Consider Perl, for instance. The tutorial manuals that people
277 normally use are non-free. How did this come about? Because the
278 authors of those manuals published them with restrictive terms---no
279 copying, no modification, source files not available---which exclude
280 them from the free software world.
282 That wasn't the first time this sort of thing happened, and it was far
283 from the last. Many times we have heard a GNU user eagerly describe a
284 manual that he is writing, his intended contribution to the community,
285 only to learn that he had ruined everything by signing a publication
286 contract to make it non-free.
288 Free documentation, like free software, is a matter of freedom, not
289 price. The problem with the non-free manual is not that publishers
290 charge a price for printed copies---that in itself is fine. (The Free
291 Software Foundation sells printed copies of manuals, too.) The
292 problem is the restrictions on the use of the manual. Free manuals
293 are available in source code form, and give you permission to copy and
294 modify. Non-free manuals do not allow this.
296 The criteria of freedom for a free manual are roughly the same as for
297 free software. Redistribution (including the normal kinds of
298 commercial redistribution) must be permitted, so that the manual can
299 accompany every copy of the program, both on-line and on paper.
301 Permission for modification of the technical content is crucial too.
302 When people modify the software, adding or changing features, if they
303 are conscientious they will change the manual too---so they can
304 provide accurate and clear documentation for the modified program. A
305 manual that leaves you no choice but to write a new manual to document
306 a changed version of the program is not really available to our
309 Some kinds of limits on the way modification is handled are
310 acceptable. For example, requirements to preserve the original
311 author's copyright notice, the distribution terms, or the list of
312 authors, are ok. It is also no problem to require modified versions
313 to include notice that they were modified. Even entire sections that
314 may not be deleted or changed are acceptable, as long as they deal
315 with nontechnical topics (like this one). These kinds of restrictions
316 are acceptable because they don't obstruct the community's normal use
319 However, it must be possible to modify all the @emph{technical}
320 content of the manual, and then distribute the result in all the usual
321 media, through all the usual channels. Otherwise, the restrictions
322 obstruct the use of the manual, it is not free, and we need another
323 manual to replace it.
325 Please spread the word about this issue. Our community continues to
326 lose manuals to proprietary publishing. If we spread the word that
327 free software needs free reference manuals and free tutorials, perhaps
328 the next person who wants to contribute by writing documentation will
329 realize, before it is too late, that only free manuals contribute to
330 the free software community.
332 If you are writing documentation, please insist on publishing it under
333 the GNU Free Documentation License or another free documentation
334 license. Remember that this decision requires your approval---you
335 don't have to let the publisher decide. Some commercial publishers
336 will use a free license if you insist, but they will not propose the
337 option; it is up to you to raise the issue and say firmly that this is
338 what you want. If the publisher you are dealing with refuses, please
339 try other publishers. If you're not sure whether a proposed license
340 is free, write to @email{licensing@@gnu.org}.
342 You can encourage commercial publishers to sell more free, copylefted
343 manuals and tutorials by buying them, and particularly by buying
344 copies from the publishers that paid for their writing or for major
345 improvements. Meanwhile, try to avoid buying non-free documentation
346 at all. Check the distribution terms of a manual before you buy it,
347 and insist that whoever seeks your business must respect your freedom.
348 Check the history of the book, and try to reward the publishers that
349 have paid or pay the authors to work on it.
351 The Free Software Foundation maintains a list of free documentation
352 published by other publishers, at
353 @url{http://www.fsf.org/doc/other-free-books.html}.
356 @unnumberedsec Contributors to @value{GDBN}
358 Richard Stallman was the original author of @value{GDBN}, and of many
359 other @sc{gnu} programs. Many others have contributed to its
360 development. This section attempts to credit major contributors. One
361 of the virtues of free software is that everyone is free to contribute
362 to it; with regret, we cannot actually acknowledge everyone here. The
363 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
364 blow-by-blow account.
366 Changes much prior to version 2.0 are lost in the mists of time.
369 @emph{Plea:} Additions to this section are particularly welcome. If you
370 or your friends (or enemies, to be evenhanded) have been unfairly
371 omitted from this list, we would like to add your names!
374 So that they may not regard their many labors as thankless, we
375 particularly thank those who shepherded @value{GDBN} through major
377 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
378 Jim Blandy (release 4.18);
379 Jason Molenda (release 4.17);
380 Stan Shebs (release 4.14);
381 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
382 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
383 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
384 Jim Kingdon (releases 3.5, 3.4, and 3.3);
385 and Randy Smith (releases 3.2, 3.1, and 3.0).
387 Richard Stallman, assisted at various times by Peter TerMaat, Chris
388 Hanson, and Richard Mlynarik, handled releases through 2.8.
390 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
391 in @value{GDBN}, with significant additional contributions from Per
392 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
393 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
394 much general update work leading to release 3.0).
396 @value{GDBN} uses the BFD subroutine library to examine multiple
397 object-file formats; BFD was a joint project of David V.
398 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
400 David Johnson wrote the original COFF support; Pace Willison did
401 the original support for encapsulated COFF.
403 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
405 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
406 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
408 Jean-Daniel Fekete contributed Sun 386i support.
409 Chris Hanson improved the HP9000 support.
410 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
411 David Johnson contributed Encore Umax support.
412 Jyrki Kuoppala contributed Altos 3068 support.
413 Jeff Law contributed HP PA and SOM support.
414 Keith Packard contributed NS32K support.
415 Doug Rabson contributed Acorn Risc Machine support.
416 Bob Rusk contributed Harris Nighthawk CX-UX support.
417 Chris Smith contributed Convex support (and Fortran debugging).
418 Jonathan Stone contributed Pyramid support.
419 Michael Tiemann contributed SPARC support.
420 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
421 Pace Willison contributed Intel 386 support.
422 Jay Vosburgh contributed Symmetry support.
423 Marko Mlinar contributed OpenRISC 1000 support.
425 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
427 Rich Schaefer and Peter Schauer helped with support of SunOS shared
430 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
431 about several machine instruction sets.
433 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
434 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
435 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
436 and RDI targets, respectively.
438 Brian Fox is the author of the readline libraries providing
439 command-line editing and command history.
441 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
442 Modula-2 support, and contributed the Languages chapter of this manual.
444 Fred Fish wrote most of the support for Unix System Vr4.
445 He also enhanced the command-completion support to cover C@t{++} overloaded
448 Hitachi America (now Renesas America), Ltd. sponsored the support for
449 H8/300, H8/500, and Super-H processors.
451 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
453 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
456 Toshiba sponsored the support for the TX39 Mips processor.
458 Matsushita sponsored the support for the MN10200 and MN10300 processors.
460 Fujitsu sponsored the support for SPARClite and FR30 processors.
462 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
465 Michael Snyder added support for tracepoints.
467 Stu Grossman wrote gdbserver.
469 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
470 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
472 The following people at the Hewlett-Packard Company contributed
473 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
474 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
475 compiler, and the Text User Interface (nee Terminal User Interface):
476 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
477 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
478 provided HP-specific information in this manual.
480 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
481 Robert Hoehne made significant contributions to the DJGPP port.
483 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
484 development since 1991. Cygnus engineers who have worked on @value{GDBN}
485 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
486 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
487 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
488 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
489 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
490 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
491 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
492 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
493 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
494 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
495 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
496 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
497 Zuhn have made contributions both large and small.
499 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
500 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
502 Jim Blandy added support for preprocessor macros, while working for Red
505 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
506 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
507 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
508 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
509 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
510 with the migration of old architectures to this new framework.
512 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
513 unwinder framework, this consisting of a fresh new design featuring
514 frame IDs, independent frame sniffers, and the sentinel frame. Mark
515 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
516 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
517 trad unwinders. The architecture-specific changes, each involving a
518 complete rewrite of the architecture's frame code, were carried out by
519 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
520 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
521 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
522 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
525 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
526 Tensilica, Inc.@: contributed support for Xtensa processors. Others
527 who have worked on the Xtensa port of @value{GDBN} in the past include
528 Steve Tjiang, John Newlin, and Scott Foehner.
530 Michael Eager and staff of Xilinx, Inc., contributed support for the
531 Xilinx MicroBlaze architecture.
534 @chapter A Sample @value{GDBN} Session
536 You can use this manual at your leisure to read all about @value{GDBN}.
537 However, a handful of commands are enough to get started using the
538 debugger. This chapter illustrates those commands.
541 In this sample session, we emphasize user input like this: @b{input},
542 to make it easier to pick out from the surrounding output.
545 @c FIXME: this example may not be appropriate for some configs, where
546 @c FIXME...primary interest is in remote use.
548 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
549 processor) exhibits the following bug: sometimes, when we change its
550 quote strings from the default, the commands used to capture one macro
551 definition within another stop working. In the following short @code{m4}
552 session, we define a macro @code{foo} which expands to @code{0000}; we
553 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
554 same thing. However, when we change the open quote string to
555 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
556 procedure fails to define a new synonym @code{baz}:
565 @b{define(bar,defn(`foo'))}
569 @b{changequote(<QUOTE>,<UNQUOTE>)}
571 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
574 m4: End of input: 0: fatal error: EOF in string
578 Let us use @value{GDBN} to try to see what is going on.
581 $ @b{@value{GDBP} m4}
582 @c FIXME: this falsifies the exact text played out, to permit smallbook
583 @c FIXME... format to come out better.
584 @value{GDBN} is free software and you are welcome to distribute copies
585 of it under certain conditions; type "show copying" to see
587 There is absolutely no warranty for @value{GDBN}; type "show warranty"
590 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
595 @value{GDBN} reads only enough symbol data to know where to find the
596 rest when needed; as a result, the first prompt comes up very quickly.
597 We now tell @value{GDBN} to use a narrower display width than usual, so
598 that examples fit in this manual.
601 (@value{GDBP}) @b{set width 70}
605 We need to see how the @code{m4} built-in @code{changequote} works.
606 Having looked at the source, we know the relevant subroutine is
607 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
608 @code{break} command.
611 (@value{GDBP}) @b{break m4_changequote}
612 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
616 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
617 control; as long as control does not reach the @code{m4_changequote}
618 subroutine, the program runs as usual:
621 (@value{GDBP}) @b{run}
622 Starting program: /work/Editorial/gdb/gnu/m4/m4
630 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
631 suspends execution of @code{m4}, displaying information about the
632 context where it stops.
635 @b{changequote(<QUOTE>,<UNQUOTE>)}
637 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
639 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
643 Now we use the command @code{n} (@code{next}) to advance execution to
644 the next line of the current function.
648 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
653 @code{set_quotes} looks like a promising subroutine. We can go into it
654 by using the command @code{s} (@code{step}) instead of @code{next}.
655 @code{step} goes to the next line to be executed in @emph{any}
656 subroutine, so it steps into @code{set_quotes}.
660 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
662 530 if (lquote != def_lquote)
666 The display that shows the subroutine where @code{m4} is now
667 suspended (and its arguments) is called a stack frame display. It
668 shows a summary of the stack. We can use the @code{backtrace}
669 command (which can also be spelled @code{bt}), to see where we are
670 in the stack as a whole: the @code{backtrace} command displays a
671 stack frame for each active subroutine.
674 (@value{GDBP}) @b{bt}
675 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
677 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
679 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
680 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
682 #4 0x79dc in expand_input () at macro.c:40
683 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
687 We step through a few more lines to see what happens. The first two
688 times, we can use @samp{s}; the next two times we use @code{n} to avoid
689 falling into the @code{xstrdup} subroutine.
693 0x3b5c 532 if (rquote != def_rquote)
695 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
696 def_lquote : xstrdup(lq);
698 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
701 538 len_lquote = strlen(rquote);
705 The last line displayed looks a little odd; we can examine the variables
706 @code{lquote} and @code{rquote} to see if they are in fact the new left
707 and right quotes we specified. We use the command @code{p}
708 (@code{print}) to see their values.
711 (@value{GDBP}) @b{p lquote}
712 $1 = 0x35d40 "<QUOTE>"
713 (@value{GDBP}) @b{p rquote}
714 $2 = 0x35d50 "<UNQUOTE>"
718 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
719 To look at some context, we can display ten lines of source
720 surrounding the current line with the @code{l} (@code{list}) command.
726 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
728 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
731 538 len_lquote = strlen(rquote);
732 539 len_rquote = strlen(lquote);
739 Let us step past the two lines that set @code{len_lquote} and
740 @code{len_rquote}, and then examine the values of those variables.
744 539 len_rquote = strlen(lquote);
747 (@value{GDBP}) @b{p len_lquote}
749 (@value{GDBP}) @b{p len_rquote}
754 That certainly looks wrong, assuming @code{len_lquote} and
755 @code{len_rquote} are meant to be the lengths of @code{lquote} and
756 @code{rquote} respectively. We can set them to better values using
757 the @code{p} command, since it can print the value of
758 any expression---and that expression can include subroutine calls and
762 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
764 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
769 Is that enough to fix the problem of using the new quotes with the
770 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
771 executing with the @code{c} (@code{continue}) command, and then try the
772 example that caused trouble initially:
778 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
785 Success! The new quotes now work just as well as the default ones. The
786 problem seems to have been just the two typos defining the wrong
787 lengths. We allow @code{m4} exit by giving it an EOF as input:
791 Program exited normally.
795 The message @samp{Program exited normally.} is from @value{GDBN}; it
796 indicates @code{m4} has finished executing. We can end our @value{GDBN}
797 session with the @value{GDBN} @code{quit} command.
800 (@value{GDBP}) @b{quit}
804 @chapter Getting In and Out of @value{GDBN}
806 This chapter discusses how to start @value{GDBN}, and how to get out of it.
810 type @samp{@value{GDBP}} to start @value{GDBN}.
812 type @kbd{quit} or @kbd{Ctrl-d} to exit.
816 * Invoking GDB:: How to start @value{GDBN}
817 * Quitting GDB:: How to quit @value{GDBN}
818 * Shell Commands:: How to use shell commands inside @value{GDBN}
819 * Logging Output:: How to log @value{GDBN}'s output to a file
823 @section Invoking @value{GDBN}
825 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
826 @value{GDBN} reads commands from the terminal until you tell it to exit.
828 You can also run @code{@value{GDBP}} with a variety of arguments and options,
829 to specify more of your debugging environment at the outset.
831 The command-line options described here are designed
832 to cover a variety of situations; in some environments, some of these
833 options may effectively be unavailable.
835 The most usual way to start @value{GDBN} is with one argument,
836 specifying an executable program:
839 @value{GDBP} @var{program}
843 You can also start with both an executable program and a core file
847 @value{GDBP} @var{program} @var{core}
850 You can, instead, specify a process ID as a second argument, if you want
851 to debug a running process:
854 @value{GDBP} @var{program} 1234
858 would attach @value{GDBN} to process @code{1234} (unless you also have a file
859 named @file{1234}; @value{GDBN} does check for a core file first).
861 Taking advantage of the second command-line argument requires a fairly
862 complete operating system; when you use @value{GDBN} as a remote
863 debugger attached to a bare board, there may not be any notion of
864 ``process'', and there is often no way to get a core dump. @value{GDBN}
865 will warn you if it is unable to attach or to read core dumps.
867 You can optionally have @code{@value{GDBP}} pass any arguments after the
868 executable file to the inferior using @code{--args}. This option stops
871 @value{GDBP} --args gcc -O2 -c foo.c
873 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
874 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
876 You can run @code{@value{GDBP}} without printing the front material, which describes
877 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
884 You can further control how @value{GDBN} starts up by using command-line
885 options. @value{GDBN} itself can remind you of the options available.
895 to display all available options and briefly describe their use
896 (@samp{@value{GDBP} -h} is a shorter equivalent).
898 All options and command line arguments you give are processed
899 in sequential order. The order makes a difference when the
900 @samp{-x} option is used.
904 * File Options:: Choosing files
905 * Mode Options:: Choosing modes
906 * Startup:: What @value{GDBN} does during startup
910 @subsection Choosing Files
912 When @value{GDBN} starts, it reads any arguments other than options as
913 specifying an executable file and core file (or process ID). This is
914 the same as if the arguments were specified by the @samp{-se} and
915 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
916 first argument that does not have an associated option flag as
917 equivalent to the @samp{-se} option followed by that argument; and the
918 second argument that does not have an associated option flag, if any, as
919 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
920 If the second argument begins with a decimal digit, @value{GDBN} will
921 first attempt to attach to it as a process, and if that fails, attempt
922 to open it as a corefile. If you have a corefile whose name begins with
923 a digit, you can prevent @value{GDBN} from treating it as a pid by
924 prefixing it with @file{./}, e.g.@: @file{./12345}.
926 If @value{GDBN} has not been configured to included core file support,
927 such as for most embedded targets, then it will complain about a second
928 argument and ignore it.
930 Many options have both long and short forms; both are shown in the
931 following list. @value{GDBN} also recognizes the long forms if you truncate
932 them, so long as enough of the option is present to be unambiguous.
933 (If you prefer, you can flag option arguments with @samp{--} rather
934 than @samp{-}, though we illustrate the more usual convention.)
936 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
937 @c way, both those who look for -foo and --foo in the index, will find
941 @item -symbols @var{file}
943 @cindex @code{--symbols}
945 Read symbol table from file @var{file}.
947 @item -exec @var{file}
949 @cindex @code{--exec}
951 Use file @var{file} as the executable file to execute when appropriate,
952 and for examining pure data in conjunction with a core dump.
956 Read symbol table from file @var{file} and use it as the executable
959 @item -core @var{file}
961 @cindex @code{--core}
963 Use file @var{file} as a core dump to examine.
965 @item -pid @var{number}
966 @itemx -p @var{number}
969 Connect to process ID @var{number}, as with the @code{attach} command.
971 @item -command @var{file}
973 @cindex @code{--command}
975 Execute commands from file @var{file}. The contents of this file is
976 evaluated exactly as the @code{source} command would.
977 @xref{Command Files,, Command files}.
979 @item -eval-command @var{command}
980 @itemx -ex @var{command}
981 @cindex @code{--eval-command}
983 Execute a single @value{GDBN} command.
985 This option may be used multiple times to call multiple commands. It may
986 also be interleaved with @samp{-command} as required.
989 @value{GDBP} -ex 'target sim' -ex 'load' \
990 -x setbreakpoints -ex 'run' a.out
993 @item -init-command @var{file}
994 @itemx -ix @var{file}
995 @cindex @code{--init-command}
997 Execute commands from file @var{file} before loading gdbinit files or the
1001 @item -init-eval-command @var{command}
1002 @itemx -iex @var{command}
1003 @cindex @code{--init-eval-command}
1005 Execute a single @value{GDBN} command before loading gdbinit files or the
1009 @item -directory @var{directory}
1010 @itemx -d @var{directory}
1011 @cindex @code{--directory}
1013 Add @var{directory} to the path to search for source and script files.
1017 @cindex @code{--readnow}
1019 Read each symbol file's entire symbol table immediately, rather than
1020 the default, which is to read it incrementally as it is needed.
1021 This makes startup slower, but makes future operations faster.
1026 @subsection Choosing Modes
1028 You can run @value{GDBN} in various alternative modes---for example, in
1029 batch mode or quiet mode.
1037 Do not execute commands found in any initialization files. Normally,
1038 @value{GDBN} executes the commands in these files after all the command
1039 options and arguments have been processed. @xref{Command Files,,Command
1045 @cindex @code{--quiet}
1046 @cindex @code{--silent}
1048 ``Quiet''. Do not print the introductory and copyright messages. These
1049 messages are also suppressed in batch mode.
1052 @cindex @code{--batch}
1053 Run in batch mode. Exit with status @code{0} after processing all the
1054 command files specified with @samp{-x} (and all commands from
1055 initialization files, if not inhibited with @samp{-n}). Exit with
1056 nonzero status if an error occurs in executing the @value{GDBN} commands
1057 in the command files. Batch mode also disables pagination, sets unlimited
1058 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1059 off} were in effect (@pxref{Messages/Warnings}).
1061 Batch mode may be useful for running @value{GDBN} as a filter, for
1062 example to download and run a program on another computer; in order to
1063 make this more useful, the message
1066 Program exited normally.
1070 (which is ordinarily issued whenever a program running under
1071 @value{GDBN} control terminates) is not issued when running in batch
1075 @cindex @code{--batch-silent}
1076 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1077 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1078 unaffected). This is much quieter than @samp{-silent} and would be useless
1079 for an interactive session.
1081 This is particularly useful when using targets that give @samp{Loading section}
1082 messages, for example.
1084 Note that targets that give their output via @value{GDBN}, as opposed to
1085 writing directly to @code{stdout}, will also be made silent.
1087 @item -return-child-result
1088 @cindex @code{--return-child-result}
1089 The return code from @value{GDBN} will be the return code from the child
1090 process (the process being debugged), with the following exceptions:
1094 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1095 internal error. In this case the exit code is the same as it would have been
1096 without @samp{-return-child-result}.
1098 The user quits with an explicit value. E.g., @samp{quit 1}.
1100 The child process never runs, or is not allowed to terminate, in which case
1101 the exit code will be -1.
1104 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1105 when @value{GDBN} is being used as a remote program loader or simulator
1110 @cindex @code{--nowindows}
1112 ``No windows''. If @value{GDBN} comes with a graphical user interface
1113 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1114 interface. If no GUI is available, this option has no effect.
1118 @cindex @code{--windows}
1120 If @value{GDBN} includes a GUI, then this option requires it to be
1123 @item -cd @var{directory}
1125 Run @value{GDBN} using @var{directory} as its working directory,
1126 instead of the current directory.
1128 @item -data-directory @var{directory}
1129 @cindex @code{--data-directory}
1130 Run @value{GDBN} using @var{directory} as its data directory.
1131 The data directory is where @value{GDBN} searches for its
1132 auxiliary files. @xref{Data Files}.
1136 @cindex @code{--fullname}
1138 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1139 subprocess. It tells @value{GDBN} to output the full file name and line
1140 number in a standard, recognizable fashion each time a stack frame is
1141 displayed (which includes each time your program stops). This
1142 recognizable format looks like two @samp{\032} characters, followed by
1143 the file name, line number and character position separated by colons,
1144 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1145 @samp{\032} characters as a signal to display the source code for the
1149 @cindex @code{--epoch}
1150 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1151 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1152 routines so as to allow Epoch to display values of expressions in a
1155 @item -annotate @var{level}
1156 @cindex @code{--annotate}
1157 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1158 effect is identical to using @samp{set annotate @var{level}}
1159 (@pxref{Annotations}). The annotation @var{level} controls how much
1160 information @value{GDBN} prints together with its prompt, values of
1161 expressions, source lines, and other types of output. Level 0 is the
1162 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1163 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1164 that control @value{GDBN}, and level 2 has been deprecated.
1166 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1170 @cindex @code{--args}
1171 Change interpretation of command line so that arguments following the
1172 executable file are passed as command line arguments to the inferior.
1173 This option stops option processing.
1175 @item -baud @var{bps}
1177 @cindex @code{--baud}
1179 Set the line speed (baud rate or bits per second) of any serial
1180 interface used by @value{GDBN} for remote debugging.
1182 @item -l @var{timeout}
1184 Set the timeout (in seconds) of any communication used by @value{GDBN}
1185 for remote debugging.
1187 @item -tty @var{device}
1188 @itemx -t @var{device}
1189 @cindex @code{--tty}
1191 Run using @var{device} for your program's standard input and output.
1192 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1194 @c resolve the situation of these eventually
1196 @cindex @code{--tui}
1197 Activate the @dfn{Text User Interface} when starting. The Text User
1198 Interface manages several text windows on the terminal, showing
1199 source, assembly, registers and @value{GDBN} command outputs
1200 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1201 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1202 Using @value{GDBN} under @sc{gnu} Emacs}).
1205 @c @cindex @code{--xdb}
1206 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1207 @c For information, see the file @file{xdb_trans.html}, which is usually
1208 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1211 @item -interpreter @var{interp}
1212 @cindex @code{--interpreter}
1213 Use the interpreter @var{interp} for interface with the controlling
1214 program or device. This option is meant to be set by programs which
1215 communicate with @value{GDBN} using it as a back end.
1216 @xref{Interpreters, , Command Interpreters}.
1218 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1219 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1220 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1221 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1222 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1223 @sc{gdb/mi} interfaces are no longer supported.
1226 @cindex @code{--write}
1227 Open the executable and core files for both reading and writing. This
1228 is equivalent to the @samp{set write on} command inside @value{GDBN}
1232 @cindex @code{--statistics}
1233 This option causes @value{GDBN} to print statistics about time and
1234 memory usage after it completes each command and returns to the prompt.
1237 @cindex @code{--version}
1238 This option causes @value{GDBN} to print its version number and
1239 no-warranty blurb, and exit.
1241 @item -use-deprecated-index-sections
1242 @cindex @code{--use-deprecated-index-sections}
1243 This option causes @value{GDBN} to read and use deprecated
1244 @samp{.gdb_index} sections from symbol files. This can speed up
1245 startup, but may result in some functionality being lost.
1246 @xref{Index Section Format}.
1251 @subsection What @value{GDBN} Does During Startup
1252 @cindex @value{GDBN} startup
1254 Here's the description of what @value{GDBN} does during session startup:
1258 Sets up the command interpreter as specified by the command line
1259 (@pxref{Mode Options, interpreter}).
1261 @anchor{Option -init-eval-command}
1263 Executes commands and command files specified by the @samp{-iex} and
1264 @samp{-ix} options in their specified order. Usually you should use the
1265 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1266 settings before @value{GDBN} init files get executed and before inferior
1271 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1272 used when building @value{GDBN}; @pxref{System-wide configuration,
1273 ,System-wide configuration and settings}) and executes all the commands in
1276 @anchor{Home Directory Init File}
1278 Reads the init file (if any) in your home directory@footnote{On
1279 DOS/Windows systems, the home directory is the one pointed to by the
1280 @code{HOME} environment variable.} and executes all the commands in
1284 Processes command line options and operands.
1286 @anchor{Init File in the Current Directory during Startup}
1288 Reads and executes the commands from init file (if any) in the current
1289 working directory as long as @samp{set auto-load local-gdbinit} is set to
1290 @samp{on} (@pxref{Init File in the Current Directory}).
1291 This is only done if the current directory is
1292 different from your home directory. Thus, you can have more than one
1293 init file, one generic in your home directory, and another, specific
1294 to the program you are debugging, in the directory where you invoke
1298 If the command line specified a program to debug, or a process to
1299 attach to, or a core file, @value{GDBN} loads any auto-loaded
1300 scripts provided for the program or for its loaded shared libraries.
1301 @xref{Auto-loading}.
1303 If you wish to disable the auto-loading during startup,
1304 you must do something like the following:
1307 $ gdb -iex "set auto-load python-scripts off" myprogram
1310 Option @samp{-ex} does not work because the auto-loading is then turned
1314 Executes commands and command files specified by the @samp{-ex} and
1315 @samp{-x} options in their specified order. @xref{Command Files}, for
1316 more details about @value{GDBN} command files.
1319 Reads the command history recorded in the @dfn{history file}.
1320 @xref{Command History}, for more details about the command history and the
1321 files where @value{GDBN} records it.
1324 Init files use the same syntax as @dfn{command files} (@pxref{Command
1325 Files}) and are processed by @value{GDBN} in the same way. The init
1326 file in your home directory can set options (such as @samp{set
1327 complaints}) that affect subsequent processing of command line options
1328 and operands. Init files are not executed if you use the @samp{-nx}
1329 option (@pxref{Mode Options, ,Choosing Modes}).
1331 To display the list of init files loaded by gdb at startup, you
1332 can use @kbd{gdb --help}.
1334 @cindex init file name
1335 @cindex @file{.gdbinit}
1336 @cindex @file{gdb.ini}
1337 The @value{GDBN} init files are normally called @file{.gdbinit}.
1338 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1339 the limitations of file names imposed by DOS filesystems. The Windows
1340 ports of @value{GDBN} use the standard name, but if they find a
1341 @file{gdb.ini} file, they warn you about that and suggest to rename
1342 the file to the standard name.
1346 @section Quitting @value{GDBN}
1347 @cindex exiting @value{GDBN}
1348 @cindex leaving @value{GDBN}
1351 @kindex quit @r{[}@var{expression}@r{]}
1352 @kindex q @r{(@code{quit})}
1353 @item quit @r{[}@var{expression}@r{]}
1355 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1356 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1357 do not supply @var{expression}, @value{GDBN} will terminate normally;
1358 otherwise it will terminate using the result of @var{expression} as the
1363 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1364 terminates the action of any @value{GDBN} command that is in progress and
1365 returns to @value{GDBN} command level. It is safe to type the interrupt
1366 character at any time because @value{GDBN} does not allow it to take effect
1367 until a time when it is safe.
1369 If you have been using @value{GDBN} to control an attached process or
1370 device, you can release it with the @code{detach} command
1371 (@pxref{Attach, ,Debugging an Already-running Process}).
1373 @node Shell Commands
1374 @section Shell Commands
1376 If you need to execute occasional shell commands during your
1377 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1378 just use the @code{shell} command.
1383 @cindex shell escape
1384 @item shell @var{command-string}
1385 @itemx !@var{command-string}
1386 Invoke a standard shell to execute @var{command-string}.
1387 Note that no space is needed between @code{!} and @var{command-string}.
1388 If it exists, the environment variable @code{SHELL} determines which
1389 shell to run. Otherwise @value{GDBN} uses the default shell
1390 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1393 The utility @code{make} is often needed in development environments.
1394 You do not have to use the @code{shell} command for this purpose in
1399 @cindex calling make
1400 @item make @var{make-args}
1401 Execute the @code{make} program with the specified
1402 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1405 @node Logging Output
1406 @section Logging Output
1407 @cindex logging @value{GDBN} output
1408 @cindex save @value{GDBN} output to a file
1410 You may want to save the output of @value{GDBN} commands to a file.
1411 There are several commands to control @value{GDBN}'s logging.
1415 @item set logging on
1417 @item set logging off
1419 @cindex logging file name
1420 @item set logging file @var{file}
1421 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1422 @item set logging overwrite [on|off]
1423 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1424 you want @code{set logging on} to overwrite the logfile instead.
1425 @item set logging redirect [on|off]
1426 By default, @value{GDBN} output will go to both the terminal and the logfile.
1427 Set @code{redirect} if you want output to go only to the log file.
1428 @kindex show logging
1430 Show the current values of the logging settings.
1434 @chapter @value{GDBN} Commands
1436 You can abbreviate a @value{GDBN} command to the first few letters of the command
1437 name, if that abbreviation is unambiguous; and you can repeat certain
1438 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1439 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1440 show you the alternatives available, if there is more than one possibility).
1443 * Command Syntax:: How to give commands to @value{GDBN}
1444 * Completion:: Command completion
1445 * Help:: How to ask @value{GDBN} for help
1448 @node Command Syntax
1449 @section Command Syntax
1451 A @value{GDBN} command is a single line of input. There is no limit on
1452 how long it can be. It starts with a command name, which is followed by
1453 arguments whose meaning depends on the command name. For example, the
1454 command @code{step} accepts an argument which is the number of times to
1455 step, as in @samp{step 5}. You can also use the @code{step} command
1456 with no arguments. Some commands do not allow any arguments.
1458 @cindex abbreviation
1459 @value{GDBN} command names may always be truncated if that abbreviation is
1460 unambiguous. Other possible command abbreviations are listed in the
1461 documentation for individual commands. In some cases, even ambiguous
1462 abbreviations are allowed; for example, @code{s} is specially defined as
1463 equivalent to @code{step} even though there are other commands whose
1464 names start with @code{s}. You can test abbreviations by using them as
1465 arguments to the @code{help} command.
1467 @cindex repeating commands
1468 @kindex RET @r{(repeat last command)}
1469 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1470 repeat the previous command. Certain commands (for example, @code{run})
1471 will not repeat this way; these are commands whose unintentional
1472 repetition might cause trouble and which you are unlikely to want to
1473 repeat. User-defined commands can disable this feature; see
1474 @ref{Define, dont-repeat}.
1476 The @code{list} and @code{x} commands, when you repeat them with
1477 @key{RET}, construct new arguments rather than repeating
1478 exactly as typed. This permits easy scanning of source or memory.
1480 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1481 output, in a way similar to the common utility @code{more}
1482 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1483 @key{RET} too many in this situation, @value{GDBN} disables command
1484 repetition after any command that generates this sort of display.
1486 @kindex # @r{(a comment)}
1488 Any text from a @kbd{#} to the end of the line is a comment; it does
1489 nothing. This is useful mainly in command files (@pxref{Command
1490 Files,,Command Files}).
1492 @cindex repeating command sequences
1493 @kindex Ctrl-o @r{(operate-and-get-next)}
1494 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1495 commands. This command accepts the current line, like @key{RET}, and
1496 then fetches the next line relative to the current line from the history
1500 @section Command Completion
1503 @cindex word completion
1504 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1505 only one possibility; it can also show you what the valid possibilities
1506 are for the next word in a command, at any time. This works for @value{GDBN}
1507 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1509 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1510 of a word. If there is only one possibility, @value{GDBN} fills in the
1511 word, and waits for you to finish the command (or press @key{RET} to
1512 enter it). For example, if you type
1514 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1515 @c complete accuracy in these examples; space introduced for clarity.
1516 @c If texinfo enhancements make it unnecessary, it would be nice to
1517 @c replace " @key" by "@key" in the following...
1519 (@value{GDBP}) info bre @key{TAB}
1523 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1524 the only @code{info} subcommand beginning with @samp{bre}:
1527 (@value{GDBP}) info breakpoints
1531 You can either press @key{RET} at this point, to run the @code{info
1532 breakpoints} command, or backspace and enter something else, if
1533 @samp{breakpoints} does not look like the command you expected. (If you
1534 were sure you wanted @code{info breakpoints} in the first place, you
1535 might as well just type @key{RET} immediately after @samp{info bre},
1536 to exploit command abbreviations rather than command completion).
1538 If there is more than one possibility for the next word when you press
1539 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1540 characters and try again, or just press @key{TAB} a second time;
1541 @value{GDBN} displays all the possible completions for that word. For
1542 example, you might want to set a breakpoint on a subroutine whose name
1543 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1544 just sounds the bell. Typing @key{TAB} again displays all the
1545 function names in your program that begin with those characters, for
1549 (@value{GDBP}) b make_ @key{TAB}
1550 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1551 make_a_section_from_file make_environ
1552 make_abs_section make_function_type
1553 make_blockvector make_pointer_type
1554 make_cleanup make_reference_type
1555 make_command make_symbol_completion_list
1556 (@value{GDBP}) b make_
1560 After displaying the available possibilities, @value{GDBN} copies your
1561 partial input (@samp{b make_} in the example) so you can finish the
1564 If you just want to see the list of alternatives in the first place, you
1565 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1566 means @kbd{@key{META} ?}. You can type this either by holding down a
1567 key designated as the @key{META} shift on your keyboard (if there is
1568 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1570 @cindex quotes in commands
1571 @cindex completion of quoted strings
1572 Sometimes the string you need, while logically a ``word'', may contain
1573 parentheses or other characters that @value{GDBN} normally excludes from
1574 its notion of a word. To permit word completion to work in this
1575 situation, you may enclose words in @code{'} (single quote marks) in
1576 @value{GDBN} commands.
1578 The most likely situation where you might need this is in typing the
1579 name of a C@t{++} function. This is because C@t{++} allows function
1580 overloading (multiple definitions of the same function, distinguished
1581 by argument type). For example, when you want to set a breakpoint you
1582 may need to distinguish whether you mean the version of @code{name}
1583 that takes an @code{int} parameter, @code{name(int)}, or the version
1584 that takes a @code{float} parameter, @code{name(float)}. To use the
1585 word-completion facilities in this situation, type a single quote
1586 @code{'} at the beginning of the function name. This alerts
1587 @value{GDBN} that it may need to consider more information than usual
1588 when you press @key{TAB} or @kbd{M-?} to request word completion:
1591 (@value{GDBP}) b 'bubble( @kbd{M-?}
1592 bubble(double,double) bubble(int,int)
1593 (@value{GDBP}) b 'bubble(
1596 In some cases, @value{GDBN} can tell that completing a name requires using
1597 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1598 completing as much as it can) if you do not type the quote in the first
1602 (@value{GDBP}) b bub @key{TAB}
1603 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1604 (@value{GDBP}) b 'bubble(
1608 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1609 you have not yet started typing the argument list when you ask for
1610 completion on an overloaded symbol.
1612 For more information about overloaded functions, see @ref{C Plus Plus
1613 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1614 overload-resolution off} to disable overload resolution;
1615 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1617 @cindex completion of structure field names
1618 @cindex structure field name completion
1619 @cindex completion of union field names
1620 @cindex union field name completion
1621 When completing in an expression which looks up a field in a
1622 structure, @value{GDBN} also tries@footnote{The completer can be
1623 confused by certain kinds of invalid expressions. Also, it only
1624 examines the static type of the expression, not the dynamic type.} to
1625 limit completions to the field names available in the type of the
1629 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1630 magic to_fputs to_rewind
1631 to_data to_isatty to_write
1632 to_delete to_put to_write_async_safe
1637 This is because the @code{gdb_stdout} is a variable of the type
1638 @code{struct ui_file} that is defined in @value{GDBN} sources as
1645 ui_file_flush_ftype *to_flush;
1646 ui_file_write_ftype *to_write;
1647 ui_file_write_async_safe_ftype *to_write_async_safe;
1648 ui_file_fputs_ftype *to_fputs;
1649 ui_file_read_ftype *to_read;
1650 ui_file_delete_ftype *to_delete;
1651 ui_file_isatty_ftype *to_isatty;
1652 ui_file_rewind_ftype *to_rewind;
1653 ui_file_put_ftype *to_put;
1660 @section Getting Help
1661 @cindex online documentation
1664 You can always ask @value{GDBN} itself for information on its commands,
1665 using the command @code{help}.
1668 @kindex h @r{(@code{help})}
1671 You can use @code{help} (abbreviated @code{h}) with no arguments to
1672 display a short list of named classes of commands:
1676 List of classes of commands:
1678 aliases -- Aliases of other commands
1679 breakpoints -- Making program stop at certain points
1680 data -- Examining data
1681 files -- Specifying and examining files
1682 internals -- Maintenance commands
1683 obscure -- Obscure features
1684 running -- Running the program
1685 stack -- Examining the stack
1686 status -- Status inquiries
1687 support -- Support facilities
1688 tracepoints -- Tracing of program execution without
1689 stopping the program
1690 user-defined -- User-defined commands
1692 Type "help" followed by a class name for a list of
1693 commands in that class.
1694 Type "help" followed by command name for full
1696 Command name abbreviations are allowed if unambiguous.
1699 @c the above line break eliminates huge line overfull...
1701 @item help @var{class}
1702 Using one of the general help classes as an argument, you can get a
1703 list of the individual commands in that class. For example, here is the
1704 help display for the class @code{status}:
1707 (@value{GDBP}) help status
1712 @c Line break in "show" line falsifies real output, but needed
1713 @c to fit in smallbook page size.
1714 info -- Generic command for showing things
1715 about the program being debugged
1716 show -- Generic command for showing things
1719 Type "help" followed by command name for full
1721 Command name abbreviations are allowed if unambiguous.
1725 @item help @var{command}
1726 With a command name as @code{help} argument, @value{GDBN} displays a
1727 short paragraph on how to use that command.
1730 @item apropos @var{args}
1731 The @code{apropos} command searches through all of the @value{GDBN}
1732 commands, and their documentation, for the regular expression specified in
1733 @var{args}. It prints out all matches found. For example:
1744 alias -- Define a new command that is an alias of an existing command
1745 aliases -- Aliases of other commands
1746 d -- Delete some breakpoints or auto-display expressions
1747 del -- Delete some breakpoints or auto-display expressions
1748 delete -- Delete some breakpoints or auto-display expressions
1753 @item complete @var{args}
1754 The @code{complete @var{args}} command lists all the possible completions
1755 for the beginning of a command. Use @var{args} to specify the beginning of the
1756 command you want completed. For example:
1762 @noindent results in:
1773 @noindent This is intended for use by @sc{gnu} Emacs.
1776 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1777 and @code{show} to inquire about the state of your program, or the state
1778 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1779 manual introduces each of them in the appropriate context. The listings
1780 under @code{info} and under @code{show} in the Index point to
1781 all the sub-commands. @xref{Index}.
1786 @kindex i @r{(@code{info})}
1788 This command (abbreviated @code{i}) is for describing the state of your
1789 program. For example, you can show the arguments passed to a function
1790 with @code{info args}, list the registers currently in use with @code{info
1791 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1792 You can get a complete list of the @code{info} sub-commands with
1793 @w{@code{help info}}.
1797 You can assign the result of an expression to an environment variable with
1798 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1799 @code{set prompt $}.
1803 In contrast to @code{info}, @code{show} is for describing the state of
1804 @value{GDBN} itself.
1805 You can change most of the things you can @code{show}, by using the
1806 related command @code{set}; for example, you can control what number
1807 system is used for displays with @code{set radix}, or simply inquire
1808 which is currently in use with @code{show radix}.
1811 To display all the settable parameters and their current
1812 values, you can use @code{show} with no arguments; you may also use
1813 @code{info set}. Both commands produce the same display.
1814 @c FIXME: "info set" violates the rule that "info" is for state of
1815 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1816 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1820 Here are three miscellaneous @code{show} subcommands, all of which are
1821 exceptional in lacking corresponding @code{set} commands:
1824 @kindex show version
1825 @cindex @value{GDBN} version number
1827 Show what version of @value{GDBN} is running. You should include this
1828 information in @value{GDBN} bug-reports. If multiple versions of
1829 @value{GDBN} are in use at your site, you may need to determine which
1830 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1831 commands are introduced, and old ones may wither away. Also, many
1832 system vendors ship variant versions of @value{GDBN}, and there are
1833 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1834 The version number is the same as the one announced when you start
1837 @kindex show copying
1838 @kindex info copying
1839 @cindex display @value{GDBN} copyright
1842 Display information about permission for copying @value{GDBN}.
1844 @kindex show warranty
1845 @kindex info warranty
1847 @itemx info warranty
1848 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1849 if your version of @value{GDBN} comes with one.
1854 @chapter Running Programs Under @value{GDBN}
1856 When you run a program under @value{GDBN}, you must first generate
1857 debugging information when you compile it.
1859 You may start @value{GDBN} with its arguments, if any, in an environment
1860 of your choice. If you are doing native debugging, you may redirect
1861 your program's input and output, debug an already running process, or
1862 kill a child process.
1865 * Compilation:: Compiling for debugging
1866 * Starting:: Starting your program
1867 * Arguments:: Your program's arguments
1868 * Environment:: Your program's environment
1870 * Working Directory:: Your program's working directory
1871 * Input/Output:: Your program's input and output
1872 * Attach:: Debugging an already-running process
1873 * Kill Process:: Killing the child process
1875 * Inferiors and Programs:: Debugging multiple inferiors and programs
1876 * Threads:: Debugging programs with multiple threads
1877 * Forks:: Debugging forks
1878 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1882 @section Compiling for Debugging
1884 In order to debug a program effectively, you need to generate
1885 debugging information when you compile it. This debugging information
1886 is stored in the object file; it describes the data type of each
1887 variable or function and the correspondence between source line numbers
1888 and addresses in the executable code.
1890 To request debugging information, specify the @samp{-g} option when you run
1893 Programs that are to be shipped to your customers are compiled with
1894 optimizations, using the @samp{-O} compiler option. However, some
1895 compilers are unable to handle the @samp{-g} and @samp{-O} options
1896 together. Using those compilers, you cannot generate optimized
1897 executables containing debugging information.
1899 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1900 without @samp{-O}, making it possible to debug optimized code. We
1901 recommend that you @emph{always} use @samp{-g} whenever you compile a
1902 program. You may think your program is correct, but there is no sense
1903 in pushing your luck. For more information, see @ref{Optimized Code}.
1905 Older versions of the @sc{gnu} C compiler permitted a variant option
1906 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1907 format; if your @sc{gnu} C compiler has this option, do not use it.
1909 @value{GDBN} knows about preprocessor macros and can show you their
1910 expansion (@pxref{Macros}). Most compilers do not include information
1911 about preprocessor macros in the debugging information if you specify
1912 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1913 the @sc{gnu} C compiler, provides macro information if you are using
1914 the DWARF debugging format, and specify the option @option{-g3}.
1916 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1917 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1918 information on @value{NGCC} options affecting debug information.
1920 You will have the best debugging experience if you use the latest
1921 version of the DWARF debugging format that your compiler supports.
1922 DWARF is currently the most expressive and best supported debugging
1923 format in @value{GDBN}.
1927 @section Starting your Program
1933 @kindex r @r{(@code{run})}
1936 Use the @code{run} command to start your program under @value{GDBN}.
1937 You must first specify the program name (except on VxWorks) with an
1938 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1939 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1940 (@pxref{Files, ,Commands to Specify Files}).
1944 If you are running your program in an execution environment that
1945 supports processes, @code{run} creates an inferior process and makes
1946 that process run your program. In some environments without processes,
1947 @code{run} jumps to the start of your program. Other targets,
1948 like @samp{remote}, are always running. If you get an error
1949 message like this one:
1952 The "remote" target does not support "run".
1953 Try "help target" or "continue".
1957 then use @code{continue} to run your program. You may need @code{load}
1958 first (@pxref{load}).
1960 The execution of a program is affected by certain information it
1961 receives from its superior. @value{GDBN} provides ways to specify this
1962 information, which you must do @emph{before} starting your program. (You
1963 can change it after starting your program, but such changes only affect
1964 your program the next time you start it.) This information may be
1965 divided into four categories:
1968 @item The @emph{arguments.}
1969 Specify the arguments to give your program as the arguments of the
1970 @code{run} command. If a shell is available on your target, the shell
1971 is used to pass the arguments, so that you may use normal conventions
1972 (such as wildcard expansion or variable substitution) in describing
1974 In Unix systems, you can control which shell is used with the
1975 @code{SHELL} environment variable.
1976 @xref{Arguments, ,Your Program's Arguments}.
1978 @item The @emph{environment.}
1979 Your program normally inherits its environment from @value{GDBN}, but you can
1980 use the @value{GDBN} commands @code{set environment} and @code{unset
1981 environment} to change parts of the environment that affect
1982 your program. @xref{Environment, ,Your Program's Environment}.
1984 @item The @emph{working directory.}
1985 Your program inherits its working directory from @value{GDBN}. You can set
1986 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1987 @xref{Working Directory, ,Your Program's Working Directory}.
1989 @item The @emph{standard input and output.}
1990 Your program normally uses the same device for standard input and
1991 standard output as @value{GDBN} is using. You can redirect input and output
1992 in the @code{run} command line, or you can use the @code{tty} command to
1993 set a different device for your program.
1994 @xref{Input/Output, ,Your Program's Input and Output}.
1997 @emph{Warning:} While input and output redirection work, you cannot use
1998 pipes to pass the output of the program you are debugging to another
1999 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2003 When you issue the @code{run} command, your program begins to execute
2004 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2005 of how to arrange for your program to stop. Once your program has
2006 stopped, you may call functions in your program, using the @code{print}
2007 or @code{call} commands. @xref{Data, ,Examining Data}.
2009 If the modification time of your symbol file has changed since the last
2010 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2011 table, and reads it again. When it does this, @value{GDBN} tries to retain
2012 your current breakpoints.
2017 @cindex run to main procedure
2018 The name of the main procedure can vary from language to language.
2019 With C or C@t{++}, the main procedure name is always @code{main}, but
2020 other languages such as Ada do not require a specific name for their
2021 main procedure. The debugger provides a convenient way to start the
2022 execution of the program and to stop at the beginning of the main
2023 procedure, depending on the language used.
2025 The @samp{start} command does the equivalent of setting a temporary
2026 breakpoint at the beginning of the main procedure and then invoking
2027 the @samp{run} command.
2029 @cindex elaboration phase
2030 Some programs contain an @dfn{elaboration} phase where some startup code is
2031 executed before the main procedure is called. This depends on the
2032 languages used to write your program. In C@t{++}, for instance,
2033 constructors for static and global objects are executed before
2034 @code{main} is called. It is therefore possible that the debugger stops
2035 before reaching the main procedure. However, the temporary breakpoint
2036 will remain to halt execution.
2038 Specify the arguments to give to your program as arguments to the
2039 @samp{start} command. These arguments will be given verbatim to the
2040 underlying @samp{run} command. Note that the same arguments will be
2041 reused if no argument is provided during subsequent calls to
2042 @samp{start} or @samp{run}.
2044 It is sometimes necessary to debug the program during elaboration. In
2045 these cases, using the @code{start} command would stop the execution of
2046 your program too late, as the program would have already completed the
2047 elaboration phase. Under these circumstances, insert breakpoints in your
2048 elaboration code before running your program.
2050 @kindex set exec-wrapper
2051 @item set exec-wrapper @var{wrapper}
2052 @itemx show exec-wrapper
2053 @itemx unset exec-wrapper
2054 When @samp{exec-wrapper} is set, the specified wrapper is used to
2055 launch programs for debugging. @value{GDBN} starts your program
2056 with a shell command of the form @kbd{exec @var{wrapper}
2057 @var{program}}. Quoting is added to @var{program} and its
2058 arguments, but not to @var{wrapper}, so you should add quotes if
2059 appropriate for your shell. The wrapper runs until it executes
2060 your program, and then @value{GDBN} takes control.
2062 You can use any program that eventually calls @code{execve} with
2063 its arguments as a wrapper. Several standard Unix utilities do
2064 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2065 with @code{exec "$@@"} will also work.
2067 For example, you can use @code{env} to pass an environment variable to
2068 the debugged program, without setting the variable in your shell's
2072 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2076 This command is available when debugging locally on most targets, excluding
2077 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2079 @kindex set disable-randomization
2080 @item set disable-randomization
2081 @itemx set disable-randomization on
2082 This option (enabled by default in @value{GDBN}) will turn off the native
2083 randomization of the virtual address space of the started program. This option
2084 is useful for multiple debugging sessions to make the execution better
2085 reproducible and memory addresses reusable across debugging sessions.
2087 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2088 On @sc{gnu}/Linux you can get the same behavior using
2091 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2094 @item set disable-randomization off
2095 Leave the behavior of the started executable unchanged. Some bugs rear their
2096 ugly heads only when the program is loaded at certain addresses. If your bug
2097 disappears when you run the program under @value{GDBN}, that might be because
2098 @value{GDBN} by default disables the address randomization on platforms, such
2099 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2100 disable-randomization off} to try to reproduce such elusive bugs.
2102 On targets where it is available, virtual address space randomization
2103 protects the programs against certain kinds of security attacks. In these
2104 cases the attacker needs to know the exact location of a concrete executable
2105 code. Randomizing its location makes it impossible to inject jumps misusing
2106 a code at its expected addresses.
2108 Prelinking shared libraries provides a startup performance advantage but it
2109 makes addresses in these libraries predictable for privileged processes by
2110 having just unprivileged access at the target system. Reading the shared
2111 library binary gives enough information for assembling the malicious code
2112 misusing it. Still even a prelinked shared library can get loaded at a new
2113 random address just requiring the regular relocation process during the
2114 startup. Shared libraries not already prelinked are always loaded at
2115 a randomly chosen address.
2117 Position independent executables (PIE) contain position independent code
2118 similar to the shared libraries and therefore such executables get loaded at
2119 a randomly chosen address upon startup. PIE executables always load even
2120 already prelinked shared libraries at a random address. You can build such
2121 executable using @command{gcc -fPIE -pie}.
2123 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2124 (as long as the randomization is enabled).
2126 @item show disable-randomization
2127 Show the current setting of the explicit disable of the native randomization of
2128 the virtual address space of the started program.
2133 @section Your Program's Arguments
2135 @cindex arguments (to your program)
2136 The arguments to your program can be specified by the arguments of the
2138 They are passed to a shell, which expands wildcard characters and
2139 performs redirection of I/O, and thence to your program. Your
2140 @code{SHELL} environment variable (if it exists) specifies what shell
2141 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2142 the default shell (@file{/bin/sh} on Unix).
2144 On non-Unix systems, the program is usually invoked directly by
2145 @value{GDBN}, which emulates I/O redirection via the appropriate system
2146 calls, and the wildcard characters are expanded by the startup code of
2147 the program, not by the shell.
2149 @code{run} with no arguments uses the same arguments used by the previous
2150 @code{run}, or those set by the @code{set args} command.
2155 Specify the arguments to be used the next time your program is run. If
2156 @code{set args} has no arguments, @code{run} executes your program
2157 with no arguments. Once you have run your program with arguments,
2158 using @code{set args} before the next @code{run} is the only way to run
2159 it again without arguments.
2163 Show the arguments to give your program when it is started.
2167 @section Your Program's Environment
2169 @cindex environment (of your program)
2170 The @dfn{environment} consists of a set of environment variables and
2171 their values. Environment variables conventionally record such things as
2172 your user name, your home directory, your terminal type, and your search
2173 path for programs to run. Usually you set up environment variables with
2174 the shell and they are inherited by all the other programs you run. When
2175 debugging, it can be useful to try running your program with a modified
2176 environment without having to start @value{GDBN} over again.
2180 @item path @var{directory}
2181 Add @var{directory} to the front of the @code{PATH} environment variable
2182 (the search path for executables) that will be passed to your program.
2183 The value of @code{PATH} used by @value{GDBN} does not change.
2184 You may specify several directory names, separated by whitespace or by a
2185 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2186 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2187 is moved to the front, so it is searched sooner.
2189 You can use the string @samp{$cwd} to refer to whatever is the current
2190 working directory at the time @value{GDBN} searches the path. If you
2191 use @samp{.} instead, it refers to the directory where you executed the
2192 @code{path} command. @value{GDBN} replaces @samp{.} in the
2193 @var{directory} argument (with the current path) before adding
2194 @var{directory} to the search path.
2195 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2196 @c document that, since repeating it would be a no-op.
2200 Display the list of search paths for executables (the @code{PATH}
2201 environment variable).
2203 @kindex show environment
2204 @item show environment @r{[}@var{varname}@r{]}
2205 Print the value of environment variable @var{varname} to be given to
2206 your program when it starts. If you do not supply @var{varname},
2207 print the names and values of all environment variables to be given to
2208 your program. You can abbreviate @code{environment} as @code{env}.
2210 @kindex set environment
2211 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2212 Set environment variable @var{varname} to @var{value}. The value
2213 changes for your program only, not for @value{GDBN} itself. @var{value} may
2214 be any string; the values of environment variables are just strings, and
2215 any interpretation is supplied by your program itself. The @var{value}
2216 parameter is optional; if it is eliminated, the variable is set to a
2218 @c "any string" here does not include leading, trailing
2219 @c blanks. Gnu asks: does anyone care?
2221 For example, this command:
2228 tells the debugged program, when subsequently run, that its user is named
2229 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2230 are not actually required.)
2232 @kindex unset environment
2233 @item unset environment @var{varname}
2234 Remove variable @var{varname} from the environment to be passed to your
2235 program. This is different from @samp{set env @var{varname} =};
2236 @code{unset environment} removes the variable from the environment,
2237 rather than assigning it an empty value.
2240 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2242 by your @code{SHELL} environment variable if it exists (or
2243 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2244 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2245 @file{.bashrc} for BASH---any variables you set in that file affect
2246 your program. You may wish to move setting of environment variables to
2247 files that are only run when you sign on, such as @file{.login} or
2250 @node Working Directory
2251 @section Your Program's Working Directory
2253 @cindex working directory (of your program)
2254 Each time you start your program with @code{run}, it inherits its
2255 working directory from the current working directory of @value{GDBN}.
2256 The @value{GDBN} working directory is initially whatever it inherited
2257 from its parent process (typically the shell), but you can specify a new
2258 working directory in @value{GDBN} with the @code{cd} command.
2260 The @value{GDBN} working directory also serves as a default for the commands
2261 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2266 @cindex change working directory
2267 @item cd @var{directory}
2268 Set the @value{GDBN} working directory to @var{directory}.
2272 Print the @value{GDBN} working directory.
2275 It is generally impossible to find the current working directory of
2276 the process being debugged (since a program can change its directory
2277 during its run). If you work on a system where @value{GDBN} is
2278 configured with the @file{/proc} support, you can use the @code{info
2279 proc} command (@pxref{SVR4 Process Information}) to find out the
2280 current working directory of the debuggee.
2283 @section Your Program's Input and Output
2288 By default, the program you run under @value{GDBN} does input and output to
2289 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2290 to its own terminal modes to interact with you, but it records the terminal
2291 modes your program was using and switches back to them when you continue
2292 running your program.
2295 @kindex info terminal
2297 Displays information recorded by @value{GDBN} about the terminal modes your
2301 You can redirect your program's input and/or output using shell
2302 redirection with the @code{run} command. For example,
2309 starts your program, diverting its output to the file @file{outfile}.
2312 @cindex controlling terminal
2313 Another way to specify where your program should do input and output is
2314 with the @code{tty} command. This command accepts a file name as
2315 argument, and causes this file to be the default for future @code{run}
2316 commands. It also resets the controlling terminal for the child
2317 process, for future @code{run} commands. For example,
2324 directs that processes started with subsequent @code{run} commands
2325 default to do input and output on the terminal @file{/dev/ttyb} and have
2326 that as their controlling terminal.
2328 An explicit redirection in @code{run} overrides the @code{tty} command's
2329 effect on the input/output device, but not its effect on the controlling
2332 When you use the @code{tty} command or redirect input in the @code{run}
2333 command, only the input @emph{for your program} is affected. The input
2334 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2335 for @code{set inferior-tty}.
2337 @cindex inferior tty
2338 @cindex set inferior controlling terminal
2339 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2340 display the name of the terminal that will be used for future runs of your
2344 @item set inferior-tty /dev/ttyb
2345 @kindex set inferior-tty
2346 Set the tty for the program being debugged to /dev/ttyb.
2348 @item show inferior-tty
2349 @kindex show inferior-tty
2350 Show the current tty for the program being debugged.
2354 @section Debugging an Already-running Process
2359 @item attach @var{process-id}
2360 This command attaches to a running process---one that was started
2361 outside @value{GDBN}. (@code{info files} shows your active
2362 targets.) The command takes as argument a process ID. The usual way to
2363 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2364 or with the @samp{jobs -l} shell command.
2366 @code{attach} does not repeat if you press @key{RET} a second time after
2367 executing the command.
2370 To use @code{attach}, your program must be running in an environment
2371 which supports processes; for example, @code{attach} does not work for
2372 programs on bare-board targets that lack an operating system. You must
2373 also have permission to send the process a signal.
2375 When you use @code{attach}, the debugger finds the program running in
2376 the process first by looking in the current working directory, then (if
2377 the program is not found) by using the source file search path
2378 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2379 the @code{file} command to load the program. @xref{Files, ,Commands to
2382 The first thing @value{GDBN} does after arranging to debug the specified
2383 process is to stop it. You can examine and modify an attached process
2384 with all the @value{GDBN} commands that are ordinarily available when
2385 you start processes with @code{run}. You can insert breakpoints; you
2386 can step and continue; you can modify storage. If you would rather the
2387 process continue running, you may use the @code{continue} command after
2388 attaching @value{GDBN} to the process.
2393 When you have finished debugging the attached process, you can use the
2394 @code{detach} command to release it from @value{GDBN} control. Detaching
2395 the process continues its execution. After the @code{detach} command,
2396 that process and @value{GDBN} become completely independent once more, and you
2397 are ready to @code{attach} another process or start one with @code{run}.
2398 @code{detach} does not repeat if you press @key{RET} again after
2399 executing the command.
2402 If you exit @value{GDBN} while you have an attached process, you detach
2403 that process. If you use the @code{run} command, you kill that process.
2404 By default, @value{GDBN} asks for confirmation if you try to do either of these
2405 things; you can control whether or not you need to confirm by using the
2406 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2410 @section Killing the Child Process
2415 Kill the child process in which your program is running under @value{GDBN}.
2418 This command is useful if you wish to debug a core dump instead of a
2419 running process. @value{GDBN} ignores any core dump file while your program
2422 On some operating systems, a program cannot be executed outside @value{GDBN}
2423 while you have breakpoints set on it inside @value{GDBN}. You can use the
2424 @code{kill} command in this situation to permit running your program
2425 outside the debugger.
2427 The @code{kill} command is also useful if you wish to recompile and
2428 relink your program, since on many systems it is impossible to modify an
2429 executable file while it is running in a process. In this case, when you
2430 next type @code{run}, @value{GDBN} notices that the file has changed, and
2431 reads the symbol table again (while trying to preserve your current
2432 breakpoint settings).
2434 @node Inferiors and Programs
2435 @section Debugging Multiple Inferiors and Programs
2437 @value{GDBN} lets you run and debug multiple programs in a single
2438 session. In addition, @value{GDBN} on some systems may let you run
2439 several programs simultaneously (otherwise you have to exit from one
2440 before starting another). In the most general case, you can have
2441 multiple threads of execution in each of multiple processes, launched
2442 from multiple executables.
2445 @value{GDBN} represents the state of each program execution with an
2446 object called an @dfn{inferior}. An inferior typically corresponds to
2447 a process, but is more general and applies also to targets that do not
2448 have processes. Inferiors may be created before a process runs, and
2449 may be retained after a process exits. Inferiors have unique
2450 identifiers that are different from process ids. Usually each
2451 inferior will also have its own distinct address space, although some
2452 embedded targets may have several inferiors running in different parts
2453 of a single address space. Each inferior may in turn have multiple
2454 threads running in it.
2456 To find out what inferiors exist at any moment, use @w{@code{info
2460 @kindex info inferiors
2461 @item info inferiors
2462 Print a list of all inferiors currently being managed by @value{GDBN}.
2464 @value{GDBN} displays for each inferior (in this order):
2468 the inferior number assigned by @value{GDBN}
2471 the target system's inferior identifier
2474 the name of the executable the inferior is running.
2479 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2480 indicates the current inferior.
2484 @c end table here to get a little more width for example
2487 (@value{GDBP}) info inferiors
2488 Num Description Executable
2489 2 process 2307 hello
2490 * 1 process 3401 goodbye
2493 To switch focus between inferiors, use the @code{inferior} command:
2496 @kindex inferior @var{infno}
2497 @item inferior @var{infno}
2498 Make inferior number @var{infno} the current inferior. The argument
2499 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2500 in the first field of the @samp{info inferiors} display.
2504 You can get multiple executables into a debugging session via the
2505 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2506 systems @value{GDBN} can add inferiors to the debug session
2507 automatically by following calls to @code{fork} and @code{exec}. To
2508 remove inferiors from the debugging session use the
2509 @w{@code{remove-inferiors}} command.
2512 @kindex add-inferior
2513 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2514 Adds @var{n} inferiors to be run using @var{executable} as the
2515 executable. @var{n} defaults to 1. If no executable is specified,
2516 the inferiors begins empty, with no program. You can still assign or
2517 change the program assigned to the inferior at any time by using the
2518 @code{file} command with the executable name as its argument.
2520 @kindex clone-inferior
2521 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2522 Adds @var{n} inferiors ready to execute the same program as inferior
2523 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2524 number of the current inferior. This is a convenient command when you
2525 want to run another instance of the inferior you are debugging.
2528 (@value{GDBP}) info inferiors
2529 Num Description Executable
2530 * 1 process 29964 helloworld
2531 (@value{GDBP}) clone-inferior
2534 (@value{GDBP}) info inferiors
2535 Num Description Executable
2537 * 1 process 29964 helloworld
2540 You can now simply switch focus to inferior 2 and run it.
2542 @kindex remove-inferiors
2543 @item remove-inferiors @var{infno}@dots{}
2544 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2545 possible to remove an inferior that is running with this command. For
2546 those, use the @code{kill} or @code{detach} command first.
2550 To quit debugging one of the running inferiors that is not the current
2551 inferior, you can either detach from it by using the @w{@code{detach
2552 inferior}} command (allowing it to run independently), or kill it
2553 using the @w{@code{kill inferiors}} command:
2556 @kindex detach inferiors @var{infno}@dots{}
2557 @item detach inferior @var{infno}@dots{}
2558 Detach from the inferior or inferiors identified by @value{GDBN}
2559 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2560 still stays on the list of inferiors shown by @code{info inferiors},
2561 but its Description will show @samp{<null>}.
2563 @kindex kill inferiors @var{infno}@dots{}
2564 @item kill inferiors @var{infno}@dots{}
2565 Kill the inferior or inferiors identified by @value{GDBN} inferior
2566 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2567 stays on the list of inferiors shown by @code{info inferiors}, but its
2568 Description will show @samp{<null>}.
2571 After the successful completion of a command such as @code{detach},
2572 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2573 a normal process exit, the inferior is still valid and listed with
2574 @code{info inferiors}, ready to be restarted.
2577 To be notified when inferiors are started or exit under @value{GDBN}'s
2578 control use @w{@code{set print inferior-events}}:
2581 @kindex set print inferior-events
2582 @cindex print messages on inferior start and exit
2583 @item set print inferior-events
2584 @itemx set print inferior-events on
2585 @itemx set print inferior-events off
2586 The @code{set print inferior-events} command allows you to enable or
2587 disable printing of messages when @value{GDBN} notices that new
2588 inferiors have started or that inferiors have exited or have been
2589 detached. By default, these messages will not be printed.
2591 @kindex show print inferior-events
2592 @item show print inferior-events
2593 Show whether messages will be printed when @value{GDBN} detects that
2594 inferiors have started, exited or have been detached.
2597 Many commands will work the same with multiple programs as with a
2598 single program: e.g., @code{print myglobal} will simply display the
2599 value of @code{myglobal} in the current inferior.
2602 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2603 get more info about the relationship of inferiors, programs, address
2604 spaces in a debug session. You can do that with the @w{@code{maint
2605 info program-spaces}} command.
2608 @kindex maint info program-spaces
2609 @item maint info program-spaces
2610 Print a list of all program spaces currently being managed by
2613 @value{GDBN} displays for each program space (in this order):
2617 the program space number assigned by @value{GDBN}
2620 the name of the executable loaded into the program space, with e.g.,
2621 the @code{file} command.
2626 An asterisk @samp{*} preceding the @value{GDBN} program space number
2627 indicates the current program space.
2629 In addition, below each program space line, @value{GDBN} prints extra
2630 information that isn't suitable to display in tabular form. For
2631 example, the list of inferiors bound to the program space.
2634 (@value{GDBP}) maint info program-spaces
2637 Bound inferiors: ID 1 (process 21561)
2641 Here we can see that no inferior is running the program @code{hello},
2642 while @code{process 21561} is running the program @code{goodbye}. On
2643 some targets, it is possible that multiple inferiors are bound to the
2644 same program space. The most common example is that of debugging both
2645 the parent and child processes of a @code{vfork} call. For example,
2648 (@value{GDBP}) maint info program-spaces
2651 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2654 Here, both inferior 2 and inferior 1 are running in the same program
2655 space as a result of inferior 1 having executed a @code{vfork} call.
2659 @section Debugging Programs with Multiple Threads
2661 @cindex threads of execution
2662 @cindex multiple threads
2663 @cindex switching threads
2664 In some operating systems, such as HP-UX and Solaris, a single program
2665 may have more than one @dfn{thread} of execution. The precise semantics
2666 of threads differ from one operating system to another, but in general
2667 the threads of a single program are akin to multiple processes---except
2668 that they share one address space (that is, they can all examine and
2669 modify the same variables). On the other hand, each thread has its own
2670 registers and execution stack, and perhaps private memory.
2672 @value{GDBN} provides these facilities for debugging multi-thread
2676 @item automatic notification of new threads
2677 @item @samp{thread @var{threadno}}, a command to switch among threads
2678 @item @samp{info threads}, a command to inquire about existing threads
2679 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2680 a command to apply a command to a list of threads
2681 @item thread-specific breakpoints
2682 @item @samp{set print thread-events}, which controls printing of
2683 messages on thread start and exit.
2684 @item @samp{set libthread-db-search-path @var{path}}, which lets
2685 the user specify which @code{libthread_db} to use if the default choice
2686 isn't compatible with the program.
2690 @emph{Warning:} These facilities are not yet available on every
2691 @value{GDBN} configuration where the operating system supports threads.
2692 If your @value{GDBN} does not support threads, these commands have no
2693 effect. For example, a system without thread support shows no output
2694 from @samp{info threads}, and always rejects the @code{thread} command,
2698 (@value{GDBP}) info threads
2699 (@value{GDBP}) thread 1
2700 Thread ID 1 not known. Use the "info threads" command to
2701 see the IDs of currently known threads.
2703 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2704 @c doesn't support threads"?
2707 @cindex focus of debugging
2708 @cindex current thread
2709 The @value{GDBN} thread debugging facility allows you to observe all
2710 threads while your program runs---but whenever @value{GDBN} takes
2711 control, one thread in particular is always the focus of debugging.
2712 This thread is called the @dfn{current thread}. Debugging commands show
2713 program information from the perspective of the current thread.
2715 @cindex @code{New} @var{systag} message
2716 @cindex thread identifier (system)
2717 @c FIXME-implementors!! It would be more helpful if the [New...] message
2718 @c included GDB's numeric thread handle, so you could just go to that
2719 @c thread without first checking `info threads'.
2720 Whenever @value{GDBN} detects a new thread in your program, it displays
2721 the target system's identification for the thread with a message in the
2722 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2723 whose form varies depending on the particular system. For example, on
2724 @sc{gnu}/Linux, you might see
2727 [New Thread 0x41e02940 (LWP 25582)]
2731 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2732 the @var{systag} is simply something like @samp{process 368}, with no
2735 @c FIXME!! (1) Does the [New...] message appear even for the very first
2736 @c thread of a program, or does it only appear for the
2737 @c second---i.e.@: when it becomes obvious we have a multithread
2739 @c (2) *Is* there necessarily a first thread always? Or do some
2740 @c multithread systems permit starting a program with multiple
2741 @c threads ab initio?
2743 @cindex thread number
2744 @cindex thread identifier (GDB)
2745 For debugging purposes, @value{GDBN} associates its own thread
2746 number---always a single integer---with each thread in your program.
2749 @kindex info threads
2750 @item info threads @r{[}@var{id}@dots{}@r{]}
2751 Display a summary of all threads currently in your program. Optional
2752 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2753 means to print information only about the specified thread or threads.
2754 @value{GDBN} displays for each thread (in this order):
2758 the thread number assigned by @value{GDBN}
2761 the target system's thread identifier (@var{systag})
2764 the thread's name, if one is known. A thread can either be named by
2765 the user (see @code{thread name}, below), or, in some cases, by the
2769 the current stack frame summary for that thread
2773 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2774 indicates the current thread.
2778 @c end table here to get a little more width for example
2781 (@value{GDBP}) info threads
2783 3 process 35 thread 27 0x34e5 in sigpause ()
2784 2 process 35 thread 23 0x34e5 in sigpause ()
2785 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2789 On Solaris, you can display more information about user threads with a
2790 Solaris-specific command:
2793 @item maint info sol-threads
2794 @kindex maint info sol-threads
2795 @cindex thread info (Solaris)
2796 Display info on Solaris user threads.
2800 @kindex thread @var{threadno}
2801 @item thread @var{threadno}
2802 Make thread number @var{threadno} the current thread. The command
2803 argument @var{threadno} is the internal @value{GDBN} thread number, as
2804 shown in the first field of the @samp{info threads} display.
2805 @value{GDBN} responds by displaying the system identifier of the thread
2806 you selected, and its current stack frame summary:
2809 (@value{GDBP}) thread 2
2810 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2811 #0 some_function (ignore=0x0) at example.c:8
2812 8 printf ("hello\n");
2816 As with the @samp{[New @dots{}]} message, the form of the text after
2817 @samp{Switching to} depends on your system's conventions for identifying
2820 @vindex $_thread@r{, convenience variable}
2821 The debugger convenience variable @samp{$_thread} contains the number
2822 of the current thread. You may find this useful in writing breakpoint
2823 conditional expressions, command scripts, and so forth. See
2824 @xref{Convenience Vars,, Convenience Variables}, for general
2825 information on convenience variables.
2827 @kindex thread apply
2828 @cindex apply command to several threads
2829 @item thread apply [@var{threadno} | all] @var{command}
2830 The @code{thread apply} command allows you to apply the named
2831 @var{command} to one or more threads. Specify the numbers of the
2832 threads that you want affected with the command argument
2833 @var{threadno}. It can be a single thread number, one of the numbers
2834 shown in the first field of the @samp{info threads} display; or it
2835 could be a range of thread numbers, as in @code{2-4}. To apply a
2836 command to all threads, type @kbd{thread apply all @var{command}}.
2839 @cindex name a thread
2840 @item thread name [@var{name}]
2841 This command assigns a name to the current thread. If no argument is
2842 given, any existing user-specified name is removed. The thread name
2843 appears in the @samp{info threads} display.
2845 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2846 determine the name of the thread as given by the OS. On these
2847 systems, a name specified with @samp{thread name} will override the
2848 system-give name, and removing the user-specified name will cause
2849 @value{GDBN} to once again display the system-specified name.
2852 @cindex search for a thread
2853 @item thread find [@var{regexp}]
2854 Search for and display thread ids whose name or @var{systag}
2855 matches the supplied regular expression.
2857 As well as being the complement to the @samp{thread name} command,
2858 this command also allows you to identify a thread by its target
2859 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2863 (@value{GDBN}) thread find 26688
2864 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2865 (@value{GDBN}) info thread 4
2867 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2870 @kindex set print thread-events
2871 @cindex print messages on thread start and exit
2872 @item set print thread-events
2873 @itemx set print thread-events on
2874 @itemx set print thread-events off
2875 The @code{set print thread-events} command allows you to enable or
2876 disable printing of messages when @value{GDBN} notices that new threads have
2877 started or that threads have exited. By default, these messages will
2878 be printed if detection of these events is supported by the target.
2879 Note that these messages cannot be disabled on all targets.
2881 @kindex show print thread-events
2882 @item show print thread-events
2883 Show whether messages will be printed when @value{GDBN} detects that threads
2884 have started and exited.
2887 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2888 more information about how @value{GDBN} behaves when you stop and start
2889 programs with multiple threads.
2891 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2892 watchpoints in programs with multiple threads.
2894 @anchor{set libthread-db-search-path}
2896 @kindex set libthread-db-search-path
2897 @cindex search path for @code{libthread_db}
2898 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2899 If this variable is set, @var{path} is a colon-separated list of
2900 directories @value{GDBN} will use to search for @code{libthread_db}.
2901 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2902 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2903 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2906 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2907 @code{libthread_db} library to obtain information about threads in the
2908 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2909 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2910 specific thread debugging library loading is enabled
2911 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2913 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2914 refers to the default system directories that are
2915 normally searched for loading shared libraries. The @samp{$sdir} entry
2916 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2917 (@pxref{libthread_db.so.1 file}).
2919 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2920 refers to the directory from which @code{libpthread}
2921 was loaded in the inferior process.
2923 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2924 @value{GDBN} attempts to initialize it with the current inferior process.
2925 If this initialization fails (which could happen because of a version
2926 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2927 will unload @code{libthread_db}, and continue with the next directory.
2928 If none of @code{libthread_db} libraries initialize successfully,
2929 @value{GDBN} will issue a warning and thread debugging will be disabled.
2931 Setting @code{libthread-db-search-path} is currently implemented
2932 only on some platforms.
2934 @kindex show libthread-db-search-path
2935 @item show libthread-db-search-path
2936 Display current libthread_db search path.
2938 @kindex set debug libthread-db
2939 @kindex show debug libthread-db
2940 @cindex debugging @code{libthread_db}
2941 @item set debug libthread-db
2942 @itemx show debug libthread-db
2943 Turns on or off display of @code{libthread_db}-related events.
2944 Use @code{1} to enable, @code{0} to disable.
2948 @section Debugging Forks
2950 @cindex fork, debugging programs which call
2951 @cindex multiple processes
2952 @cindex processes, multiple
2953 On most systems, @value{GDBN} has no special support for debugging
2954 programs which create additional processes using the @code{fork}
2955 function. When a program forks, @value{GDBN} will continue to debug the
2956 parent process and the child process will run unimpeded. If you have
2957 set a breakpoint in any code which the child then executes, the child
2958 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2959 will cause it to terminate.
2961 However, if you want to debug the child process there is a workaround
2962 which isn't too painful. Put a call to @code{sleep} in the code which
2963 the child process executes after the fork. It may be useful to sleep
2964 only if a certain environment variable is set, or a certain file exists,
2965 so that the delay need not occur when you don't want to run @value{GDBN}
2966 on the child. While the child is sleeping, use the @code{ps} program to
2967 get its process ID. Then tell @value{GDBN} (a new invocation of
2968 @value{GDBN} if you are also debugging the parent process) to attach to
2969 the child process (@pxref{Attach}). From that point on you can debug
2970 the child process just like any other process which you attached to.
2972 On some systems, @value{GDBN} provides support for debugging programs that
2973 create additional processes using the @code{fork} or @code{vfork} functions.
2974 Currently, the only platforms with this feature are HP-UX (11.x and later
2975 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2977 By default, when a program forks, @value{GDBN} will continue to debug
2978 the parent process and the child process will run unimpeded.
2980 If you want to follow the child process instead of the parent process,
2981 use the command @w{@code{set follow-fork-mode}}.
2984 @kindex set follow-fork-mode
2985 @item set follow-fork-mode @var{mode}
2986 Set the debugger response to a program call of @code{fork} or
2987 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2988 process. The @var{mode} argument can be:
2992 The original process is debugged after a fork. The child process runs
2993 unimpeded. This is the default.
2996 The new process is debugged after a fork. The parent process runs
3001 @kindex show follow-fork-mode
3002 @item show follow-fork-mode
3003 Display the current debugger response to a @code{fork} or @code{vfork} call.
3006 @cindex debugging multiple processes
3007 On Linux, if you want to debug both the parent and child processes, use the
3008 command @w{@code{set detach-on-fork}}.
3011 @kindex set detach-on-fork
3012 @item set detach-on-fork @var{mode}
3013 Tells gdb whether to detach one of the processes after a fork, or
3014 retain debugger control over them both.
3018 The child process (or parent process, depending on the value of
3019 @code{follow-fork-mode}) will be detached and allowed to run
3020 independently. This is the default.
3023 Both processes will be held under the control of @value{GDBN}.
3024 One process (child or parent, depending on the value of
3025 @code{follow-fork-mode}) is debugged as usual, while the other
3030 @kindex show detach-on-fork
3031 @item show detach-on-fork
3032 Show whether detach-on-fork mode is on/off.
3035 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3036 will retain control of all forked processes (including nested forks).
3037 You can list the forked processes under the control of @value{GDBN} by
3038 using the @w{@code{info inferiors}} command, and switch from one fork
3039 to another by using the @code{inferior} command (@pxref{Inferiors and
3040 Programs, ,Debugging Multiple Inferiors and Programs}).
3042 To quit debugging one of the forked processes, you can either detach
3043 from it by using the @w{@code{detach inferiors}} command (allowing it
3044 to run independently), or kill it using the @w{@code{kill inferiors}}
3045 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3048 If you ask to debug a child process and a @code{vfork} is followed by an
3049 @code{exec}, @value{GDBN} executes the new target up to the first
3050 breakpoint in the new target. If you have a breakpoint set on
3051 @code{main} in your original program, the breakpoint will also be set on
3052 the child process's @code{main}.
3054 On some systems, when a child process is spawned by @code{vfork}, you
3055 cannot debug the child or parent until an @code{exec} call completes.
3057 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3058 call executes, the new target restarts. To restart the parent
3059 process, use the @code{file} command with the parent executable name
3060 as its argument. By default, after an @code{exec} call executes,
3061 @value{GDBN} discards the symbols of the previous executable image.
3062 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3066 @kindex set follow-exec-mode
3067 @item set follow-exec-mode @var{mode}
3069 Set debugger response to a program call of @code{exec}. An
3070 @code{exec} call replaces the program image of a process.
3072 @code{follow-exec-mode} can be:
3076 @value{GDBN} creates a new inferior and rebinds the process to this
3077 new inferior. The program the process was running before the
3078 @code{exec} call can be restarted afterwards by restarting the
3084 (@value{GDBP}) info inferiors
3086 Id Description Executable
3089 process 12020 is executing new program: prog2
3090 Program exited normally.
3091 (@value{GDBP}) info inferiors
3092 Id Description Executable
3098 @value{GDBN} keeps the process bound to the same inferior. The new
3099 executable image replaces the previous executable loaded in the
3100 inferior. Restarting the inferior after the @code{exec} call, with
3101 e.g., the @code{run} command, restarts the executable the process was
3102 running after the @code{exec} call. This is the default mode.
3107 (@value{GDBP}) info inferiors
3108 Id Description Executable
3111 process 12020 is executing new program: prog2
3112 Program exited normally.
3113 (@value{GDBP}) info inferiors
3114 Id Description Executable
3121 You can use the @code{catch} command to make @value{GDBN} stop whenever
3122 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3123 Catchpoints, ,Setting Catchpoints}.
3125 @node Checkpoint/Restart
3126 @section Setting a @emph{Bookmark} to Return to Later
3131 @cindex snapshot of a process
3132 @cindex rewind program state
3134 On certain operating systems@footnote{Currently, only
3135 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3136 program's state, called a @dfn{checkpoint}, and come back to it
3139 Returning to a checkpoint effectively undoes everything that has
3140 happened in the program since the @code{checkpoint} was saved. This
3141 includes changes in memory, registers, and even (within some limits)
3142 system state. Effectively, it is like going back in time to the
3143 moment when the checkpoint was saved.
3145 Thus, if you're stepping thru a program and you think you're
3146 getting close to the point where things go wrong, you can save
3147 a checkpoint. Then, if you accidentally go too far and miss
3148 the critical statement, instead of having to restart your program
3149 from the beginning, you can just go back to the checkpoint and
3150 start again from there.
3152 This can be especially useful if it takes a lot of time or
3153 steps to reach the point where you think the bug occurs.
3155 To use the @code{checkpoint}/@code{restart} method of debugging:
3160 Save a snapshot of the debugged program's current execution state.
3161 The @code{checkpoint} command takes no arguments, but each checkpoint
3162 is assigned a small integer id, similar to a breakpoint id.
3164 @kindex info checkpoints
3165 @item info checkpoints
3166 List the checkpoints that have been saved in the current debugging
3167 session. For each checkpoint, the following information will be
3174 @item Source line, or label
3177 @kindex restart @var{checkpoint-id}
3178 @item restart @var{checkpoint-id}
3179 Restore the program state that was saved as checkpoint number
3180 @var{checkpoint-id}. All program variables, registers, stack frames
3181 etc.@: will be returned to the values that they had when the checkpoint
3182 was saved. In essence, gdb will ``wind back the clock'' to the point
3183 in time when the checkpoint was saved.
3185 Note that breakpoints, @value{GDBN} variables, command history etc.
3186 are not affected by restoring a checkpoint. In general, a checkpoint
3187 only restores things that reside in the program being debugged, not in
3190 @kindex delete checkpoint @var{checkpoint-id}
3191 @item delete checkpoint @var{checkpoint-id}
3192 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3196 Returning to a previously saved checkpoint will restore the user state
3197 of the program being debugged, plus a significant subset of the system
3198 (OS) state, including file pointers. It won't ``un-write'' data from
3199 a file, but it will rewind the file pointer to the previous location,
3200 so that the previously written data can be overwritten. For files
3201 opened in read mode, the pointer will also be restored so that the
3202 previously read data can be read again.
3204 Of course, characters that have been sent to a printer (or other
3205 external device) cannot be ``snatched back'', and characters received
3206 from eg.@: a serial device can be removed from internal program buffers,
3207 but they cannot be ``pushed back'' into the serial pipeline, ready to
3208 be received again. Similarly, the actual contents of files that have
3209 been changed cannot be restored (at this time).
3211 However, within those constraints, you actually can ``rewind'' your
3212 program to a previously saved point in time, and begin debugging it
3213 again --- and you can change the course of events so as to debug a
3214 different execution path this time.
3216 @cindex checkpoints and process id
3217 Finally, there is one bit of internal program state that will be
3218 different when you return to a checkpoint --- the program's process
3219 id. Each checkpoint will have a unique process id (or @var{pid}),
3220 and each will be different from the program's original @var{pid}.
3221 If your program has saved a local copy of its process id, this could
3222 potentially pose a problem.
3224 @subsection A Non-obvious Benefit of Using Checkpoints
3226 On some systems such as @sc{gnu}/Linux, address space randomization
3227 is performed on new processes for security reasons. This makes it
3228 difficult or impossible to set a breakpoint, or watchpoint, on an
3229 absolute address if you have to restart the program, since the
3230 absolute location of a symbol will change from one execution to the
3233 A checkpoint, however, is an @emph{identical} copy of a process.
3234 Therefore if you create a checkpoint at (eg.@:) the start of main,
3235 and simply return to that checkpoint instead of restarting the
3236 process, you can avoid the effects of address randomization and
3237 your symbols will all stay in the same place.
3240 @chapter Stopping and Continuing
3242 The principal purposes of using a debugger are so that you can stop your
3243 program before it terminates; or so that, if your program runs into
3244 trouble, you can investigate and find out why.
3246 Inside @value{GDBN}, your program may stop for any of several reasons,
3247 such as a signal, a breakpoint, or reaching a new line after a
3248 @value{GDBN} command such as @code{step}. You may then examine and
3249 change variables, set new breakpoints or remove old ones, and then
3250 continue execution. Usually, the messages shown by @value{GDBN} provide
3251 ample explanation of the status of your program---but you can also
3252 explicitly request this information at any time.
3255 @kindex info program
3257 Display information about the status of your program: whether it is
3258 running or not, what process it is, and why it stopped.
3262 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3263 * Continuing and Stepping:: Resuming execution
3264 * Skipping Over Functions and Files::
3265 Skipping over functions and files
3267 * Thread Stops:: Stopping and starting multi-thread programs
3271 @section Breakpoints, Watchpoints, and Catchpoints
3274 A @dfn{breakpoint} makes your program stop whenever a certain point in
3275 the program is reached. For each breakpoint, you can add conditions to
3276 control in finer detail whether your program stops. You can set
3277 breakpoints with the @code{break} command and its variants (@pxref{Set
3278 Breaks, ,Setting Breakpoints}), to specify the place where your program
3279 should stop by line number, function name or exact address in the
3282 On some systems, you can set breakpoints in shared libraries before
3283 the executable is run. There is a minor limitation on HP-UX systems:
3284 you must wait until the executable is run in order to set breakpoints
3285 in shared library routines that are not called directly by the program
3286 (for example, routines that are arguments in a @code{pthread_create}
3290 @cindex data breakpoints
3291 @cindex memory tracing
3292 @cindex breakpoint on memory address
3293 @cindex breakpoint on variable modification
3294 A @dfn{watchpoint} is a special breakpoint that stops your program
3295 when the value of an expression changes. The expression may be a value
3296 of a variable, or it could involve values of one or more variables
3297 combined by operators, such as @samp{a + b}. This is sometimes called
3298 @dfn{data breakpoints}. You must use a different command to set
3299 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3300 from that, you can manage a watchpoint like any other breakpoint: you
3301 enable, disable, and delete both breakpoints and watchpoints using the
3304 You can arrange to have values from your program displayed automatically
3305 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3309 @cindex breakpoint on events
3310 A @dfn{catchpoint} is another special breakpoint that stops your program
3311 when a certain kind of event occurs, such as the throwing of a C@t{++}
3312 exception or the loading of a library. As with watchpoints, you use a
3313 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3314 Catchpoints}), but aside from that, you can manage a catchpoint like any
3315 other breakpoint. (To stop when your program receives a signal, use the
3316 @code{handle} command; see @ref{Signals, ,Signals}.)
3318 @cindex breakpoint numbers
3319 @cindex numbers for breakpoints
3320 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3321 catchpoint when you create it; these numbers are successive integers
3322 starting with one. In many of the commands for controlling various
3323 features of breakpoints you use the breakpoint number to say which
3324 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3325 @dfn{disabled}; if disabled, it has no effect on your program until you
3328 @cindex breakpoint ranges
3329 @cindex ranges of breakpoints
3330 Some @value{GDBN} commands accept a range of breakpoints on which to
3331 operate. A breakpoint range is either a single breakpoint number, like
3332 @samp{5}, or two such numbers, in increasing order, separated by a
3333 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3334 all breakpoints in that range are operated on.
3337 * Set Breaks:: Setting breakpoints
3338 * Set Watchpoints:: Setting watchpoints
3339 * Set Catchpoints:: Setting catchpoints
3340 * Delete Breaks:: Deleting breakpoints
3341 * Disabling:: Disabling breakpoints
3342 * Conditions:: Break conditions
3343 * Break Commands:: Breakpoint command lists
3344 * Save Breakpoints:: How to save breakpoints in a file
3345 * Error in Breakpoints:: ``Cannot insert breakpoints''
3346 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3350 @subsection Setting Breakpoints
3352 @c FIXME LMB what does GDB do if no code on line of breakpt?
3353 @c consider in particular declaration with/without initialization.
3355 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3358 @kindex b @r{(@code{break})}
3359 @vindex $bpnum@r{, convenience variable}
3360 @cindex latest breakpoint
3361 Breakpoints are set with the @code{break} command (abbreviated
3362 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3363 number of the breakpoint you've set most recently; see @ref{Convenience
3364 Vars,, Convenience Variables}, for a discussion of what you can do with
3365 convenience variables.
3368 @item break @var{location}
3369 Set a breakpoint at the given @var{location}, which can specify a
3370 function name, a line number, or an address of an instruction.
3371 (@xref{Specify Location}, for a list of all the possible ways to
3372 specify a @var{location}.) The breakpoint will stop your program just
3373 before it executes any of the code in the specified @var{location}.
3375 When using source languages that permit overloading of symbols, such as
3376 C@t{++}, a function name may refer to more than one possible place to break.
3377 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3380 It is also possible to insert a breakpoint that will stop the program
3381 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3382 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3385 When called without any arguments, @code{break} sets a breakpoint at
3386 the next instruction to be executed in the selected stack frame
3387 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3388 innermost, this makes your program stop as soon as control
3389 returns to that frame. This is similar to the effect of a
3390 @code{finish} command in the frame inside the selected frame---except
3391 that @code{finish} does not leave an active breakpoint. If you use
3392 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3393 the next time it reaches the current location; this may be useful
3396 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3397 least one instruction has been executed. If it did not do this, you
3398 would be unable to proceed past a breakpoint without first disabling the
3399 breakpoint. This rule applies whether or not the breakpoint already
3400 existed when your program stopped.
3402 @item break @dots{} if @var{cond}
3403 Set a breakpoint with condition @var{cond}; evaluate the expression
3404 @var{cond} each time the breakpoint is reached, and stop only if the
3405 value is nonzero---that is, if @var{cond} evaluates as true.
3406 @samp{@dots{}} stands for one of the possible arguments described
3407 above (or no argument) specifying where to break. @xref{Conditions,
3408 ,Break Conditions}, for more information on breakpoint conditions.
3411 @item tbreak @var{args}
3412 Set a breakpoint enabled only for one stop. @var{args} are the
3413 same as for the @code{break} command, and the breakpoint is set in the same
3414 way, but the breakpoint is automatically deleted after the first time your
3415 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3418 @cindex hardware breakpoints
3419 @item hbreak @var{args}
3420 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3421 @code{break} command and the breakpoint is set in the same way, but the
3422 breakpoint requires hardware support and some target hardware may not
3423 have this support. The main purpose of this is EPROM/ROM code
3424 debugging, so you can set a breakpoint at an instruction without
3425 changing the instruction. This can be used with the new trap-generation
3426 provided by SPARClite DSU and most x86-based targets. These targets
3427 will generate traps when a program accesses some data or instruction
3428 address that is assigned to the debug registers. However the hardware
3429 breakpoint registers can take a limited number of breakpoints. For
3430 example, on the DSU, only two data breakpoints can be set at a time, and
3431 @value{GDBN} will reject this command if more than two are used. Delete
3432 or disable unused hardware breakpoints before setting new ones
3433 (@pxref{Disabling, ,Disabling Breakpoints}).
3434 @xref{Conditions, ,Break Conditions}.
3435 For remote targets, you can restrict the number of hardware
3436 breakpoints @value{GDBN} will use, see @ref{set remote
3437 hardware-breakpoint-limit}.
3440 @item thbreak @var{args}
3441 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3442 are the same as for the @code{hbreak} command and the breakpoint is set in
3443 the same way. However, like the @code{tbreak} command,
3444 the breakpoint is automatically deleted after the
3445 first time your program stops there. Also, like the @code{hbreak}
3446 command, the breakpoint requires hardware support and some target hardware
3447 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3448 See also @ref{Conditions, ,Break Conditions}.
3451 @cindex regular expression
3452 @cindex breakpoints at functions matching a regexp
3453 @cindex set breakpoints in many functions
3454 @item rbreak @var{regex}
3455 Set breakpoints on all functions matching the regular expression
3456 @var{regex}. This command sets an unconditional breakpoint on all
3457 matches, printing a list of all breakpoints it set. Once these
3458 breakpoints are set, they are treated just like the breakpoints set with
3459 the @code{break} command. You can delete them, disable them, or make
3460 them conditional the same way as any other breakpoint.
3462 The syntax of the regular expression is the standard one used with tools
3463 like @file{grep}. Note that this is different from the syntax used by
3464 shells, so for instance @code{foo*} matches all functions that include
3465 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3466 @code{.*} leading and trailing the regular expression you supply, so to
3467 match only functions that begin with @code{foo}, use @code{^foo}.
3469 @cindex non-member C@t{++} functions, set breakpoint in
3470 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3471 breakpoints on overloaded functions that are not members of any special
3474 @cindex set breakpoints on all functions
3475 The @code{rbreak} command can be used to set breakpoints in
3476 @strong{all} the functions in a program, like this:
3479 (@value{GDBP}) rbreak .
3482 @item rbreak @var{file}:@var{regex}
3483 If @code{rbreak} is called with a filename qualification, it limits
3484 the search for functions matching the given regular expression to the
3485 specified @var{file}. This can be used, for example, to set breakpoints on
3486 every function in a given file:
3489 (@value{GDBP}) rbreak file.c:.
3492 The colon separating the filename qualifier from the regex may
3493 optionally be surrounded by spaces.
3495 @kindex info breakpoints
3496 @cindex @code{$_} and @code{info breakpoints}
3497 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3498 @itemx info break @r{[}@var{n}@dots{}@r{]}
3499 Print a table of all breakpoints, watchpoints, and catchpoints set and
3500 not deleted. Optional argument @var{n} means print information only
3501 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3502 For each breakpoint, following columns are printed:
3505 @item Breakpoint Numbers
3507 Breakpoint, watchpoint, or catchpoint.
3509 Whether the breakpoint is marked to be disabled or deleted when hit.
3510 @item Enabled or Disabled
3511 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3512 that are not enabled.
3514 Where the breakpoint is in your program, as a memory address. For a
3515 pending breakpoint whose address is not yet known, this field will
3516 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3517 library that has the symbol or line referred by breakpoint is loaded.
3518 See below for details. A breakpoint with several locations will
3519 have @samp{<MULTIPLE>} in this field---see below for details.
3521 Where the breakpoint is in the source for your program, as a file and
3522 line number. For a pending breakpoint, the original string passed to
3523 the breakpoint command will be listed as it cannot be resolved until
3524 the appropriate shared library is loaded in the future.
3528 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3529 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3530 @value{GDBN} on the host's side. If it is ``target'', then the condition
3531 is evaluated by the target. The @code{info break} command shows
3532 the condition on the line following the affected breakpoint, together with
3533 its condition evaluation mode in between parentheses.
3535 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3536 allowed to have a condition specified for it. The condition is not parsed for
3537 validity until a shared library is loaded that allows the pending
3538 breakpoint to resolve to a valid location.
3541 @code{info break} with a breakpoint
3542 number @var{n} as argument lists only that breakpoint. The
3543 convenience variable @code{$_} and the default examining-address for
3544 the @code{x} command are set to the address of the last breakpoint
3545 listed (@pxref{Memory, ,Examining Memory}).
3548 @code{info break} displays a count of the number of times the breakpoint
3549 has been hit. This is especially useful in conjunction with the
3550 @code{ignore} command. You can ignore a large number of breakpoint
3551 hits, look at the breakpoint info to see how many times the breakpoint
3552 was hit, and then run again, ignoring one less than that number. This
3553 will get you quickly to the last hit of that breakpoint.
3556 For a breakpoints with an enable count (xref) greater than 1,
3557 @code{info break} also displays that count.
3561 @value{GDBN} allows you to set any number of breakpoints at the same place in
3562 your program. There is nothing silly or meaningless about this. When
3563 the breakpoints are conditional, this is even useful
3564 (@pxref{Conditions, ,Break Conditions}).
3566 @cindex multiple locations, breakpoints
3567 @cindex breakpoints, multiple locations
3568 It is possible that a breakpoint corresponds to several locations
3569 in your program. Examples of this situation are:
3573 Multiple functions in the program may have the same name.
3576 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3577 instances of the function body, used in different cases.
3580 For a C@t{++} template function, a given line in the function can
3581 correspond to any number of instantiations.
3584 For an inlined function, a given source line can correspond to
3585 several places where that function is inlined.
3588 In all those cases, @value{GDBN} will insert a breakpoint at all
3589 the relevant locations.
3591 A breakpoint with multiple locations is displayed in the breakpoint
3592 table using several rows---one header row, followed by one row for
3593 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3594 address column. The rows for individual locations contain the actual
3595 addresses for locations, and show the functions to which those
3596 locations belong. The number column for a location is of the form
3597 @var{breakpoint-number}.@var{location-number}.
3602 Num Type Disp Enb Address What
3603 1 breakpoint keep y <MULTIPLE>
3605 breakpoint already hit 1 time
3606 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3607 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3610 Each location can be individually enabled or disabled by passing
3611 @var{breakpoint-number}.@var{location-number} as argument to the
3612 @code{enable} and @code{disable} commands. Note that you cannot
3613 delete the individual locations from the list, you can only delete the
3614 entire list of locations that belong to their parent breakpoint (with
3615 the @kbd{delete @var{num}} command, where @var{num} is the number of
3616 the parent breakpoint, 1 in the above example). Disabling or enabling
3617 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3618 that belong to that breakpoint.
3620 @cindex pending breakpoints
3621 It's quite common to have a breakpoint inside a shared library.
3622 Shared libraries can be loaded and unloaded explicitly,
3623 and possibly repeatedly, as the program is executed. To support
3624 this use case, @value{GDBN} updates breakpoint locations whenever
3625 any shared library is loaded or unloaded. Typically, you would
3626 set a breakpoint in a shared library at the beginning of your
3627 debugging session, when the library is not loaded, and when the
3628 symbols from the library are not available. When you try to set
3629 breakpoint, @value{GDBN} will ask you if you want to set
3630 a so called @dfn{pending breakpoint}---breakpoint whose address
3631 is not yet resolved.
3633 After the program is run, whenever a new shared library is loaded,
3634 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3635 shared library contains the symbol or line referred to by some
3636 pending breakpoint, that breakpoint is resolved and becomes an
3637 ordinary breakpoint. When a library is unloaded, all breakpoints
3638 that refer to its symbols or source lines become pending again.
3640 This logic works for breakpoints with multiple locations, too. For
3641 example, if you have a breakpoint in a C@t{++} template function, and
3642 a newly loaded shared library has an instantiation of that template,
3643 a new location is added to the list of locations for the breakpoint.
3645 Except for having unresolved address, pending breakpoints do not
3646 differ from regular breakpoints. You can set conditions or commands,
3647 enable and disable them and perform other breakpoint operations.
3649 @value{GDBN} provides some additional commands for controlling what
3650 happens when the @samp{break} command cannot resolve breakpoint
3651 address specification to an address:
3653 @kindex set breakpoint pending
3654 @kindex show breakpoint pending
3656 @item set breakpoint pending auto
3657 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3658 location, it queries you whether a pending breakpoint should be created.
3660 @item set breakpoint pending on
3661 This indicates that an unrecognized breakpoint location should automatically
3662 result in a pending breakpoint being created.
3664 @item set breakpoint pending off
3665 This indicates that pending breakpoints are not to be created. Any
3666 unrecognized breakpoint location results in an error. This setting does
3667 not affect any pending breakpoints previously created.
3669 @item show breakpoint pending
3670 Show the current behavior setting for creating pending breakpoints.
3673 The settings above only affect the @code{break} command and its
3674 variants. Once breakpoint is set, it will be automatically updated
3675 as shared libraries are loaded and unloaded.
3677 @cindex automatic hardware breakpoints
3678 For some targets, @value{GDBN} can automatically decide if hardware or
3679 software breakpoints should be used, depending on whether the
3680 breakpoint address is read-only or read-write. This applies to
3681 breakpoints set with the @code{break} command as well as to internal
3682 breakpoints set by commands like @code{next} and @code{finish}. For
3683 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3686 You can control this automatic behaviour with the following commands::
3688 @kindex set breakpoint auto-hw
3689 @kindex show breakpoint auto-hw
3691 @item set breakpoint auto-hw on
3692 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3693 will try to use the target memory map to decide if software or hardware
3694 breakpoint must be used.
3696 @item set breakpoint auto-hw off
3697 This indicates @value{GDBN} should not automatically select breakpoint
3698 type. If the target provides a memory map, @value{GDBN} will warn when
3699 trying to set software breakpoint at a read-only address.
3702 @value{GDBN} normally implements breakpoints by replacing the program code
3703 at the breakpoint address with a special instruction, which, when
3704 executed, given control to the debugger. By default, the program
3705 code is so modified only when the program is resumed. As soon as
3706 the program stops, @value{GDBN} restores the original instructions. This
3707 behaviour guards against leaving breakpoints inserted in the
3708 target should gdb abrubptly disconnect. However, with slow remote
3709 targets, inserting and removing breakpoint can reduce the performance.
3710 This behavior can be controlled with the following commands::
3712 @kindex set breakpoint always-inserted
3713 @kindex show breakpoint always-inserted
3715 @item set breakpoint always-inserted off
3716 All breakpoints, including newly added by the user, are inserted in
3717 the target only when the target is resumed. All breakpoints are
3718 removed from the target when it stops.
3720 @item set breakpoint always-inserted on
3721 Causes all breakpoints to be inserted in the target at all times. If
3722 the user adds a new breakpoint, or changes an existing breakpoint, the
3723 breakpoints in the target are updated immediately. A breakpoint is
3724 removed from the target only when breakpoint itself is removed.
3726 @cindex non-stop mode, and @code{breakpoint always-inserted}
3727 @item set breakpoint always-inserted auto
3728 This is the default mode. If @value{GDBN} is controlling the inferior
3729 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3730 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3731 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3732 @code{breakpoint always-inserted} mode is off.
3735 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3736 when a breakpoint breaks. If the condition is true, then the process being
3737 debugged stops, otherwise the process is resumed.
3739 If the target supports evaluating conditions on its end, @value{GDBN} may
3740 download the breakpoint, together with its conditions, to it.
3742 This feature can be controlled via the following commands:
3744 @kindex set breakpoint condition-evaluation
3745 @kindex show breakpoint condition-evaluation
3747 @item set breakpoint condition-evaluation host
3748 This option commands @value{GDBN} to evaluate the breakpoint
3749 conditions on the host's side. Unconditional breakpoints are sent to
3750 the target which in turn receives the triggers and reports them back to GDB
3751 for condition evaluation. This is the standard evaluation mode.
3753 @item set breakpoint condition-evaluation target
3754 This option commands @value{GDBN} to download breakpoint conditions
3755 to the target at the moment of their insertion. The target
3756 is responsible for evaluating the conditional expression and reporting
3757 breakpoint stop events back to @value{GDBN} whenever the condition
3758 is true. Due to limitations of target-side evaluation, some conditions
3759 cannot be evaluated there, e.g., conditions that depend on local data
3760 that is only known to the host. Examples include
3761 conditional expressions involving convenience variables, complex types
3762 that cannot be handled by the agent expression parser and expressions
3763 that are too long to be sent over to the target, specially when the
3764 target is a remote system. In these cases, the conditions will be
3765 evaluated by @value{GDBN}.
3767 @item set breakpoint condition-evaluation auto
3768 This is the default mode. If the target supports evaluating breakpoint
3769 conditions on its end, @value{GDBN} will download breakpoint conditions to
3770 the target (limitations mentioned previously apply). If the target does
3771 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3772 to evaluating all these conditions on the host's side.
3776 @cindex negative breakpoint numbers
3777 @cindex internal @value{GDBN} breakpoints
3778 @value{GDBN} itself sometimes sets breakpoints in your program for
3779 special purposes, such as proper handling of @code{longjmp} (in C
3780 programs). These internal breakpoints are assigned negative numbers,
3781 starting with @code{-1}; @samp{info breakpoints} does not display them.
3782 You can see these breakpoints with the @value{GDBN} maintenance command
3783 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3786 @node Set Watchpoints
3787 @subsection Setting Watchpoints
3789 @cindex setting watchpoints
3790 You can use a watchpoint to stop execution whenever the value of an
3791 expression changes, without having to predict a particular place where
3792 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3793 The expression may be as simple as the value of a single variable, or
3794 as complex as many variables combined by operators. Examples include:
3798 A reference to the value of a single variable.
3801 An address cast to an appropriate data type. For example,
3802 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3803 address (assuming an @code{int} occupies 4 bytes).
3806 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3807 expression can use any operators valid in the program's native
3808 language (@pxref{Languages}).
3811 You can set a watchpoint on an expression even if the expression can
3812 not be evaluated yet. For instance, you can set a watchpoint on
3813 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3814 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3815 the expression produces a valid value. If the expression becomes
3816 valid in some other way than changing a variable (e.g.@: if the memory
3817 pointed to by @samp{*global_ptr} becomes readable as the result of a
3818 @code{malloc} call), @value{GDBN} may not stop until the next time
3819 the expression changes.
3821 @cindex software watchpoints
3822 @cindex hardware watchpoints
3823 Depending on your system, watchpoints may be implemented in software or
3824 hardware. @value{GDBN} does software watchpointing by single-stepping your
3825 program and testing the variable's value each time, which is hundreds of
3826 times slower than normal execution. (But this may still be worth it, to
3827 catch errors where you have no clue what part of your program is the
3830 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3831 x86-based targets, @value{GDBN} includes support for hardware
3832 watchpoints, which do not slow down the running of your program.
3836 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3837 Set a watchpoint for an expression. @value{GDBN} will break when the
3838 expression @var{expr} is written into by the program and its value
3839 changes. The simplest (and the most popular) use of this command is
3840 to watch the value of a single variable:
3843 (@value{GDBP}) watch foo
3846 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3847 argument, @value{GDBN} breaks only when the thread identified by
3848 @var{threadnum} changes the value of @var{expr}. If any other threads
3849 change the value of @var{expr}, @value{GDBN} will not break. Note
3850 that watchpoints restricted to a single thread in this way only work
3851 with Hardware Watchpoints.
3853 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3854 (see below). The @code{-location} argument tells @value{GDBN} to
3855 instead watch the memory referred to by @var{expr}. In this case,
3856 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3857 and watch the memory at that address. The type of the result is used
3858 to determine the size of the watched memory. If the expression's
3859 result does not have an address, then @value{GDBN} will print an
3862 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3863 of masked watchpoints, if the current architecture supports this
3864 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3865 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3866 to an address to watch. The mask specifies that some bits of an address
3867 (the bits which are reset in the mask) should be ignored when matching
3868 the address accessed by the inferior against the watchpoint address.
3869 Thus, a masked watchpoint watches many addresses simultaneously---those
3870 addresses whose unmasked bits are identical to the unmasked bits in the
3871 watchpoint address. The @code{mask} argument implies @code{-location}.
3875 (@value{GDBP}) watch foo mask 0xffff00ff
3876 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3880 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3881 Set a watchpoint that will break when the value of @var{expr} is read
3885 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3886 Set a watchpoint that will break when @var{expr} is either read from
3887 or written into by the program.
3889 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3890 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3891 This command prints a list of watchpoints, using the same format as
3892 @code{info break} (@pxref{Set Breaks}).
3895 If you watch for a change in a numerically entered address you need to
3896 dereference it, as the address itself is just a constant number which will
3897 never change. @value{GDBN} refuses to create a watchpoint that watches
3898 a never-changing value:
3901 (@value{GDBP}) watch 0x600850
3902 Cannot watch constant value 0x600850.
3903 (@value{GDBP}) watch *(int *) 0x600850
3904 Watchpoint 1: *(int *) 6293584
3907 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3908 watchpoints execute very quickly, and the debugger reports a change in
3909 value at the exact instruction where the change occurs. If @value{GDBN}
3910 cannot set a hardware watchpoint, it sets a software watchpoint, which
3911 executes more slowly and reports the change in value at the next
3912 @emph{statement}, not the instruction, after the change occurs.
3914 @cindex use only software watchpoints
3915 You can force @value{GDBN} to use only software watchpoints with the
3916 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3917 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3918 the underlying system supports them. (Note that hardware-assisted
3919 watchpoints that were set @emph{before} setting
3920 @code{can-use-hw-watchpoints} to zero will still use the hardware
3921 mechanism of watching expression values.)
3924 @item set can-use-hw-watchpoints
3925 @kindex set can-use-hw-watchpoints
3926 Set whether or not to use hardware watchpoints.
3928 @item show can-use-hw-watchpoints
3929 @kindex show can-use-hw-watchpoints
3930 Show the current mode of using hardware watchpoints.
3933 For remote targets, you can restrict the number of hardware
3934 watchpoints @value{GDBN} will use, see @ref{set remote
3935 hardware-breakpoint-limit}.
3937 When you issue the @code{watch} command, @value{GDBN} reports
3940 Hardware watchpoint @var{num}: @var{expr}
3944 if it was able to set a hardware watchpoint.
3946 Currently, the @code{awatch} and @code{rwatch} commands can only set
3947 hardware watchpoints, because accesses to data that don't change the
3948 value of the watched expression cannot be detected without examining
3949 every instruction as it is being executed, and @value{GDBN} does not do
3950 that currently. If @value{GDBN} finds that it is unable to set a
3951 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3952 will print a message like this:
3955 Expression cannot be implemented with read/access watchpoint.
3958 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3959 data type of the watched expression is wider than what a hardware
3960 watchpoint on the target machine can handle. For example, some systems
3961 can only watch regions that are up to 4 bytes wide; on such systems you
3962 cannot set hardware watchpoints for an expression that yields a
3963 double-precision floating-point number (which is typically 8 bytes
3964 wide). As a work-around, it might be possible to break the large region
3965 into a series of smaller ones and watch them with separate watchpoints.
3967 If you set too many hardware watchpoints, @value{GDBN} might be unable
3968 to insert all of them when you resume the execution of your program.
3969 Since the precise number of active watchpoints is unknown until such
3970 time as the program is about to be resumed, @value{GDBN} might not be
3971 able to warn you about this when you set the watchpoints, and the
3972 warning will be printed only when the program is resumed:
3975 Hardware watchpoint @var{num}: Could not insert watchpoint
3979 If this happens, delete or disable some of the watchpoints.
3981 Watching complex expressions that reference many variables can also
3982 exhaust the resources available for hardware-assisted watchpoints.
3983 That's because @value{GDBN} needs to watch every variable in the
3984 expression with separately allocated resources.
3986 If you call a function interactively using @code{print} or @code{call},
3987 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3988 kind of breakpoint or the call completes.
3990 @value{GDBN} automatically deletes watchpoints that watch local
3991 (automatic) variables, or expressions that involve such variables, when
3992 they go out of scope, that is, when the execution leaves the block in
3993 which these variables were defined. In particular, when the program
3994 being debugged terminates, @emph{all} local variables go out of scope,
3995 and so only watchpoints that watch global variables remain set. If you
3996 rerun the program, you will need to set all such watchpoints again. One
3997 way of doing that would be to set a code breakpoint at the entry to the
3998 @code{main} function and when it breaks, set all the watchpoints.
4000 @cindex watchpoints and threads
4001 @cindex threads and watchpoints
4002 In multi-threaded programs, watchpoints will detect changes to the
4003 watched expression from every thread.
4006 @emph{Warning:} In multi-threaded programs, software watchpoints
4007 have only limited usefulness. If @value{GDBN} creates a software
4008 watchpoint, it can only watch the value of an expression @emph{in a
4009 single thread}. If you are confident that the expression can only
4010 change due to the current thread's activity (and if you are also
4011 confident that no other thread can become current), then you can use
4012 software watchpoints as usual. However, @value{GDBN} may not notice
4013 when a non-current thread's activity changes the expression. (Hardware
4014 watchpoints, in contrast, watch an expression in all threads.)
4017 @xref{set remote hardware-watchpoint-limit}.
4019 @node Set Catchpoints
4020 @subsection Setting Catchpoints
4021 @cindex catchpoints, setting
4022 @cindex exception handlers
4023 @cindex event handling
4025 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4026 kinds of program events, such as C@t{++} exceptions or the loading of a
4027 shared library. Use the @code{catch} command to set a catchpoint.
4031 @item catch @var{event}
4032 Stop when @var{event} occurs. @var{event} can be any of the following:
4035 @cindex stop on C@t{++} exceptions
4036 The throwing of a C@t{++} exception.
4039 The catching of a C@t{++} exception.
4042 @cindex Ada exception catching
4043 @cindex catch Ada exceptions
4044 An Ada exception being raised. If an exception name is specified
4045 at the end of the command (eg @code{catch exception Program_Error}),
4046 the debugger will stop only when this specific exception is raised.
4047 Otherwise, the debugger stops execution when any Ada exception is raised.
4049 When inserting an exception catchpoint on a user-defined exception whose
4050 name is identical to one of the exceptions defined by the language, the
4051 fully qualified name must be used as the exception name. Otherwise,
4052 @value{GDBN} will assume that it should stop on the pre-defined exception
4053 rather than the user-defined one. For instance, assuming an exception
4054 called @code{Constraint_Error} is defined in package @code{Pck}, then
4055 the command to use to catch such exceptions is @kbd{catch exception
4056 Pck.Constraint_Error}.
4058 @item exception unhandled
4059 An exception that was raised but is not handled by the program.
4062 A failed Ada assertion.
4065 @cindex break on fork/exec
4066 A call to @code{exec}. This is currently only available for HP-UX
4070 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4071 @cindex break on a system call.
4072 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4073 syscall is a mechanism for application programs to request a service
4074 from the operating system (OS) or one of the OS system services.
4075 @value{GDBN} can catch some or all of the syscalls issued by the
4076 debuggee, and show the related information for each syscall. If no
4077 argument is specified, calls to and returns from all system calls
4080 @var{name} can be any system call name that is valid for the
4081 underlying OS. Just what syscalls are valid depends on the OS. On
4082 GNU and Unix systems, you can find the full list of valid syscall
4083 names on @file{/usr/include/asm/unistd.h}.
4085 @c For MS-Windows, the syscall names and the corresponding numbers
4086 @c can be found, e.g., on this URL:
4087 @c http://www.metasploit.com/users/opcode/syscalls.html
4088 @c but we don't support Windows syscalls yet.
4090 Normally, @value{GDBN} knows in advance which syscalls are valid for
4091 each OS, so you can use the @value{GDBN} command-line completion
4092 facilities (@pxref{Completion,, command completion}) to list the
4095 You may also specify the system call numerically. A syscall's
4096 number is the value passed to the OS's syscall dispatcher to
4097 identify the requested service. When you specify the syscall by its
4098 name, @value{GDBN} uses its database of syscalls to convert the name
4099 into the corresponding numeric code, but using the number directly
4100 may be useful if @value{GDBN}'s database does not have the complete
4101 list of syscalls on your system (e.g., because @value{GDBN} lags
4102 behind the OS upgrades).
4104 The example below illustrates how this command works if you don't provide
4108 (@value{GDBP}) catch syscall
4109 Catchpoint 1 (syscall)
4111 Starting program: /tmp/catch-syscall
4113 Catchpoint 1 (call to syscall 'close'), \
4114 0xffffe424 in __kernel_vsyscall ()
4118 Catchpoint 1 (returned from syscall 'close'), \
4119 0xffffe424 in __kernel_vsyscall ()
4123 Here is an example of catching a system call by name:
4126 (@value{GDBP}) catch syscall chroot
4127 Catchpoint 1 (syscall 'chroot' [61])
4129 Starting program: /tmp/catch-syscall
4131 Catchpoint 1 (call to syscall 'chroot'), \
4132 0xffffe424 in __kernel_vsyscall ()
4136 Catchpoint 1 (returned from syscall 'chroot'), \
4137 0xffffe424 in __kernel_vsyscall ()
4141 An example of specifying a system call numerically. In the case
4142 below, the syscall number has a corresponding entry in the XML
4143 file, so @value{GDBN} finds its name and prints it:
4146 (@value{GDBP}) catch syscall 252
4147 Catchpoint 1 (syscall(s) 'exit_group')
4149 Starting program: /tmp/catch-syscall
4151 Catchpoint 1 (call to syscall 'exit_group'), \
4152 0xffffe424 in __kernel_vsyscall ()
4156 Program exited normally.
4160 However, there can be situations when there is no corresponding name
4161 in XML file for that syscall number. In this case, @value{GDBN} prints
4162 a warning message saying that it was not able to find the syscall name,
4163 but the catchpoint will be set anyway. See the example below:
4166 (@value{GDBP}) catch syscall 764
4167 warning: The number '764' does not represent a known syscall.
4168 Catchpoint 2 (syscall 764)
4172 If you configure @value{GDBN} using the @samp{--without-expat} option,
4173 it will not be able to display syscall names. Also, if your
4174 architecture does not have an XML file describing its system calls,
4175 you will not be able to see the syscall names. It is important to
4176 notice that these two features are used for accessing the syscall
4177 name database. In either case, you will see a warning like this:
4180 (@value{GDBP}) catch syscall
4181 warning: Could not open "syscalls/i386-linux.xml"
4182 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4183 GDB will not be able to display syscall names.
4184 Catchpoint 1 (syscall)
4188 Of course, the file name will change depending on your architecture and system.
4190 Still using the example above, you can also try to catch a syscall by its
4191 number. In this case, you would see something like:
4194 (@value{GDBP}) catch syscall 252
4195 Catchpoint 1 (syscall(s) 252)
4198 Again, in this case @value{GDBN} would not be able to display syscall's names.
4201 A call to @code{fork}. This is currently only available for HP-UX
4205 A call to @code{vfork}. This is currently only available for HP-UX
4208 @item load @r{[}regexp@r{]}
4209 @itemx unload @r{[}regexp@r{]}
4210 The loading or unloading of a shared library. If @var{regexp} is
4211 given, then the catchpoint will stop only if the regular expression
4212 matches one of the affected libraries.
4216 @item tcatch @var{event}
4217 Set a catchpoint that is enabled only for one stop. The catchpoint is
4218 automatically deleted after the first time the event is caught.
4222 Use the @code{info break} command to list the current catchpoints.
4224 There are currently some limitations to C@t{++} exception handling
4225 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4229 If you call a function interactively, @value{GDBN} normally returns
4230 control to you when the function has finished executing. If the call
4231 raises an exception, however, the call may bypass the mechanism that
4232 returns control to you and cause your program either to abort or to
4233 simply continue running until it hits a breakpoint, catches a signal
4234 that @value{GDBN} is listening for, or exits. This is the case even if
4235 you set a catchpoint for the exception; catchpoints on exceptions are
4236 disabled within interactive calls.
4239 You cannot raise an exception interactively.
4242 You cannot install an exception handler interactively.
4245 @cindex raise exceptions
4246 Sometimes @code{catch} is not the best way to debug exception handling:
4247 if you need to know exactly where an exception is raised, it is better to
4248 stop @emph{before} the exception handler is called, since that way you
4249 can see the stack before any unwinding takes place. If you set a
4250 breakpoint in an exception handler instead, it may not be easy to find
4251 out where the exception was raised.
4253 To stop just before an exception handler is called, you need some
4254 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4255 raised by calling a library function named @code{__raise_exception}
4256 which has the following ANSI C interface:
4259 /* @var{addr} is where the exception identifier is stored.
4260 @var{id} is the exception identifier. */
4261 void __raise_exception (void **addr, void *id);
4265 To make the debugger catch all exceptions before any stack
4266 unwinding takes place, set a breakpoint on @code{__raise_exception}
4267 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4269 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4270 that depends on the value of @var{id}, you can stop your program when
4271 a specific exception is raised. You can use multiple conditional
4272 breakpoints to stop your program when any of a number of exceptions are
4277 @subsection Deleting Breakpoints
4279 @cindex clearing breakpoints, watchpoints, catchpoints
4280 @cindex deleting breakpoints, watchpoints, catchpoints
4281 It is often necessary to eliminate a breakpoint, watchpoint, or
4282 catchpoint once it has done its job and you no longer want your program
4283 to stop there. This is called @dfn{deleting} the breakpoint. A
4284 breakpoint that has been deleted no longer exists; it is forgotten.
4286 With the @code{clear} command you can delete breakpoints according to
4287 where they are in your program. With the @code{delete} command you can
4288 delete individual breakpoints, watchpoints, or catchpoints by specifying
4289 their breakpoint numbers.
4291 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4292 automatically ignores breakpoints on the first instruction to be executed
4293 when you continue execution without changing the execution address.
4298 Delete any breakpoints at the next instruction to be executed in the
4299 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4300 the innermost frame is selected, this is a good way to delete a
4301 breakpoint where your program just stopped.
4303 @item clear @var{location}
4304 Delete any breakpoints set at the specified @var{location}.
4305 @xref{Specify Location}, for the various forms of @var{location}; the
4306 most useful ones are listed below:
4309 @item clear @var{function}
4310 @itemx clear @var{filename}:@var{function}
4311 Delete any breakpoints set at entry to the named @var{function}.
4313 @item clear @var{linenum}
4314 @itemx clear @var{filename}:@var{linenum}
4315 Delete any breakpoints set at or within the code of the specified
4316 @var{linenum} of the specified @var{filename}.
4319 @cindex delete breakpoints
4321 @kindex d @r{(@code{delete})}
4322 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4323 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4324 ranges specified as arguments. If no argument is specified, delete all
4325 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4326 confirm off}). You can abbreviate this command as @code{d}.
4330 @subsection Disabling Breakpoints
4332 @cindex enable/disable a breakpoint
4333 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4334 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4335 it had been deleted, but remembers the information on the breakpoint so
4336 that you can @dfn{enable} it again later.
4338 You disable and enable breakpoints, watchpoints, and catchpoints with
4339 the @code{enable} and @code{disable} commands, optionally specifying
4340 one or more breakpoint numbers as arguments. Use @code{info break} to
4341 print a list of all breakpoints, watchpoints, and catchpoints if you
4342 do not know which numbers to use.
4344 Disabling and enabling a breakpoint that has multiple locations
4345 affects all of its locations.
4347 A breakpoint, watchpoint, or catchpoint can have any of several
4348 different states of enablement:
4352 Enabled. The breakpoint stops your program. A breakpoint set
4353 with the @code{break} command starts out in this state.
4355 Disabled. The breakpoint has no effect on your program.
4357 Enabled once. The breakpoint stops your program, but then becomes
4360 Enabled for a count. The breakpoint stops your program for the next
4361 N times, then becomes disabled.
4363 Enabled for deletion. The breakpoint stops your program, but
4364 immediately after it does so it is deleted permanently. A breakpoint
4365 set with the @code{tbreak} command starts out in this state.
4368 You can use the following commands to enable or disable breakpoints,
4369 watchpoints, and catchpoints:
4373 @kindex dis @r{(@code{disable})}
4374 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4375 Disable the specified breakpoints---or all breakpoints, if none are
4376 listed. A disabled breakpoint has no effect but is not forgotten. All
4377 options such as ignore-counts, conditions and commands are remembered in
4378 case the breakpoint is enabled again later. You may abbreviate
4379 @code{disable} as @code{dis}.
4382 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4383 Enable the specified breakpoints (or all defined breakpoints). They
4384 become effective once again in stopping your program.
4386 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4387 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4388 of these breakpoints immediately after stopping your program.
4390 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4391 Enable the specified breakpoints temporarily. @value{GDBN} records
4392 @var{count} with each of the specified breakpoints, and decrements a
4393 breakpoint's count when it is hit. When any count reaches 0,
4394 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4395 count (@pxref{Conditions, ,Break Conditions}), that will be
4396 decremented to 0 before @var{count} is affected.
4398 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4399 Enable the specified breakpoints to work once, then die. @value{GDBN}
4400 deletes any of these breakpoints as soon as your program stops there.
4401 Breakpoints set by the @code{tbreak} command start out in this state.
4404 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4405 @c confusing: tbreak is also initially enabled.
4406 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4407 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4408 subsequently, they become disabled or enabled only when you use one of
4409 the commands above. (The command @code{until} can set and delete a
4410 breakpoint of its own, but it does not change the state of your other
4411 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4415 @subsection Break Conditions
4416 @cindex conditional breakpoints
4417 @cindex breakpoint conditions
4419 @c FIXME what is scope of break condition expr? Context where wanted?
4420 @c in particular for a watchpoint?
4421 The simplest sort of breakpoint breaks every time your program reaches a
4422 specified place. You can also specify a @dfn{condition} for a
4423 breakpoint. A condition is just a Boolean expression in your
4424 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4425 a condition evaluates the expression each time your program reaches it,
4426 and your program stops only if the condition is @emph{true}.
4428 This is the converse of using assertions for program validation; in that
4429 situation, you want to stop when the assertion is violated---that is,
4430 when the condition is false. In C, if you want to test an assertion expressed
4431 by the condition @var{assert}, you should set the condition
4432 @samp{! @var{assert}} on the appropriate breakpoint.
4434 Conditions are also accepted for watchpoints; you may not need them,
4435 since a watchpoint is inspecting the value of an expression anyhow---but
4436 it might be simpler, say, to just set a watchpoint on a variable name,
4437 and specify a condition that tests whether the new value is an interesting
4440 Break conditions can have side effects, and may even call functions in
4441 your program. This can be useful, for example, to activate functions
4442 that log program progress, or to use your own print functions to
4443 format special data structures. The effects are completely predictable
4444 unless there is another enabled breakpoint at the same address. (In
4445 that case, @value{GDBN} might see the other breakpoint first and stop your
4446 program without checking the condition of this one.) Note that
4447 breakpoint commands are usually more convenient and flexible than break
4449 purpose of performing side effects when a breakpoint is reached
4450 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4452 Breakpoint conditions can also be evaluated on the target's side if
4453 the target supports it. Instead of evaluating the conditions locally,
4454 @value{GDBN} encodes the expression into an agent expression
4455 (@pxref{Agent Expressions}) suitable for execution on the target,
4456 independently of @value{GDBN}. Global variables become raw memory
4457 locations, locals become stack accesses, and so forth.
4459 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4460 when its condition evaluates to true. This mechanism may provide faster
4461 response times depending on the performance characteristics of the target
4462 since it does not need to keep @value{GDBN} informed about
4463 every breakpoint trigger, even those with false conditions.
4465 Break conditions can be specified when a breakpoint is set, by using
4466 @samp{if} in the arguments to the @code{break} command. @xref{Set
4467 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4468 with the @code{condition} command.
4470 You can also use the @code{if} keyword with the @code{watch} command.
4471 The @code{catch} command does not recognize the @code{if} keyword;
4472 @code{condition} is the only way to impose a further condition on a
4477 @item condition @var{bnum} @var{expression}
4478 Specify @var{expression} as the break condition for breakpoint,
4479 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4480 breakpoint @var{bnum} stops your program only if the value of
4481 @var{expression} is true (nonzero, in C). When you use
4482 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4483 syntactic correctness, and to determine whether symbols in it have
4484 referents in the context of your breakpoint. If @var{expression} uses
4485 symbols not referenced in the context of the breakpoint, @value{GDBN}
4486 prints an error message:
4489 No symbol "foo" in current context.
4494 not actually evaluate @var{expression} at the time the @code{condition}
4495 command (or a command that sets a breakpoint with a condition, like
4496 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4498 @item condition @var{bnum}
4499 Remove the condition from breakpoint number @var{bnum}. It becomes
4500 an ordinary unconditional breakpoint.
4503 @cindex ignore count (of breakpoint)
4504 A special case of a breakpoint condition is to stop only when the
4505 breakpoint has been reached a certain number of times. This is so
4506 useful that there is a special way to do it, using the @dfn{ignore
4507 count} of the breakpoint. Every breakpoint has an ignore count, which
4508 is an integer. Most of the time, the ignore count is zero, and
4509 therefore has no effect. But if your program reaches a breakpoint whose
4510 ignore count is positive, then instead of stopping, it just decrements
4511 the ignore count by one and continues. As a result, if the ignore count
4512 value is @var{n}, the breakpoint does not stop the next @var{n} times
4513 your program reaches it.
4517 @item ignore @var{bnum} @var{count}
4518 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4519 The next @var{count} times the breakpoint is reached, your program's
4520 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4523 To make the breakpoint stop the next time it is reached, specify
4526 When you use @code{continue} to resume execution of your program from a
4527 breakpoint, you can specify an ignore count directly as an argument to
4528 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4529 Stepping,,Continuing and Stepping}.
4531 If a breakpoint has a positive ignore count and a condition, the
4532 condition is not checked. Once the ignore count reaches zero,
4533 @value{GDBN} resumes checking the condition.
4535 You could achieve the effect of the ignore count with a condition such
4536 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4537 is decremented each time. @xref{Convenience Vars, ,Convenience
4541 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4544 @node Break Commands
4545 @subsection Breakpoint Command Lists
4547 @cindex breakpoint commands
4548 You can give any breakpoint (or watchpoint or catchpoint) a series of
4549 commands to execute when your program stops due to that breakpoint. For
4550 example, you might want to print the values of certain expressions, or
4551 enable other breakpoints.
4555 @kindex end@r{ (breakpoint commands)}
4556 @item commands @r{[}@var{range}@dots{}@r{]}
4557 @itemx @dots{} @var{command-list} @dots{}
4559 Specify a list of commands for the given breakpoints. The commands
4560 themselves appear on the following lines. Type a line containing just
4561 @code{end} to terminate the commands.
4563 To remove all commands from a breakpoint, type @code{commands} and
4564 follow it immediately with @code{end}; that is, give no commands.
4566 With no argument, @code{commands} refers to the last breakpoint,
4567 watchpoint, or catchpoint set (not to the breakpoint most recently
4568 encountered). If the most recent breakpoints were set with a single
4569 command, then the @code{commands} will apply to all the breakpoints
4570 set by that command. This applies to breakpoints set by
4571 @code{rbreak}, and also applies when a single @code{break} command
4572 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4576 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4577 disabled within a @var{command-list}.
4579 You can use breakpoint commands to start your program up again. Simply
4580 use the @code{continue} command, or @code{step}, or any other command
4581 that resumes execution.
4583 Any other commands in the command list, after a command that resumes
4584 execution, are ignored. This is because any time you resume execution
4585 (even with a simple @code{next} or @code{step}), you may encounter
4586 another breakpoint---which could have its own command list, leading to
4587 ambiguities about which list to execute.
4590 If the first command you specify in a command list is @code{silent}, the
4591 usual message about stopping at a breakpoint is not printed. This may
4592 be desirable for breakpoints that are to print a specific message and
4593 then continue. If none of the remaining commands print anything, you
4594 see no sign that the breakpoint was reached. @code{silent} is
4595 meaningful only at the beginning of a breakpoint command list.
4597 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4598 print precisely controlled output, and are often useful in silent
4599 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4601 For example, here is how you could use breakpoint commands to print the
4602 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4608 printf "x is %d\n",x
4613 One application for breakpoint commands is to compensate for one bug so
4614 you can test for another. Put a breakpoint just after the erroneous line
4615 of code, give it a condition to detect the case in which something
4616 erroneous has been done, and give it commands to assign correct values
4617 to any variables that need them. End with the @code{continue} command
4618 so that your program does not stop, and start with the @code{silent}
4619 command so that no output is produced. Here is an example:
4630 @node Save Breakpoints
4631 @subsection How to save breakpoints to a file
4633 To save breakpoint definitions to a file use the @w{@code{save
4634 breakpoints}} command.
4637 @kindex save breakpoints
4638 @cindex save breakpoints to a file for future sessions
4639 @item save breakpoints [@var{filename}]
4640 This command saves all current breakpoint definitions together with
4641 their commands and ignore counts, into a file @file{@var{filename}}
4642 suitable for use in a later debugging session. This includes all
4643 types of breakpoints (breakpoints, watchpoints, catchpoints,
4644 tracepoints). To read the saved breakpoint definitions, use the
4645 @code{source} command (@pxref{Command Files}). Note that watchpoints
4646 with expressions involving local variables may fail to be recreated
4647 because it may not be possible to access the context where the
4648 watchpoint is valid anymore. Because the saved breakpoint definitions
4649 are simply a sequence of @value{GDBN} commands that recreate the
4650 breakpoints, you can edit the file in your favorite editing program,
4651 and remove the breakpoint definitions you're not interested in, or
4652 that can no longer be recreated.
4655 @c @ifclear BARETARGET
4656 @node Error in Breakpoints
4657 @subsection ``Cannot insert breakpoints''
4659 If you request too many active hardware-assisted breakpoints and
4660 watchpoints, you will see this error message:
4662 @c FIXME: the precise wording of this message may change; the relevant
4663 @c source change is not committed yet (Sep 3, 1999).
4665 Stopped; cannot insert breakpoints.
4666 You may have requested too many hardware breakpoints and watchpoints.
4670 This message is printed when you attempt to resume the program, since
4671 only then @value{GDBN} knows exactly how many hardware breakpoints and
4672 watchpoints it needs to insert.
4674 When this message is printed, you need to disable or remove some of the
4675 hardware-assisted breakpoints and watchpoints, and then continue.
4677 @node Breakpoint-related Warnings
4678 @subsection ``Breakpoint address adjusted...''
4679 @cindex breakpoint address adjusted
4681 Some processor architectures place constraints on the addresses at
4682 which breakpoints may be placed. For architectures thus constrained,
4683 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4684 with the constraints dictated by the architecture.
4686 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4687 a VLIW architecture in which a number of RISC-like instructions may be
4688 bundled together for parallel execution. The FR-V architecture
4689 constrains the location of a breakpoint instruction within such a
4690 bundle to the instruction with the lowest address. @value{GDBN}
4691 honors this constraint by adjusting a breakpoint's address to the
4692 first in the bundle.
4694 It is not uncommon for optimized code to have bundles which contain
4695 instructions from different source statements, thus it may happen that
4696 a breakpoint's address will be adjusted from one source statement to
4697 another. Since this adjustment may significantly alter @value{GDBN}'s
4698 breakpoint related behavior from what the user expects, a warning is
4699 printed when the breakpoint is first set and also when the breakpoint
4702 A warning like the one below is printed when setting a breakpoint
4703 that's been subject to address adjustment:
4706 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4709 Such warnings are printed both for user settable and @value{GDBN}'s
4710 internal breakpoints. If you see one of these warnings, you should
4711 verify that a breakpoint set at the adjusted address will have the
4712 desired affect. If not, the breakpoint in question may be removed and
4713 other breakpoints may be set which will have the desired behavior.
4714 E.g., it may be sufficient to place the breakpoint at a later
4715 instruction. A conditional breakpoint may also be useful in some
4716 cases to prevent the breakpoint from triggering too often.
4718 @value{GDBN} will also issue a warning when stopping at one of these
4719 adjusted breakpoints:
4722 warning: Breakpoint 1 address previously adjusted from 0x00010414
4726 When this warning is encountered, it may be too late to take remedial
4727 action except in cases where the breakpoint is hit earlier or more
4728 frequently than expected.
4730 @node Continuing and Stepping
4731 @section Continuing and Stepping
4735 @cindex resuming execution
4736 @dfn{Continuing} means resuming program execution until your program
4737 completes normally. In contrast, @dfn{stepping} means executing just
4738 one more ``step'' of your program, where ``step'' may mean either one
4739 line of source code, or one machine instruction (depending on what
4740 particular command you use). Either when continuing or when stepping,
4741 your program may stop even sooner, due to a breakpoint or a signal. (If
4742 it stops due to a signal, you may want to use @code{handle}, or use
4743 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4747 @kindex c @r{(@code{continue})}
4748 @kindex fg @r{(resume foreground execution)}
4749 @item continue @r{[}@var{ignore-count}@r{]}
4750 @itemx c @r{[}@var{ignore-count}@r{]}
4751 @itemx fg @r{[}@var{ignore-count}@r{]}
4752 Resume program execution, at the address where your program last stopped;
4753 any breakpoints set at that address are bypassed. The optional argument
4754 @var{ignore-count} allows you to specify a further number of times to
4755 ignore a breakpoint at this location; its effect is like that of
4756 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4758 The argument @var{ignore-count} is meaningful only when your program
4759 stopped due to a breakpoint. At other times, the argument to
4760 @code{continue} is ignored.
4762 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4763 debugged program is deemed to be the foreground program) are provided
4764 purely for convenience, and have exactly the same behavior as
4768 To resume execution at a different place, you can use @code{return}
4769 (@pxref{Returning, ,Returning from a Function}) to go back to the
4770 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4771 Different Address}) to go to an arbitrary location in your program.
4773 A typical technique for using stepping is to set a breakpoint
4774 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4775 beginning of the function or the section of your program where a problem
4776 is believed to lie, run your program until it stops at that breakpoint,
4777 and then step through the suspect area, examining the variables that are
4778 interesting, until you see the problem happen.
4782 @kindex s @r{(@code{step})}
4784 Continue running your program until control reaches a different source
4785 line, then stop it and return control to @value{GDBN}. This command is
4786 abbreviated @code{s}.
4789 @c "without debugging information" is imprecise; actually "without line
4790 @c numbers in the debugging information". (gcc -g1 has debugging info but
4791 @c not line numbers). But it seems complex to try to make that
4792 @c distinction here.
4793 @emph{Warning:} If you use the @code{step} command while control is
4794 within a function that was compiled without debugging information,
4795 execution proceeds until control reaches a function that does have
4796 debugging information. Likewise, it will not step into a function which
4797 is compiled without debugging information. To step through functions
4798 without debugging information, use the @code{stepi} command, described
4802 The @code{step} command only stops at the first instruction of a source
4803 line. This prevents the multiple stops that could otherwise occur in
4804 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4805 to stop if a function that has debugging information is called within
4806 the line. In other words, @code{step} @emph{steps inside} any functions
4807 called within the line.
4809 Also, the @code{step} command only enters a function if there is line
4810 number information for the function. Otherwise it acts like the
4811 @code{next} command. This avoids problems when using @code{cc -gl}
4812 on MIPS machines. Previously, @code{step} entered subroutines if there
4813 was any debugging information about the routine.
4815 @item step @var{count}
4816 Continue running as in @code{step}, but do so @var{count} times. If a
4817 breakpoint is reached, or a signal not related to stepping occurs before
4818 @var{count} steps, stepping stops right away.
4821 @kindex n @r{(@code{next})}
4822 @item next @r{[}@var{count}@r{]}
4823 Continue to the next source line in the current (innermost) stack frame.
4824 This is similar to @code{step}, but function calls that appear within
4825 the line of code are executed without stopping. Execution stops when
4826 control reaches a different line of code at the original stack level
4827 that was executing when you gave the @code{next} command. This command
4828 is abbreviated @code{n}.
4830 An argument @var{count} is a repeat count, as for @code{step}.
4833 @c FIX ME!! Do we delete this, or is there a way it fits in with
4834 @c the following paragraph? --- Vctoria
4836 @c @code{next} within a function that lacks debugging information acts like
4837 @c @code{step}, but any function calls appearing within the code of the
4838 @c function are executed without stopping.
4840 The @code{next} command only stops at the first instruction of a
4841 source line. This prevents multiple stops that could otherwise occur in
4842 @code{switch} statements, @code{for} loops, etc.
4844 @kindex set step-mode
4846 @cindex functions without line info, and stepping
4847 @cindex stepping into functions with no line info
4848 @itemx set step-mode on
4849 The @code{set step-mode on} command causes the @code{step} command to
4850 stop at the first instruction of a function which contains no debug line
4851 information rather than stepping over it.
4853 This is useful in cases where you may be interested in inspecting the
4854 machine instructions of a function which has no symbolic info and do not
4855 want @value{GDBN} to automatically skip over this function.
4857 @item set step-mode off
4858 Causes the @code{step} command to step over any functions which contains no
4859 debug information. This is the default.
4861 @item show step-mode
4862 Show whether @value{GDBN} will stop in or step over functions without
4863 source line debug information.
4866 @kindex fin @r{(@code{finish})}
4868 Continue running until just after function in the selected stack frame
4869 returns. Print the returned value (if any). This command can be
4870 abbreviated as @code{fin}.
4872 Contrast this with the @code{return} command (@pxref{Returning,
4873 ,Returning from a Function}).
4876 @kindex u @r{(@code{until})}
4877 @cindex run until specified location
4880 Continue running until a source line past the current line, in the
4881 current stack frame, is reached. This command is used to avoid single
4882 stepping through a loop more than once. It is like the @code{next}
4883 command, except that when @code{until} encounters a jump, it
4884 automatically continues execution until the program counter is greater
4885 than the address of the jump.
4887 This means that when you reach the end of a loop after single stepping
4888 though it, @code{until} makes your program continue execution until it
4889 exits the loop. In contrast, a @code{next} command at the end of a loop
4890 simply steps back to the beginning of the loop, which forces you to step
4891 through the next iteration.
4893 @code{until} always stops your program if it attempts to exit the current
4896 @code{until} may produce somewhat counterintuitive results if the order
4897 of machine code does not match the order of the source lines. For
4898 example, in the following excerpt from a debugging session, the @code{f}
4899 (@code{frame}) command shows that execution is stopped at line
4900 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4904 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4906 (@value{GDBP}) until
4907 195 for ( ; argc > 0; NEXTARG) @{
4910 This happened because, for execution efficiency, the compiler had
4911 generated code for the loop closure test at the end, rather than the
4912 start, of the loop---even though the test in a C @code{for}-loop is
4913 written before the body of the loop. The @code{until} command appeared
4914 to step back to the beginning of the loop when it advanced to this
4915 expression; however, it has not really gone to an earlier
4916 statement---not in terms of the actual machine code.
4918 @code{until} with no argument works by means of single
4919 instruction stepping, and hence is slower than @code{until} with an
4922 @item until @var{location}
4923 @itemx u @var{location}
4924 Continue running your program until either the specified location is
4925 reached, or the current stack frame returns. @var{location} is any of
4926 the forms described in @ref{Specify Location}.
4927 This form of the command uses temporary breakpoints, and
4928 hence is quicker than @code{until} without an argument. The specified
4929 location is actually reached only if it is in the current frame. This
4930 implies that @code{until} can be used to skip over recursive function
4931 invocations. For instance in the code below, if the current location is
4932 line @code{96}, issuing @code{until 99} will execute the program up to
4933 line @code{99} in the same invocation of factorial, i.e., after the inner
4934 invocations have returned.
4937 94 int factorial (int value)
4939 96 if (value > 1) @{
4940 97 value *= factorial (value - 1);
4947 @kindex advance @var{location}
4948 @itemx advance @var{location}
4949 Continue running the program up to the given @var{location}. An argument is
4950 required, which should be of one of the forms described in
4951 @ref{Specify Location}.
4952 Execution will also stop upon exit from the current stack
4953 frame. This command is similar to @code{until}, but @code{advance} will
4954 not skip over recursive function calls, and the target location doesn't
4955 have to be in the same frame as the current one.
4959 @kindex si @r{(@code{stepi})}
4961 @itemx stepi @var{arg}
4963 Execute one machine instruction, then stop and return to the debugger.
4965 It is often useful to do @samp{display/i $pc} when stepping by machine
4966 instructions. This makes @value{GDBN} automatically display the next
4967 instruction to be executed, each time your program stops. @xref{Auto
4968 Display,, Automatic Display}.
4970 An argument is a repeat count, as in @code{step}.
4974 @kindex ni @r{(@code{nexti})}
4976 @itemx nexti @var{arg}
4978 Execute one machine instruction, but if it is a function call,
4979 proceed until the function returns.
4981 An argument is a repeat count, as in @code{next}.
4984 @node Skipping Over Functions and Files
4985 @section Skipping Over Functions and Files
4986 @cindex skipping over functions and files
4988 The program you are debugging may contain some functions which are
4989 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4990 skip a function or all functions in a file when stepping.
4992 For example, consider the following C function:
5003 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5004 are not interested in stepping through @code{boring}. If you run @code{step}
5005 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5006 step over both @code{foo} and @code{boring}!
5008 One solution is to @code{step} into @code{boring} and use the @code{finish}
5009 command to immediately exit it. But this can become tedious if @code{boring}
5010 is called from many places.
5012 A more flexible solution is to execute @kbd{skip boring}. This instructs
5013 @value{GDBN} never to step into @code{boring}. Now when you execute
5014 @code{step} at line 103, you'll step over @code{boring} and directly into
5017 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5018 example, @code{skip file boring.c}.
5021 @kindex skip function
5022 @item skip @r{[}@var{linespec}@r{]}
5023 @itemx skip function @r{[}@var{linespec}@r{]}
5024 After running this command, the function named by @var{linespec} or the
5025 function containing the line named by @var{linespec} will be skipped over when
5026 stepping. @xref{Specify Location}.
5028 If you do not specify @var{linespec}, the function you're currently debugging
5031 (If you have a function called @code{file} that you want to skip, use
5032 @kbd{skip function file}.)
5035 @item skip file @r{[}@var{filename}@r{]}
5036 After running this command, any function whose source lives in @var{filename}
5037 will be skipped over when stepping.
5039 If you do not specify @var{filename}, functions whose source lives in the file
5040 you're currently debugging will be skipped.
5043 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5044 These are the commands for managing your list of skips:
5048 @item info skip @r{[}@var{range}@r{]}
5049 Print details about the specified skip(s). If @var{range} is not specified,
5050 print a table with details about all functions and files marked for skipping.
5051 @code{info skip} prints the following information about each skip:
5055 A number identifying this skip.
5057 The type of this skip, either @samp{function} or @samp{file}.
5058 @item Enabled or Disabled
5059 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5061 For function skips, this column indicates the address in memory of the function
5062 being skipped. If you've set a function skip on a function which has not yet
5063 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5064 which has the function is loaded, @code{info skip} will show the function's
5067 For file skips, this field contains the filename being skipped. For functions
5068 skips, this field contains the function name and its line number in the file
5069 where it is defined.
5073 @item skip delete @r{[}@var{range}@r{]}
5074 Delete the specified skip(s). If @var{range} is not specified, delete all
5078 @item skip enable @r{[}@var{range}@r{]}
5079 Enable the specified skip(s). If @var{range} is not specified, enable all
5082 @kindex skip disable
5083 @item skip disable @r{[}@var{range}@r{]}
5084 Disable the specified skip(s). If @var{range} is not specified, disable all
5093 A signal is an asynchronous event that can happen in a program. The
5094 operating system defines the possible kinds of signals, and gives each
5095 kind a name and a number. For example, in Unix @code{SIGINT} is the
5096 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5097 @code{SIGSEGV} is the signal a program gets from referencing a place in
5098 memory far away from all the areas in use; @code{SIGALRM} occurs when
5099 the alarm clock timer goes off (which happens only if your program has
5100 requested an alarm).
5102 @cindex fatal signals
5103 Some signals, including @code{SIGALRM}, are a normal part of the
5104 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5105 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5106 program has not specified in advance some other way to handle the signal.
5107 @code{SIGINT} does not indicate an error in your program, but it is normally
5108 fatal so it can carry out the purpose of the interrupt: to kill the program.
5110 @value{GDBN} has the ability to detect any occurrence of a signal in your
5111 program. You can tell @value{GDBN} in advance what to do for each kind of
5114 @cindex handling signals
5115 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5116 @code{SIGALRM} be silently passed to your program
5117 (so as not to interfere with their role in the program's functioning)
5118 but to stop your program immediately whenever an error signal happens.
5119 You can change these settings with the @code{handle} command.
5122 @kindex info signals
5126 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5127 handle each one. You can use this to see the signal numbers of all
5128 the defined types of signals.
5130 @item info signals @var{sig}
5131 Similar, but print information only about the specified signal number.
5133 @code{info handle} is an alias for @code{info signals}.
5136 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5137 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5138 can be the number of a signal or its name (with or without the
5139 @samp{SIG} at the beginning); a list of signal numbers of the form
5140 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5141 known signals. Optional arguments @var{keywords}, described below,
5142 say what change to make.
5146 The keywords allowed by the @code{handle} command can be abbreviated.
5147 Their full names are:
5151 @value{GDBN} should not stop your program when this signal happens. It may
5152 still print a message telling you that the signal has come in.
5155 @value{GDBN} should stop your program when this signal happens. This implies
5156 the @code{print} keyword as well.
5159 @value{GDBN} should print a message when this signal happens.
5162 @value{GDBN} should not mention the occurrence of the signal at all. This
5163 implies the @code{nostop} keyword as well.
5167 @value{GDBN} should allow your program to see this signal; your program
5168 can handle the signal, or else it may terminate if the signal is fatal
5169 and not handled. @code{pass} and @code{noignore} are synonyms.
5173 @value{GDBN} should not allow your program to see this signal.
5174 @code{nopass} and @code{ignore} are synonyms.
5178 When a signal stops your program, the signal is not visible to the
5180 continue. Your program sees the signal then, if @code{pass} is in
5181 effect for the signal in question @emph{at that time}. In other words,
5182 after @value{GDBN} reports a signal, you can use the @code{handle}
5183 command with @code{pass} or @code{nopass} to control whether your
5184 program sees that signal when you continue.
5186 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5187 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5188 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5191 You can also use the @code{signal} command to prevent your program from
5192 seeing a signal, or cause it to see a signal it normally would not see,
5193 or to give it any signal at any time. For example, if your program stopped
5194 due to some sort of memory reference error, you might store correct
5195 values into the erroneous variables and continue, hoping to see more
5196 execution; but your program would probably terminate immediately as
5197 a result of the fatal signal once it saw the signal. To prevent this,
5198 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5201 @cindex extra signal information
5202 @anchor{extra signal information}
5204 On some targets, @value{GDBN} can inspect extra signal information
5205 associated with the intercepted signal, before it is actually
5206 delivered to the program being debugged. This information is exported
5207 by the convenience variable @code{$_siginfo}, and consists of data
5208 that is passed by the kernel to the signal handler at the time of the
5209 receipt of a signal. The data type of the information itself is
5210 target dependent. You can see the data type using the @code{ptype
5211 $_siginfo} command. On Unix systems, it typically corresponds to the
5212 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5215 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5216 referenced address that raised a segmentation fault.
5220 (@value{GDBP}) continue
5221 Program received signal SIGSEGV, Segmentation fault.
5222 0x0000000000400766 in main ()
5224 (@value{GDBP}) ptype $_siginfo
5231 struct @{...@} _kill;
5232 struct @{...@} _timer;
5234 struct @{...@} _sigchld;
5235 struct @{...@} _sigfault;
5236 struct @{...@} _sigpoll;
5239 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5243 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5244 $1 = (void *) 0x7ffff7ff7000
5248 Depending on target support, @code{$_siginfo} may also be writable.
5251 @section Stopping and Starting Multi-thread Programs
5253 @cindex stopped threads
5254 @cindex threads, stopped
5256 @cindex continuing threads
5257 @cindex threads, continuing
5259 @value{GDBN} supports debugging programs with multiple threads
5260 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5261 are two modes of controlling execution of your program within the
5262 debugger. In the default mode, referred to as @dfn{all-stop mode},
5263 when any thread in your program stops (for example, at a breakpoint
5264 or while being stepped), all other threads in the program are also stopped by
5265 @value{GDBN}. On some targets, @value{GDBN} also supports
5266 @dfn{non-stop mode}, in which other threads can continue to run freely while
5267 you examine the stopped thread in the debugger.
5270 * All-Stop Mode:: All threads stop when GDB takes control
5271 * Non-Stop Mode:: Other threads continue to execute
5272 * Background Execution:: Running your program asynchronously
5273 * Thread-Specific Breakpoints:: Controlling breakpoints
5274 * Interrupted System Calls:: GDB may interfere with system calls
5275 * Observer Mode:: GDB does not alter program behavior
5279 @subsection All-Stop Mode
5281 @cindex all-stop mode
5283 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5284 @emph{all} threads of execution stop, not just the current thread. This
5285 allows you to examine the overall state of the program, including
5286 switching between threads, without worrying that things may change
5289 Conversely, whenever you restart the program, @emph{all} threads start
5290 executing. @emph{This is true even when single-stepping} with commands
5291 like @code{step} or @code{next}.
5293 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5294 Since thread scheduling is up to your debugging target's operating
5295 system (not controlled by @value{GDBN}), other threads may
5296 execute more than one statement while the current thread completes a
5297 single step. Moreover, in general other threads stop in the middle of a
5298 statement, rather than at a clean statement boundary, when the program
5301 You might even find your program stopped in another thread after
5302 continuing or even single-stepping. This happens whenever some other
5303 thread runs into a breakpoint, a signal, or an exception before the
5304 first thread completes whatever you requested.
5306 @cindex automatic thread selection
5307 @cindex switching threads automatically
5308 @cindex threads, automatic switching
5309 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5310 signal, it automatically selects the thread where that breakpoint or
5311 signal happened. @value{GDBN} alerts you to the context switch with a
5312 message such as @samp{[Switching to Thread @var{n}]} to identify the
5315 On some OSes, you can modify @value{GDBN}'s default behavior by
5316 locking the OS scheduler to allow only a single thread to run.
5319 @item set scheduler-locking @var{mode}
5320 @cindex scheduler locking mode
5321 @cindex lock scheduler
5322 Set the scheduler locking mode. If it is @code{off}, then there is no
5323 locking and any thread may run at any time. If @code{on}, then only the
5324 current thread may run when the inferior is resumed. The @code{step}
5325 mode optimizes for single-stepping; it prevents other threads
5326 from preempting the current thread while you are stepping, so that
5327 the focus of debugging does not change unexpectedly.
5328 Other threads only rarely (or never) get a chance to run
5329 when you step. They are more likely to run when you @samp{next} over a
5330 function call, and they are completely free to run when you use commands
5331 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5332 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5333 the current thread away from the thread that you are debugging.
5335 @item show scheduler-locking
5336 Display the current scheduler locking mode.
5339 @cindex resume threads of multiple processes simultaneously
5340 By default, when you issue one of the execution commands such as
5341 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5342 threads of the current inferior to run. For example, if @value{GDBN}
5343 is attached to two inferiors, each with two threads, the
5344 @code{continue} command resumes only the two threads of the current
5345 inferior. This is useful, for example, when you debug a program that
5346 forks and you want to hold the parent stopped (so that, for instance,
5347 it doesn't run to exit), while you debug the child. In other
5348 situations, you may not be interested in inspecting the current state
5349 of any of the processes @value{GDBN} is attached to, and you may want
5350 to resume them all until some breakpoint is hit. In the latter case,
5351 you can instruct @value{GDBN} to allow all threads of all the
5352 inferiors to run with the @w{@code{set schedule-multiple}} command.
5355 @kindex set schedule-multiple
5356 @item set schedule-multiple
5357 Set the mode for allowing threads of multiple processes to be resumed
5358 when an execution command is issued. When @code{on}, all threads of
5359 all processes are allowed to run. When @code{off}, only the threads
5360 of the current process are resumed. The default is @code{off}. The
5361 @code{scheduler-locking} mode takes precedence when set to @code{on},
5362 or while you are stepping and set to @code{step}.
5364 @item show schedule-multiple
5365 Display the current mode for resuming the execution of threads of
5370 @subsection Non-Stop Mode
5372 @cindex non-stop mode
5374 @c This section is really only a place-holder, and needs to be expanded
5375 @c with more details.
5377 For some multi-threaded targets, @value{GDBN} supports an optional
5378 mode of operation in which you can examine stopped program threads in
5379 the debugger while other threads continue to execute freely. This
5380 minimizes intrusion when debugging live systems, such as programs
5381 where some threads have real-time constraints or must continue to
5382 respond to external events. This is referred to as @dfn{non-stop} mode.
5384 In non-stop mode, when a thread stops to report a debugging event,
5385 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5386 threads as well, in contrast to the all-stop mode behavior. Additionally,
5387 execution commands such as @code{continue} and @code{step} apply by default
5388 only to the current thread in non-stop mode, rather than all threads as
5389 in all-stop mode. This allows you to control threads explicitly in
5390 ways that are not possible in all-stop mode --- for example, stepping
5391 one thread while allowing others to run freely, stepping
5392 one thread while holding all others stopped, or stepping several threads
5393 independently and simultaneously.
5395 To enter non-stop mode, use this sequence of commands before you run
5396 or attach to your program:
5399 # Enable the async interface.
5402 # If using the CLI, pagination breaks non-stop.
5405 # Finally, turn it on!
5409 You can use these commands to manipulate the non-stop mode setting:
5412 @kindex set non-stop
5413 @item set non-stop on
5414 Enable selection of non-stop mode.
5415 @item set non-stop off
5416 Disable selection of non-stop mode.
5417 @kindex show non-stop
5419 Show the current non-stop enablement setting.
5422 Note these commands only reflect whether non-stop mode is enabled,
5423 not whether the currently-executing program is being run in non-stop mode.
5424 In particular, the @code{set non-stop} preference is only consulted when
5425 @value{GDBN} starts or connects to the target program, and it is generally
5426 not possible to switch modes once debugging has started. Furthermore,
5427 since not all targets support non-stop mode, even when you have enabled
5428 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5431 In non-stop mode, all execution commands apply only to the current thread
5432 by default. That is, @code{continue} only continues one thread.
5433 To continue all threads, issue @code{continue -a} or @code{c -a}.
5435 You can use @value{GDBN}'s background execution commands
5436 (@pxref{Background Execution}) to run some threads in the background
5437 while you continue to examine or step others from @value{GDBN}.
5438 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5439 always executed asynchronously in non-stop mode.
5441 Suspending execution is done with the @code{interrupt} command when
5442 running in the background, or @kbd{Ctrl-c} during foreground execution.
5443 In all-stop mode, this stops the whole process;
5444 but in non-stop mode the interrupt applies only to the current thread.
5445 To stop the whole program, use @code{interrupt -a}.
5447 Other execution commands do not currently support the @code{-a} option.
5449 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5450 that thread current, as it does in all-stop mode. This is because the
5451 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5452 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5453 changed to a different thread just as you entered a command to operate on the
5454 previously current thread.
5456 @node Background Execution
5457 @subsection Background Execution
5459 @cindex foreground execution
5460 @cindex background execution
5461 @cindex asynchronous execution
5462 @cindex execution, foreground, background and asynchronous
5464 @value{GDBN}'s execution commands have two variants: the normal
5465 foreground (synchronous) behavior, and a background
5466 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5467 the program to report that some thread has stopped before prompting for
5468 another command. In background execution, @value{GDBN} immediately gives
5469 a command prompt so that you can issue other commands while your program runs.
5471 You need to explicitly enable asynchronous mode before you can use
5472 background execution commands. You can use these commands to
5473 manipulate the asynchronous mode setting:
5476 @kindex set target-async
5477 @item set target-async on
5478 Enable asynchronous mode.
5479 @item set target-async off
5480 Disable asynchronous mode.
5481 @kindex show target-async
5482 @item show target-async
5483 Show the current target-async setting.
5486 If the target doesn't support async mode, @value{GDBN} issues an error
5487 message if you attempt to use the background execution commands.
5489 To specify background execution, add a @code{&} to the command. For example,
5490 the background form of the @code{continue} command is @code{continue&}, or
5491 just @code{c&}. The execution commands that accept background execution
5497 @xref{Starting, , Starting your Program}.
5501 @xref{Attach, , Debugging an Already-running Process}.
5505 @xref{Continuing and Stepping, step}.
5509 @xref{Continuing and Stepping, stepi}.
5513 @xref{Continuing and Stepping, next}.
5517 @xref{Continuing and Stepping, nexti}.
5521 @xref{Continuing and Stepping, continue}.
5525 @xref{Continuing and Stepping, finish}.
5529 @xref{Continuing and Stepping, until}.
5533 Background execution is especially useful in conjunction with non-stop
5534 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5535 However, you can also use these commands in the normal all-stop mode with
5536 the restriction that you cannot issue another execution command until the
5537 previous one finishes. Examples of commands that are valid in all-stop
5538 mode while the program is running include @code{help} and @code{info break}.
5540 You can interrupt your program while it is running in the background by
5541 using the @code{interrupt} command.
5548 Suspend execution of the running program. In all-stop mode,
5549 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5550 only the current thread. To stop the whole program in non-stop mode,
5551 use @code{interrupt -a}.
5554 @node Thread-Specific Breakpoints
5555 @subsection Thread-Specific Breakpoints
5557 When your program has multiple threads (@pxref{Threads,, Debugging
5558 Programs with Multiple Threads}), you can choose whether to set
5559 breakpoints on all threads, or on a particular thread.
5562 @cindex breakpoints and threads
5563 @cindex thread breakpoints
5564 @kindex break @dots{} thread @var{threadno}
5565 @item break @var{linespec} thread @var{threadno}
5566 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5567 @var{linespec} specifies source lines; there are several ways of
5568 writing them (@pxref{Specify Location}), but the effect is always to
5569 specify some source line.
5571 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5572 to specify that you only want @value{GDBN} to stop the program when a
5573 particular thread reaches this breakpoint. @var{threadno} is one of the
5574 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5575 column of the @samp{info threads} display.
5577 If you do not specify @samp{thread @var{threadno}} when you set a
5578 breakpoint, the breakpoint applies to @emph{all} threads of your
5581 You can use the @code{thread} qualifier on conditional breakpoints as
5582 well; in this case, place @samp{thread @var{threadno}} before or
5583 after the breakpoint condition, like this:
5586 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5591 @node Interrupted System Calls
5592 @subsection Interrupted System Calls
5594 @cindex thread breakpoints and system calls
5595 @cindex system calls and thread breakpoints
5596 @cindex premature return from system calls
5597 There is an unfortunate side effect when using @value{GDBN} to debug
5598 multi-threaded programs. If one thread stops for a
5599 breakpoint, or for some other reason, and another thread is blocked in a
5600 system call, then the system call may return prematurely. This is a
5601 consequence of the interaction between multiple threads and the signals
5602 that @value{GDBN} uses to implement breakpoints and other events that
5605 To handle this problem, your program should check the return value of
5606 each system call and react appropriately. This is good programming
5609 For example, do not write code like this:
5615 The call to @code{sleep} will return early if a different thread stops
5616 at a breakpoint or for some other reason.
5618 Instead, write this:
5623 unslept = sleep (unslept);
5626 A system call is allowed to return early, so the system is still
5627 conforming to its specification. But @value{GDBN} does cause your
5628 multi-threaded program to behave differently than it would without
5631 Also, @value{GDBN} uses internal breakpoints in the thread library to
5632 monitor certain events such as thread creation and thread destruction.
5633 When such an event happens, a system call in another thread may return
5634 prematurely, even though your program does not appear to stop.
5637 @subsection Observer Mode
5639 If you want to build on non-stop mode and observe program behavior
5640 without any chance of disruption by @value{GDBN}, you can set
5641 variables to disable all of the debugger's attempts to modify state,
5642 whether by writing memory, inserting breakpoints, etc. These operate
5643 at a low level, intercepting operations from all commands.
5645 When all of these are set to @code{off}, then @value{GDBN} is said to
5646 be @dfn{observer mode}. As a convenience, the variable
5647 @code{observer} can be set to disable these, plus enable non-stop
5650 Note that @value{GDBN} will not prevent you from making nonsensical
5651 combinations of these settings. For instance, if you have enabled
5652 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5653 then breakpoints that work by writing trap instructions into the code
5654 stream will still not be able to be placed.
5659 @item set observer on
5660 @itemx set observer off
5661 When set to @code{on}, this disables all the permission variables
5662 below (except for @code{insert-fast-tracepoints}), plus enables
5663 non-stop debugging. Setting this to @code{off} switches back to
5664 normal debugging, though remaining in non-stop mode.
5667 Show whether observer mode is on or off.
5669 @kindex may-write-registers
5670 @item set may-write-registers on
5671 @itemx set may-write-registers off
5672 This controls whether @value{GDBN} will attempt to alter the values of
5673 registers, such as with assignment expressions in @code{print}, or the
5674 @code{jump} command. It defaults to @code{on}.
5676 @item show may-write-registers
5677 Show the current permission to write registers.
5679 @kindex may-write-memory
5680 @item set may-write-memory on
5681 @itemx set may-write-memory off
5682 This controls whether @value{GDBN} will attempt to alter the contents
5683 of memory, such as with assignment expressions in @code{print}. It
5684 defaults to @code{on}.
5686 @item show may-write-memory
5687 Show the current permission to write memory.
5689 @kindex may-insert-breakpoints
5690 @item set may-insert-breakpoints on
5691 @itemx set may-insert-breakpoints off
5692 This controls whether @value{GDBN} will attempt to insert breakpoints.
5693 This affects all breakpoints, including internal breakpoints defined
5694 by @value{GDBN}. It defaults to @code{on}.
5696 @item show may-insert-breakpoints
5697 Show the current permission to insert breakpoints.
5699 @kindex may-insert-tracepoints
5700 @item set may-insert-tracepoints on
5701 @itemx set may-insert-tracepoints off
5702 This controls whether @value{GDBN} will attempt to insert (regular)
5703 tracepoints at the beginning of a tracing experiment. It affects only
5704 non-fast tracepoints, fast tracepoints being under the control of
5705 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5707 @item show may-insert-tracepoints
5708 Show the current permission to insert tracepoints.
5710 @kindex may-insert-fast-tracepoints
5711 @item set may-insert-fast-tracepoints on
5712 @itemx set may-insert-fast-tracepoints off
5713 This controls whether @value{GDBN} will attempt to insert fast
5714 tracepoints at the beginning of a tracing experiment. It affects only
5715 fast tracepoints, regular (non-fast) tracepoints being under the
5716 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5718 @item show may-insert-fast-tracepoints
5719 Show the current permission to insert fast tracepoints.
5721 @kindex may-interrupt
5722 @item set may-interrupt on
5723 @itemx set may-interrupt off
5724 This controls whether @value{GDBN} will attempt to interrupt or stop
5725 program execution. When this variable is @code{off}, the
5726 @code{interrupt} command will have no effect, nor will
5727 @kbd{Ctrl-c}. It defaults to @code{on}.
5729 @item show may-interrupt
5730 Show the current permission to interrupt or stop the program.
5734 @node Reverse Execution
5735 @chapter Running programs backward
5736 @cindex reverse execution
5737 @cindex running programs backward
5739 When you are debugging a program, it is not unusual to realize that
5740 you have gone too far, and some event of interest has already happened.
5741 If the target environment supports it, @value{GDBN} can allow you to
5742 ``rewind'' the program by running it backward.
5744 A target environment that supports reverse execution should be able
5745 to ``undo'' the changes in machine state that have taken place as the
5746 program was executing normally. Variables, registers etc.@: should
5747 revert to their previous values. Obviously this requires a great
5748 deal of sophistication on the part of the target environment; not
5749 all target environments can support reverse execution.
5751 When a program is executed in reverse, the instructions that
5752 have most recently been executed are ``un-executed'', in reverse
5753 order. The program counter runs backward, following the previous
5754 thread of execution in reverse. As each instruction is ``un-executed'',
5755 the values of memory and/or registers that were changed by that
5756 instruction are reverted to their previous states. After executing
5757 a piece of source code in reverse, all side effects of that code
5758 should be ``undone'', and all variables should be returned to their
5759 prior values@footnote{
5760 Note that some side effects are easier to undo than others. For instance,
5761 memory and registers are relatively easy, but device I/O is hard. Some
5762 targets may be able undo things like device I/O, and some may not.
5764 The contract between @value{GDBN} and the reverse executing target
5765 requires only that the target do something reasonable when
5766 @value{GDBN} tells it to execute backwards, and then report the
5767 results back to @value{GDBN}. Whatever the target reports back to
5768 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5769 assumes that the memory and registers that the target reports are in a
5770 consistant state, but @value{GDBN} accepts whatever it is given.
5773 If you are debugging in a target environment that supports
5774 reverse execution, @value{GDBN} provides the following commands.
5777 @kindex reverse-continue
5778 @kindex rc @r{(@code{reverse-continue})}
5779 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5780 @itemx rc @r{[}@var{ignore-count}@r{]}
5781 Beginning at the point where your program last stopped, start executing
5782 in reverse. Reverse execution will stop for breakpoints and synchronous
5783 exceptions (signals), just like normal execution. Behavior of
5784 asynchronous signals depends on the target environment.
5786 @kindex reverse-step
5787 @kindex rs @r{(@code{step})}
5788 @item reverse-step @r{[}@var{count}@r{]}
5789 Run the program backward until control reaches the start of a
5790 different source line; then stop it, and return control to @value{GDBN}.
5792 Like the @code{step} command, @code{reverse-step} will only stop
5793 at the beginning of a source line. It ``un-executes'' the previously
5794 executed source line. If the previous source line included calls to
5795 debuggable functions, @code{reverse-step} will step (backward) into
5796 the called function, stopping at the beginning of the @emph{last}
5797 statement in the called function (typically a return statement).
5799 Also, as with the @code{step} command, if non-debuggable functions are
5800 called, @code{reverse-step} will run thru them backward without stopping.
5802 @kindex reverse-stepi
5803 @kindex rsi @r{(@code{reverse-stepi})}
5804 @item reverse-stepi @r{[}@var{count}@r{]}
5805 Reverse-execute one machine instruction. Note that the instruction
5806 to be reverse-executed is @emph{not} the one pointed to by the program
5807 counter, but the instruction executed prior to that one. For instance,
5808 if the last instruction was a jump, @code{reverse-stepi} will take you
5809 back from the destination of the jump to the jump instruction itself.
5811 @kindex reverse-next
5812 @kindex rn @r{(@code{reverse-next})}
5813 @item reverse-next @r{[}@var{count}@r{]}
5814 Run backward to the beginning of the previous line executed in
5815 the current (innermost) stack frame. If the line contains function
5816 calls, they will be ``un-executed'' without stopping. Starting from
5817 the first line of a function, @code{reverse-next} will take you back
5818 to the caller of that function, @emph{before} the function was called,
5819 just as the normal @code{next} command would take you from the last
5820 line of a function back to its return to its caller
5821 @footnote{Unless the code is too heavily optimized.}.
5823 @kindex reverse-nexti
5824 @kindex rni @r{(@code{reverse-nexti})}
5825 @item reverse-nexti @r{[}@var{count}@r{]}
5826 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5827 in reverse, except that called functions are ``un-executed'' atomically.
5828 That is, if the previously executed instruction was a return from
5829 another function, @code{reverse-nexti} will continue to execute
5830 in reverse until the call to that function (from the current stack
5833 @kindex reverse-finish
5834 @item reverse-finish
5835 Just as the @code{finish} command takes you to the point where the
5836 current function returns, @code{reverse-finish} takes you to the point
5837 where it was called. Instead of ending up at the end of the current
5838 function invocation, you end up at the beginning.
5840 @kindex set exec-direction
5841 @item set exec-direction
5842 Set the direction of target execution.
5843 @itemx set exec-direction reverse
5844 @cindex execute forward or backward in time
5845 @value{GDBN} will perform all execution commands in reverse, until the
5846 exec-direction mode is changed to ``forward''. Affected commands include
5847 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5848 command cannot be used in reverse mode.
5849 @item set exec-direction forward
5850 @value{GDBN} will perform all execution commands in the normal fashion.
5851 This is the default.
5855 @node Process Record and Replay
5856 @chapter Recording Inferior's Execution and Replaying It
5857 @cindex process record and replay
5858 @cindex recording inferior's execution and replaying it
5860 On some platforms, @value{GDBN} provides a special @dfn{process record
5861 and replay} target that can record a log of the process execution, and
5862 replay it later with both forward and reverse execution commands.
5865 When this target is in use, if the execution log includes the record
5866 for the next instruction, @value{GDBN} will debug in @dfn{replay
5867 mode}. In the replay mode, the inferior does not really execute code
5868 instructions. Instead, all the events that normally happen during
5869 code execution are taken from the execution log. While code is not
5870 really executed in replay mode, the values of registers (including the
5871 program counter register) and the memory of the inferior are still
5872 changed as they normally would. Their contents are taken from the
5876 If the record for the next instruction is not in the execution log,
5877 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5878 inferior executes normally, and @value{GDBN} records the execution log
5881 The process record and replay target supports reverse execution
5882 (@pxref{Reverse Execution}), even if the platform on which the
5883 inferior runs does not. However, the reverse execution is limited in
5884 this case by the range of the instructions recorded in the execution
5885 log. In other words, reverse execution on platforms that don't
5886 support it directly can only be done in the replay mode.
5888 When debugging in the reverse direction, @value{GDBN} will work in
5889 replay mode as long as the execution log includes the record for the
5890 previous instruction; otherwise, it will work in record mode, if the
5891 platform supports reverse execution, or stop if not.
5893 For architecture environments that support process record and replay,
5894 @value{GDBN} provides the following commands:
5897 @kindex target record
5901 This command starts the process record and replay target. The process
5902 record and replay target can only debug a process that is already
5903 running. Therefore, you need first to start the process with the
5904 @kbd{run} or @kbd{start} commands, and then start the recording with
5905 the @kbd{target record} command.
5907 Both @code{record} and @code{rec} are aliases of @code{target record}.
5909 @cindex displaced stepping, and process record and replay
5910 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5911 will be automatically disabled when process record and replay target
5912 is started. That's because the process record and replay target
5913 doesn't support displaced stepping.
5915 @cindex non-stop mode, and process record and replay
5916 @cindex asynchronous execution, and process record and replay
5917 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5918 the asynchronous execution mode (@pxref{Background Execution}), the
5919 process record and replay target cannot be started because it doesn't
5920 support these two modes.
5925 Stop the process record and replay target. When process record and
5926 replay target stops, the entire execution log will be deleted and the
5927 inferior will either be terminated, or will remain in its final state.
5929 When you stop the process record and replay target in record mode (at
5930 the end of the execution log), the inferior will be stopped at the
5931 next instruction that would have been recorded. In other words, if
5932 you record for a while and then stop recording, the inferior process
5933 will be left in the same state as if the recording never happened.
5935 On the other hand, if the process record and replay target is stopped
5936 while in replay mode (that is, not at the end of the execution log,
5937 but at some earlier point), the inferior process will become ``live''
5938 at that earlier state, and it will then be possible to continue the
5939 usual ``live'' debugging of the process from that state.
5941 When the inferior process exits, or @value{GDBN} detaches from it,
5942 process record and replay target will automatically stop itself.
5945 @item record save @var{filename}
5946 Save the execution log to a file @file{@var{filename}}.
5947 Default filename is @file{gdb_record.@var{process_id}}, where
5948 @var{process_id} is the process ID of the inferior.
5950 @kindex record restore
5951 @item record restore @var{filename}
5952 Restore the execution log from a file @file{@var{filename}}.
5953 File must have been created with @code{record save}.
5955 @kindex set record insn-number-max
5956 @item set record insn-number-max @var{limit}
5957 Set the limit of instructions to be recorded. Default value is 200000.
5959 If @var{limit} is a positive number, then @value{GDBN} will start
5960 deleting instructions from the log once the number of the record
5961 instructions becomes greater than @var{limit}. For every new recorded
5962 instruction, @value{GDBN} will delete the earliest recorded
5963 instruction to keep the number of recorded instructions at the limit.
5964 (Since deleting recorded instructions loses information, @value{GDBN}
5965 lets you control what happens when the limit is reached, by means of
5966 the @code{stop-at-limit} option, described below.)
5968 If @var{limit} is zero, @value{GDBN} will never delete recorded
5969 instructions from the execution log. The number of recorded
5970 instructions is unlimited in this case.
5972 @kindex show record insn-number-max
5973 @item show record insn-number-max
5974 Show the limit of instructions to be recorded.
5976 @kindex set record stop-at-limit
5977 @item set record stop-at-limit
5978 Control the behavior when the number of recorded instructions reaches
5979 the limit. If ON (the default), @value{GDBN} will stop when the limit
5980 is reached for the first time and ask you whether you want to stop the
5981 inferior or continue running it and recording the execution log. If
5982 you decide to continue recording, each new recorded instruction will
5983 cause the oldest one to be deleted.
5985 If this option is OFF, @value{GDBN} will automatically delete the
5986 oldest record to make room for each new one, without asking.
5988 @kindex show record stop-at-limit
5989 @item show record stop-at-limit
5990 Show the current setting of @code{stop-at-limit}.
5992 @kindex set record memory-query
5993 @item set record memory-query
5994 Control the behavior when @value{GDBN} is unable to record memory
5995 changes caused by an instruction. If ON, @value{GDBN} will query
5996 whether to stop the inferior in that case.
5998 If this option is OFF (the default), @value{GDBN} will automatically
5999 ignore the effect of such instructions on memory. Later, when
6000 @value{GDBN} replays this execution log, it will mark the log of this
6001 instruction as not accessible, and it will not affect the replay
6004 @kindex show record memory-query
6005 @item show record memory-query
6006 Show the current setting of @code{memory-query}.
6010 Show various statistics about the state of process record and its
6011 in-memory execution log buffer, including:
6015 Whether in record mode or replay mode.
6017 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6019 Highest recorded instruction number.
6021 Current instruction about to be replayed (if in replay mode).
6023 Number of instructions contained in the execution log.
6025 Maximum number of instructions that may be contained in the execution log.
6028 @kindex record delete
6031 When record target runs in replay mode (``in the past''), delete the
6032 subsequent execution log and begin to record a new execution log starting
6033 from the current address. This means you will abandon the previously
6034 recorded ``future'' and begin recording a new ``future''.
6039 @chapter Examining the Stack
6041 When your program has stopped, the first thing you need to know is where it
6042 stopped and how it got there.
6045 Each time your program performs a function call, information about the call
6047 That information includes the location of the call in your program,
6048 the arguments of the call,
6049 and the local variables of the function being called.
6050 The information is saved in a block of data called a @dfn{stack frame}.
6051 The stack frames are allocated in a region of memory called the @dfn{call
6054 When your program stops, the @value{GDBN} commands for examining the
6055 stack allow you to see all of this information.
6057 @cindex selected frame
6058 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6059 @value{GDBN} commands refer implicitly to the selected frame. In
6060 particular, whenever you ask @value{GDBN} for the value of a variable in
6061 your program, the value is found in the selected frame. There are
6062 special @value{GDBN} commands to select whichever frame you are
6063 interested in. @xref{Selection, ,Selecting a Frame}.
6065 When your program stops, @value{GDBN} automatically selects the
6066 currently executing frame and describes it briefly, similar to the
6067 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6070 * Frames:: Stack frames
6071 * Backtrace:: Backtraces
6072 * Selection:: Selecting a frame
6073 * Frame Info:: Information on a frame
6078 @section Stack Frames
6080 @cindex frame, definition
6082 The call stack is divided up into contiguous pieces called @dfn{stack
6083 frames}, or @dfn{frames} for short; each frame is the data associated
6084 with one call to one function. The frame contains the arguments given
6085 to the function, the function's local variables, and the address at
6086 which the function is executing.
6088 @cindex initial frame
6089 @cindex outermost frame
6090 @cindex innermost frame
6091 When your program is started, the stack has only one frame, that of the
6092 function @code{main}. This is called the @dfn{initial} frame or the
6093 @dfn{outermost} frame. Each time a function is called, a new frame is
6094 made. Each time a function returns, the frame for that function invocation
6095 is eliminated. If a function is recursive, there can be many frames for
6096 the same function. The frame for the function in which execution is
6097 actually occurring is called the @dfn{innermost} frame. This is the most
6098 recently created of all the stack frames that still exist.
6100 @cindex frame pointer
6101 Inside your program, stack frames are identified by their addresses. A
6102 stack frame consists of many bytes, each of which has its own address; each
6103 kind of computer has a convention for choosing one byte whose
6104 address serves as the address of the frame. Usually this address is kept
6105 in a register called the @dfn{frame pointer register}
6106 (@pxref{Registers, $fp}) while execution is going on in that frame.
6108 @cindex frame number
6109 @value{GDBN} assigns numbers to all existing stack frames, starting with
6110 zero for the innermost frame, one for the frame that called it,
6111 and so on upward. These numbers do not really exist in your program;
6112 they are assigned by @value{GDBN} to give you a way of designating stack
6113 frames in @value{GDBN} commands.
6115 @c The -fomit-frame-pointer below perennially causes hbox overflow
6116 @c underflow problems.
6117 @cindex frameless execution
6118 Some compilers provide a way to compile functions so that they operate
6119 without stack frames. (For example, the @value{NGCC} option
6121 @samp{-fomit-frame-pointer}
6123 generates functions without a frame.)
6124 This is occasionally done with heavily used library functions to save
6125 the frame setup time. @value{GDBN} has limited facilities for dealing
6126 with these function invocations. If the innermost function invocation
6127 has no stack frame, @value{GDBN} nevertheless regards it as though
6128 it had a separate frame, which is numbered zero as usual, allowing
6129 correct tracing of the function call chain. However, @value{GDBN} has
6130 no provision for frameless functions elsewhere in the stack.
6133 @kindex frame@r{, command}
6134 @cindex current stack frame
6135 @item frame @var{args}
6136 The @code{frame} command allows you to move from one stack frame to another,
6137 and to print the stack frame you select. @var{args} may be either the
6138 address of the frame or the stack frame number. Without an argument,
6139 @code{frame} prints the current stack frame.
6141 @kindex select-frame
6142 @cindex selecting frame silently
6144 The @code{select-frame} command allows you to move from one stack frame
6145 to another without printing the frame. This is the silent version of
6153 @cindex call stack traces
6154 A backtrace is a summary of how your program got where it is. It shows one
6155 line per frame, for many frames, starting with the currently executing
6156 frame (frame zero), followed by its caller (frame one), and on up the
6161 @kindex bt @r{(@code{backtrace})}
6164 Print a backtrace of the entire stack: one line per frame for all
6165 frames in the stack.
6167 You can stop the backtrace at any time by typing the system interrupt
6168 character, normally @kbd{Ctrl-c}.
6170 @item backtrace @var{n}
6172 Similar, but print only the innermost @var{n} frames.
6174 @item backtrace -@var{n}
6176 Similar, but print only the outermost @var{n} frames.
6178 @item backtrace full
6180 @itemx bt full @var{n}
6181 @itemx bt full -@var{n}
6182 Print the values of the local variables also. @var{n} specifies the
6183 number of frames to print, as described above.
6188 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6189 are additional aliases for @code{backtrace}.
6191 @cindex multiple threads, backtrace
6192 In a multi-threaded program, @value{GDBN} by default shows the
6193 backtrace only for the current thread. To display the backtrace for
6194 several or all of the threads, use the command @code{thread apply}
6195 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6196 apply all backtrace}, @value{GDBN} will display the backtrace for all
6197 the threads; this is handy when you debug a core dump of a
6198 multi-threaded program.
6200 Each line in the backtrace shows the frame number and the function name.
6201 The program counter value is also shown---unless you use @code{set
6202 print address off}. The backtrace also shows the source file name and
6203 line number, as well as the arguments to the function. The program
6204 counter value is omitted if it is at the beginning of the code for that
6207 Here is an example of a backtrace. It was made with the command
6208 @samp{bt 3}, so it shows the innermost three frames.
6212 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6214 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6215 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6217 (More stack frames follow...)
6222 The display for frame zero does not begin with a program counter
6223 value, indicating that your program has stopped at the beginning of the
6224 code for line @code{993} of @code{builtin.c}.
6227 The value of parameter @code{data} in frame 1 has been replaced by
6228 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6229 only if it is a scalar (integer, pointer, enumeration, etc). See command
6230 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6231 on how to configure the way function parameter values are printed.
6233 @cindex optimized out, in backtrace
6234 @cindex function call arguments, optimized out
6235 If your program was compiled with optimizations, some compilers will
6236 optimize away arguments passed to functions if those arguments are
6237 never used after the call. Such optimizations generate code that
6238 passes arguments through registers, but doesn't store those arguments
6239 in the stack frame. @value{GDBN} has no way of displaying such
6240 arguments in stack frames other than the innermost one. Here's what
6241 such a backtrace might look like:
6245 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6247 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6248 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6250 (More stack frames follow...)
6255 The values of arguments that were not saved in their stack frames are
6256 shown as @samp{<optimized out>}.
6258 If you need to display the values of such optimized-out arguments,
6259 either deduce that from other variables whose values depend on the one
6260 you are interested in, or recompile without optimizations.
6262 @cindex backtrace beyond @code{main} function
6263 @cindex program entry point
6264 @cindex startup code, and backtrace
6265 Most programs have a standard user entry point---a place where system
6266 libraries and startup code transition into user code. For C this is
6267 @code{main}@footnote{
6268 Note that embedded programs (the so-called ``free-standing''
6269 environment) are not required to have a @code{main} function as the
6270 entry point. They could even have multiple entry points.}.
6271 When @value{GDBN} finds the entry function in a backtrace
6272 it will terminate the backtrace, to avoid tracing into highly
6273 system-specific (and generally uninteresting) code.
6275 If you need to examine the startup code, or limit the number of levels
6276 in a backtrace, you can change this behavior:
6279 @item set backtrace past-main
6280 @itemx set backtrace past-main on
6281 @kindex set backtrace
6282 Backtraces will continue past the user entry point.
6284 @item set backtrace past-main off
6285 Backtraces will stop when they encounter the user entry point. This is the
6288 @item show backtrace past-main
6289 @kindex show backtrace
6290 Display the current user entry point backtrace policy.
6292 @item set backtrace past-entry
6293 @itemx set backtrace past-entry on
6294 Backtraces will continue past the internal entry point of an application.
6295 This entry point is encoded by the linker when the application is built,
6296 and is likely before the user entry point @code{main} (or equivalent) is called.
6298 @item set backtrace past-entry off
6299 Backtraces will stop when they encounter the internal entry point of an
6300 application. This is the default.
6302 @item show backtrace past-entry
6303 Display the current internal entry point backtrace policy.
6305 @item set backtrace limit @var{n}
6306 @itemx set backtrace limit 0
6307 @cindex backtrace limit
6308 Limit the backtrace to @var{n} levels. A value of zero means
6311 @item show backtrace limit
6312 Display the current limit on backtrace levels.
6316 @section Selecting a Frame
6318 Most commands for examining the stack and other data in your program work on
6319 whichever stack frame is selected at the moment. Here are the commands for
6320 selecting a stack frame; all of them finish by printing a brief description
6321 of the stack frame just selected.
6324 @kindex frame@r{, selecting}
6325 @kindex f @r{(@code{frame})}
6328 Select frame number @var{n}. Recall that frame zero is the innermost
6329 (currently executing) frame, frame one is the frame that called the
6330 innermost one, and so on. The highest-numbered frame is the one for
6333 @item frame @var{addr}
6335 Select the frame at address @var{addr}. This is useful mainly if the
6336 chaining of stack frames has been damaged by a bug, making it
6337 impossible for @value{GDBN} to assign numbers properly to all frames. In
6338 addition, this can be useful when your program has multiple stacks and
6339 switches between them.
6341 On the SPARC architecture, @code{frame} needs two addresses to
6342 select an arbitrary frame: a frame pointer and a stack pointer.
6344 On the MIPS and Alpha architecture, it needs two addresses: a stack
6345 pointer and a program counter.
6347 On the 29k architecture, it needs three addresses: a register stack
6348 pointer, a program counter, and a memory stack pointer.
6352 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6353 advances toward the outermost frame, to higher frame numbers, to frames
6354 that have existed longer. @var{n} defaults to one.
6357 @kindex do @r{(@code{down})}
6359 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6360 advances toward the innermost frame, to lower frame numbers, to frames
6361 that were created more recently. @var{n} defaults to one. You may
6362 abbreviate @code{down} as @code{do}.
6365 All of these commands end by printing two lines of output describing the
6366 frame. The first line shows the frame number, the function name, the
6367 arguments, and the source file and line number of execution in that
6368 frame. The second line shows the text of that source line.
6376 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6378 10 read_input_file (argv[i]);
6382 After such a printout, the @code{list} command with no arguments
6383 prints ten lines centered on the point of execution in the frame.
6384 You can also edit the program at the point of execution with your favorite
6385 editing program by typing @code{edit}.
6386 @xref{List, ,Printing Source Lines},
6390 @kindex down-silently
6392 @item up-silently @var{n}
6393 @itemx down-silently @var{n}
6394 These two commands are variants of @code{up} and @code{down},
6395 respectively; they differ in that they do their work silently, without
6396 causing display of the new frame. They are intended primarily for use
6397 in @value{GDBN} command scripts, where the output might be unnecessary and
6402 @section Information About a Frame
6404 There are several other commands to print information about the selected
6410 When used without any argument, this command does not change which
6411 frame is selected, but prints a brief description of the currently
6412 selected stack frame. It can be abbreviated @code{f}. With an
6413 argument, this command is used to select a stack frame.
6414 @xref{Selection, ,Selecting a Frame}.
6417 @kindex info f @r{(@code{info frame})}
6420 This command prints a verbose description of the selected stack frame,
6425 the address of the frame
6427 the address of the next frame down (called by this frame)
6429 the address of the next frame up (caller of this frame)
6431 the language in which the source code corresponding to this frame is written
6433 the address of the frame's arguments
6435 the address of the frame's local variables
6437 the program counter saved in it (the address of execution in the caller frame)
6439 which registers were saved in the frame
6442 @noindent The verbose description is useful when
6443 something has gone wrong that has made the stack format fail to fit
6444 the usual conventions.
6446 @item info frame @var{addr}
6447 @itemx info f @var{addr}
6448 Print a verbose description of the frame at address @var{addr}, without
6449 selecting that frame. The selected frame remains unchanged by this
6450 command. This requires the same kind of address (more than one for some
6451 architectures) that you specify in the @code{frame} command.
6452 @xref{Selection, ,Selecting a Frame}.
6456 Print the arguments of the selected frame, each on a separate line.
6460 Print the local variables of the selected frame, each on a separate
6461 line. These are all variables (declared either static or automatic)
6462 accessible at the point of execution of the selected frame.
6468 @chapter Examining Source Files
6470 @value{GDBN} can print parts of your program's source, since the debugging
6471 information recorded in the program tells @value{GDBN} what source files were
6472 used to build it. When your program stops, @value{GDBN} spontaneously prints
6473 the line where it stopped. Likewise, when you select a stack frame
6474 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6475 execution in that frame has stopped. You can print other portions of
6476 source files by explicit command.
6478 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6479 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6480 @value{GDBN} under @sc{gnu} Emacs}.
6483 * List:: Printing source lines
6484 * Specify Location:: How to specify code locations
6485 * Edit:: Editing source files
6486 * Search:: Searching source files
6487 * Source Path:: Specifying source directories
6488 * Machine Code:: Source and machine code
6492 @section Printing Source Lines
6495 @kindex l @r{(@code{list})}
6496 To print lines from a source file, use the @code{list} command
6497 (abbreviated @code{l}). By default, ten lines are printed.
6498 There are several ways to specify what part of the file you want to
6499 print; see @ref{Specify Location}, for the full list.
6501 Here are the forms of the @code{list} command most commonly used:
6504 @item list @var{linenum}
6505 Print lines centered around line number @var{linenum} in the
6506 current source file.
6508 @item list @var{function}
6509 Print lines centered around the beginning of function
6513 Print more lines. If the last lines printed were printed with a
6514 @code{list} command, this prints lines following the last lines
6515 printed; however, if the last line printed was a solitary line printed
6516 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6517 Stack}), this prints lines centered around that line.
6520 Print lines just before the lines last printed.
6523 @cindex @code{list}, how many lines to display
6524 By default, @value{GDBN} prints ten source lines with any of these forms of
6525 the @code{list} command. You can change this using @code{set listsize}:
6528 @kindex set listsize
6529 @item set listsize @var{count}
6530 Make the @code{list} command display @var{count} source lines (unless
6531 the @code{list} argument explicitly specifies some other number).
6533 @kindex show listsize
6535 Display the number of lines that @code{list} prints.
6538 Repeating a @code{list} command with @key{RET} discards the argument,
6539 so it is equivalent to typing just @code{list}. This is more useful
6540 than listing the same lines again. An exception is made for an
6541 argument of @samp{-}; that argument is preserved in repetition so that
6542 each repetition moves up in the source file.
6544 In general, the @code{list} command expects you to supply zero, one or two
6545 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6546 of writing them (@pxref{Specify Location}), but the effect is always
6547 to specify some source line.
6549 Here is a complete description of the possible arguments for @code{list}:
6552 @item list @var{linespec}
6553 Print lines centered around the line specified by @var{linespec}.
6555 @item list @var{first},@var{last}
6556 Print lines from @var{first} to @var{last}. Both arguments are
6557 linespecs. When a @code{list} command has two linespecs, and the
6558 source file of the second linespec is omitted, this refers to
6559 the same source file as the first linespec.
6561 @item list ,@var{last}
6562 Print lines ending with @var{last}.
6564 @item list @var{first},
6565 Print lines starting with @var{first}.
6568 Print lines just after the lines last printed.
6571 Print lines just before the lines last printed.
6574 As described in the preceding table.
6577 @node Specify Location
6578 @section Specifying a Location
6579 @cindex specifying location
6582 Several @value{GDBN} commands accept arguments that specify a location
6583 of your program's code. Since @value{GDBN} is a source-level
6584 debugger, a location usually specifies some line in the source code;
6585 for that reason, locations are also known as @dfn{linespecs}.
6587 Here are all the different ways of specifying a code location that
6588 @value{GDBN} understands:
6592 Specifies the line number @var{linenum} of the current source file.
6595 @itemx +@var{offset}
6596 Specifies the line @var{offset} lines before or after the @dfn{current
6597 line}. For the @code{list} command, the current line is the last one
6598 printed; for the breakpoint commands, this is the line at which
6599 execution stopped in the currently selected @dfn{stack frame}
6600 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6601 used as the second of the two linespecs in a @code{list} command,
6602 this specifies the line @var{offset} lines up or down from the first
6605 @item @var{filename}:@var{linenum}
6606 Specifies the line @var{linenum} in the source file @var{filename}.
6607 If @var{filename} is a relative file name, then it will match any
6608 source file name with the same trailing components. For example, if
6609 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6610 name of @file{/build/trunk/gcc/expr.c}, but not
6611 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6613 @item @var{function}
6614 Specifies the line that begins the body of the function @var{function}.
6615 For example, in C, this is the line with the open brace.
6617 @item @var{function}:@var{label}
6618 Specifies the line where @var{label} appears in @var{function}.
6620 @item @var{filename}:@var{function}
6621 Specifies the line that begins the body of the function @var{function}
6622 in the file @var{filename}. You only need the file name with a
6623 function name to avoid ambiguity when there are identically named
6624 functions in different source files.
6627 Specifies the line at which the label named @var{label} appears.
6628 @value{GDBN} searches for the label in the function corresponding to
6629 the currently selected stack frame. If there is no current selected
6630 stack frame (for instance, if the inferior is not running), then
6631 @value{GDBN} will not search for a label.
6633 @item *@var{address}
6634 Specifies the program address @var{address}. For line-oriented
6635 commands, such as @code{list} and @code{edit}, this specifies a source
6636 line that contains @var{address}. For @code{break} and other
6637 breakpoint oriented commands, this can be used to set breakpoints in
6638 parts of your program which do not have debugging information or
6641 Here @var{address} may be any expression valid in the current working
6642 language (@pxref{Languages, working language}) that specifies a code
6643 address. In addition, as a convenience, @value{GDBN} extends the
6644 semantics of expressions used in locations to cover the situations
6645 that frequently happen during debugging. Here are the various forms
6649 @item @var{expression}
6650 Any expression valid in the current working language.
6652 @item @var{funcaddr}
6653 An address of a function or procedure derived from its name. In C,
6654 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6655 simply the function's name @var{function} (and actually a special case
6656 of a valid expression). In Pascal and Modula-2, this is
6657 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6658 (although the Pascal form also works).
6660 This form specifies the address of the function's first instruction,
6661 before the stack frame and arguments have been set up.
6663 @item '@var{filename}'::@var{funcaddr}
6664 Like @var{funcaddr} above, but also specifies the name of the source
6665 file explicitly. This is useful if the name of the function does not
6666 specify the function unambiguously, e.g., if there are several
6667 functions with identical names in different source files.
6674 @section Editing Source Files
6675 @cindex editing source files
6678 @kindex e @r{(@code{edit})}
6679 To edit the lines in a source file, use the @code{edit} command.
6680 The editing program of your choice
6681 is invoked with the current line set to
6682 the active line in the program.
6683 Alternatively, there are several ways to specify what part of the file you
6684 want to print if you want to see other parts of the program:
6687 @item edit @var{location}
6688 Edit the source file specified by @code{location}. Editing starts at
6689 that @var{location}, e.g., at the specified source line of the
6690 specified file. @xref{Specify Location}, for all the possible forms
6691 of the @var{location} argument; here are the forms of the @code{edit}
6692 command most commonly used:
6695 @item edit @var{number}
6696 Edit the current source file with @var{number} as the active line number.
6698 @item edit @var{function}
6699 Edit the file containing @var{function} at the beginning of its definition.
6704 @subsection Choosing your Editor
6705 You can customize @value{GDBN} to use any editor you want
6707 The only restriction is that your editor (say @code{ex}), recognizes the
6708 following command-line syntax:
6710 ex +@var{number} file
6712 The optional numeric value +@var{number} specifies the number of the line in
6713 the file where to start editing.}.
6714 By default, it is @file{@value{EDITOR}}, but you can change this
6715 by setting the environment variable @code{EDITOR} before using
6716 @value{GDBN}. For example, to configure @value{GDBN} to use the
6717 @code{vi} editor, you could use these commands with the @code{sh} shell:
6723 or in the @code{csh} shell,
6725 setenv EDITOR /usr/bin/vi
6730 @section Searching Source Files
6731 @cindex searching source files
6733 There are two commands for searching through the current source file for a
6738 @kindex forward-search
6739 @item forward-search @var{regexp}
6740 @itemx search @var{regexp}
6741 The command @samp{forward-search @var{regexp}} checks each line,
6742 starting with the one following the last line listed, for a match for
6743 @var{regexp}. It lists the line that is found. You can use the
6744 synonym @samp{search @var{regexp}} or abbreviate the command name as
6747 @kindex reverse-search
6748 @item reverse-search @var{regexp}
6749 The command @samp{reverse-search @var{regexp}} checks each line, starting
6750 with the one before the last line listed and going backward, for a match
6751 for @var{regexp}. It lists the line that is found. You can abbreviate
6752 this command as @code{rev}.
6756 @section Specifying Source Directories
6759 @cindex directories for source files
6760 Executable programs sometimes do not record the directories of the source
6761 files from which they were compiled, just the names. Even when they do,
6762 the directories could be moved between the compilation and your debugging
6763 session. @value{GDBN} has a list of directories to search for source files;
6764 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6765 it tries all the directories in the list, in the order they are present
6766 in the list, until it finds a file with the desired name.
6768 For example, suppose an executable references the file
6769 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6770 @file{/mnt/cross}. The file is first looked up literally; if this
6771 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6772 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6773 message is printed. @value{GDBN} does not look up the parts of the
6774 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6775 Likewise, the subdirectories of the source path are not searched: if
6776 the source path is @file{/mnt/cross}, and the binary refers to
6777 @file{foo.c}, @value{GDBN} would not find it under
6778 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6780 Plain file names, relative file names with leading directories, file
6781 names containing dots, etc.@: are all treated as described above; for
6782 instance, if the source path is @file{/mnt/cross}, and the source file
6783 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6784 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6785 that---@file{/mnt/cross/foo.c}.
6787 Note that the executable search path is @emph{not} used to locate the
6790 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6791 any information it has cached about where source files are found and where
6792 each line is in the file.
6796 When you start @value{GDBN}, its source path includes only @samp{cdir}
6797 and @samp{cwd}, in that order.
6798 To add other directories, use the @code{directory} command.
6800 The search path is used to find both program source files and @value{GDBN}
6801 script files (read using the @samp{-command} option and @samp{source} command).
6803 In addition to the source path, @value{GDBN} provides a set of commands
6804 that manage a list of source path substitution rules. A @dfn{substitution
6805 rule} specifies how to rewrite source directories stored in the program's
6806 debug information in case the sources were moved to a different
6807 directory between compilation and debugging. A rule is made of
6808 two strings, the first specifying what needs to be rewritten in
6809 the path, and the second specifying how it should be rewritten.
6810 In @ref{set substitute-path}, we name these two parts @var{from} and
6811 @var{to} respectively. @value{GDBN} does a simple string replacement
6812 of @var{from} with @var{to} at the start of the directory part of the
6813 source file name, and uses that result instead of the original file
6814 name to look up the sources.
6816 Using the previous example, suppose the @file{foo-1.0} tree has been
6817 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6818 @value{GDBN} to replace @file{/usr/src} in all source path names with
6819 @file{/mnt/cross}. The first lookup will then be
6820 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6821 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6822 substitution rule, use the @code{set substitute-path} command
6823 (@pxref{set substitute-path}).
6825 To avoid unexpected substitution results, a rule is applied only if the
6826 @var{from} part of the directory name ends at a directory separator.
6827 For instance, a rule substituting @file{/usr/source} into
6828 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6829 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6830 is applied only at the beginning of the directory name, this rule will
6831 not be applied to @file{/root/usr/source/baz.c} either.
6833 In many cases, you can achieve the same result using the @code{directory}
6834 command. However, @code{set substitute-path} can be more efficient in
6835 the case where the sources are organized in a complex tree with multiple
6836 subdirectories. With the @code{directory} command, you need to add each
6837 subdirectory of your project. If you moved the entire tree while
6838 preserving its internal organization, then @code{set substitute-path}
6839 allows you to direct the debugger to all the sources with one single
6842 @code{set substitute-path} is also more than just a shortcut command.
6843 The source path is only used if the file at the original location no
6844 longer exists. On the other hand, @code{set substitute-path} modifies
6845 the debugger behavior to look at the rewritten location instead. So, if
6846 for any reason a source file that is not relevant to your executable is
6847 located at the original location, a substitution rule is the only
6848 method available to point @value{GDBN} at the new location.
6850 @cindex @samp{--with-relocated-sources}
6851 @cindex default source path substitution
6852 You can configure a default source path substitution rule by
6853 configuring @value{GDBN} with the
6854 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6855 should be the name of a directory under @value{GDBN}'s configured
6856 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6857 directory names in debug information under @var{dir} will be adjusted
6858 automatically if the installed @value{GDBN} is moved to a new
6859 location. This is useful if @value{GDBN}, libraries or executables
6860 with debug information and corresponding source code are being moved
6864 @item directory @var{dirname} @dots{}
6865 @item dir @var{dirname} @dots{}
6866 Add directory @var{dirname} to the front of the source path. Several
6867 directory names may be given to this command, separated by @samp{:}
6868 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6869 part of absolute file names) or
6870 whitespace. You may specify a directory that is already in the source
6871 path; this moves it forward, so @value{GDBN} searches it sooner.
6875 @vindex $cdir@r{, convenience variable}
6876 @vindex $cwd@r{, convenience variable}
6877 @cindex compilation directory
6878 @cindex current directory
6879 @cindex working directory
6880 @cindex directory, current
6881 @cindex directory, compilation
6882 You can use the string @samp{$cdir} to refer to the compilation
6883 directory (if one is recorded), and @samp{$cwd} to refer to the current
6884 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6885 tracks the current working directory as it changes during your @value{GDBN}
6886 session, while the latter is immediately expanded to the current
6887 directory at the time you add an entry to the source path.
6890 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6892 @c RET-repeat for @code{directory} is explicitly disabled, but since
6893 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6895 @item set directories @var{path-list}
6896 @kindex set directories
6897 Set the source path to @var{path-list}.
6898 @samp{$cdir:$cwd} are added if missing.
6900 @item show directories
6901 @kindex show directories
6902 Print the source path: show which directories it contains.
6904 @anchor{set substitute-path}
6905 @item set substitute-path @var{from} @var{to}
6906 @kindex set substitute-path
6907 Define a source path substitution rule, and add it at the end of the
6908 current list of existing substitution rules. If a rule with the same
6909 @var{from} was already defined, then the old rule is also deleted.
6911 For example, if the file @file{/foo/bar/baz.c} was moved to
6912 @file{/mnt/cross/baz.c}, then the command
6915 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6919 will tell @value{GDBN} to replace @samp{/usr/src} with
6920 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6921 @file{baz.c} even though it was moved.
6923 In the case when more than one substitution rule have been defined,
6924 the rules are evaluated one by one in the order where they have been
6925 defined. The first one matching, if any, is selected to perform
6928 For instance, if we had entered the following commands:
6931 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6932 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6936 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6937 @file{/mnt/include/defs.h} by using the first rule. However, it would
6938 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6939 @file{/mnt/src/lib/foo.c}.
6942 @item unset substitute-path [path]
6943 @kindex unset substitute-path
6944 If a path is specified, search the current list of substitution rules
6945 for a rule that would rewrite that path. Delete that rule if found.
6946 A warning is emitted by the debugger if no rule could be found.
6948 If no path is specified, then all substitution rules are deleted.
6950 @item show substitute-path [path]
6951 @kindex show substitute-path
6952 If a path is specified, then print the source path substitution rule
6953 which would rewrite that path, if any.
6955 If no path is specified, then print all existing source path substitution
6960 If your source path is cluttered with directories that are no longer of
6961 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6962 versions of source. You can correct the situation as follows:
6966 Use @code{directory} with no argument to reset the source path to its default value.
6969 Use @code{directory} with suitable arguments to reinstall the
6970 directories you want in the source path. You can add all the
6971 directories in one command.
6975 @section Source and Machine Code
6976 @cindex source line and its code address
6978 You can use the command @code{info line} to map source lines to program
6979 addresses (and vice versa), and the command @code{disassemble} to display
6980 a range of addresses as machine instructions. You can use the command
6981 @code{set disassemble-next-line} to set whether to disassemble next
6982 source line when execution stops. When run under @sc{gnu} Emacs
6983 mode, the @code{info line} command causes the arrow to point to the
6984 line specified. Also, @code{info line} prints addresses in symbolic form as
6989 @item info line @var{linespec}
6990 Print the starting and ending addresses of the compiled code for
6991 source line @var{linespec}. You can specify source lines in any of
6992 the ways documented in @ref{Specify Location}.
6995 For example, we can use @code{info line} to discover the location of
6996 the object code for the first line of function
6997 @code{m4_changequote}:
6999 @c FIXME: I think this example should also show the addresses in
7000 @c symbolic form, as they usually would be displayed.
7002 (@value{GDBP}) info line m4_changequote
7003 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7007 @cindex code address and its source line
7008 We can also inquire (using @code{*@var{addr}} as the form for
7009 @var{linespec}) what source line covers a particular address:
7011 (@value{GDBP}) info line *0x63ff
7012 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7015 @cindex @code{$_} and @code{info line}
7016 @cindex @code{x} command, default address
7017 @kindex x@r{(examine), and} info line
7018 After @code{info line}, the default address for the @code{x} command
7019 is changed to the starting address of the line, so that @samp{x/i} is
7020 sufficient to begin examining the machine code (@pxref{Memory,
7021 ,Examining Memory}). Also, this address is saved as the value of the
7022 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7027 @cindex assembly instructions
7028 @cindex instructions, assembly
7029 @cindex machine instructions
7030 @cindex listing machine instructions
7032 @itemx disassemble /m
7033 @itemx disassemble /r
7034 This specialized command dumps a range of memory as machine
7035 instructions. It can also print mixed source+disassembly by specifying
7036 the @code{/m} modifier and print the raw instructions in hex as well as
7037 in symbolic form by specifying the @code{/r}.
7038 The default memory range is the function surrounding the
7039 program counter of the selected frame. A single argument to this
7040 command is a program counter value; @value{GDBN} dumps the function
7041 surrounding this value. When two arguments are given, they should
7042 be separated by a comma, possibly surrounded by whitespace. The
7043 arguments specify a range of addresses to dump, in one of two forms:
7046 @item @var{start},@var{end}
7047 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7048 @item @var{start},+@var{length}
7049 the addresses from @var{start} (inclusive) to
7050 @code{@var{start}+@var{length}} (exclusive).
7054 When 2 arguments are specified, the name of the function is also
7055 printed (since there could be several functions in the given range).
7057 The argument(s) can be any expression yielding a numeric value, such as
7058 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7060 If the range of memory being disassembled contains current program counter,
7061 the instruction at that location is shown with a @code{=>} marker.
7064 The following example shows the disassembly of a range of addresses of
7065 HP PA-RISC 2.0 code:
7068 (@value{GDBP}) disas 0x32c4, 0x32e4
7069 Dump of assembler code from 0x32c4 to 0x32e4:
7070 0x32c4 <main+204>: addil 0,dp
7071 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7072 0x32cc <main+212>: ldil 0x3000,r31
7073 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7074 0x32d4 <main+220>: ldo 0(r31),rp
7075 0x32d8 <main+224>: addil -0x800,dp
7076 0x32dc <main+228>: ldo 0x588(r1),r26
7077 0x32e0 <main+232>: ldil 0x3000,r31
7078 End of assembler dump.
7081 Here is an example showing mixed source+assembly for Intel x86, when the
7082 program is stopped just after function prologue:
7085 (@value{GDBP}) disas /m main
7086 Dump of assembler code for function main:
7088 0x08048330 <+0>: push %ebp
7089 0x08048331 <+1>: mov %esp,%ebp
7090 0x08048333 <+3>: sub $0x8,%esp
7091 0x08048336 <+6>: and $0xfffffff0,%esp
7092 0x08048339 <+9>: sub $0x10,%esp
7094 6 printf ("Hello.\n");
7095 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7096 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7100 0x08048348 <+24>: mov $0x0,%eax
7101 0x0804834d <+29>: leave
7102 0x0804834e <+30>: ret
7104 End of assembler dump.
7107 Here is another example showing raw instructions in hex for AMD x86-64,
7110 (gdb) disas /r 0x400281,+10
7111 Dump of assembler code from 0x400281 to 0x40028b:
7112 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7113 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7114 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7115 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7116 End of assembler dump.
7119 Some architectures have more than one commonly-used set of instruction
7120 mnemonics or other syntax.
7122 For programs that were dynamically linked and use shared libraries,
7123 instructions that call functions or branch to locations in the shared
7124 libraries might show a seemingly bogus location---it's actually a
7125 location of the relocation table. On some architectures, @value{GDBN}
7126 might be able to resolve these to actual function names.
7129 @kindex set disassembly-flavor
7130 @cindex Intel disassembly flavor
7131 @cindex AT&T disassembly flavor
7132 @item set disassembly-flavor @var{instruction-set}
7133 Select the instruction set to use when disassembling the
7134 program via the @code{disassemble} or @code{x/i} commands.
7136 Currently this command is only defined for the Intel x86 family. You
7137 can set @var{instruction-set} to either @code{intel} or @code{att}.
7138 The default is @code{att}, the AT&T flavor used by default by Unix
7139 assemblers for x86-based targets.
7141 @kindex show disassembly-flavor
7142 @item show disassembly-flavor
7143 Show the current setting of the disassembly flavor.
7147 @kindex set disassemble-next-line
7148 @kindex show disassemble-next-line
7149 @item set disassemble-next-line
7150 @itemx show disassemble-next-line
7151 Control whether or not @value{GDBN} will disassemble the next source
7152 line or instruction when execution stops. If ON, @value{GDBN} will
7153 display disassembly of the next source line when execution of the
7154 program being debugged stops. This is @emph{in addition} to
7155 displaying the source line itself, which @value{GDBN} always does if
7156 possible. If the next source line cannot be displayed for some reason
7157 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7158 info in the debug info), @value{GDBN} will display disassembly of the
7159 next @emph{instruction} instead of showing the next source line. If
7160 AUTO, @value{GDBN} will display disassembly of next instruction only
7161 if the source line cannot be displayed. This setting causes
7162 @value{GDBN} to display some feedback when you step through a function
7163 with no line info or whose source file is unavailable. The default is
7164 OFF, which means never display the disassembly of the next line or
7170 @chapter Examining Data
7172 @cindex printing data
7173 @cindex examining data
7176 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7177 @c document because it is nonstandard... Under Epoch it displays in a
7178 @c different window or something like that.
7179 The usual way to examine data in your program is with the @code{print}
7180 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7181 evaluates and prints the value of an expression of the language your
7182 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7183 Different Languages}). It may also print the expression using a
7184 Python-based pretty-printer (@pxref{Pretty Printing}).
7187 @item print @var{expr}
7188 @itemx print /@var{f} @var{expr}
7189 @var{expr} is an expression (in the source language). By default the
7190 value of @var{expr} is printed in a format appropriate to its data type;
7191 you can choose a different format by specifying @samp{/@var{f}}, where
7192 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7196 @itemx print /@var{f}
7197 @cindex reprint the last value
7198 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7199 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7200 conveniently inspect the same value in an alternative format.
7203 A more low-level way of examining data is with the @code{x} command.
7204 It examines data in memory at a specified address and prints it in a
7205 specified format. @xref{Memory, ,Examining Memory}.
7207 If you are interested in information about types, or about how the
7208 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7209 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7212 @cindex exploring hierarchical data structures
7214 Another way of examining values of expressions and type information is
7215 through the Python extension command @code{explore} (available only if
7216 the @value{GDBN} build is configured with @code{--with-python}). It
7217 offers an interactive way to start at the highest level (or, the most
7218 abstract level) of the data type of an expression (or, the data type
7219 itself) and explore all the way down to leaf scalar values/fields
7220 embedded in the higher level data types.
7223 @item explore @var{arg}
7224 @var{arg} is either an expression (in the source language), or a type
7225 visible in the current context of the program being debugged.
7228 The working of the @code{explore} command can be illustrated with an
7229 example. If a data type @code{struct ComplexStruct} is defined in your
7239 struct ComplexStruct
7241 struct SimpleStruct *ss_p;
7247 followed by variable declarations as
7250 struct SimpleStruct ss = @{ 10, 1.11 @};
7251 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7255 then, the value of the variable @code{cs} can be explored using the
7256 @code{explore} command as follows.
7260 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7261 the following fields:
7263 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7264 arr = <Enter 1 to explore this field of type `int [10]'>
7266 Enter the field number of choice:
7270 Since the fields of @code{cs} are not scalar values, you are being
7271 prompted to chose the field you want to explore. Let's say you choose
7272 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7273 pointer, you will be asked if it is pointing to a single value. From
7274 the declaration of @code{cs} above, it is indeed pointing to a single
7275 value, hence you enter @code{y}. If you enter @code{n}, then you will
7276 be asked if it were pointing to an array of values, in which case this
7277 field will be explored as if it were an array.
7280 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7281 Continue exploring it as a pointer to a single value [y/n]: y
7282 The value of `*(cs.ss_p)' is a struct/class of type `struct
7283 SimpleStruct' with the following fields:
7285 i = 10 .. (Value of type `int')
7286 d = 1.1100000000000001 .. (Value of type `double')
7288 Press enter to return to parent value:
7292 If the field @code{arr} of @code{cs} was chosen for exploration by
7293 entering @code{1} earlier, then since it is as array, you will be
7294 prompted to enter the index of the element in the array that you want
7298 `cs.arr' is an array of `int'.
7299 Enter the index of the element you want to explore in `cs.arr': 5
7301 `(cs.arr)[5]' is a scalar value of type `int'.
7305 Press enter to return to parent value:
7308 In general, at any stage of exploration, you can go deeper towards the
7309 leaf values by responding to the prompts appropriately, or hit the
7310 return key to return to the enclosing data structure (the @i{higher}
7311 level data structure).
7313 Similar to exploring values, you can use the @code{explore} command to
7314 explore types. Instead of specifying a value (which is typically a
7315 variable name or an expression valid in the current context of the
7316 program being debugged), you specify a type name. If you consider the
7317 same example as above, your can explore the type
7318 @code{struct ComplexStruct} by passing the argument
7319 @code{struct ComplexStruct} to the @code{explore} command.
7322 (gdb) explore struct ComplexStruct
7326 By responding to the prompts appropriately in the subsequent interactive
7327 session, you can explore the type @code{struct ComplexStruct} in a
7328 manner similar to how the value @code{cs} was explored in the above
7331 The @code{explore} command also has two sub-commands,
7332 @code{explore value} and @code{explore type}. The former sub-command is
7333 a way to explicitly specify that value exploration of the argument is
7334 being invoked, while the latter is a way to explicitly specify that type
7335 exploration of the argument is being invoked.
7338 @item explore value @var{expr}
7339 @cindex explore value
7340 This sub-command of @code{explore} explores the value of the
7341 expression @var{expr} (if @var{expr} is an expression valid in the
7342 current context of the program being debugged). The behavior of this
7343 command is identical to that of the behavior of the @code{explore}
7344 command being passed the argument @var{expr}.
7346 @item explore type @var{arg}
7347 @cindex explore type
7348 This sub-command of @code{explore} explores the type of @var{arg} (if
7349 @var{arg} is a type visible in the current context of program being
7350 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7351 is an expression valid in the current context of the program being
7352 debugged). If @var{arg} is a type, then the behavior of this command is
7353 identical to that of the @code{explore} command being passed the
7354 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7355 this command will be identical to that of the @code{explore} command
7356 being passed the type of @var{arg} as the argument.
7360 * Expressions:: Expressions
7361 * Ambiguous Expressions:: Ambiguous Expressions
7362 * Variables:: Program variables
7363 * Arrays:: Artificial arrays
7364 * Output Formats:: Output formats
7365 * Memory:: Examining memory
7366 * Auto Display:: Automatic display
7367 * Print Settings:: Print settings
7368 * Pretty Printing:: Python pretty printing
7369 * Value History:: Value history
7370 * Convenience Vars:: Convenience variables
7371 * Registers:: Registers
7372 * Floating Point Hardware:: Floating point hardware
7373 * Vector Unit:: Vector Unit
7374 * OS Information:: Auxiliary data provided by operating system
7375 * Memory Region Attributes:: Memory region attributes
7376 * Dump/Restore Files:: Copy between memory and a file
7377 * Core File Generation:: Cause a program dump its core
7378 * Character Sets:: Debugging programs that use a different
7379 character set than GDB does
7380 * Caching Remote Data:: Data caching for remote targets
7381 * Searching Memory:: Searching memory for a sequence of bytes
7385 @section Expressions
7388 @code{print} and many other @value{GDBN} commands accept an expression and
7389 compute its value. Any kind of constant, variable or operator defined
7390 by the programming language you are using is valid in an expression in
7391 @value{GDBN}. This includes conditional expressions, function calls,
7392 casts, and string constants. It also includes preprocessor macros, if
7393 you compiled your program to include this information; see
7396 @cindex arrays in expressions
7397 @value{GDBN} supports array constants in expressions input by
7398 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7399 you can use the command @code{print @{1, 2, 3@}} to create an array
7400 of three integers. If you pass an array to a function or assign it
7401 to a program variable, @value{GDBN} copies the array to memory that
7402 is @code{malloc}ed in the target program.
7404 Because C is so widespread, most of the expressions shown in examples in
7405 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7406 Languages}, for information on how to use expressions in other
7409 In this section, we discuss operators that you can use in @value{GDBN}
7410 expressions regardless of your programming language.
7412 @cindex casts, in expressions
7413 Casts are supported in all languages, not just in C, because it is so
7414 useful to cast a number into a pointer in order to examine a structure
7415 at that address in memory.
7416 @c FIXME: casts supported---Mod2 true?
7418 @value{GDBN} supports these operators, in addition to those common
7419 to programming languages:
7423 @samp{@@} is a binary operator for treating parts of memory as arrays.
7424 @xref{Arrays, ,Artificial Arrays}, for more information.
7427 @samp{::} allows you to specify a variable in terms of the file or
7428 function where it is defined. @xref{Variables, ,Program Variables}.
7430 @cindex @{@var{type}@}
7431 @cindex type casting memory
7432 @cindex memory, viewing as typed object
7433 @cindex casts, to view memory
7434 @item @{@var{type}@} @var{addr}
7435 Refers to an object of type @var{type} stored at address @var{addr} in
7436 memory. @var{addr} may be any expression whose value is an integer or
7437 pointer (but parentheses are required around binary operators, just as in
7438 a cast). This construct is allowed regardless of what kind of data is
7439 normally supposed to reside at @var{addr}.
7442 @node Ambiguous Expressions
7443 @section Ambiguous Expressions
7444 @cindex ambiguous expressions
7446 Expressions can sometimes contain some ambiguous elements. For instance,
7447 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7448 a single function name to be defined several times, for application in
7449 different contexts. This is called @dfn{overloading}. Another example
7450 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7451 templates and is typically instantiated several times, resulting in
7452 the same function name being defined in different contexts.
7454 In some cases and depending on the language, it is possible to adjust
7455 the expression to remove the ambiguity. For instance in C@t{++}, you
7456 can specify the signature of the function you want to break on, as in
7457 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7458 qualified name of your function often makes the expression unambiguous
7461 When an ambiguity that needs to be resolved is detected, the debugger
7462 has the capability to display a menu of numbered choices for each
7463 possibility, and then waits for the selection with the prompt @samp{>}.
7464 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7465 aborts the current command. If the command in which the expression was
7466 used allows more than one choice to be selected, the next option in the
7467 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7470 For example, the following session excerpt shows an attempt to set a
7471 breakpoint at the overloaded symbol @code{String::after}.
7472 We choose three particular definitions of that function name:
7474 @c FIXME! This is likely to change to show arg type lists, at least
7477 (@value{GDBP}) b String::after
7480 [2] file:String.cc; line number:867
7481 [3] file:String.cc; line number:860
7482 [4] file:String.cc; line number:875
7483 [5] file:String.cc; line number:853
7484 [6] file:String.cc; line number:846
7485 [7] file:String.cc; line number:735
7487 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7488 Breakpoint 2 at 0xb344: file String.cc, line 875.
7489 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7490 Multiple breakpoints were set.
7491 Use the "delete" command to delete unwanted
7498 @kindex set multiple-symbols
7499 @item set multiple-symbols @var{mode}
7500 @cindex multiple-symbols menu
7502 This option allows you to adjust the debugger behavior when an expression
7505 By default, @var{mode} is set to @code{all}. If the command with which
7506 the expression is used allows more than one choice, then @value{GDBN}
7507 automatically selects all possible choices. For instance, inserting
7508 a breakpoint on a function using an ambiguous name results in a breakpoint
7509 inserted on each possible match. However, if a unique choice must be made,
7510 then @value{GDBN} uses the menu to help you disambiguate the expression.
7511 For instance, printing the address of an overloaded function will result
7512 in the use of the menu.
7514 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7515 when an ambiguity is detected.
7517 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7518 an error due to the ambiguity and the command is aborted.
7520 @kindex show multiple-symbols
7521 @item show multiple-symbols
7522 Show the current value of the @code{multiple-symbols} setting.
7526 @section Program Variables
7528 The most common kind of expression to use is the name of a variable
7531 Variables in expressions are understood in the selected stack frame
7532 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7536 global (or file-static)
7543 visible according to the scope rules of the
7544 programming language from the point of execution in that frame
7547 @noindent This means that in the function
7562 you can examine and use the variable @code{a} whenever your program is
7563 executing within the function @code{foo}, but you can only use or
7564 examine the variable @code{b} while your program is executing inside
7565 the block where @code{b} is declared.
7567 @cindex variable name conflict
7568 There is an exception: you can refer to a variable or function whose
7569 scope is a single source file even if the current execution point is not
7570 in this file. But it is possible to have more than one such variable or
7571 function with the same name (in different source files). If that
7572 happens, referring to that name has unpredictable effects. If you wish,
7573 you can specify a static variable in a particular function or file by
7574 using the colon-colon (@code{::}) notation:
7576 @cindex colon-colon, context for variables/functions
7578 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7579 @cindex @code{::}, context for variables/functions
7582 @var{file}::@var{variable}
7583 @var{function}::@var{variable}
7587 Here @var{file} or @var{function} is the name of the context for the
7588 static @var{variable}. In the case of file names, you can use quotes to
7589 make sure @value{GDBN} parses the file name as a single word---for example,
7590 to print a global value of @code{x} defined in @file{f2.c}:
7593 (@value{GDBP}) p 'f2.c'::x
7596 The @code{::} notation is normally used for referring to
7597 static variables, since you typically disambiguate uses of local variables
7598 in functions by selecting the appropriate frame and using the
7599 simple name of the variable. However, you may also use this notation
7600 to refer to local variables in frames enclosing the selected frame:
7609 process (a); /* Stop here */
7620 For example, if there is a breakpoint at the commented line,
7621 here is what you might see
7622 when the program stops after executing the call @code{bar(0)}:
7627 (@value{GDBP}) p bar::a
7630 #2 0x080483d0 in foo (a=5) at foobar.c:12
7633 (@value{GDBP}) p bar::a
7637 @cindex C@t{++} scope resolution
7638 These uses of @samp{::} are very rarely in conflict with the very similar
7639 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7640 scope resolution operator in @value{GDBN} expressions.
7641 @c FIXME: Um, so what happens in one of those rare cases where it's in
7644 @cindex wrong values
7645 @cindex variable values, wrong
7646 @cindex function entry/exit, wrong values of variables
7647 @cindex optimized code, wrong values of variables
7649 @emph{Warning:} Occasionally, a local variable may appear to have the
7650 wrong value at certain points in a function---just after entry to a new
7651 scope, and just before exit.
7653 You may see this problem when you are stepping by machine instructions.
7654 This is because, on most machines, it takes more than one instruction to
7655 set up a stack frame (including local variable definitions); if you are
7656 stepping by machine instructions, variables may appear to have the wrong
7657 values until the stack frame is completely built. On exit, it usually
7658 also takes more than one machine instruction to destroy a stack frame;
7659 after you begin stepping through that group of instructions, local
7660 variable definitions may be gone.
7662 This may also happen when the compiler does significant optimizations.
7663 To be sure of always seeing accurate values, turn off all optimization
7666 @cindex ``No symbol "foo" in current context''
7667 Another possible effect of compiler optimizations is to optimize
7668 unused variables out of existence, or assign variables to registers (as
7669 opposed to memory addresses). Depending on the support for such cases
7670 offered by the debug info format used by the compiler, @value{GDBN}
7671 might not be able to display values for such local variables. If that
7672 happens, @value{GDBN} will print a message like this:
7675 No symbol "foo" in current context.
7678 To solve such problems, either recompile without optimizations, or use a
7679 different debug info format, if the compiler supports several such
7680 formats. @xref{Compilation}, for more information on choosing compiler
7681 options. @xref{C, ,C and C@t{++}}, for more information about debug
7682 info formats that are best suited to C@t{++} programs.
7684 If you ask to print an object whose contents are unknown to
7685 @value{GDBN}, e.g., because its data type is not completely specified
7686 by the debug information, @value{GDBN} will say @samp{<incomplete
7687 type>}. @xref{Symbols, incomplete type}, for more about this.
7689 If you append @kbd{@@entry} string to a function parameter name you get its
7690 value at the time the function got called. If the value is not available an
7691 error message is printed. Entry values are available only with some compilers.
7692 Entry values are normally also printed at the function parameter list according
7693 to @ref{set print entry-values}.
7696 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7702 (gdb) print i@@entry
7706 Strings are identified as arrays of @code{char} values without specified
7707 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7708 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7709 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7710 defines literal string type @code{"char"} as @code{char} without a sign.
7715 signed char var1[] = "A";
7718 You get during debugging
7723 $2 = @{65 'A', 0 '\0'@}
7727 @section Artificial Arrays
7729 @cindex artificial array
7731 @kindex @@@r{, referencing memory as an array}
7732 It is often useful to print out several successive objects of the
7733 same type in memory; a section of an array, or an array of
7734 dynamically determined size for which only a pointer exists in the
7737 You can do this by referring to a contiguous span of memory as an
7738 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7739 operand of @samp{@@} should be the first element of the desired array
7740 and be an individual object. The right operand should be the desired length
7741 of the array. The result is an array value whose elements are all of
7742 the type of the left argument. The first element is actually the left
7743 argument; the second element comes from bytes of memory immediately
7744 following those that hold the first element, and so on. Here is an
7745 example. If a program says
7748 int *array = (int *) malloc (len * sizeof (int));
7752 you can print the contents of @code{array} with
7758 The left operand of @samp{@@} must reside in memory. Array values made
7759 with @samp{@@} in this way behave just like other arrays in terms of
7760 subscripting, and are coerced to pointers when used in expressions.
7761 Artificial arrays most often appear in expressions via the value history
7762 (@pxref{Value History, ,Value History}), after printing one out.
7764 Another way to create an artificial array is to use a cast.
7765 This re-interprets a value as if it were an array.
7766 The value need not be in memory:
7768 (@value{GDBP}) p/x (short[2])0x12345678
7769 $1 = @{0x1234, 0x5678@}
7772 As a convenience, if you leave the array length out (as in
7773 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7774 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7776 (@value{GDBP}) p/x (short[])0x12345678
7777 $2 = @{0x1234, 0x5678@}
7780 Sometimes the artificial array mechanism is not quite enough; in
7781 moderately complex data structures, the elements of interest may not
7782 actually be adjacent---for example, if you are interested in the values
7783 of pointers in an array. One useful work-around in this situation is
7784 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7785 Variables}) as a counter in an expression that prints the first
7786 interesting value, and then repeat that expression via @key{RET}. For
7787 instance, suppose you have an array @code{dtab} of pointers to
7788 structures, and you are interested in the values of a field @code{fv}
7789 in each structure. Here is an example of what you might type:
7799 @node Output Formats
7800 @section Output Formats
7802 @cindex formatted output
7803 @cindex output formats
7804 By default, @value{GDBN} prints a value according to its data type. Sometimes
7805 this is not what you want. For example, you might want to print a number
7806 in hex, or a pointer in decimal. Or you might want to view data in memory
7807 at a certain address as a character string or as an instruction. To do
7808 these things, specify an @dfn{output format} when you print a value.
7810 The simplest use of output formats is to say how to print a value
7811 already computed. This is done by starting the arguments of the
7812 @code{print} command with a slash and a format letter. The format
7813 letters supported are:
7817 Regard the bits of the value as an integer, and print the integer in
7821 Print as integer in signed decimal.
7824 Print as integer in unsigned decimal.
7827 Print as integer in octal.
7830 Print as integer in binary. The letter @samp{t} stands for ``two''.
7831 @footnote{@samp{b} cannot be used because these format letters are also
7832 used with the @code{x} command, where @samp{b} stands for ``byte'';
7833 see @ref{Memory,,Examining Memory}.}
7836 @cindex unknown address, locating
7837 @cindex locate address
7838 Print as an address, both absolute in hexadecimal and as an offset from
7839 the nearest preceding symbol. You can use this format used to discover
7840 where (in what function) an unknown address is located:
7843 (@value{GDBP}) p/a 0x54320
7844 $3 = 0x54320 <_initialize_vx+396>
7848 The command @code{info symbol 0x54320} yields similar results.
7849 @xref{Symbols, info symbol}.
7852 Regard as an integer and print it as a character constant. This
7853 prints both the numerical value and its character representation. The
7854 character representation is replaced with the octal escape @samp{\nnn}
7855 for characters outside the 7-bit @sc{ascii} range.
7857 Without this format, @value{GDBN} displays @code{char},
7858 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7859 constants. Single-byte members of vectors are displayed as integer
7863 Regard the bits of the value as a floating point number and print
7864 using typical floating point syntax.
7867 @cindex printing strings
7868 @cindex printing byte arrays
7869 Regard as a string, if possible. With this format, pointers to single-byte
7870 data are displayed as null-terminated strings and arrays of single-byte data
7871 are displayed as fixed-length strings. Other values are displayed in their
7874 Without this format, @value{GDBN} displays pointers to and arrays of
7875 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7876 strings. Single-byte members of a vector are displayed as an integer
7880 @cindex raw printing
7881 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7882 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7883 Printing}). This typically results in a higher-level display of the
7884 value's contents. The @samp{r} format bypasses any Python
7885 pretty-printer which might exist.
7888 For example, to print the program counter in hex (@pxref{Registers}), type
7895 Note that no space is required before the slash; this is because command
7896 names in @value{GDBN} cannot contain a slash.
7898 To reprint the last value in the value history with a different format,
7899 you can use the @code{print} command with just a format and no
7900 expression. For example, @samp{p/x} reprints the last value in hex.
7903 @section Examining Memory
7905 You can use the command @code{x} (for ``examine'') to examine memory in
7906 any of several formats, independently of your program's data types.
7908 @cindex examining memory
7910 @kindex x @r{(examine memory)}
7911 @item x/@var{nfu} @var{addr}
7914 Use the @code{x} command to examine memory.
7917 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7918 much memory to display and how to format it; @var{addr} is an
7919 expression giving the address where you want to start displaying memory.
7920 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7921 Several commands set convenient defaults for @var{addr}.
7924 @item @var{n}, the repeat count
7925 The repeat count is a decimal integer; the default is 1. It specifies
7926 how much memory (counting by units @var{u}) to display.
7927 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7930 @item @var{f}, the display format
7931 The display format is one of the formats used by @code{print}
7932 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7933 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7934 The default is @samp{x} (hexadecimal) initially. The default changes
7935 each time you use either @code{x} or @code{print}.
7937 @item @var{u}, the unit size
7938 The unit size is any of
7944 Halfwords (two bytes).
7946 Words (four bytes). This is the initial default.
7948 Giant words (eight bytes).
7951 Each time you specify a unit size with @code{x}, that size becomes the
7952 default unit the next time you use @code{x}. For the @samp{i} format,
7953 the unit size is ignored and is normally not written. For the @samp{s} format,
7954 the unit size defaults to @samp{b}, unless it is explicitly given.
7955 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7956 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7957 Note that the results depend on the programming language of the
7958 current compilation unit. If the language is C, the @samp{s}
7959 modifier will use the UTF-16 encoding while @samp{w} will use
7960 UTF-32. The encoding is set by the programming language and cannot
7963 @item @var{addr}, starting display address
7964 @var{addr} is the address where you want @value{GDBN} to begin displaying
7965 memory. The expression need not have a pointer value (though it may);
7966 it is always interpreted as an integer address of a byte of memory.
7967 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7968 @var{addr} is usually just after the last address examined---but several
7969 other commands also set the default address: @code{info breakpoints} (to
7970 the address of the last breakpoint listed), @code{info line} (to the
7971 starting address of a line), and @code{print} (if you use it to display
7972 a value from memory).
7975 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7976 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7977 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7978 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7979 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7981 Since the letters indicating unit sizes are all distinct from the
7982 letters specifying output formats, you do not have to remember whether
7983 unit size or format comes first; either order works. The output
7984 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7985 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7987 Even though the unit size @var{u} is ignored for the formats @samp{s}
7988 and @samp{i}, you might still want to use a count @var{n}; for example,
7989 @samp{3i} specifies that you want to see three machine instructions,
7990 including any operands. For convenience, especially when used with
7991 the @code{display} command, the @samp{i} format also prints branch delay
7992 slot instructions, if any, beyond the count specified, which immediately
7993 follow the last instruction that is within the count. The command
7994 @code{disassemble} gives an alternative way of inspecting machine
7995 instructions; see @ref{Machine Code,,Source and Machine Code}.
7997 All the defaults for the arguments to @code{x} are designed to make it
7998 easy to continue scanning memory with minimal specifications each time
7999 you use @code{x}. For example, after you have inspected three machine
8000 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8001 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8002 the repeat count @var{n} is used again; the other arguments default as
8003 for successive uses of @code{x}.
8005 When examining machine instructions, the instruction at current program
8006 counter is shown with a @code{=>} marker. For example:
8009 (@value{GDBP}) x/5i $pc-6
8010 0x804837f <main+11>: mov %esp,%ebp
8011 0x8048381 <main+13>: push %ecx
8012 0x8048382 <main+14>: sub $0x4,%esp
8013 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8014 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8017 @cindex @code{$_}, @code{$__}, and value history
8018 The addresses and contents printed by the @code{x} command are not saved
8019 in the value history because there is often too much of them and they
8020 would get in the way. Instead, @value{GDBN} makes these values available for
8021 subsequent use in expressions as values of the convenience variables
8022 @code{$_} and @code{$__}. After an @code{x} command, the last address
8023 examined is available for use in expressions in the convenience variable
8024 @code{$_}. The contents of that address, as examined, are available in
8025 the convenience variable @code{$__}.
8027 If the @code{x} command has a repeat count, the address and contents saved
8028 are from the last memory unit printed; this is not the same as the last
8029 address printed if several units were printed on the last line of output.
8031 @cindex remote memory comparison
8032 @cindex verify remote memory image
8033 When you are debugging a program running on a remote target machine
8034 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8035 remote machine's memory against the executable file you downloaded to
8036 the target. The @code{compare-sections} command is provided for such
8040 @kindex compare-sections
8041 @item compare-sections @r{[}@var{section-name}@r{]}
8042 Compare the data of a loadable section @var{section-name} in the
8043 executable file of the program being debugged with the same section in
8044 the remote machine's memory, and report any mismatches. With no
8045 arguments, compares all loadable sections. This command's
8046 availability depends on the target's support for the @code{"qCRC"}
8051 @section Automatic Display
8052 @cindex automatic display
8053 @cindex display of expressions
8055 If you find that you want to print the value of an expression frequently
8056 (to see how it changes), you might want to add it to the @dfn{automatic
8057 display list} so that @value{GDBN} prints its value each time your program stops.
8058 Each expression added to the list is given a number to identify it;
8059 to remove an expression from the list, you specify that number.
8060 The automatic display looks like this:
8064 3: bar[5] = (struct hack *) 0x3804
8068 This display shows item numbers, expressions and their current values. As with
8069 displays you request manually using @code{x} or @code{print}, you can
8070 specify the output format you prefer; in fact, @code{display} decides
8071 whether to use @code{print} or @code{x} depending your format
8072 specification---it uses @code{x} if you specify either the @samp{i}
8073 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8077 @item display @var{expr}
8078 Add the expression @var{expr} to the list of expressions to display
8079 each time your program stops. @xref{Expressions, ,Expressions}.
8081 @code{display} does not repeat if you press @key{RET} again after using it.
8083 @item display/@var{fmt} @var{expr}
8084 For @var{fmt} specifying only a display format and not a size or
8085 count, add the expression @var{expr} to the auto-display list but
8086 arrange to display it each time in the specified format @var{fmt}.
8087 @xref{Output Formats,,Output Formats}.
8089 @item display/@var{fmt} @var{addr}
8090 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8091 number of units, add the expression @var{addr} as a memory address to
8092 be examined each time your program stops. Examining means in effect
8093 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8096 For example, @samp{display/i $pc} can be helpful, to see the machine
8097 instruction about to be executed each time execution stops (@samp{$pc}
8098 is a common name for the program counter; @pxref{Registers, ,Registers}).
8101 @kindex delete display
8103 @item undisplay @var{dnums}@dots{}
8104 @itemx delete display @var{dnums}@dots{}
8105 Remove items from the list of expressions to display. Specify the
8106 numbers of the displays that you want affected with the command
8107 argument @var{dnums}. It can be a single display number, one of the
8108 numbers shown in the first field of the @samp{info display} display;
8109 or it could be a range of display numbers, as in @code{2-4}.
8111 @code{undisplay} does not repeat if you press @key{RET} after using it.
8112 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8114 @kindex disable display
8115 @item disable display @var{dnums}@dots{}
8116 Disable the display of item numbers @var{dnums}. A disabled display
8117 item is not printed automatically, but is not forgotten. It may be
8118 enabled again later. Specify the numbers of the displays that you
8119 want affected with the command argument @var{dnums}. It can be a
8120 single display number, one of the numbers shown in the first field of
8121 the @samp{info display} display; or it could be a range of display
8122 numbers, as in @code{2-4}.
8124 @kindex enable display
8125 @item enable display @var{dnums}@dots{}
8126 Enable display of item numbers @var{dnums}. It becomes effective once
8127 again in auto display of its expression, until you specify otherwise.
8128 Specify the numbers of the displays that you want affected with the
8129 command argument @var{dnums}. It can be a single display number, one
8130 of the numbers shown in the first field of the @samp{info display}
8131 display; or it could be a range of display numbers, as in @code{2-4}.
8134 Display the current values of the expressions on the list, just as is
8135 done when your program stops.
8137 @kindex info display
8139 Print the list of expressions previously set up to display
8140 automatically, each one with its item number, but without showing the
8141 values. This includes disabled expressions, which are marked as such.
8142 It also includes expressions which would not be displayed right now
8143 because they refer to automatic variables not currently available.
8146 @cindex display disabled out of scope
8147 If a display expression refers to local variables, then it does not make
8148 sense outside the lexical context for which it was set up. Such an
8149 expression is disabled when execution enters a context where one of its
8150 variables is not defined. For example, if you give the command
8151 @code{display last_char} while inside a function with an argument
8152 @code{last_char}, @value{GDBN} displays this argument while your program
8153 continues to stop inside that function. When it stops elsewhere---where
8154 there is no variable @code{last_char}---the display is disabled
8155 automatically. The next time your program stops where @code{last_char}
8156 is meaningful, you can enable the display expression once again.
8158 @node Print Settings
8159 @section Print Settings
8161 @cindex format options
8162 @cindex print settings
8163 @value{GDBN} provides the following ways to control how arrays, structures,
8164 and symbols are printed.
8167 These settings are useful for debugging programs in any language:
8171 @item set print address
8172 @itemx set print address on
8173 @cindex print/don't print memory addresses
8174 @value{GDBN} prints memory addresses showing the location of stack
8175 traces, structure values, pointer values, breakpoints, and so forth,
8176 even when it also displays the contents of those addresses. The default
8177 is @code{on}. For example, this is what a stack frame display looks like with
8178 @code{set print address on}:
8183 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8185 530 if (lquote != def_lquote)
8189 @item set print address off
8190 Do not print addresses when displaying their contents. For example,
8191 this is the same stack frame displayed with @code{set print address off}:
8195 (@value{GDBP}) set print addr off
8197 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8198 530 if (lquote != def_lquote)
8202 You can use @samp{set print address off} to eliminate all machine
8203 dependent displays from the @value{GDBN} interface. For example, with
8204 @code{print address off}, you should get the same text for backtraces on
8205 all machines---whether or not they involve pointer arguments.
8208 @item show print address
8209 Show whether or not addresses are to be printed.
8212 When @value{GDBN} prints a symbolic address, it normally prints the
8213 closest earlier symbol plus an offset. If that symbol does not uniquely
8214 identify the address (for example, it is a name whose scope is a single
8215 source file), you may need to clarify. One way to do this is with
8216 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8217 you can set @value{GDBN} to print the source file and line number when
8218 it prints a symbolic address:
8221 @item set print symbol-filename on
8222 @cindex source file and line of a symbol
8223 @cindex symbol, source file and line
8224 Tell @value{GDBN} to print the source file name and line number of a
8225 symbol in the symbolic form of an address.
8227 @item set print symbol-filename off
8228 Do not print source file name and line number of a symbol. This is the
8231 @item show print symbol-filename
8232 Show whether or not @value{GDBN} will print the source file name and
8233 line number of a symbol in the symbolic form of an address.
8236 Another situation where it is helpful to show symbol filenames and line
8237 numbers is when disassembling code; @value{GDBN} shows you the line
8238 number and source file that corresponds to each instruction.
8240 Also, you may wish to see the symbolic form only if the address being
8241 printed is reasonably close to the closest earlier symbol:
8244 @item set print max-symbolic-offset @var{max-offset}
8245 @cindex maximum value for offset of closest symbol
8246 Tell @value{GDBN} to only display the symbolic form of an address if the
8247 offset between the closest earlier symbol and the address is less than
8248 @var{max-offset}. The default is 0, which tells @value{GDBN}
8249 to always print the symbolic form of an address if any symbol precedes it.
8251 @item show print max-symbolic-offset
8252 Ask how large the maximum offset is that @value{GDBN} prints in a
8256 @cindex wild pointer, interpreting
8257 @cindex pointer, finding referent
8258 If you have a pointer and you are not sure where it points, try
8259 @samp{set print symbol-filename on}. Then you can determine the name
8260 and source file location of the variable where it points, using
8261 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8262 For example, here @value{GDBN} shows that a variable @code{ptt} points
8263 at another variable @code{t}, defined in @file{hi2.c}:
8266 (@value{GDBP}) set print symbol-filename on
8267 (@value{GDBP}) p/a ptt
8268 $4 = 0xe008 <t in hi2.c>
8272 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8273 does not show the symbol name and filename of the referent, even with
8274 the appropriate @code{set print} options turned on.
8277 Other settings control how different kinds of objects are printed:
8280 @item set print array
8281 @itemx set print array on
8282 @cindex pretty print arrays
8283 Pretty print arrays. This format is more convenient to read,
8284 but uses more space. The default is off.
8286 @item set print array off
8287 Return to compressed format for arrays.
8289 @item show print array
8290 Show whether compressed or pretty format is selected for displaying
8293 @cindex print array indexes
8294 @item set print array-indexes
8295 @itemx set print array-indexes on
8296 Print the index of each element when displaying arrays. May be more
8297 convenient to locate a given element in the array or quickly find the
8298 index of a given element in that printed array. The default is off.
8300 @item set print array-indexes off
8301 Stop printing element indexes when displaying arrays.
8303 @item show print array-indexes
8304 Show whether the index of each element is printed when displaying
8307 @item set print elements @var{number-of-elements}
8308 @cindex number of array elements to print
8309 @cindex limit on number of printed array elements
8310 Set a limit on how many elements of an array @value{GDBN} will print.
8311 If @value{GDBN} is printing a large array, it stops printing after it has
8312 printed the number of elements set by the @code{set print elements} command.
8313 This limit also applies to the display of strings.
8314 When @value{GDBN} starts, this limit is set to 200.
8315 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8317 @item show print elements
8318 Display the number of elements of a large array that @value{GDBN} will print.
8319 If the number is 0, then the printing is unlimited.
8321 @item set print frame-arguments @var{value}
8322 @kindex set print frame-arguments
8323 @cindex printing frame argument values
8324 @cindex print all frame argument values
8325 @cindex print frame argument values for scalars only
8326 @cindex do not print frame argument values
8327 This command allows to control how the values of arguments are printed
8328 when the debugger prints a frame (@pxref{Frames}). The possible
8333 The values of all arguments are printed.
8336 Print the value of an argument only if it is a scalar. The value of more
8337 complex arguments such as arrays, structures, unions, etc, is replaced
8338 by @code{@dots{}}. This is the default. Here is an example where
8339 only scalar arguments are shown:
8342 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8347 None of the argument values are printed. Instead, the value of each argument
8348 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8351 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8356 By default, only scalar arguments are printed. This command can be used
8357 to configure the debugger to print the value of all arguments, regardless
8358 of their type. However, it is often advantageous to not print the value
8359 of more complex parameters. For instance, it reduces the amount of
8360 information printed in each frame, making the backtrace more readable.
8361 Also, it improves performance when displaying Ada frames, because
8362 the computation of large arguments can sometimes be CPU-intensive,
8363 especially in large applications. Setting @code{print frame-arguments}
8364 to @code{scalars} (the default) or @code{none} avoids this computation,
8365 thus speeding up the display of each Ada frame.
8367 @item show print frame-arguments
8368 Show how the value of arguments should be displayed when printing a frame.
8370 @anchor{set print entry-values}
8371 @item set print entry-values @var{value}
8372 @kindex set print entry-values
8373 Set printing of frame argument values at function entry. In some cases
8374 @value{GDBN} can determine the value of function argument which was passed by
8375 the function caller, even if the value was modified inside the called function
8376 and therefore is different. With optimized code, the current value could be
8377 unavailable, but the entry value may still be known.
8379 The default value is @code{default} (see below for its description). Older
8380 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8381 this feature will behave in the @code{default} setting the same way as with the
8384 This functionality is currently supported only by DWARF 2 debugging format and
8385 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8386 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8389 The @var{value} parameter can be one of the following:
8393 Print only actual parameter values, never print values from function entry
8397 #0 different (val=6)
8398 #0 lost (val=<optimized out>)
8400 #0 invalid (val=<optimized out>)
8404 Print only parameter values from function entry point. The actual parameter
8405 values are never printed.
8407 #0 equal (val@@entry=5)
8408 #0 different (val@@entry=5)
8409 #0 lost (val@@entry=5)
8410 #0 born (val@@entry=<optimized out>)
8411 #0 invalid (val@@entry=<optimized out>)
8415 Print only parameter values from function entry point. If value from function
8416 entry point is not known while the actual value is known, print the actual
8417 value for such parameter.
8419 #0 equal (val@@entry=5)
8420 #0 different (val@@entry=5)
8421 #0 lost (val@@entry=5)
8423 #0 invalid (val@@entry=<optimized out>)
8427 Print actual parameter values. If actual parameter value is not known while
8428 value from function entry point is known, print the entry point value for such
8432 #0 different (val=6)
8433 #0 lost (val@@entry=5)
8435 #0 invalid (val=<optimized out>)
8439 Always print both the actual parameter value and its value from function entry
8440 point, even if values of one or both are not available due to compiler
8443 #0 equal (val=5, val@@entry=5)
8444 #0 different (val=6, val@@entry=5)
8445 #0 lost (val=<optimized out>, val@@entry=5)
8446 #0 born (val=10, val@@entry=<optimized out>)
8447 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8451 Print the actual parameter value if it is known and also its value from
8452 function entry point if it is known. If neither is known, print for the actual
8453 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8454 values are known and identical, print the shortened
8455 @code{param=param@@entry=VALUE} notation.
8457 #0 equal (val=val@@entry=5)
8458 #0 different (val=6, val@@entry=5)
8459 #0 lost (val@@entry=5)
8461 #0 invalid (val=<optimized out>)
8465 Always print the actual parameter value. Print also its value from function
8466 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8467 if both values are known and identical, print the shortened
8468 @code{param=param@@entry=VALUE} notation.
8470 #0 equal (val=val@@entry=5)
8471 #0 different (val=6, val@@entry=5)
8472 #0 lost (val=<optimized out>, val@@entry=5)
8474 #0 invalid (val=<optimized out>)
8478 For analysis messages on possible failures of frame argument values at function
8479 entry resolution see @ref{set debug entry-values}.
8481 @item show print entry-values
8482 Show the method being used for printing of frame argument values at function
8485 @item set print repeats
8486 @cindex repeated array elements
8487 Set the threshold for suppressing display of repeated array
8488 elements. When the number of consecutive identical elements of an
8489 array exceeds the threshold, @value{GDBN} prints the string
8490 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8491 identical repetitions, instead of displaying the identical elements
8492 themselves. Setting the threshold to zero will cause all elements to
8493 be individually printed. The default threshold is 10.
8495 @item show print repeats
8496 Display the current threshold for printing repeated identical
8499 @item set print null-stop
8500 @cindex @sc{null} elements in arrays
8501 Cause @value{GDBN} to stop printing the characters of an array when the first
8502 @sc{null} is encountered. This is useful when large arrays actually
8503 contain only short strings.
8506 @item show print null-stop
8507 Show whether @value{GDBN} stops printing an array on the first
8508 @sc{null} character.
8510 @item set print pretty on
8511 @cindex print structures in indented form
8512 @cindex indentation in structure display
8513 Cause @value{GDBN} to print structures in an indented format with one member
8514 per line, like this:
8529 @item set print pretty off
8530 Cause @value{GDBN} to print structures in a compact format, like this:
8534 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8535 meat = 0x54 "Pork"@}
8540 This is the default format.
8542 @item show print pretty
8543 Show which format @value{GDBN} is using to print structures.
8545 @item set print sevenbit-strings on
8546 @cindex eight-bit characters in strings
8547 @cindex octal escapes in strings
8548 Print using only seven-bit characters; if this option is set,
8549 @value{GDBN} displays any eight-bit characters (in strings or
8550 character values) using the notation @code{\}@var{nnn}. This setting is
8551 best if you are working in English (@sc{ascii}) and you use the
8552 high-order bit of characters as a marker or ``meta'' bit.
8554 @item set print sevenbit-strings off
8555 Print full eight-bit characters. This allows the use of more
8556 international character sets, and is the default.
8558 @item show print sevenbit-strings
8559 Show whether or not @value{GDBN} is printing only seven-bit characters.
8561 @item set print union on
8562 @cindex unions in structures, printing
8563 Tell @value{GDBN} to print unions which are contained in structures
8564 and other unions. This is the default setting.
8566 @item set print union off
8567 Tell @value{GDBN} not to print unions which are contained in
8568 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8571 @item show print union
8572 Ask @value{GDBN} whether or not it will print unions which are contained in
8573 structures and other unions.
8575 For example, given the declarations
8578 typedef enum @{Tree, Bug@} Species;
8579 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8580 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8591 struct thing foo = @{Tree, @{Acorn@}@};
8595 with @code{set print union on} in effect @samp{p foo} would print
8598 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8602 and with @code{set print union off} in effect it would print
8605 $1 = @{it = Tree, form = @{...@}@}
8609 @code{set print union} affects programs written in C-like languages
8615 These settings are of interest when debugging C@t{++} programs:
8618 @cindex demangling C@t{++} names
8619 @item set print demangle
8620 @itemx set print demangle on
8621 Print C@t{++} names in their source form rather than in the encoded
8622 (``mangled'') form passed to the assembler and linker for type-safe
8623 linkage. The default is on.
8625 @item show print demangle
8626 Show whether C@t{++} names are printed in mangled or demangled form.
8628 @item set print asm-demangle
8629 @itemx set print asm-demangle on
8630 Print C@t{++} names in their source form rather than their mangled form, even
8631 in assembler code printouts such as instruction disassemblies.
8634 @item show print asm-demangle
8635 Show whether C@t{++} names in assembly listings are printed in mangled
8638 @cindex C@t{++} symbol decoding style
8639 @cindex symbol decoding style, C@t{++}
8640 @kindex set demangle-style
8641 @item set demangle-style @var{style}
8642 Choose among several encoding schemes used by different compilers to
8643 represent C@t{++} names. The choices for @var{style} are currently:
8647 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8650 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8651 This is the default.
8654 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8657 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8660 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8661 @strong{Warning:} this setting alone is not sufficient to allow
8662 debugging @code{cfront}-generated executables. @value{GDBN} would
8663 require further enhancement to permit that.
8666 If you omit @var{style}, you will see a list of possible formats.
8668 @item show demangle-style
8669 Display the encoding style currently in use for decoding C@t{++} symbols.
8671 @item set print object
8672 @itemx set print object on
8673 @cindex derived type of an object, printing
8674 @cindex display derived types
8675 When displaying a pointer to an object, identify the @emph{actual}
8676 (derived) type of the object rather than the @emph{declared} type, using
8677 the virtual function table. Note that the virtual function table is
8678 required---this feature can only work for objects that have run-time
8679 type identification; a single virtual method in the object's declared
8680 type is sufficient. Note that this setting is also taken into account when
8681 working with variable objects via MI (@pxref{GDB/MI}).
8683 @item set print object off
8684 Display only the declared type of objects, without reference to the
8685 virtual function table. This is the default setting.
8687 @item show print object
8688 Show whether actual, or declared, object types are displayed.
8690 @item set print static-members
8691 @itemx set print static-members on
8692 @cindex static members of C@t{++} objects
8693 Print static members when displaying a C@t{++} object. The default is on.
8695 @item set print static-members off
8696 Do not print static members when displaying a C@t{++} object.
8698 @item show print static-members
8699 Show whether C@t{++} static members are printed or not.
8701 @item set print pascal_static-members
8702 @itemx set print pascal_static-members on
8703 @cindex static members of Pascal objects
8704 @cindex Pascal objects, static members display
8705 Print static members when displaying a Pascal object. The default is on.
8707 @item set print pascal_static-members off
8708 Do not print static members when displaying a Pascal object.
8710 @item show print pascal_static-members
8711 Show whether Pascal static members are printed or not.
8713 @c These don't work with HP ANSI C++ yet.
8714 @item set print vtbl
8715 @itemx set print vtbl on
8716 @cindex pretty print C@t{++} virtual function tables
8717 @cindex virtual functions (C@t{++}) display
8718 @cindex VTBL display
8719 Pretty print C@t{++} virtual function tables. The default is off.
8720 (The @code{vtbl} commands do not work on programs compiled with the HP
8721 ANSI C@t{++} compiler (@code{aCC}).)
8723 @item set print vtbl off
8724 Do not pretty print C@t{++} virtual function tables.
8726 @item show print vtbl
8727 Show whether C@t{++} virtual function tables are pretty printed, or not.
8730 @node Pretty Printing
8731 @section Pretty Printing
8733 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8734 Python code. It greatly simplifies the display of complex objects. This
8735 mechanism works for both MI and the CLI.
8738 * Pretty-Printer Introduction:: Introduction to pretty-printers
8739 * Pretty-Printer Example:: An example pretty-printer
8740 * Pretty-Printer Commands:: Pretty-printer commands
8743 @node Pretty-Printer Introduction
8744 @subsection Pretty-Printer Introduction
8746 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8747 registered for the value. If there is then @value{GDBN} invokes the
8748 pretty-printer to print the value. Otherwise the value is printed normally.
8750 Pretty-printers are normally named. This makes them easy to manage.
8751 The @samp{info pretty-printer} command will list all the installed
8752 pretty-printers with their names.
8753 If a pretty-printer can handle multiple data types, then its
8754 @dfn{subprinters} are the printers for the individual data types.
8755 Each such subprinter has its own name.
8756 The format of the name is @var{printer-name};@var{subprinter-name}.
8758 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8759 Typically they are automatically loaded and registered when the corresponding
8760 debug information is loaded, thus making them available without having to
8761 do anything special.
8763 There are three places where a pretty-printer can be registered.
8767 Pretty-printers registered globally are available when debugging
8771 Pretty-printers registered with a program space are available only
8772 when debugging that program.
8773 @xref{Progspaces In Python}, for more details on program spaces in Python.
8776 Pretty-printers registered with an objfile are loaded and unloaded
8777 with the corresponding objfile (e.g., shared library).
8778 @xref{Objfiles In Python}, for more details on objfiles in Python.
8781 @xref{Selecting Pretty-Printers}, for further information on how
8782 pretty-printers are selected,
8784 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8787 @node Pretty-Printer Example
8788 @subsection Pretty-Printer Example
8790 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8793 (@value{GDBP}) print s
8795 static npos = 4294967295,
8797 <std::allocator<char>> = @{
8798 <__gnu_cxx::new_allocator<char>> = @{
8799 <No data fields>@}, <No data fields>
8801 members of std::basic_string<char, std::char_traits<char>,
8802 std::allocator<char> >::_Alloc_hider:
8803 _M_p = 0x804a014 "abcd"
8808 With a pretty-printer for @code{std::string} only the contents are printed:
8811 (@value{GDBP}) print s
8815 @node Pretty-Printer Commands
8816 @subsection Pretty-Printer Commands
8817 @cindex pretty-printer commands
8820 @kindex info pretty-printer
8821 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8822 Print the list of installed pretty-printers.
8823 This includes disabled pretty-printers, which are marked as such.
8825 @var{object-regexp} is a regular expression matching the objects
8826 whose pretty-printers to list.
8827 Objects can be @code{global}, the program space's file
8828 (@pxref{Progspaces In Python}),
8829 and the object files within that program space (@pxref{Objfiles In Python}).
8830 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8831 looks up a printer from these three objects.
8833 @var{name-regexp} is a regular expression matching the name of the printers
8836 @kindex disable pretty-printer
8837 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8838 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8839 A disabled pretty-printer is not forgotten, it may be enabled again later.
8841 @kindex enable pretty-printer
8842 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8843 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8848 Suppose we have three pretty-printers installed: one from library1.so
8849 named @code{foo} that prints objects of type @code{foo}, and
8850 another from library2.so named @code{bar} that prints two types of objects,
8851 @code{bar1} and @code{bar2}.
8854 (gdb) info pretty-printer
8861 (gdb) info pretty-printer library2
8866 (gdb) disable pretty-printer library1
8868 2 of 3 printers enabled
8869 (gdb) info pretty-printer
8876 (gdb) disable pretty-printer library2 bar:bar1
8878 1 of 3 printers enabled
8879 (gdb) info pretty-printer library2
8886 (gdb) disable pretty-printer library2 bar
8888 0 of 3 printers enabled
8889 (gdb) info pretty-printer library2
8898 Note that for @code{bar} the entire printer can be disabled,
8899 as can each individual subprinter.
8902 @section Value History
8904 @cindex value history
8905 @cindex history of values printed by @value{GDBN}
8906 Values printed by the @code{print} command are saved in the @value{GDBN}
8907 @dfn{value history}. This allows you to refer to them in other expressions.
8908 Values are kept until the symbol table is re-read or discarded
8909 (for example with the @code{file} or @code{symbol-file} commands).
8910 When the symbol table changes, the value history is discarded,
8911 since the values may contain pointers back to the types defined in the
8916 @cindex history number
8917 The values printed are given @dfn{history numbers} by which you can
8918 refer to them. These are successive integers starting with one.
8919 @code{print} shows you the history number assigned to a value by
8920 printing @samp{$@var{num} = } before the value; here @var{num} is the
8923 To refer to any previous value, use @samp{$} followed by the value's
8924 history number. The way @code{print} labels its output is designed to
8925 remind you of this. Just @code{$} refers to the most recent value in
8926 the history, and @code{$$} refers to the value before that.
8927 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8928 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8929 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8931 For example, suppose you have just printed a pointer to a structure and
8932 want to see the contents of the structure. It suffices to type
8938 If you have a chain of structures where the component @code{next} points
8939 to the next one, you can print the contents of the next one with this:
8946 You can print successive links in the chain by repeating this
8947 command---which you can do by just typing @key{RET}.
8949 Note that the history records values, not expressions. If the value of
8950 @code{x} is 4 and you type these commands:
8958 then the value recorded in the value history by the @code{print} command
8959 remains 4 even though the value of @code{x} has changed.
8964 Print the last ten values in the value history, with their item numbers.
8965 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8966 values} does not change the history.
8968 @item show values @var{n}
8969 Print ten history values centered on history item number @var{n}.
8972 Print ten history values just after the values last printed. If no more
8973 values are available, @code{show values +} produces no display.
8976 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8977 same effect as @samp{show values +}.
8979 @node Convenience Vars
8980 @section Convenience Variables
8982 @cindex convenience variables
8983 @cindex user-defined variables
8984 @value{GDBN} provides @dfn{convenience variables} that you can use within
8985 @value{GDBN} to hold on to a value and refer to it later. These variables
8986 exist entirely within @value{GDBN}; they are not part of your program, and
8987 setting a convenience variable has no direct effect on further execution
8988 of your program. That is why you can use them freely.
8990 Convenience variables are prefixed with @samp{$}. Any name preceded by
8991 @samp{$} can be used for a convenience variable, unless it is one of
8992 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8993 (Value history references, in contrast, are @emph{numbers} preceded
8994 by @samp{$}. @xref{Value History, ,Value History}.)
8996 You can save a value in a convenience variable with an assignment
8997 expression, just as you would set a variable in your program.
9001 set $foo = *object_ptr
9005 would save in @code{$foo} the value contained in the object pointed to by
9008 Using a convenience variable for the first time creates it, but its
9009 value is @code{void} until you assign a new value. You can alter the
9010 value with another assignment at any time.
9012 Convenience variables have no fixed types. You can assign a convenience
9013 variable any type of value, including structures and arrays, even if
9014 that variable already has a value of a different type. The convenience
9015 variable, when used as an expression, has the type of its current value.
9018 @kindex show convenience
9019 @cindex show all user variables
9020 @item show convenience
9021 Print a list of convenience variables used so far, and their values.
9022 Abbreviated @code{show conv}.
9024 @kindex init-if-undefined
9025 @cindex convenience variables, initializing
9026 @item init-if-undefined $@var{variable} = @var{expression}
9027 Set a convenience variable if it has not already been set. This is useful
9028 for user-defined commands that keep some state. It is similar, in concept,
9029 to using local static variables with initializers in C (except that
9030 convenience variables are global). It can also be used to allow users to
9031 override default values used in a command script.
9033 If the variable is already defined then the expression is not evaluated so
9034 any side-effects do not occur.
9037 One of the ways to use a convenience variable is as a counter to be
9038 incremented or a pointer to be advanced. For example, to print
9039 a field from successive elements of an array of structures:
9043 print bar[$i++]->contents
9047 Repeat that command by typing @key{RET}.
9049 Some convenience variables are created automatically by @value{GDBN} and given
9050 values likely to be useful.
9053 @vindex $_@r{, convenience variable}
9055 The variable @code{$_} is automatically set by the @code{x} command to
9056 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9057 commands which provide a default address for @code{x} to examine also
9058 set @code{$_} to that address; these commands include @code{info line}
9059 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9060 except when set by the @code{x} command, in which case it is a pointer
9061 to the type of @code{$__}.
9063 @vindex $__@r{, convenience variable}
9065 The variable @code{$__} is automatically set by the @code{x} command
9066 to the value found in the last address examined. Its type is chosen
9067 to match the format in which the data was printed.
9070 @vindex $_exitcode@r{, convenience variable}
9071 The variable @code{$_exitcode} is automatically set to the exit code when
9072 the program being debugged terminates.
9075 @vindex $_sdata@r{, inspect, convenience variable}
9076 The variable @code{$_sdata} contains extra collected static tracepoint
9077 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9078 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9079 if extra static tracepoint data has not been collected.
9082 @vindex $_siginfo@r{, convenience variable}
9083 The variable @code{$_siginfo} contains extra signal information
9084 (@pxref{extra signal information}). Note that @code{$_siginfo}
9085 could be empty, if the application has not yet received any signals.
9086 For example, it will be empty before you execute the @code{run} command.
9089 @vindex $_tlb@r{, convenience variable}
9090 The variable @code{$_tlb} is automatically set when debugging
9091 applications running on MS-Windows in native mode or connected to
9092 gdbserver that supports the @code{qGetTIBAddr} request.
9093 @xref{General Query Packets}.
9094 This variable contains the address of the thread information block.
9098 On HP-UX systems, if you refer to a function or variable name that
9099 begins with a dollar sign, @value{GDBN} searches for a user or system
9100 name first, before it searches for a convenience variable.
9102 @cindex convenience functions
9103 @value{GDBN} also supplies some @dfn{convenience functions}. These
9104 have a syntax similar to convenience variables. A convenience
9105 function can be used in an expression just like an ordinary function;
9106 however, a convenience function is implemented internally to
9111 @kindex help function
9112 @cindex show all convenience functions
9113 Print a list of all convenience functions.
9120 You can refer to machine register contents, in expressions, as variables
9121 with names starting with @samp{$}. The names of registers are different
9122 for each machine; use @code{info registers} to see the names used on
9126 @kindex info registers
9127 @item info registers
9128 Print the names and values of all registers except floating-point
9129 and vector registers (in the selected stack frame).
9131 @kindex info all-registers
9132 @cindex floating point registers
9133 @item info all-registers
9134 Print the names and values of all registers, including floating-point
9135 and vector registers (in the selected stack frame).
9137 @item info registers @var{regname} @dots{}
9138 Print the @dfn{relativized} value of each specified register @var{regname}.
9139 As discussed in detail below, register values are normally relative to
9140 the selected stack frame. @var{regname} may be any register name valid on
9141 the machine you are using, with or without the initial @samp{$}.
9144 @cindex stack pointer register
9145 @cindex program counter register
9146 @cindex process status register
9147 @cindex frame pointer register
9148 @cindex standard registers
9149 @value{GDBN} has four ``standard'' register names that are available (in
9150 expressions) on most machines---whenever they do not conflict with an
9151 architecture's canonical mnemonics for registers. The register names
9152 @code{$pc} and @code{$sp} are used for the program counter register and
9153 the stack pointer. @code{$fp} is used for a register that contains a
9154 pointer to the current stack frame, and @code{$ps} is used for a
9155 register that contains the processor status. For example,
9156 you could print the program counter in hex with
9163 or print the instruction to be executed next with
9170 or add four to the stack pointer@footnote{This is a way of removing
9171 one word from the stack, on machines where stacks grow downward in
9172 memory (most machines, nowadays). This assumes that the innermost
9173 stack frame is selected; setting @code{$sp} is not allowed when other
9174 stack frames are selected. To pop entire frames off the stack,
9175 regardless of machine architecture, use @code{return};
9176 see @ref{Returning, ,Returning from a Function}.} with
9182 Whenever possible, these four standard register names are available on
9183 your machine even though the machine has different canonical mnemonics,
9184 so long as there is no conflict. The @code{info registers} command
9185 shows the canonical names. For example, on the SPARC, @code{info
9186 registers} displays the processor status register as @code{$psr} but you
9187 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9188 is an alias for the @sc{eflags} register.
9190 @value{GDBN} always considers the contents of an ordinary register as an
9191 integer when the register is examined in this way. Some machines have
9192 special registers which can hold nothing but floating point; these
9193 registers are considered to have floating point values. There is no way
9194 to refer to the contents of an ordinary register as floating point value
9195 (although you can @emph{print} it as a floating point value with
9196 @samp{print/f $@var{regname}}).
9198 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9199 means that the data format in which the register contents are saved by
9200 the operating system is not the same one that your program normally
9201 sees. For example, the registers of the 68881 floating point
9202 coprocessor are always saved in ``extended'' (raw) format, but all C
9203 programs expect to work with ``double'' (virtual) format. In such
9204 cases, @value{GDBN} normally works with the virtual format only (the format
9205 that makes sense for your program), but the @code{info registers} command
9206 prints the data in both formats.
9208 @cindex SSE registers (x86)
9209 @cindex MMX registers (x86)
9210 Some machines have special registers whose contents can be interpreted
9211 in several different ways. For example, modern x86-based machines
9212 have SSE and MMX registers that can hold several values packed
9213 together in several different formats. @value{GDBN} refers to such
9214 registers in @code{struct} notation:
9217 (@value{GDBP}) print $xmm1
9219 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9220 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9221 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9222 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9223 v4_int32 = @{0, 20657912, 11, 13@},
9224 v2_int64 = @{88725056443645952, 55834574859@},
9225 uint128 = 0x0000000d0000000b013b36f800000000
9230 To set values of such registers, you need to tell @value{GDBN} which
9231 view of the register you wish to change, as if you were assigning
9232 value to a @code{struct} member:
9235 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9238 Normally, register values are relative to the selected stack frame
9239 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9240 value that the register would contain if all stack frames farther in
9241 were exited and their saved registers restored. In order to see the
9242 true contents of hardware registers, you must select the innermost
9243 frame (with @samp{frame 0}).
9245 However, @value{GDBN} must deduce where registers are saved, from the machine
9246 code generated by your compiler. If some registers are not saved, or if
9247 @value{GDBN} is unable to locate the saved registers, the selected stack
9248 frame makes no difference.
9250 @node Floating Point Hardware
9251 @section Floating Point Hardware
9252 @cindex floating point
9254 Depending on the configuration, @value{GDBN} may be able to give
9255 you more information about the status of the floating point hardware.
9260 Display hardware-dependent information about the floating
9261 point unit. The exact contents and layout vary depending on the
9262 floating point chip. Currently, @samp{info float} is supported on
9263 the ARM and x86 machines.
9267 @section Vector Unit
9270 Depending on the configuration, @value{GDBN} may be able to give you
9271 more information about the status of the vector unit.
9276 Display information about the vector unit. The exact contents and
9277 layout vary depending on the hardware.
9280 @node OS Information
9281 @section Operating System Auxiliary Information
9282 @cindex OS information
9284 @value{GDBN} provides interfaces to useful OS facilities that can help
9285 you debug your program.
9287 @cindex @code{ptrace} system call
9288 @cindex @code{struct user} contents
9289 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9290 machines), it interfaces with the inferior via the @code{ptrace}
9291 system call. The operating system creates a special sata structure,
9292 called @code{struct user}, for this interface. You can use the
9293 command @code{info udot} to display the contents of this data
9299 Display the contents of the @code{struct user} maintained by the OS
9300 kernel for the program being debugged. @value{GDBN} displays the
9301 contents of @code{struct user} as a list of hex numbers, similar to
9302 the @code{examine} command.
9305 @cindex auxiliary vector
9306 @cindex vector, auxiliary
9307 Some operating systems supply an @dfn{auxiliary vector} to programs at
9308 startup. This is akin to the arguments and environment that you
9309 specify for a program, but contains a system-dependent variety of
9310 binary values that tell system libraries important details about the
9311 hardware, operating system, and process. Each value's purpose is
9312 identified by an integer tag; the meanings are well-known but system-specific.
9313 Depending on the configuration and operating system facilities,
9314 @value{GDBN} may be able to show you this information. For remote
9315 targets, this functionality may further depend on the remote stub's
9316 support of the @samp{qXfer:auxv:read} packet, see
9317 @ref{qXfer auxiliary vector read}.
9322 Display the auxiliary vector of the inferior, which can be either a
9323 live process or a core dump file. @value{GDBN} prints each tag value
9324 numerically, and also shows names and text descriptions for recognized
9325 tags. Some values in the vector are numbers, some bit masks, and some
9326 pointers to strings or other data. @value{GDBN} displays each value in the
9327 most appropriate form for a recognized tag, and in hexadecimal for
9328 an unrecognized tag.
9331 On some targets, @value{GDBN} can access operating-system-specific information
9332 and display it to user, without interpretation. For remote targets,
9333 this functionality depends on the remote stub's support of the
9334 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9339 List the types of OS information available for the target. If the
9340 target does not return a list of possible types, this command will
9343 @kindex info os processes
9344 @item info os processes
9345 Display the list of processes on the target. For each process,
9346 @value{GDBN} prints the process identifier, the name of the user, and
9347 the command corresponding to the process.
9350 @node Memory Region Attributes
9351 @section Memory Region Attributes
9352 @cindex memory region attributes
9354 @dfn{Memory region attributes} allow you to describe special handling
9355 required by regions of your target's memory. @value{GDBN} uses
9356 attributes to determine whether to allow certain types of memory
9357 accesses; whether to use specific width accesses; and whether to cache
9358 target memory. By default the description of memory regions is
9359 fetched from the target (if the current target supports this), but the
9360 user can override the fetched regions.
9362 Defined memory regions can be individually enabled and disabled. When a
9363 memory region is disabled, @value{GDBN} uses the default attributes when
9364 accessing memory in that region. Similarly, if no memory regions have
9365 been defined, @value{GDBN} uses the default attributes when accessing
9368 When a memory region is defined, it is given a number to identify it;
9369 to enable, disable, or remove a memory region, you specify that number.
9373 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9374 Define a memory region bounded by @var{lower} and @var{upper} with
9375 attributes @var{attributes}@dots{}, and add it to the list of regions
9376 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9377 case: it is treated as the target's maximum memory address.
9378 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9381 Discard any user changes to the memory regions and use target-supplied
9382 regions, if available, or no regions if the target does not support.
9385 @item delete mem @var{nums}@dots{}
9386 Remove memory regions @var{nums}@dots{} from the list of regions
9387 monitored by @value{GDBN}.
9390 @item disable mem @var{nums}@dots{}
9391 Disable monitoring of memory regions @var{nums}@dots{}.
9392 A disabled memory region is not forgotten.
9393 It may be enabled again later.
9396 @item enable mem @var{nums}@dots{}
9397 Enable monitoring of memory regions @var{nums}@dots{}.
9401 Print a table of all defined memory regions, with the following columns
9405 @item Memory Region Number
9406 @item Enabled or Disabled.
9407 Enabled memory regions are marked with @samp{y}.
9408 Disabled memory regions are marked with @samp{n}.
9411 The address defining the inclusive lower bound of the memory region.
9414 The address defining the exclusive upper bound of the memory region.
9417 The list of attributes set for this memory region.
9422 @subsection Attributes
9424 @subsubsection Memory Access Mode
9425 The access mode attributes set whether @value{GDBN} may make read or
9426 write accesses to a memory region.
9428 While these attributes prevent @value{GDBN} from performing invalid
9429 memory accesses, they do nothing to prevent the target system, I/O DMA,
9430 etc.@: from accessing memory.
9434 Memory is read only.
9436 Memory is write only.
9438 Memory is read/write. This is the default.
9441 @subsubsection Memory Access Size
9442 The access size attribute tells @value{GDBN} to use specific sized
9443 accesses in the memory region. Often memory mapped device registers
9444 require specific sized accesses. If no access size attribute is
9445 specified, @value{GDBN} may use accesses of any size.
9449 Use 8 bit memory accesses.
9451 Use 16 bit memory accesses.
9453 Use 32 bit memory accesses.
9455 Use 64 bit memory accesses.
9458 @c @subsubsection Hardware/Software Breakpoints
9459 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9460 @c will use hardware or software breakpoints for the internal breakpoints
9461 @c used by the step, next, finish, until, etc. commands.
9465 @c Always use hardware breakpoints
9466 @c @item swbreak (default)
9469 @subsubsection Data Cache
9470 The data cache attributes set whether @value{GDBN} will cache target
9471 memory. While this generally improves performance by reducing debug
9472 protocol overhead, it can lead to incorrect results because @value{GDBN}
9473 does not know about volatile variables or memory mapped device
9478 Enable @value{GDBN} to cache target memory.
9480 Disable @value{GDBN} from caching target memory. This is the default.
9483 @subsection Memory Access Checking
9484 @value{GDBN} can be instructed to refuse accesses to memory that is
9485 not explicitly described. This can be useful if accessing such
9486 regions has undesired effects for a specific target, or to provide
9487 better error checking. The following commands control this behaviour.
9490 @kindex set mem inaccessible-by-default
9491 @item set mem inaccessible-by-default [on|off]
9492 If @code{on} is specified, make @value{GDBN} treat memory not
9493 explicitly described by the memory ranges as non-existent and refuse accesses
9494 to such memory. The checks are only performed if there's at least one
9495 memory range defined. If @code{off} is specified, make @value{GDBN}
9496 treat the memory not explicitly described by the memory ranges as RAM.
9497 The default value is @code{on}.
9498 @kindex show mem inaccessible-by-default
9499 @item show mem inaccessible-by-default
9500 Show the current handling of accesses to unknown memory.
9504 @c @subsubsection Memory Write Verification
9505 @c The memory write verification attributes set whether @value{GDBN}
9506 @c will re-reads data after each write to verify the write was successful.
9510 @c @item noverify (default)
9513 @node Dump/Restore Files
9514 @section Copy Between Memory and a File
9515 @cindex dump/restore files
9516 @cindex append data to a file
9517 @cindex dump data to a file
9518 @cindex restore data from a file
9520 You can use the commands @code{dump}, @code{append}, and
9521 @code{restore} to copy data between target memory and a file. The
9522 @code{dump} and @code{append} commands write data to a file, and the
9523 @code{restore} command reads data from a file back into the inferior's
9524 memory. Files may be in binary, Motorola S-record, Intel hex, or
9525 Tektronix Hex format; however, @value{GDBN} can only append to binary
9531 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9532 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9533 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9534 or the value of @var{expr}, to @var{filename} in the given format.
9536 The @var{format} parameter may be any one of:
9543 Motorola S-record format.
9545 Tektronix Hex format.
9548 @value{GDBN} uses the same definitions of these formats as the
9549 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9550 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9554 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9555 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9556 Append the contents of memory from @var{start_addr} to @var{end_addr},
9557 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9558 (@value{GDBN} can only append data to files in raw binary form.)
9561 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9562 Restore the contents of file @var{filename} into memory. The
9563 @code{restore} command can automatically recognize any known @sc{bfd}
9564 file format, except for raw binary. To restore a raw binary file you
9565 must specify the optional keyword @code{binary} after the filename.
9567 If @var{bias} is non-zero, its value will be added to the addresses
9568 contained in the file. Binary files always start at address zero, so
9569 they will be restored at address @var{bias}. Other bfd files have
9570 a built-in location; they will be restored at offset @var{bias}
9573 If @var{start} and/or @var{end} are non-zero, then only data between
9574 file offset @var{start} and file offset @var{end} will be restored.
9575 These offsets are relative to the addresses in the file, before
9576 the @var{bias} argument is applied.
9580 @node Core File Generation
9581 @section How to Produce a Core File from Your Program
9582 @cindex dump core from inferior
9584 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9585 image of a running process and its process status (register values
9586 etc.). Its primary use is post-mortem debugging of a program that
9587 crashed while it ran outside a debugger. A program that crashes
9588 automatically produces a core file, unless this feature is disabled by
9589 the user. @xref{Files}, for information on invoking @value{GDBN} in
9590 the post-mortem debugging mode.
9592 Occasionally, you may wish to produce a core file of the program you
9593 are debugging in order to preserve a snapshot of its state.
9594 @value{GDBN} has a special command for that.
9598 @kindex generate-core-file
9599 @item generate-core-file [@var{file}]
9600 @itemx gcore [@var{file}]
9601 Produce a core dump of the inferior process. The optional argument
9602 @var{file} specifies the file name where to put the core dump. If not
9603 specified, the file name defaults to @file{core.@var{pid}}, where
9604 @var{pid} is the inferior process ID.
9606 Note that this command is implemented only for some systems (as of
9607 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9610 @node Character Sets
9611 @section Character Sets
9612 @cindex character sets
9614 @cindex translating between character sets
9615 @cindex host character set
9616 @cindex target character set
9618 If the program you are debugging uses a different character set to
9619 represent characters and strings than the one @value{GDBN} uses itself,
9620 @value{GDBN} can automatically translate between the character sets for
9621 you. The character set @value{GDBN} uses we call the @dfn{host
9622 character set}; the one the inferior program uses we call the
9623 @dfn{target character set}.
9625 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9626 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9627 remote protocol (@pxref{Remote Debugging}) to debug a program
9628 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9629 then the host character set is Latin-1, and the target character set is
9630 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9631 target-charset EBCDIC-US}, then @value{GDBN} translates between
9632 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9633 character and string literals in expressions.
9635 @value{GDBN} has no way to automatically recognize which character set
9636 the inferior program uses; you must tell it, using the @code{set
9637 target-charset} command, described below.
9639 Here are the commands for controlling @value{GDBN}'s character set
9643 @item set target-charset @var{charset}
9644 @kindex set target-charset
9645 Set the current target character set to @var{charset}. To display the
9646 list of supported target character sets, type
9647 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9649 @item set host-charset @var{charset}
9650 @kindex set host-charset
9651 Set the current host character set to @var{charset}.
9653 By default, @value{GDBN} uses a host character set appropriate to the
9654 system it is running on; you can override that default using the
9655 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9656 automatically determine the appropriate host character set. In this
9657 case, @value{GDBN} uses @samp{UTF-8}.
9659 @value{GDBN} can only use certain character sets as its host character
9660 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9661 @value{GDBN} will list the host character sets it supports.
9663 @item set charset @var{charset}
9665 Set the current host and target character sets to @var{charset}. As
9666 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9667 @value{GDBN} will list the names of the character sets that can be used
9668 for both host and target.
9671 @kindex show charset
9672 Show the names of the current host and target character sets.
9674 @item show host-charset
9675 @kindex show host-charset
9676 Show the name of the current host character set.
9678 @item show target-charset
9679 @kindex show target-charset
9680 Show the name of the current target character set.
9682 @item set target-wide-charset @var{charset}
9683 @kindex set target-wide-charset
9684 Set the current target's wide character set to @var{charset}. This is
9685 the character set used by the target's @code{wchar_t} type. To
9686 display the list of supported wide character sets, type
9687 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9689 @item show target-wide-charset
9690 @kindex show target-wide-charset
9691 Show the name of the current target's wide character set.
9694 Here is an example of @value{GDBN}'s character set support in action.
9695 Assume that the following source code has been placed in the file
9696 @file{charset-test.c}:
9702 = @{72, 101, 108, 108, 111, 44, 32, 119,
9703 111, 114, 108, 100, 33, 10, 0@};
9704 char ibm1047_hello[]
9705 = @{200, 133, 147, 147, 150, 107, 64, 166,
9706 150, 153, 147, 132, 90, 37, 0@};
9710 printf ("Hello, world!\n");
9714 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9715 containing the string @samp{Hello, world!} followed by a newline,
9716 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9718 We compile the program, and invoke the debugger on it:
9721 $ gcc -g charset-test.c -o charset-test
9722 $ gdb -nw charset-test
9723 GNU gdb 2001-12-19-cvs
9724 Copyright 2001 Free Software Foundation, Inc.
9729 We can use the @code{show charset} command to see what character sets
9730 @value{GDBN} is currently using to interpret and display characters and
9734 (@value{GDBP}) show charset
9735 The current host and target character set is `ISO-8859-1'.
9739 For the sake of printing this manual, let's use @sc{ascii} as our
9740 initial character set:
9742 (@value{GDBP}) set charset ASCII
9743 (@value{GDBP}) show charset
9744 The current host and target character set is `ASCII'.
9748 Let's assume that @sc{ascii} is indeed the correct character set for our
9749 host system --- in other words, let's assume that if @value{GDBN} prints
9750 characters using the @sc{ascii} character set, our terminal will display
9751 them properly. Since our current target character set is also
9752 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9755 (@value{GDBP}) print ascii_hello
9756 $1 = 0x401698 "Hello, world!\n"
9757 (@value{GDBP}) print ascii_hello[0]
9762 @value{GDBN} uses the target character set for character and string
9763 literals you use in expressions:
9766 (@value{GDBP}) print '+'
9771 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9774 @value{GDBN} relies on the user to tell it which character set the
9775 target program uses. If we print @code{ibm1047_hello} while our target
9776 character set is still @sc{ascii}, we get jibberish:
9779 (@value{GDBP}) print ibm1047_hello
9780 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9781 (@value{GDBP}) print ibm1047_hello[0]
9786 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9787 @value{GDBN} tells us the character sets it supports:
9790 (@value{GDBP}) set target-charset
9791 ASCII EBCDIC-US IBM1047 ISO-8859-1
9792 (@value{GDBP}) set target-charset
9795 We can select @sc{ibm1047} as our target character set, and examine the
9796 program's strings again. Now the @sc{ascii} string is wrong, but
9797 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9798 target character set, @sc{ibm1047}, to the host character set,
9799 @sc{ascii}, and they display correctly:
9802 (@value{GDBP}) set target-charset IBM1047
9803 (@value{GDBP}) show charset
9804 The current host character set is `ASCII'.
9805 The current target character set is `IBM1047'.
9806 (@value{GDBP}) print ascii_hello
9807 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9808 (@value{GDBP}) print ascii_hello[0]
9810 (@value{GDBP}) print ibm1047_hello
9811 $8 = 0x4016a8 "Hello, world!\n"
9812 (@value{GDBP}) print ibm1047_hello[0]
9817 As above, @value{GDBN} uses the target character set for character and
9818 string literals you use in expressions:
9821 (@value{GDBP}) print '+'
9826 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9829 @node Caching Remote Data
9830 @section Caching Data of Remote Targets
9831 @cindex caching data of remote targets
9833 @value{GDBN} caches data exchanged between the debugger and a
9834 remote target (@pxref{Remote Debugging}). Such caching generally improves
9835 performance, because it reduces the overhead of the remote protocol by
9836 bundling memory reads and writes into large chunks. Unfortunately, simply
9837 caching everything would lead to incorrect results, since @value{GDBN}
9838 does not necessarily know anything about volatile values, memory-mapped I/O
9839 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9840 memory can be changed @emph{while} a gdb command is executing.
9841 Therefore, by default, @value{GDBN} only caches data
9842 known to be on the stack@footnote{In non-stop mode, it is moderately
9843 rare for a running thread to modify the stack of a stopped thread
9844 in a way that would interfere with a backtrace, and caching of
9845 stack reads provides a significant speed up of remote backtraces.}.
9846 Other regions of memory can be explicitly marked as
9847 cacheable; see @pxref{Memory Region Attributes}.
9850 @kindex set remotecache
9851 @item set remotecache on
9852 @itemx set remotecache off
9853 This option no longer does anything; it exists for compatibility
9856 @kindex show remotecache
9857 @item show remotecache
9858 Show the current state of the obsolete remotecache flag.
9860 @kindex set stack-cache
9861 @item set stack-cache on
9862 @itemx set stack-cache off
9863 Enable or disable caching of stack accesses. When @code{ON}, use
9864 caching. By default, this option is @code{ON}.
9866 @kindex show stack-cache
9867 @item show stack-cache
9868 Show the current state of data caching for memory accesses.
9871 @item info dcache @r{[}line@r{]}
9872 Print the information about the data cache performance. The
9873 information displayed includes the dcache width and depth, and for
9874 each cache line, its number, address, and how many times it was
9875 referenced. This command is useful for debugging the data cache
9878 If a line number is specified, the contents of that line will be
9881 @item set dcache size @var{size}
9883 @kindex set dcache size
9884 Set maximum number of entries in dcache (dcache depth above).
9886 @item set dcache line-size @var{line-size}
9887 @cindex dcache line-size
9888 @kindex set dcache line-size
9889 Set number of bytes each dcache entry caches (dcache width above).
9890 Must be a power of 2.
9892 @item show dcache size
9893 @kindex show dcache size
9894 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9896 @item show dcache line-size
9897 @kindex show dcache line-size
9898 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9902 @node Searching Memory
9903 @section Search Memory
9904 @cindex searching memory
9906 Memory can be searched for a particular sequence of bytes with the
9907 @code{find} command.
9911 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9912 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9913 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9914 etc. The search begins at address @var{start_addr} and continues for either
9915 @var{len} bytes or through to @var{end_addr} inclusive.
9918 @var{s} and @var{n} are optional parameters.
9919 They may be specified in either order, apart or together.
9922 @item @var{s}, search query size
9923 The size of each search query value.
9929 halfwords (two bytes)
9933 giant words (eight bytes)
9936 All values are interpreted in the current language.
9937 This means, for example, that if the current source language is C/C@t{++}
9938 then searching for the string ``hello'' includes the trailing '\0'.
9940 If the value size is not specified, it is taken from the
9941 value's type in the current language.
9942 This is useful when one wants to specify the search
9943 pattern as a mixture of types.
9944 Note that this means, for example, that in the case of C-like languages
9945 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9946 which is typically four bytes.
9948 @item @var{n}, maximum number of finds
9949 The maximum number of matches to print. The default is to print all finds.
9952 You can use strings as search values. Quote them with double-quotes
9954 The string value is copied into the search pattern byte by byte,
9955 regardless of the endianness of the target and the size specification.
9957 The address of each match found is printed as well as a count of the
9958 number of matches found.
9960 The address of the last value found is stored in convenience variable
9962 A count of the number of matches is stored in @samp{$numfound}.
9964 For example, if stopped at the @code{printf} in this function:
9970 static char hello[] = "hello-hello";
9971 static struct @{ char c; short s; int i; @}
9972 __attribute__ ((packed)) mixed
9973 = @{ 'c', 0x1234, 0x87654321 @};
9974 printf ("%s\n", hello);
9979 you get during debugging:
9982 (gdb) find &hello[0], +sizeof(hello), "hello"
9983 0x804956d <hello.1620+6>
9985 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9986 0x8049567 <hello.1620>
9987 0x804956d <hello.1620+6>
9989 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9990 0x8049567 <hello.1620>
9992 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9993 0x8049560 <mixed.1625>
9995 (gdb) print $numfound
9998 $2 = (void *) 0x8049560
10001 @node Optimized Code
10002 @chapter Debugging Optimized Code
10003 @cindex optimized code, debugging
10004 @cindex debugging optimized code
10006 Almost all compilers support optimization. With optimization
10007 disabled, the compiler generates assembly code that corresponds
10008 directly to your source code, in a simplistic way. As the compiler
10009 applies more powerful optimizations, the generated assembly code
10010 diverges from your original source code. With help from debugging
10011 information generated by the compiler, @value{GDBN} can map from
10012 the running program back to constructs from your original source.
10014 @value{GDBN} is more accurate with optimization disabled. If you
10015 can recompile without optimization, it is easier to follow the
10016 progress of your program during debugging. But, there are many cases
10017 where you may need to debug an optimized version.
10019 When you debug a program compiled with @samp{-g -O}, remember that the
10020 optimizer has rearranged your code; the debugger shows you what is
10021 really there. Do not be too surprised when the execution path does not
10022 exactly match your source file! An extreme example: if you define a
10023 variable, but never use it, @value{GDBN} never sees that
10024 variable---because the compiler optimizes it out of existence.
10026 Some things do not work as well with @samp{-g -O} as with just
10027 @samp{-g}, particularly on machines with instruction scheduling. If in
10028 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10029 please report it to us as a bug (including a test case!).
10030 @xref{Variables}, for more information about debugging optimized code.
10033 * Inline Functions:: How @value{GDBN} presents inlining
10034 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10037 @node Inline Functions
10038 @section Inline Functions
10039 @cindex inline functions, debugging
10041 @dfn{Inlining} is an optimization that inserts a copy of the function
10042 body directly at each call site, instead of jumping to a shared
10043 routine. @value{GDBN} displays inlined functions just like
10044 non-inlined functions. They appear in backtraces. You can view their
10045 arguments and local variables, step into them with @code{step}, skip
10046 them with @code{next}, and escape from them with @code{finish}.
10047 You can check whether a function was inlined by using the
10048 @code{info frame} command.
10050 For @value{GDBN} to support inlined functions, the compiler must
10051 record information about inlining in the debug information ---
10052 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10053 other compilers do also. @value{GDBN} only supports inlined functions
10054 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10055 do not emit two required attributes (@samp{DW_AT_call_file} and
10056 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10057 function calls with earlier versions of @value{NGCC}. It instead
10058 displays the arguments and local variables of inlined functions as
10059 local variables in the caller.
10061 The body of an inlined function is directly included at its call site;
10062 unlike a non-inlined function, there are no instructions devoted to
10063 the call. @value{GDBN} still pretends that the call site and the
10064 start of the inlined function are different instructions. Stepping to
10065 the call site shows the call site, and then stepping again shows
10066 the first line of the inlined function, even though no additional
10067 instructions are executed.
10069 This makes source-level debugging much clearer; you can see both the
10070 context of the call and then the effect of the call. Only stepping by
10071 a single instruction using @code{stepi} or @code{nexti} does not do
10072 this; single instruction steps always show the inlined body.
10074 There are some ways that @value{GDBN} does not pretend that inlined
10075 function calls are the same as normal calls:
10079 Setting breakpoints at the call site of an inlined function may not
10080 work, because the call site does not contain any code. @value{GDBN}
10081 may incorrectly move the breakpoint to the next line of the enclosing
10082 function, after the call. This limitation will be removed in a future
10083 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10084 or inside the inlined function instead.
10087 @value{GDBN} cannot locate the return value of inlined calls after
10088 using the @code{finish} command. This is a limitation of compiler-generated
10089 debugging information; after @code{finish}, you can step to the next line
10090 and print a variable where your program stored the return value.
10094 @node Tail Call Frames
10095 @section Tail Call Frames
10096 @cindex tail call frames, debugging
10098 Function @code{B} can call function @code{C} in its very last statement. In
10099 unoptimized compilation the call of @code{C} is immediately followed by return
10100 instruction at the end of @code{B} code. Optimizing compiler may replace the
10101 call and return in function @code{B} into one jump to function @code{C}
10102 instead. Such use of a jump instruction is called @dfn{tail call}.
10104 During execution of function @code{C}, there will be no indication in the
10105 function call stack frames that it was tail-called from @code{B}. If function
10106 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10107 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10108 some cases @value{GDBN} can determine that @code{C} was tail-called from
10109 @code{B}, and it will then create fictitious call frame for that, with the
10110 return address set up as if @code{B} called @code{C} normally.
10112 This functionality is currently supported only by DWARF 2 debugging format and
10113 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10114 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10117 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10118 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10122 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10124 Stack level 1, frame at 0x7fffffffda30:
10125 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10126 tail call frame, caller of frame at 0x7fffffffda30
10127 source language c++.
10128 Arglist at unknown address.
10129 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10132 The detection of all the possible code path executions can find them ambiguous.
10133 There is no execution history stored (possible @ref{Reverse Execution} is never
10134 used for this purpose) and the last known caller could have reached the known
10135 callee by multiple different jump sequences. In such case @value{GDBN} still
10136 tries to show at least all the unambiguous top tail callers and all the
10137 unambiguous bottom tail calees, if any.
10140 @anchor{set debug entry-values}
10141 @item set debug entry-values
10142 @kindex set debug entry-values
10143 When set to on, enables printing of analysis messages for both frame argument
10144 values at function entry and tail calls. It will show all the possible valid
10145 tail calls code paths it has considered. It will also print the intersection
10146 of them with the final unambiguous (possibly partial or even empty) code path
10149 @item show debug entry-values
10150 @kindex show debug entry-values
10151 Show the current state of analysis messages printing for both frame argument
10152 values at function entry and tail calls.
10155 The analysis messages for tail calls can for example show why the virtual tail
10156 call frame for function @code{c} has not been recognized (due to the indirect
10157 reference by variable @code{x}):
10160 static void __attribute__((noinline, noclone)) c (void);
10161 void (*x) (void) = c;
10162 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10163 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10164 int main (void) @{ x (); return 0; @}
10166 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10167 DW_TAG_GNU_call_site 0x40039a in main
10169 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10172 #1 0x000000000040039a in main () at t.c:5
10175 Another possibility is an ambiguous virtual tail call frames resolution:
10179 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10180 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10181 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10182 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10183 static void __attribute__((noinline, noclone)) b (void)
10184 @{ if (i) c (); else e (); @}
10185 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10186 int main (void) @{ a (); return 0; @}
10188 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10189 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10190 tailcall: reduced: 0x4004d2(a) |
10193 #1 0x00000000004004d2 in a () at t.c:8
10194 #2 0x0000000000400395 in main () at t.c:9
10197 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10198 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10200 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10201 @ifset HAVE_MAKEINFO_CLICK
10202 @set ARROW @click{}
10203 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10204 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10206 @ifclear HAVE_MAKEINFO_CLICK
10208 @set CALLSEQ1B @value{CALLSEQ1A}
10209 @set CALLSEQ2B @value{CALLSEQ2A}
10212 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10213 The code can have possible execution paths @value{CALLSEQ1B} or
10214 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10216 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10217 has found. It then finds another possible calling sequcen - that one is
10218 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10219 printed as the @code{reduced:} calling sequence. That one could have many
10220 futher @code{compare:} and @code{reduced:} statements as long as there remain
10221 any non-ambiguous sequence entries.
10223 For the frame of function @code{b} in both cases there are different possible
10224 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10225 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10226 therefore this one is displayed to the user while the ambiguous frames are
10229 There can be also reasons why printing of frame argument values at function
10234 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10235 static void __attribute__((noinline, noclone)) a (int i);
10236 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10237 static void __attribute__((noinline, noclone)) a (int i)
10238 @{ if (i) b (i - 1); else c (0); @}
10239 int main (void) @{ a (5); return 0; @}
10242 #0 c (i=i@@entry=0) at t.c:2
10243 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10244 function "a" at 0x400420 can call itself via tail calls
10245 i=<optimized out>) at t.c:6
10246 #2 0x000000000040036e in main () at t.c:7
10249 @value{GDBN} cannot find out from the inferior state if and how many times did
10250 function @code{a} call itself (via function @code{b}) as these calls would be
10251 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10252 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10253 prints @code{<optimized out>} instead.
10256 @chapter C Preprocessor Macros
10258 Some languages, such as C and C@t{++}, provide a way to define and invoke
10259 ``preprocessor macros'' which expand into strings of tokens.
10260 @value{GDBN} can evaluate expressions containing macro invocations, show
10261 the result of macro expansion, and show a macro's definition, including
10262 where it was defined.
10264 You may need to compile your program specially to provide @value{GDBN}
10265 with information about preprocessor macros. Most compilers do not
10266 include macros in their debugging information, even when you compile
10267 with the @option{-g} flag. @xref{Compilation}.
10269 A program may define a macro at one point, remove that definition later,
10270 and then provide a different definition after that. Thus, at different
10271 points in the program, a macro may have different definitions, or have
10272 no definition at all. If there is a current stack frame, @value{GDBN}
10273 uses the macros in scope at that frame's source code line. Otherwise,
10274 @value{GDBN} uses the macros in scope at the current listing location;
10277 Whenever @value{GDBN} evaluates an expression, it always expands any
10278 macro invocations present in the expression. @value{GDBN} also provides
10279 the following commands for working with macros explicitly.
10283 @kindex macro expand
10284 @cindex macro expansion, showing the results of preprocessor
10285 @cindex preprocessor macro expansion, showing the results of
10286 @cindex expanding preprocessor macros
10287 @item macro expand @var{expression}
10288 @itemx macro exp @var{expression}
10289 Show the results of expanding all preprocessor macro invocations in
10290 @var{expression}. Since @value{GDBN} simply expands macros, but does
10291 not parse the result, @var{expression} need not be a valid expression;
10292 it can be any string of tokens.
10295 @item macro expand-once @var{expression}
10296 @itemx macro exp1 @var{expression}
10297 @cindex expand macro once
10298 @i{(This command is not yet implemented.)} Show the results of
10299 expanding those preprocessor macro invocations that appear explicitly in
10300 @var{expression}. Macro invocations appearing in that expansion are
10301 left unchanged. This command allows you to see the effect of a
10302 particular macro more clearly, without being confused by further
10303 expansions. Since @value{GDBN} simply expands macros, but does not
10304 parse the result, @var{expression} need not be a valid expression; it
10305 can be any string of tokens.
10308 @cindex macro definition, showing
10309 @cindex definition of a macro, showing
10310 @cindex macros, from debug info
10311 @item info macro [-a|-all] [--] @var{macro}
10312 Show the current definition or all definitions of the named @var{macro},
10313 and describe the source location or compiler command-line where that
10314 definition was established. The optional double dash is to signify the end of
10315 argument processing and the beginning of @var{macro} for non C-like macros where
10316 the macro may begin with a hyphen.
10318 @kindex info macros
10319 @item info macros @var{linespec}
10320 Show all macro definitions that are in effect at the location specified
10321 by @var{linespec}, and describe the source location or compiler
10322 command-line where those definitions were established.
10324 @kindex macro define
10325 @cindex user-defined macros
10326 @cindex defining macros interactively
10327 @cindex macros, user-defined
10328 @item macro define @var{macro} @var{replacement-list}
10329 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10330 Introduce a definition for a preprocessor macro named @var{macro},
10331 invocations of which are replaced by the tokens given in
10332 @var{replacement-list}. The first form of this command defines an
10333 ``object-like'' macro, which takes no arguments; the second form
10334 defines a ``function-like'' macro, which takes the arguments given in
10337 A definition introduced by this command is in scope in every
10338 expression evaluated in @value{GDBN}, until it is removed with the
10339 @code{macro undef} command, described below. The definition overrides
10340 all definitions for @var{macro} present in the program being debugged,
10341 as well as any previous user-supplied definition.
10343 @kindex macro undef
10344 @item macro undef @var{macro}
10345 Remove any user-supplied definition for the macro named @var{macro}.
10346 This command only affects definitions provided with the @code{macro
10347 define} command, described above; it cannot remove definitions present
10348 in the program being debugged.
10352 List all the macros defined using the @code{macro define} command.
10355 @cindex macros, example of debugging with
10356 Here is a transcript showing the above commands in action. First, we
10357 show our source files:
10362 #include "sample.h"
10365 #define ADD(x) (M + x)
10370 printf ("Hello, world!\n");
10372 printf ("We're so creative.\n");
10374 printf ("Goodbye, world!\n");
10381 Now, we compile the program using the @sc{gnu} C compiler,
10382 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10383 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10384 and @option{-gdwarf-4}; we recommend always choosing the most recent
10385 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10386 includes information about preprocessor macros in the debugging
10390 $ gcc -gdwarf-2 -g3 sample.c -o sample
10394 Now, we start @value{GDBN} on our sample program:
10398 GNU gdb 2002-05-06-cvs
10399 Copyright 2002 Free Software Foundation, Inc.
10400 GDB is free software, @dots{}
10404 We can expand macros and examine their definitions, even when the
10405 program is not running. @value{GDBN} uses the current listing position
10406 to decide which macro definitions are in scope:
10409 (@value{GDBP}) list main
10412 5 #define ADD(x) (M + x)
10417 10 printf ("Hello, world!\n");
10419 12 printf ("We're so creative.\n");
10420 (@value{GDBP}) info macro ADD
10421 Defined at /home/jimb/gdb/macros/play/sample.c:5
10422 #define ADD(x) (M + x)
10423 (@value{GDBP}) info macro Q
10424 Defined at /home/jimb/gdb/macros/play/sample.h:1
10425 included at /home/jimb/gdb/macros/play/sample.c:2
10427 (@value{GDBP}) macro expand ADD(1)
10428 expands to: (42 + 1)
10429 (@value{GDBP}) macro expand-once ADD(1)
10430 expands to: once (M + 1)
10434 In the example above, note that @code{macro expand-once} expands only
10435 the macro invocation explicit in the original text --- the invocation of
10436 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10437 which was introduced by @code{ADD}.
10439 Once the program is running, @value{GDBN} uses the macro definitions in
10440 force at the source line of the current stack frame:
10443 (@value{GDBP}) break main
10444 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10446 Starting program: /home/jimb/gdb/macros/play/sample
10448 Breakpoint 1, main () at sample.c:10
10449 10 printf ("Hello, world!\n");
10453 At line 10, the definition of the macro @code{N} at line 9 is in force:
10456 (@value{GDBP}) info macro N
10457 Defined at /home/jimb/gdb/macros/play/sample.c:9
10459 (@value{GDBP}) macro expand N Q M
10460 expands to: 28 < 42
10461 (@value{GDBP}) print N Q M
10466 As we step over directives that remove @code{N}'s definition, and then
10467 give it a new definition, @value{GDBN} finds the definition (or lack
10468 thereof) in force at each point:
10471 (@value{GDBP}) next
10473 12 printf ("We're so creative.\n");
10474 (@value{GDBP}) info macro N
10475 The symbol `N' has no definition as a C/C++ preprocessor macro
10476 at /home/jimb/gdb/macros/play/sample.c:12
10477 (@value{GDBP}) next
10479 14 printf ("Goodbye, world!\n");
10480 (@value{GDBP}) info macro N
10481 Defined at /home/jimb/gdb/macros/play/sample.c:13
10483 (@value{GDBP}) macro expand N Q M
10484 expands to: 1729 < 42
10485 (@value{GDBP}) print N Q M
10490 In addition to source files, macros can be defined on the compilation command
10491 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10492 such a way, @value{GDBN} displays the location of their definition as line zero
10493 of the source file submitted to the compiler.
10496 (@value{GDBP}) info macro __STDC__
10497 Defined at /home/jimb/gdb/macros/play/sample.c:0
10504 @chapter Tracepoints
10505 @c This chapter is based on the documentation written by Michael
10506 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10508 @cindex tracepoints
10509 In some applications, it is not feasible for the debugger to interrupt
10510 the program's execution long enough for the developer to learn
10511 anything helpful about its behavior. If the program's correctness
10512 depends on its real-time behavior, delays introduced by a debugger
10513 might cause the program to change its behavior drastically, or perhaps
10514 fail, even when the code itself is correct. It is useful to be able
10515 to observe the program's behavior without interrupting it.
10517 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10518 specify locations in the program, called @dfn{tracepoints}, and
10519 arbitrary expressions to evaluate when those tracepoints are reached.
10520 Later, using the @code{tfind} command, you can examine the values
10521 those expressions had when the program hit the tracepoints. The
10522 expressions may also denote objects in memory---structures or arrays,
10523 for example---whose values @value{GDBN} should record; while visiting
10524 a particular tracepoint, you may inspect those objects as if they were
10525 in memory at that moment. However, because @value{GDBN} records these
10526 values without interacting with you, it can do so quickly and
10527 unobtrusively, hopefully not disturbing the program's behavior.
10529 The tracepoint facility is currently available only for remote
10530 targets. @xref{Targets}. In addition, your remote target must know
10531 how to collect trace data. This functionality is implemented in the
10532 remote stub; however, none of the stubs distributed with @value{GDBN}
10533 support tracepoints as of this writing. The format of the remote
10534 packets used to implement tracepoints are described in @ref{Tracepoint
10537 It is also possible to get trace data from a file, in a manner reminiscent
10538 of corefiles; you specify the filename, and use @code{tfind} to search
10539 through the file. @xref{Trace Files}, for more details.
10541 This chapter describes the tracepoint commands and features.
10544 * Set Tracepoints::
10545 * Analyze Collected Data::
10546 * Tracepoint Variables::
10550 @node Set Tracepoints
10551 @section Commands to Set Tracepoints
10553 Before running such a @dfn{trace experiment}, an arbitrary number of
10554 tracepoints can be set. A tracepoint is actually a special type of
10555 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10556 standard breakpoint commands. For instance, as with breakpoints,
10557 tracepoint numbers are successive integers starting from one, and many
10558 of the commands associated with tracepoints take the tracepoint number
10559 as their argument, to identify which tracepoint to work on.
10561 For each tracepoint, you can specify, in advance, some arbitrary set
10562 of data that you want the target to collect in the trace buffer when
10563 it hits that tracepoint. The collected data can include registers,
10564 local variables, or global data. Later, you can use @value{GDBN}
10565 commands to examine the values these data had at the time the
10566 tracepoint was hit.
10568 Tracepoints do not support every breakpoint feature. Ignore counts on
10569 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10570 commands when they are hit. Tracepoints may not be thread-specific
10573 @cindex fast tracepoints
10574 Some targets may support @dfn{fast tracepoints}, which are inserted in
10575 a different way (such as with a jump instead of a trap), that is
10576 faster but possibly restricted in where they may be installed.
10578 @cindex static tracepoints
10579 @cindex markers, static tracepoints
10580 @cindex probing markers, static tracepoints
10581 Regular and fast tracepoints are dynamic tracing facilities, meaning
10582 that they can be used to insert tracepoints at (almost) any location
10583 in the target. Some targets may also support controlling @dfn{static
10584 tracepoints} from @value{GDBN}. With static tracing, a set of
10585 instrumentation points, also known as @dfn{markers}, are embedded in
10586 the target program, and can be activated or deactivated by name or
10587 address. These are usually placed at locations which facilitate
10588 investigating what the target is actually doing. @value{GDBN}'s
10589 support for static tracing includes being able to list instrumentation
10590 points, and attach them with @value{GDBN} defined high level
10591 tracepoints that expose the whole range of convenience of
10592 @value{GDBN}'s tracepoints support. Namely, support for collecting
10593 registers values and values of global or local (to the instrumentation
10594 point) variables; tracepoint conditions and trace state variables.
10595 The act of installing a @value{GDBN} static tracepoint on an
10596 instrumentation point, or marker, is referred to as @dfn{probing} a
10597 static tracepoint marker.
10599 @code{gdbserver} supports tracepoints on some target systems.
10600 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10602 This section describes commands to set tracepoints and associated
10603 conditions and actions.
10606 * Create and Delete Tracepoints::
10607 * Enable and Disable Tracepoints::
10608 * Tracepoint Passcounts::
10609 * Tracepoint Conditions::
10610 * Trace State Variables::
10611 * Tracepoint Actions::
10612 * Listing Tracepoints::
10613 * Listing Static Tracepoint Markers::
10614 * Starting and Stopping Trace Experiments::
10615 * Tracepoint Restrictions::
10618 @node Create and Delete Tracepoints
10619 @subsection Create and Delete Tracepoints
10622 @cindex set tracepoint
10624 @item trace @var{location}
10625 The @code{trace} command is very similar to the @code{break} command.
10626 Its argument @var{location} can be a source line, a function name, or
10627 an address in the target program. @xref{Specify Location}. The
10628 @code{trace} command defines a tracepoint, which is a point in the
10629 target program where the debugger will briefly stop, collect some
10630 data, and then allow the program to continue. Setting a tracepoint or
10631 changing its actions takes effect immediately if the remote stub
10632 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10634 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10635 these changes don't take effect until the next @code{tstart}
10636 command, and once a trace experiment is running, further changes will
10637 not have any effect until the next trace experiment starts. In addition,
10638 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10639 address is not yet resolved. (This is similar to pending breakpoints.)
10640 Pending tracepoints are not downloaded to the target and not installed
10641 until they are resolved. The resolution of pending tracepoints requires
10642 @value{GDBN} support---when debugging with the remote target, and
10643 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10644 tracing}), pending tracepoints can not be resolved (and downloaded to
10645 the remote stub) while @value{GDBN} is disconnected.
10647 Here are some examples of using the @code{trace} command:
10650 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10652 (@value{GDBP}) @b{trace +2} // 2 lines forward
10654 (@value{GDBP}) @b{trace my_function} // first source line of function
10656 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10658 (@value{GDBP}) @b{trace *0x2117c4} // an address
10662 You can abbreviate @code{trace} as @code{tr}.
10664 @item trace @var{location} if @var{cond}
10665 Set a tracepoint with condition @var{cond}; evaluate the expression
10666 @var{cond} each time the tracepoint is reached, and collect data only
10667 if the value is nonzero---that is, if @var{cond} evaluates as true.
10668 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10669 information on tracepoint conditions.
10671 @item ftrace @var{location} [ if @var{cond} ]
10672 @cindex set fast tracepoint
10673 @cindex fast tracepoints, setting
10675 The @code{ftrace} command sets a fast tracepoint. For targets that
10676 support them, fast tracepoints will use a more efficient but possibly
10677 less general technique to trigger data collection, such as a jump
10678 instruction instead of a trap, or some sort of hardware support. It
10679 may not be possible to create a fast tracepoint at the desired
10680 location, in which case the command will exit with an explanatory
10683 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10686 On 32-bit x86-architecture systems, fast tracepoints normally need to
10687 be placed at an instruction that is 5 bytes or longer, but can be
10688 placed at 4-byte instructions if the low 64K of memory of the target
10689 program is available to install trampolines. Some Unix-type systems,
10690 such as @sc{gnu}/Linux, exclude low addresses from the program's
10691 address space; but for instance with the Linux kernel it is possible
10692 to let @value{GDBN} use this area by doing a @command{sysctl} command
10693 to set the @code{mmap_min_addr} kernel parameter, as in
10696 sudo sysctl -w vm.mmap_min_addr=32768
10700 which sets the low address to 32K, which leaves plenty of room for
10701 trampolines. The minimum address should be set to a page boundary.
10703 @item strace @var{location} [ if @var{cond} ]
10704 @cindex set static tracepoint
10705 @cindex static tracepoints, setting
10706 @cindex probe static tracepoint marker
10708 The @code{strace} command sets a static tracepoint. For targets that
10709 support it, setting a static tracepoint probes a static
10710 instrumentation point, or marker, found at @var{location}. It may not
10711 be possible to set a static tracepoint at the desired location, in
10712 which case the command will exit with an explanatory message.
10714 @value{GDBN} handles arguments to @code{strace} exactly as for
10715 @code{trace}, with the addition that the user can also specify
10716 @code{-m @var{marker}} as @var{location}. This probes the marker
10717 identified by the @var{marker} string identifier. This identifier
10718 depends on the static tracepoint backend library your program is
10719 using. You can find all the marker identifiers in the @samp{ID} field
10720 of the @code{info static-tracepoint-markers} command output.
10721 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10722 Markers}. For example, in the following small program using the UST
10728 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10733 the marker id is composed of joining the first two arguments to the
10734 @code{trace_mark} call with a slash, which translates to:
10737 (@value{GDBP}) info static-tracepoint-markers
10738 Cnt Enb ID Address What
10739 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10745 so you may probe the marker above with:
10748 (@value{GDBP}) strace -m ust/bar33
10751 Static tracepoints accept an extra collect action --- @code{collect
10752 $_sdata}. This collects arbitrary user data passed in the probe point
10753 call to the tracing library. In the UST example above, you'll see
10754 that the third argument to @code{trace_mark} is a printf-like format
10755 string. The user data is then the result of running that formating
10756 string against the following arguments. Note that @code{info
10757 static-tracepoint-markers} command output lists that format string in
10758 the @samp{Data:} field.
10760 You can inspect this data when analyzing the trace buffer, by printing
10761 the $_sdata variable like any other variable available to
10762 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10765 @cindex last tracepoint number
10766 @cindex recent tracepoint number
10767 @cindex tracepoint number
10768 The convenience variable @code{$tpnum} records the tracepoint number
10769 of the most recently set tracepoint.
10771 @kindex delete tracepoint
10772 @cindex tracepoint deletion
10773 @item delete tracepoint @r{[}@var{num}@r{]}
10774 Permanently delete one or more tracepoints. With no argument, the
10775 default is to delete all tracepoints. Note that the regular
10776 @code{delete} command can remove tracepoints also.
10781 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10783 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10787 You can abbreviate this command as @code{del tr}.
10790 @node Enable and Disable Tracepoints
10791 @subsection Enable and Disable Tracepoints
10793 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10796 @kindex disable tracepoint
10797 @item disable tracepoint @r{[}@var{num}@r{]}
10798 Disable tracepoint @var{num}, or all tracepoints if no argument
10799 @var{num} is given. A disabled tracepoint will have no effect during
10800 a trace experiment, but it is not forgotten. You can re-enable
10801 a disabled tracepoint using the @code{enable tracepoint} command.
10802 If the command is issued during a trace experiment and the debug target
10803 has support for disabling tracepoints during a trace experiment, then the
10804 change will be effective immediately. Otherwise, it will be applied to the
10805 next trace experiment.
10807 @kindex enable tracepoint
10808 @item enable tracepoint @r{[}@var{num}@r{]}
10809 Enable tracepoint @var{num}, or all tracepoints. If this command is
10810 issued during a trace experiment and the debug target supports enabling
10811 tracepoints during a trace experiment, then the enabled tracepoints will
10812 become effective immediately. Otherwise, they will become effective the
10813 next time a trace experiment is run.
10816 @node Tracepoint Passcounts
10817 @subsection Tracepoint Passcounts
10821 @cindex tracepoint pass count
10822 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10823 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10824 automatically stop a trace experiment. If a tracepoint's passcount is
10825 @var{n}, then the trace experiment will be automatically stopped on
10826 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10827 @var{num} is not specified, the @code{passcount} command sets the
10828 passcount of the most recently defined tracepoint. If no passcount is
10829 given, the trace experiment will run until stopped explicitly by the
10835 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10836 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10838 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10839 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10840 (@value{GDBP}) @b{trace foo}
10841 (@value{GDBP}) @b{pass 3}
10842 (@value{GDBP}) @b{trace bar}
10843 (@value{GDBP}) @b{pass 2}
10844 (@value{GDBP}) @b{trace baz}
10845 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10846 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10847 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10848 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10852 @node Tracepoint Conditions
10853 @subsection Tracepoint Conditions
10854 @cindex conditional tracepoints
10855 @cindex tracepoint conditions
10857 The simplest sort of tracepoint collects data every time your program
10858 reaches a specified place. You can also specify a @dfn{condition} for
10859 a tracepoint. A condition is just a Boolean expression in your
10860 programming language (@pxref{Expressions, ,Expressions}). A
10861 tracepoint with a condition evaluates the expression each time your
10862 program reaches it, and data collection happens only if the condition
10865 Tracepoint conditions can be specified when a tracepoint is set, by
10866 using @samp{if} in the arguments to the @code{trace} command.
10867 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10868 also be set or changed at any time with the @code{condition} command,
10869 just as with breakpoints.
10871 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10872 the conditional expression itself. Instead, @value{GDBN} encodes the
10873 expression into an agent expression (@pxref{Agent Expressions})
10874 suitable for execution on the target, independently of @value{GDBN}.
10875 Global variables become raw memory locations, locals become stack
10876 accesses, and so forth.
10878 For instance, suppose you have a function that is usually called
10879 frequently, but should not be called after an error has occurred. You
10880 could use the following tracepoint command to collect data about calls
10881 of that function that happen while the error code is propagating
10882 through the program; an unconditional tracepoint could end up
10883 collecting thousands of useless trace frames that you would have to
10887 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10890 @node Trace State Variables
10891 @subsection Trace State Variables
10892 @cindex trace state variables
10894 A @dfn{trace state variable} is a special type of variable that is
10895 created and managed by target-side code. The syntax is the same as
10896 that for GDB's convenience variables (a string prefixed with ``$''),
10897 but they are stored on the target. They must be created explicitly,
10898 using a @code{tvariable} command. They are always 64-bit signed
10901 Trace state variables are remembered by @value{GDBN}, and downloaded
10902 to the target along with tracepoint information when the trace
10903 experiment starts. There are no intrinsic limits on the number of
10904 trace state variables, beyond memory limitations of the target.
10906 @cindex convenience variables, and trace state variables
10907 Although trace state variables are managed by the target, you can use
10908 them in print commands and expressions as if they were convenience
10909 variables; @value{GDBN} will get the current value from the target
10910 while the trace experiment is running. Trace state variables share
10911 the same namespace as other ``$'' variables, which means that you
10912 cannot have trace state variables with names like @code{$23} or
10913 @code{$pc}, nor can you have a trace state variable and a convenience
10914 variable with the same name.
10918 @item tvariable $@var{name} [ = @var{expression} ]
10920 The @code{tvariable} command creates a new trace state variable named
10921 @code{$@var{name}}, and optionally gives it an initial value of
10922 @var{expression}. @var{expression} is evaluated when this command is
10923 entered; the result will be converted to an integer if possible,
10924 otherwise @value{GDBN} will report an error. A subsequent
10925 @code{tvariable} command specifying the same name does not create a
10926 variable, but instead assigns the supplied initial value to the
10927 existing variable of that name, overwriting any previous initial
10928 value. The default initial value is 0.
10930 @item info tvariables
10931 @kindex info tvariables
10932 List all the trace state variables along with their initial values.
10933 Their current values may also be displayed, if the trace experiment is
10936 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10937 @kindex delete tvariable
10938 Delete the given trace state variables, or all of them if no arguments
10943 @node Tracepoint Actions
10944 @subsection Tracepoint Action Lists
10948 @cindex tracepoint actions
10949 @item actions @r{[}@var{num}@r{]}
10950 This command will prompt for a list of actions to be taken when the
10951 tracepoint is hit. If the tracepoint number @var{num} is not
10952 specified, this command sets the actions for the one that was most
10953 recently defined (so that you can define a tracepoint and then say
10954 @code{actions} without bothering about its number). You specify the
10955 actions themselves on the following lines, one action at a time, and
10956 terminate the actions list with a line containing just @code{end}. So
10957 far, the only defined actions are @code{collect}, @code{teval}, and
10958 @code{while-stepping}.
10960 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10961 Commands, ,Breakpoint Command Lists}), except that only the defined
10962 actions are allowed; any other @value{GDBN} command is rejected.
10964 @cindex remove actions from a tracepoint
10965 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10966 and follow it immediately with @samp{end}.
10969 (@value{GDBP}) @b{collect @var{data}} // collect some data
10971 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10973 (@value{GDBP}) @b{end} // signals the end of actions.
10976 In the following example, the action list begins with @code{collect}
10977 commands indicating the things to be collected when the tracepoint is
10978 hit. Then, in order to single-step and collect additional data
10979 following the tracepoint, a @code{while-stepping} command is used,
10980 followed by the list of things to be collected after each step in a
10981 sequence of single steps. The @code{while-stepping} command is
10982 terminated by its own separate @code{end} command. Lastly, the action
10983 list is terminated by an @code{end} command.
10986 (@value{GDBP}) @b{trace foo}
10987 (@value{GDBP}) @b{actions}
10988 Enter actions for tracepoint 1, one per line:
10991 > while-stepping 12
10992 > collect $pc, arr[i]
10997 @kindex collect @r{(tracepoints)}
10998 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10999 Collect values of the given expressions when the tracepoint is hit.
11000 This command accepts a comma-separated list of any valid expressions.
11001 In addition to global, static, or local variables, the following
11002 special arguments are supported:
11006 Collect all registers.
11009 Collect all function arguments.
11012 Collect all local variables.
11015 Collect the return address. This is helpful if you want to see more
11019 @vindex $_sdata@r{, collect}
11020 Collect static tracepoint marker specific data. Only available for
11021 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11022 Lists}. On the UST static tracepoints library backend, an
11023 instrumentation point resembles a @code{printf} function call. The
11024 tracing library is able to collect user specified data formatted to a
11025 character string using the format provided by the programmer that
11026 instrumented the program. Other backends have similar mechanisms.
11027 Here's an example of a UST marker call:
11030 const char master_name[] = "$your_name";
11031 trace_mark(channel1, marker1, "hello %s", master_name)
11034 In this case, collecting @code{$_sdata} collects the string
11035 @samp{hello $yourname}. When analyzing the trace buffer, you can
11036 inspect @samp{$_sdata} like any other variable available to
11040 You can give several consecutive @code{collect} commands, each one
11041 with a single argument, or one @code{collect} command with several
11042 arguments separated by commas; the effect is the same.
11044 The optional @var{mods} changes the usual handling of the arguments.
11045 @code{s} requests that pointers to chars be handled as strings, in
11046 particular collecting the contents of the memory being pointed at, up
11047 to the first zero. The upper bound is by default the value of the
11048 @code{print elements} variable; if @code{s} is followed by a decimal
11049 number, that is the upper bound instead. So for instance
11050 @samp{collect/s25 mystr} collects as many as 25 characters at
11053 The command @code{info scope} (@pxref{Symbols, info scope}) is
11054 particularly useful for figuring out what data to collect.
11056 @kindex teval @r{(tracepoints)}
11057 @item teval @var{expr1}, @var{expr2}, @dots{}
11058 Evaluate the given expressions when the tracepoint is hit. This
11059 command accepts a comma-separated list of expressions. The results
11060 are discarded, so this is mainly useful for assigning values to trace
11061 state variables (@pxref{Trace State Variables}) without adding those
11062 values to the trace buffer, as would be the case if the @code{collect}
11065 @kindex while-stepping @r{(tracepoints)}
11066 @item while-stepping @var{n}
11067 Perform @var{n} single-step instruction traces after the tracepoint,
11068 collecting new data after each step. The @code{while-stepping}
11069 command is followed by the list of what to collect while stepping
11070 (followed by its own @code{end} command):
11073 > while-stepping 12
11074 > collect $regs, myglobal
11080 Note that @code{$pc} is not automatically collected by
11081 @code{while-stepping}; you need to explicitly collect that register if
11082 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11085 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11086 @kindex set default-collect
11087 @cindex default collection action
11088 This variable is a list of expressions to collect at each tracepoint
11089 hit. It is effectively an additional @code{collect} action prepended
11090 to every tracepoint action list. The expressions are parsed
11091 individually for each tracepoint, so for instance a variable named
11092 @code{xyz} may be interpreted as a global for one tracepoint, and a
11093 local for another, as appropriate to the tracepoint's location.
11095 @item show default-collect
11096 @kindex show default-collect
11097 Show the list of expressions that are collected by default at each
11102 @node Listing Tracepoints
11103 @subsection Listing Tracepoints
11106 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11107 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11108 @cindex information about tracepoints
11109 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11110 Display information about the tracepoint @var{num}. If you don't
11111 specify a tracepoint number, displays information about all the
11112 tracepoints defined so far. The format is similar to that used for
11113 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11114 command, simply restricting itself to tracepoints.
11116 A tracepoint's listing may include additional information specific to
11121 its passcount as given by the @code{passcount @var{n}} command
11125 (@value{GDBP}) @b{info trace}
11126 Num Type Disp Enb Address What
11127 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11129 collect globfoo, $regs
11138 This command can be abbreviated @code{info tp}.
11141 @node Listing Static Tracepoint Markers
11142 @subsection Listing Static Tracepoint Markers
11145 @kindex info static-tracepoint-markers
11146 @cindex information about static tracepoint markers
11147 @item info static-tracepoint-markers
11148 Display information about all static tracepoint markers defined in the
11151 For each marker, the following columns are printed:
11155 An incrementing counter, output to help readability. This is not a
11158 The marker ID, as reported by the target.
11159 @item Enabled or Disabled
11160 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11161 that are not enabled.
11163 Where the marker is in your program, as a memory address.
11165 Where the marker is in the source for your program, as a file and line
11166 number. If the debug information included in the program does not
11167 allow @value{GDBN} to locate the source of the marker, this column
11168 will be left blank.
11172 In addition, the following information may be printed for each marker:
11176 User data passed to the tracing library by the marker call. In the
11177 UST backend, this is the format string passed as argument to the
11179 @item Static tracepoints probing the marker
11180 The list of static tracepoints attached to the marker.
11184 (@value{GDBP}) info static-tracepoint-markers
11185 Cnt ID Enb Address What
11186 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11187 Data: number1 %d number2 %d
11188 Probed by static tracepoints: #2
11189 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11195 @node Starting and Stopping Trace Experiments
11196 @subsection Starting and Stopping Trace Experiments
11199 @kindex tstart [ @var{notes} ]
11200 @cindex start a new trace experiment
11201 @cindex collected data discarded
11203 This command starts the trace experiment, and begins collecting data.
11204 It has the side effect of discarding all the data collected in the
11205 trace buffer during the previous trace experiment. If any arguments
11206 are supplied, they are taken as a note and stored with the trace
11207 experiment's state. The notes may be arbitrary text, and are
11208 especially useful with disconnected tracing in a multi-user context;
11209 the notes can explain what the trace is doing, supply user contact
11210 information, and so forth.
11212 @kindex tstop [ @var{notes} ]
11213 @cindex stop a running trace experiment
11215 This command stops the trace experiment. If any arguments are
11216 supplied, they are recorded with the experiment as a note. This is
11217 useful if you are stopping a trace started by someone else, for
11218 instance if the trace is interfering with the system's behavior and
11219 needs to be stopped quickly.
11221 @strong{Note}: a trace experiment and data collection may stop
11222 automatically if any tracepoint's passcount is reached
11223 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11226 @cindex status of trace data collection
11227 @cindex trace experiment, status of
11229 This command displays the status of the current trace data
11233 Here is an example of the commands we described so far:
11236 (@value{GDBP}) @b{trace gdb_c_test}
11237 (@value{GDBP}) @b{actions}
11238 Enter actions for tracepoint #1, one per line.
11239 > collect $regs,$locals,$args
11240 > while-stepping 11
11244 (@value{GDBP}) @b{tstart}
11245 [time passes @dots{}]
11246 (@value{GDBP}) @b{tstop}
11249 @anchor{disconnected tracing}
11250 @cindex disconnected tracing
11251 You can choose to continue running the trace experiment even if
11252 @value{GDBN} disconnects from the target, voluntarily or
11253 involuntarily. For commands such as @code{detach}, the debugger will
11254 ask what you want to do with the trace. But for unexpected
11255 terminations (@value{GDBN} crash, network outage), it would be
11256 unfortunate to lose hard-won trace data, so the variable
11257 @code{disconnected-tracing} lets you decide whether the trace should
11258 continue running without @value{GDBN}.
11261 @item set disconnected-tracing on
11262 @itemx set disconnected-tracing off
11263 @kindex set disconnected-tracing
11264 Choose whether a tracing run should continue to run if @value{GDBN}
11265 has disconnected from the target. Note that @code{detach} or
11266 @code{quit} will ask you directly what to do about a running trace no
11267 matter what this variable's setting, so the variable is mainly useful
11268 for handling unexpected situations, such as loss of the network.
11270 @item show disconnected-tracing
11271 @kindex show disconnected-tracing
11272 Show the current choice for disconnected tracing.
11276 When you reconnect to the target, the trace experiment may or may not
11277 still be running; it might have filled the trace buffer in the
11278 meantime, or stopped for one of the other reasons. If it is running,
11279 it will continue after reconnection.
11281 Upon reconnection, the target will upload information about the
11282 tracepoints in effect. @value{GDBN} will then compare that
11283 information to the set of tracepoints currently defined, and attempt
11284 to match them up, allowing for the possibility that the numbers may
11285 have changed due to creation and deletion in the meantime. If one of
11286 the target's tracepoints does not match any in @value{GDBN}, the
11287 debugger will create a new tracepoint, so that you have a number with
11288 which to specify that tracepoint. This matching-up process is
11289 necessarily heuristic, and it may result in useless tracepoints being
11290 created; you may simply delete them if they are of no use.
11292 @cindex circular trace buffer
11293 If your target agent supports a @dfn{circular trace buffer}, then you
11294 can run a trace experiment indefinitely without filling the trace
11295 buffer; when space runs out, the agent deletes already-collected trace
11296 frames, oldest first, until there is enough room to continue
11297 collecting. This is especially useful if your tracepoints are being
11298 hit too often, and your trace gets terminated prematurely because the
11299 buffer is full. To ask for a circular trace buffer, simply set
11300 @samp{circular-trace-buffer} to on. You can set this at any time,
11301 including during tracing; if the agent can do it, it will change
11302 buffer handling on the fly, otherwise it will not take effect until
11306 @item set circular-trace-buffer on
11307 @itemx set circular-trace-buffer off
11308 @kindex set circular-trace-buffer
11309 Choose whether a tracing run should use a linear or circular buffer
11310 for trace data. A linear buffer will not lose any trace data, but may
11311 fill up prematurely, while a circular buffer will discard old trace
11312 data, but it will have always room for the latest tracepoint hits.
11314 @item show circular-trace-buffer
11315 @kindex show circular-trace-buffer
11316 Show the current choice for the trace buffer. Note that this may not
11317 match the agent's current buffer handling, nor is it guaranteed to
11318 match the setting that might have been in effect during a past run,
11319 for instance if you are looking at frames from a trace file.
11324 @item set trace-user @var{text}
11325 @kindex set trace-user
11327 @item show trace-user
11328 @kindex show trace-user
11330 @item set trace-notes @var{text}
11331 @kindex set trace-notes
11332 Set the trace run's notes.
11334 @item show trace-notes
11335 @kindex show trace-notes
11336 Show the trace run's notes.
11338 @item set trace-stop-notes @var{text}
11339 @kindex set trace-stop-notes
11340 Set the trace run's stop notes. The handling of the note is as for
11341 @code{tstop} arguments; the set command is convenient way to fix a
11342 stop note that is mistaken or incomplete.
11344 @item show trace-stop-notes
11345 @kindex show trace-stop-notes
11346 Show the trace run's stop notes.
11350 @node Tracepoint Restrictions
11351 @subsection Tracepoint Restrictions
11353 @cindex tracepoint restrictions
11354 There are a number of restrictions on the use of tracepoints. As
11355 described above, tracepoint data gathering occurs on the target
11356 without interaction from @value{GDBN}. Thus the full capabilities of
11357 the debugger are not available during data gathering, and then at data
11358 examination time, you will be limited by only having what was
11359 collected. The following items describe some common problems, but it
11360 is not exhaustive, and you may run into additional difficulties not
11366 Tracepoint expressions are intended to gather objects (lvalues). Thus
11367 the full flexibility of GDB's expression evaluator is not available.
11368 You cannot call functions, cast objects to aggregate types, access
11369 convenience variables or modify values (except by assignment to trace
11370 state variables). Some language features may implicitly call
11371 functions (for instance Objective-C fields with accessors), and therefore
11372 cannot be collected either.
11375 Collection of local variables, either individually or in bulk with
11376 @code{$locals} or @code{$args}, during @code{while-stepping} may
11377 behave erratically. The stepping action may enter a new scope (for
11378 instance by stepping into a function), or the location of the variable
11379 may change (for instance it is loaded into a register). The
11380 tracepoint data recorded uses the location information for the
11381 variables that is correct for the tracepoint location. When the
11382 tracepoint is created, it is not possible, in general, to determine
11383 where the steps of a @code{while-stepping} sequence will advance the
11384 program---particularly if a conditional branch is stepped.
11387 Collection of an incompletely-initialized or partially-destroyed object
11388 may result in something that @value{GDBN} cannot display, or displays
11389 in a misleading way.
11392 When @value{GDBN} displays a pointer to character it automatically
11393 dereferences the pointer to also display characters of the string
11394 being pointed to. However, collecting the pointer during tracing does
11395 not automatically collect the string. You need to explicitly
11396 dereference the pointer and provide size information if you want to
11397 collect not only the pointer, but the memory pointed to. For example,
11398 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11402 It is not possible to collect a complete stack backtrace at a
11403 tracepoint. Instead, you may collect the registers and a few hundred
11404 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11405 (adjust to use the name of the actual stack pointer register on your
11406 target architecture, and the amount of stack you wish to capture).
11407 Then the @code{backtrace} command will show a partial backtrace when
11408 using a trace frame. The number of stack frames that can be examined
11409 depends on the sizes of the frames in the collected stack. Note that
11410 if you ask for a block so large that it goes past the bottom of the
11411 stack, the target agent may report an error trying to read from an
11415 If you do not collect registers at a tracepoint, @value{GDBN} can
11416 infer that the value of @code{$pc} must be the same as the address of
11417 the tracepoint and use that when you are looking at a trace frame
11418 for that tracepoint. However, this cannot work if the tracepoint has
11419 multiple locations (for instance if it was set in a function that was
11420 inlined), or if it has a @code{while-stepping} loop. In those cases
11421 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11426 @node Analyze Collected Data
11427 @section Using the Collected Data
11429 After the tracepoint experiment ends, you use @value{GDBN} commands
11430 for examining the trace data. The basic idea is that each tracepoint
11431 collects a trace @dfn{snapshot} every time it is hit and another
11432 snapshot every time it single-steps. All these snapshots are
11433 consecutively numbered from zero and go into a buffer, and you can
11434 examine them later. The way you examine them is to @dfn{focus} on a
11435 specific trace snapshot. When the remote stub is focused on a trace
11436 snapshot, it will respond to all @value{GDBN} requests for memory and
11437 registers by reading from the buffer which belongs to that snapshot,
11438 rather than from @emph{real} memory or registers of the program being
11439 debugged. This means that @strong{all} @value{GDBN} commands
11440 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11441 behave as if we were currently debugging the program state as it was
11442 when the tracepoint occurred. Any requests for data that are not in
11443 the buffer will fail.
11446 * tfind:: How to select a trace snapshot
11447 * tdump:: How to display all data for a snapshot
11448 * save tracepoints:: How to save tracepoints for a future run
11452 @subsection @code{tfind @var{n}}
11455 @cindex select trace snapshot
11456 @cindex find trace snapshot
11457 The basic command for selecting a trace snapshot from the buffer is
11458 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11459 counting from zero. If no argument @var{n} is given, the next
11460 snapshot is selected.
11462 Here are the various forms of using the @code{tfind} command.
11466 Find the first snapshot in the buffer. This is a synonym for
11467 @code{tfind 0} (since 0 is the number of the first snapshot).
11470 Stop debugging trace snapshots, resume @emph{live} debugging.
11473 Same as @samp{tfind none}.
11476 No argument means find the next trace snapshot.
11479 Find the previous trace snapshot before the current one. This permits
11480 retracing earlier steps.
11482 @item tfind tracepoint @var{num}
11483 Find the next snapshot associated with tracepoint @var{num}. Search
11484 proceeds forward from the last examined trace snapshot. If no
11485 argument @var{num} is given, it means find the next snapshot collected
11486 for the same tracepoint as the current snapshot.
11488 @item tfind pc @var{addr}
11489 Find the next snapshot associated with the value @var{addr} of the
11490 program counter. Search proceeds forward from the last examined trace
11491 snapshot. If no argument @var{addr} is given, it means find the next
11492 snapshot with the same value of PC as the current snapshot.
11494 @item tfind outside @var{addr1}, @var{addr2}
11495 Find the next snapshot whose PC is outside the given range of
11496 addresses (exclusive).
11498 @item tfind range @var{addr1}, @var{addr2}
11499 Find the next snapshot whose PC is between @var{addr1} and
11500 @var{addr2} (inclusive).
11502 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11503 Find the next snapshot associated with the source line @var{n}. If
11504 the optional argument @var{file} is given, refer to line @var{n} in
11505 that source file. Search proceeds forward from the last examined
11506 trace snapshot. If no argument @var{n} is given, it means find the
11507 next line other than the one currently being examined; thus saying
11508 @code{tfind line} repeatedly can appear to have the same effect as
11509 stepping from line to line in a @emph{live} debugging session.
11512 The default arguments for the @code{tfind} commands are specifically
11513 designed to make it easy to scan through the trace buffer. For
11514 instance, @code{tfind} with no argument selects the next trace
11515 snapshot, and @code{tfind -} with no argument selects the previous
11516 trace snapshot. So, by giving one @code{tfind} command, and then
11517 simply hitting @key{RET} repeatedly you can examine all the trace
11518 snapshots in order. Or, by saying @code{tfind -} and then hitting
11519 @key{RET} repeatedly you can examine the snapshots in reverse order.
11520 The @code{tfind line} command with no argument selects the snapshot
11521 for the next source line executed. The @code{tfind pc} command with
11522 no argument selects the next snapshot with the same program counter
11523 (PC) as the current frame. The @code{tfind tracepoint} command with
11524 no argument selects the next trace snapshot collected by the same
11525 tracepoint as the current one.
11527 In addition to letting you scan through the trace buffer manually,
11528 these commands make it easy to construct @value{GDBN} scripts that
11529 scan through the trace buffer and print out whatever collected data
11530 you are interested in. Thus, if we want to examine the PC, FP, and SP
11531 registers from each trace frame in the buffer, we can say this:
11534 (@value{GDBP}) @b{tfind start}
11535 (@value{GDBP}) @b{while ($trace_frame != -1)}
11536 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11537 $trace_frame, $pc, $sp, $fp
11541 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11542 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11543 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11544 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11545 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11546 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11547 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11548 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11549 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11550 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11551 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11554 Or, if we want to examine the variable @code{X} at each source line in
11558 (@value{GDBP}) @b{tfind start}
11559 (@value{GDBP}) @b{while ($trace_frame != -1)}
11560 > printf "Frame %d, X == %d\n", $trace_frame, X
11570 @subsection @code{tdump}
11572 @cindex dump all data collected at tracepoint
11573 @cindex tracepoint data, display
11575 This command takes no arguments. It prints all the data collected at
11576 the current trace snapshot.
11579 (@value{GDBP}) @b{trace 444}
11580 (@value{GDBP}) @b{actions}
11581 Enter actions for tracepoint #2, one per line:
11582 > collect $regs, $locals, $args, gdb_long_test
11585 (@value{GDBP}) @b{tstart}
11587 (@value{GDBP}) @b{tfind line 444}
11588 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11590 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11592 (@value{GDBP}) @b{tdump}
11593 Data collected at tracepoint 2, trace frame 1:
11594 d0 0xc4aa0085 -995491707
11598 d4 0x71aea3d 119204413
11601 d7 0x380035 3670069
11602 a0 0x19e24a 1696330
11603 a1 0x3000668 50333288
11605 a3 0x322000 3284992
11606 a4 0x3000698 50333336
11607 a5 0x1ad3cc 1758156
11608 fp 0x30bf3c 0x30bf3c
11609 sp 0x30bf34 0x30bf34
11611 pc 0x20b2c8 0x20b2c8
11615 p = 0x20e5b4 "gdb-test"
11622 gdb_long_test = 17 '\021'
11627 @code{tdump} works by scanning the tracepoint's current collection
11628 actions and printing the value of each expression listed. So
11629 @code{tdump} can fail, if after a run, you change the tracepoint's
11630 actions to mention variables that were not collected during the run.
11632 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11633 uses the collected value of @code{$pc} to distinguish between trace
11634 frames that were collected at the tracepoint hit, and frames that were
11635 collected while stepping. This allows it to correctly choose whether
11636 to display the basic list of collections, or the collections from the
11637 body of the while-stepping loop. However, if @code{$pc} was not collected,
11638 then @code{tdump} will always attempt to dump using the basic collection
11639 list, and may fail if a while-stepping frame does not include all the
11640 same data that is collected at the tracepoint hit.
11641 @c This is getting pretty arcane, example would be good.
11643 @node save tracepoints
11644 @subsection @code{save tracepoints @var{filename}}
11645 @kindex save tracepoints
11646 @kindex save-tracepoints
11647 @cindex save tracepoints for future sessions
11649 This command saves all current tracepoint definitions together with
11650 their actions and passcounts, into a file @file{@var{filename}}
11651 suitable for use in a later debugging session. To read the saved
11652 tracepoint definitions, use the @code{source} command (@pxref{Command
11653 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11654 alias for @w{@code{save tracepoints}}
11656 @node Tracepoint Variables
11657 @section Convenience Variables for Tracepoints
11658 @cindex tracepoint variables
11659 @cindex convenience variables for tracepoints
11662 @vindex $trace_frame
11663 @item (int) $trace_frame
11664 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11665 snapshot is selected.
11667 @vindex $tracepoint
11668 @item (int) $tracepoint
11669 The tracepoint for the current trace snapshot.
11671 @vindex $trace_line
11672 @item (int) $trace_line
11673 The line number for the current trace snapshot.
11675 @vindex $trace_file
11676 @item (char []) $trace_file
11677 The source file for the current trace snapshot.
11679 @vindex $trace_func
11680 @item (char []) $trace_func
11681 The name of the function containing @code{$tracepoint}.
11684 Note: @code{$trace_file} is not suitable for use in @code{printf},
11685 use @code{output} instead.
11687 Here's a simple example of using these convenience variables for
11688 stepping through all the trace snapshots and printing some of their
11689 data. Note that these are not the same as trace state variables,
11690 which are managed by the target.
11693 (@value{GDBP}) @b{tfind start}
11695 (@value{GDBP}) @b{while $trace_frame != -1}
11696 > output $trace_file
11697 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11703 @section Using Trace Files
11704 @cindex trace files
11706 In some situations, the target running a trace experiment may no
11707 longer be available; perhaps it crashed, or the hardware was needed
11708 for a different activity. To handle these cases, you can arrange to
11709 dump the trace data into a file, and later use that file as a source
11710 of trace data, via the @code{target tfile} command.
11715 @item tsave [ -r ] @var{filename}
11716 Save the trace data to @var{filename}. By default, this command
11717 assumes that @var{filename} refers to the host filesystem, so if
11718 necessary @value{GDBN} will copy raw trace data up from the target and
11719 then save it. If the target supports it, you can also supply the
11720 optional argument @code{-r} (``remote'') to direct the target to save
11721 the data directly into @var{filename} in its own filesystem, which may be
11722 more efficient if the trace buffer is very large. (Note, however, that
11723 @code{target tfile} can only read from files accessible to the host.)
11725 @kindex target tfile
11727 @item target tfile @var{filename}
11728 Use the file named @var{filename} as a source of trace data. Commands
11729 that examine data work as they do with a live target, but it is not
11730 possible to run any new trace experiments. @code{tstatus} will report
11731 the state of the trace run at the moment the data was saved, as well
11732 as the current trace frame you are examining. @var{filename} must be
11733 on a filesystem accessible to the host.
11738 @chapter Debugging Programs That Use Overlays
11741 If your program is too large to fit completely in your target system's
11742 memory, you can sometimes use @dfn{overlays} to work around this
11743 problem. @value{GDBN} provides some support for debugging programs that
11747 * How Overlays Work:: A general explanation of overlays.
11748 * Overlay Commands:: Managing overlays in @value{GDBN}.
11749 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11750 mapped by asking the inferior.
11751 * Overlay Sample Program:: A sample program using overlays.
11754 @node How Overlays Work
11755 @section How Overlays Work
11756 @cindex mapped overlays
11757 @cindex unmapped overlays
11758 @cindex load address, overlay's
11759 @cindex mapped address
11760 @cindex overlay area
11762 Suppose you have a computer whose instruction address space is only 64
11763 kilobytes long, but which has much more memory which can be accessed by
11764 other means: special instructions, segment registers, or memory
11765 management hardware, for example. Suppose further that you want to
11766 adapt a program which is larger than 64 kilobytes to run on this system.
11768 One solution is to identify modules of your program which are relatively
11769 independent, and need not call each other directly; call these modules
11770 @dfn{overlays}. Separate the overlays from the main program, and place
11771 their machine code in the larger memory. Place your main program in
11772 instruction memory, but leave at least enough space there to hold the
11773 largest overlay as well.
11775 Now, to call a function located in an overlay, you must first copy that
11776 overlay's machine code from the large memory into the space set aside
11777 for it in the instruction memory, and then jump to its entry point
11780 @c NB: In the below the mapped area's size is greater or equal to the
11781 @c size of all overlays. This is intentional to remind the developer
11782 @c that overlays don't necessarily need to be the same size.
11786 Data Instruction Larger
11787 Address Space Address Space Address Space
11788 +-----------+ +-----------+ +-----------+
11790 +-----------+ +-----------+ +-----------+<-- overlay 1
11791 | program | | main | .----| overlay 1 | load address
11792 | variables | | program | | +-----------+
11793 | and heap | | | | | |
11794 +-----------+ | | | +-----------+<-- overlay 2
11795 | | +-----------+ | | | load address
11796 +-----------+ | | | .-| overlay 2 |
11798 mapped --->+-----------+ | | +-----------+
11799 address | | | | | |
11800 | overlay | <-' | | |
11801 | area | <---' +-----------+<-- overlay 3
11802 | | <---. | | load address
11803 +-----------+ `--| overlay 3 |
11810 @anchor{A code overlay}A code overlay
11814 The diagram (@pxref{A code overlay}) shows a system with separate data
11815 and instruction address spaces. To map an overlay, the program copies
11816 its code from the larger address space to the instruction address space.
11817 Since the overlays shown here all use the same mapped address, only one
11818 may be mapped at a time. For a system with a single address space for
11819 data and instructions, the diagram would be similar, except that the
11820 program variables and heap would share an address space with the main
11821 program and the overlay area.
11823 An overlay loaded into instruction memory and ready for use is called a
11824 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11825 instruction memory. An overlay not present (or only partially present)
11826 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11827 is its address in the larger memory. The mapped address is also called
11828 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11829 called the @dfn{load memory address}, or @dfn{LMA}.
11831 Unfortunately, overlays are not a completely transparent way to adapt a
11832 program to limited instruction memory. They introduce a new set of
11833 global constraints you must keep in mind as you design your program:
11838 Before calling or returning to a function in an overlay, your program
11839 must make sure that overlay is actually mapped. Otherwise, the call or
11840 return will transfer control to the right address, but in the wrong
11841 overlay, and your program will probably crash.
11844 If the process of mapping an overlay is expensive on your system, you
11845 will need to choose your overlays carefully to minimize their effect on
11846 your program's performance.
11849 The executable file you load onto your system must contain each
11850 overlay's instructions, appearing at the overlay's load address, not its
11851 mapped address. However, each overlay's instructions must be relocated
11852 and its symbols defined as if the overlay were at its mapped address.
11853 You can use GNU linker scripts to specify different load and relocation
11854 addresses for pieces of your program; see @ref{Overlay Description,,,
11855 ld.info, Using ld: the GNU linker}.
11858 The procedure for loading executable files onto your system must be able
11859 to load their contents into the larger address space as well as the
11860 instruction and data spaces.
11864 The overlay system described above is rather simple, and could be
11865 improved in many ways:
11870 If your system has suitable bank switch registers or memory management
11871 hardware, you could use those facilities to make an overlay's load area
11872 contents simply appear at their mapped address in instruction space.
11873 This would probably be faster than copying the overlay to its mapped
11874 area in the usual way.
11877 If your overlays are small enough, you could set aside more than one
11878 overlay area, and have more than one overlay mapped at a time.
11881 You can use overlays to manage data, as well as instructions. In
11882 general, data overlays are even less transparent to your design than
11883 code overlays: whereas code overlays only require care when you call or
11884 return to functions, data overlays require care every time you access
11885 the data. Also, if you change the contents of a data overlay, you
11886 must copy its contents back out to its load address before you can copy a
11887 different data overlay into the same mapped area.
11892 @node Overlay Commands
11893 @section Overlay Commands
11895 To use @value{GDBN}'s overlay support, each overlay in your program must
11896 correspond to a separate section of the executable file. The section's
11897 virtual memory address and load memory address must be the overlay's
11898 mapped and load addresses. Identifying overlays with sections allows
11899 @value{GDBN} to determine the appropriate address of a function or
11900 variable, depending on whether the overlay is mapped or not.
11902 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11903 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11908 Disable @value{GDBN}'s overlay support. When overlay support is
11909 disabled, @value{GDBN} assumes that all functions and variables are
11910 always present at their mapped addresses. By default, @value{GDBN}'s
11911 overlay support is disabled.
11913 @item overlay manual
11914 @cindex manual overlay debugging
11915 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11916 relies on you to tell it which overlays are mapped, and which are not,
11917 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11918 commands described below.
11920 @item overlay map-overlay @var{overlay}
11921 @itemx overlay map @var{overlay}
11922 @cindex map an overlay
11923 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11924 be the name of the object file section containing the overlay. When an
11925 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11926 functions and variables at their mapped addresses. @value{GDBN} assumes
11927 that any other overlays whose mapped ranges overlap that of
11928 @var{overlay} are now unmapped.
11930 @item overlay unmap-overlay @var{overlay}
11931 @itemx overlay unmap @var{overlay}
11932 @cindex unmap an overlay
11933 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11934 must be the name of the object file section containing the overlay.
11935 When an overlay is unmapped, @value{GDBN} assumes it can find the
11936 overlay's functions and variables at their load addresses.
11939 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11940 consults a data structure the overlay manager maintains in the inferior
11941 to see which overlays are mapped. For details, see @ref{Automatic
11942 Overlay Debugging}.
11944 @item overlay load-target
11945 @itemx overlay load
11946 @cindex reloading the overlay table
11947 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11948 re-reads the table @value{GDBN} automatically each time the inferior
11949 stops, so this command should only be necessary if you have changed the
11950 overlay mapping yourself using @value{GDBN}. This command is only
11951 useful when using automatic overlay debugging.
11953 @item overlay list-overlays
11954 @itemx overlay list
11955 @cindex listing mapped overlays
11956 Display a list of the overlays currently mapped, along with their mapped
11957 addresses, load addresses, and sizes.
11961 Normally, when @value{GDBN} prints a code address, it includes the name
11962 of the function the address falls in:
11965 (@value{GDBP}) print main
11966 $3 = @{int ()@} 0x11a0 <main>
11969 When overlay debugging is enabled, @value{GDBN} recognizes code in
11970 unmapped overlays, and prints the names of unmapped functions with
11971 asterisks around them. For example, if @code{foo} is a function in an
11972 unmapped overlay, @value{GDBN} prints it this way:
11975 (@value{GDBP}) overlay list
11976 No sections are mapped.
11977 (@value{GDBP}) print foo
11978 $5 = @{int (int)@} 0x100000 <*foo*>
11981 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11985 (@value{GDBP}) overlay list
11986 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11987 mapped at 0x1016 - 0x104a
11988 (@value{GDBP}) print foo
11989 $6 = @{int (int)@} 0x1016 <foo>
11992 When overlay debugging is enabled, @value{GDBN} can find the correct
11993 address for functions and variables in an overlay, whether or not the
11994 overlay is mapped. This allows most @value{GDBN} commands, like
11995 @code{break} and @code{disassemble}, to work normally, even on unmapped
11996 code. However, @value{GDBN}'s breakpoint support has some limitations:
12000 @cindex breakpoints in overlays
12001 @cindex overlays, setting breakpoints in
12002 You can set breakpoints in functions in unmapped overlays, as long as
12003 @value{GDBN} can write to the overlay at its load address.
12005 @value{GDBN} can not set hardware or simulator-based breakpoints in
12006 unmapped overlays. However, if you set a breakpoint at the end of your
12007 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12008 you are using manual overlay management), @value{GDBN} will re-set its
12009 breakpoints properly.
12013 @node Automatic Overlay Debugging
12014 @section Automatic Overlay Debugging
12015 @cindex automatic overlay debugging
12017 @value{GDBN} can automatically track which overlays are mapped and which
12018 are not, given some simple co-operation from the overlay manager in the
12019 inferior. If you enable automatic overlay debugging with the
12020 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12021 looks in the inferior's memory for certain variables describing the
12022 current state of the overlays.
12024 Here are the variables your overlay manager must define to support
12025 @value{GDBN}'s automatic overlay debugging:
12029 @item @code{_ovly_table}:
12030 This variable must be an array of the following structures:
12035 /* The overlay's mapped address. */
12038 /* The size of the overlay, in bytes. */
12039 unsigned long size;
12041 /* The overlay's load address. */
12044 /* Non-zero if the overlay is currently mapped;
12046 unsigned long mapped;
12050 @item @code{_novlys}:
12051 This variable must be a four-byte signed integer, holding the total
12052 number of elements in @code{_ovly_table}.
12056 To decide whether a particular overlay is mapped or not, @value{GDBN}
12057 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12058 @code{lma} members equal the VMA and LMA of the overlay's section in the
12059 executable file. When @value{GDBN} finds a matching entry, it consults
12060 the entry's @code{mapped} member to determine whether the overlay is
12063 In addition, your overlay manager may define a function called
12064 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12065 will silently set a breakpoint there. If the overlay manager then
12066 calls this function whenever it has changed the overlay table, this
12067 will enable @value{GDBN} to accurately keep track of which overlays
12068 are in program memory, and update any breakpoints that may be set
12069 in overlays. This will allow breakpoints to work even if the
12070 overlays are kept in ROM or other non-writable memory while they
12071 are not being executed.
12073 @node Overlay Sample Program
12074 @section Overlay Sample Program
12075 @cindex overlay example program
12077 When linking a program which uses overlays, you must place the overlays
12078 at their load addresses, while relocating them to run at their mapped
12079 addresses. To do this, you must write a linker script (@pxref{Overlay
12080 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12081 since linker scripts are specific to a particular host system, target
12082 architecture, and target memory layout, this manual cannot provide
12083 portable sample code demonstrating @value{GDBN}'s overlay support.
12085 However, the @value{GDBN} source distribution does contain an overlaid
12086 program, with linker scripts for a few systems, as part of its test
12087 suite. The program consists of the following files from
12088 @file{gdb/testsuite/gdb.base}:
12092 The main program file.
12094 A simple overlay manager, used by @file{overlays.c}.
12099 Overlay modules, loaded and used by @file{overlays.c}.
12102 Linker scripts for linking the test program on the @code{d10v-elf}
12103 and @code{m32r-elf} targets.
12106 You can build the test program using the @code{d10v-elf} GCC
12107 cross-compiler like this:
12110 $ d10v-elf-gcc -g -c overlays.c
12111 $ d10v-elf-gcc -g -c ovlymgr.c
12112 $ d10v-elf-gcc -g -c foo.c
12113 $ d10v-elf-gcc -g -c bar.c
12114 $ d10v-elf-gcc -g -c baz.c
12115 $ d10v-elf-gcc -g -c grbx.c
12116 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12117 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12120 The build process is identical for any other architecture, except that
12121 you must substitute the appropriate compiler and linker script for the
12122 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12126 @chapter Using @value{GDBN} with Different Languages
12129 Although programming languages generally have common aspects, they are
12130 rarely expressed in the same manner. For instance, in ANSI C,
12131 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12132 Modula-2, it is accomplished by @code{p^}. Values can also be
12133 represented (and displayed) differently. Hex numbers in C appear as
12134 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12136 @cindex working language
12137 Language-specific information is built into @value{GDBN} for some languages,
12138 allowing you to express operations like the above in your program's
12139 native language, and allowing @value{GDBN} to output values in a manner
12140 consistent with the syntax of your program's native language. The
12141 language you use to build expressions is called the @dfn{working
12145 * Setting:: Switching between source languages
12146 * Show:: Displaying the language
12147 * Checks:: Type and range checks
12148 * Supported Languages:: Supported languages
12149 * Unsupported Languages:: Unsupported languages
12153 @section Switching Between Source Languages
12155 There are two ways to control the working language---either have @value{GDBN}
12156 set it automatically, or select it manually yourself. You can use the
12157 @code{set language} command for either purpose. On startup, @value{GDBN}
12158 defaults to setting the language automatically. The working language is
12159 used to determine how expressions you type are interpreted, how values
12162 In addition to the working language, every source file that
12163 @value{GDBN} knows about has its own working language. For some object
12164 file formats, the compiler might indicate which language a particular
12165 source file is in. However, most of the time @value{GDBN} infers the
12166 language from the name of the file. The language of a source file
12167 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12168 show each frame appropriately for its own language. There is no way to
12169 set the language of a source file from within @value{GDBN}, but you can
12170 set the language associated with a filename extension. @xref{Show, ,
12171 Displaying the Language}.
12173 This is most commonly a problem when you use a program, such
12174 as @code{cfront} or @code{f2c}, that generates C but is written in
12175 another language. In that case, make the
12176 program use @code{#line} directives in its C output; that way
12177 @value{GDBN} will know the correct language of the source code of the original
12178 program, and will display that source code, not the generated C code.
12181 * Filenames:: Filename extensions and languages.
12182 * Manually:: Setting the working language manually
12183 * Automatically:: Having @value{GDBN} infer the source language
12187 @subsection List of Filename Extensions and Languages
12189 If a source file name ends in one of the following extensions, then
12190 @value{GDBN} infers that its language is the one indicated.
12208 C@t{++} source file
12214 Objective-C source file
12218 Fortran source file
12221 Modula-2 source file
12225 Assembler source file. This actually behaves almost like C, but
12226 @value{GDBN} does not skip over function prologues when stepping.
12229 In addition, you may set the language associated with a filename
12230 extension. @xref{Show, , Displaying the Language}.
12233 @subsection Setting the Working Language
12235 If you allow @value{GDBN} to set the language automatically,
12236 expressions are interpreted the same way in your debugging session and
12239 @kindex set language
12240 If you wish, you may set the language manually. To do this, issue the
12241 command @samp{set language @var{lang}}, where @var{lang} is the name of
12242 a language, such as
12243 @code{c} or @code{modula-2}.
12244 For a list of the supported languages, type @samp{set language}.
12246 Setting the language manually prevents @value{GDBN} from updating the working
12247 language automatically. This can lead to confusion if you try
12248 to debug a program when the working language is not the same as the
12249 source language, when an expression is acceptable to both
12250 languages---but means different things. For instance, if the current
12251 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12259 might not have the effect you intended. In C, this means to add
12260 @code{b} and @code{c} and place the result in @code{a}. The result
12261 printed would be the value of @code{a}. In Modula-2, this means to compare
12262 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12264 @node Automatically
12265 @subsection Having @value{GDBN} Infer the Source Language
12267 To have @value{GDBN} set the working language automatically, use
12268 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12269 then infers the working language. That is, when your program stops in a
12270 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12271 working language to the language recorded for the function in that
12272 frame. If the language for a frame is unknown (that is, if the function
12273 or block corresponding to the frame was defined in a source file that
12274 does not have a recognized extension), the current working language is
12275 not changed, and @value{GDBN} issues a warning.
12277 This may not seem necessary for most programs, which are written
12278 entirely in one source language. However, program modules and libraries
12279 written in one source language can be used by a main program written in
12280 a different source language. Using @samp{set language auto} in this
12281 case frees you from having to set the working language manually.
12284 @section Displaying the Language
12286 The following commands help you find out which language is the
12287 working language, and also what language source files were written in.
12290 @item show language
12291 @kindex show language
12292 Display the current working language. This is the
12293 language you can use with commands such as @code{print} to
12294 build and compute expressions that may involve variables in your program.
12297 @kindex info frame@r{, show the source language}
12298 Display the source language for this frame. This language becomes the
12299 working language if you use an identifier from this frame.
12300 @xref{Frame Info, ,Information about a Frame}, to identify the other
12301 information listed here.
12304 @kindex info source@r{, show the source language}
12305 Display the source language of this source file.
12306 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12307 information listed here.
12310 In unusual circumstances, you may have source files with extensions
12311 not in the standard list. You can then set the extension associated
12312 with a language explicitly:
12315 @item set extension-language @var{ext} @var{language}
12316 @kindex set extension-language
12317 Tell @value{GDBN} that source files with extension @var{ext} are to be
12318 assumed as written in the source language @var{language}.
12320 @item info extensions
12321 @kindex info extensions
12322 List all the filename extensions and the associated languages.
12326 @section Type and Range Checking
12329 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12330 checking are included, but they do not yet have any effect. This
12331 section documents the intended facilities.
12333 @c FIXME remove warning when type/range code added
12335 Some languages are designed to guard you against making seemingly common
12336 errors through a series of compile- and run-time checks. These include
12337 checking the type of arguments to functions and operators, and making
12338 sure mathematical overflows are caught at run time. Checks such as
12339 these help to ensure a program's correctness once it has been compiled
12340 by eliminating type mismatches, and providing active checks for range
12341 errors when your program is running.
12343 @value{GDBN} can check for conditions like the above if you wish.
12344 Although @value{GDBN} does not check the statements in your program,
12345 it can check expressions entered directly into @value{GDBN} for
12346 evaluation via the @code{print} command, for example. As with the
12347 working language, @value{GDBN} can also decide whether or not to check
12348 automatically based on your program's source language.
12349 @xref{Supported Languages, ,Supported Languages}, for the default
12350 settings of supported languages.
12353 * Type Checking:: An overview of type checking
12354 * Range Checking:: An overview of range checking
12357 @cindex type checking
12358 @cindex checks, type
12359 @node Type Checking
12360 @subsection An Overview of Type Checking
12362 Some languages, such as Modula-2, are strongly typed, meaning that the
12363 arguments to operators and functions have to be of the correct type,
12364 otherwise an error occurs. These checks prevent type mismatch
12365 errors from ever causing any run-time problems. For example,
12373 The second example fails because the @code{CARDINAL} 1 is not
12374 type-compatible with the @code{REAL} 2.3.
12376 For the expressions you use in @value{GDBN} commands, you can tell the
12377 @value{GDBN} type checker to skip checking;
12378 to treat any mismatches as errors and abandon the expression;
12379 or to only issue warnings when type mismatches occur,
12380 but evaluate the expression anyway. When you choose the last of
12381 these, @value{GDBN} evaluates expressions like the second example above, but
12382 also issues a warning.
12384 Even if you turn type checking off, there may be other reasons
12385 related to type that prevent @value{GDBN} from evaluating an expression.
12386 For instance, @value{GDBN} does not know how to add an @code{int} and
12387 a @code{struct foo}. These particular type errors have nothing to do
12388 with the language in use, and usually arise from expressions, such as
12389 the one described above, which make little sense to evaluate anyway.
12391 Each language defines to what degree it is strict about type. For
12392 instance, both Modula-2 and C require the arguments to arithmetical
12393 operators to be numbers. In C, enumerated types and pointers can be
12394 represented as numbers, so that they are valid arguments to mathematical
12395 operators. @xref{Supported Languages, ,Supported Languages}, for further
12396 details on specific languages.
12398 @value{GDBN} provides some additional commands for controlling the type checker:
12400 @kindex set check type
12401 @kindex show check type
12403 @item set check type auto
12404 Set type checking on or off based on the current working language.
12405 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12408 @item set check type on
12409 @itemx set check type off
12410 Set type checking on or off, overriding the default setting for the
12411 current working language. Issue a warning if the setting does not
12412 match the language default. If any type mismatches occur in
12413 evaluating an expression while type checking is on, @value{GDBN} prints a
12414 message and aborts evaluation of the expression.
12416 @item set check type warn
12417 Cause the type checker to issue warnings, but to always attempt to
12418 evaluate the expression. Evaluating the expression may still
12419 be impossible for other reasons. For example, @value{GDBN} cannot add
12420 numbers and structures.
12423 Show the current setting of the type checker, and whether or not @value{GDBN}
12424 is setting it automatically.
12427 @cindex range checking
12428 @cindex checks, range
12429 @node Range Checking
12430 @subsection An Overview of Range Checking
12432 In some languages (such as Modula-2), it is an error to exceed the
12433 bounds of a type; this is enforced with run-time checks. Such range
12434 checking is meant to ensure program correctness by making sure
12435 computations do not overflow, or indices on an array element access do
12436 not exceed the bounds of the array.
12438 For expressions you use in @value{GDBN} commands, you can tell
12439 @value{GDBN} to treat range errors in one of three ways: ignore them,
12440 always treat them as errors and abandon the expression, or issue
12441 warnings but evaluate the expression anyway.
12443 A range error can result from numerical overflow, from exceeding an
12444 array index bound, or when you type a constant that is not a member
12445 of any type. Some languages, however, do not treat overflows as an
12446 error. In many implementations of C, mathematical overflow causes the
12447 result to ``wrap around'' to lower values---for example, if @var{m} is
12448 the largest integer value, and @var{s} is the smallest, then
12451 @var{m} + 1 @result{} @var{s}
12454 This, too, is specific to individual languages, and in some cases
12455 specific to individual compilers or machines. @xref{Supported Languages, ,
12456 Supported Languages}, for further details on specific languages.
12458 @value{GDBN} provides some additional commands for controlling the range checker:
12460 @kindex set check range
12461 @kindex show check range
12463 @item set check range auto
12464 Set range checking on or off based on the current working language.
12465 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12468 @item set check range on
12469 @itemx set check range off
12470 Set range checking on or off, overriding the default setting for the
12471 current working language. A warning is issued if the setting does not
12472 match the language default. If a range error occurs and range checking is on,
12473 then a message is printed and evaluation of the expression is aborted.
12475 @item set check range warn
12476 Output messages when the @value{GDBN} range checker detects a range error,
12477 but attempt to evaluate the expression anyway. Evaluating the
12478 expression may still be impossible for other reasons, such as accessing
12479 memory that the process does not own (a typical example from many Unix
12483 Show the current setting of the range checker, and whether or not it is
12484 being set automatically by @value{GDBN}.
12487 @node Supported Languages
12488 @section Supported Languages
12490 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
12491 OpenCL C, Pascal, assembly, Modula-2, and Ada.
12492 @c This is false ...
12493 Some @value{GDBN} features may be used in expressions regardless of the
12494 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12495 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12496 ,Expressions}) can be used with the constructs of any supported
12499 The following sections detail to what degree each source language is
12500 supported by @value{GDBN}. These sections are not meant to be language
12501 tutorials or references, but serve only as a reference guide to what the
12502 @value{GDBN} expression parser accepts, and what input and output
12503 formats should look like for different languages. There are many good
12504 books written on each of these languages; please look to these for a
12505 language reference or tutorial.
12508 * C:: C and C@t{++}
12511 * Objective-C:: Objective-C
12512 * OpenCL C:: OpenCL C
12513 * Fortran:: Fortran
12515 * Modula-2:: Modula-2
12520 @subsection C and C@t{++}
12522 @cindex C and C@t{++}
12523 @cindex expressions in C or C@t{++}
12525 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12526 to both languages. Whenever this is the case, we discuss those languages
12530 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12531 @cindex @sc{gnu} C@t{++}
12532 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12533 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12534 effectively, you must compile your C@t{++} programs with a supported
12535 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12536 compiler (@code{aCC}).
12539 * C Operators:: C and C@t{++} operators
12540 * C Constants:: C and C@t{++} constants
12541 * C Plus Plus Expressions:: C@t{++} expressions
12542 * C Defaults:: Default settings for C and C@t{++}
12543 * C Checks:: C and C@t{++} type and range checks
12544 * Debugging C:: @value{GDBN} and C
12545 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12546 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12550 @subsubsection C and C@t{++} Operators
12552 @cindex C and C@t{++} operators
12554 Operators must be defined on values of specific types. For instance,
12555 @code{+} is defined on numbers, but not on structures. Operators are
12556 often defined on groups of types.
12558 For the purposes of C and C@t{++}, the following definitions hold:
12563 @emph{Integral types} include @code{int} with any of its storage-class
12564 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12567 @emph{Floating-point types} include @code{float}, @code{double}, and
12568 @code{long double} (if supported by the target platform).
12571 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12574 @emph{Scalar types} include all of the above.
12579 The following operators are supported. They are listed here
12580 in order of increasing precedence:
12584 The comma or sequencing operator. Expressions in a comma-separated list
12585 are evaluated from left to right, with the result of the entire
12586 expression being the last expression evaluated.
12589 Assignment. The value of an assignment expression is the value
12590 assigned. Defined on scalar types.
12593 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12594 and translated to @w{@code{@var{a} = @var{a op b}}}.
12595 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12596 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12597 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12600 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12601 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12605 Logical @sc{or}. Defined on integral types.
12608 Logical @sc{and}. Defined on integral types.
12611 Bitwise @sc{or}. Defined on integral types.
12614 Bitwise exclusive-@sc{or}. Defined on integral types.
12617 Bitwise @sc{and}. Defined on integral types.
12620 Equality and inequality. Defined on scalar types. The value of these
12621 expressions is 0 for false and non-zero for true.
12623 @item <@r{, }>@r{, }<=@r{, }>=
12624 Less than, greater than, less than or equal, greater than or equal.
12625 Defined on scalar types. The value of these expressions is 0 for false
12626 and non-zero for true.
12629 left shift, and right shift. Defined on integral types.
12632 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12635 Addition and subtraction. Defined on integral types, floating-point types and
12638 @item *@r{, }/@r{, }%
12639 Multiplication, division, and modulus. Multiplication and division are
12640 defined on integral and floating-point types. Modulus is defined on
12644 Increment and decrement. When appearing before a variable, the
12645 operation is performed before the variable is used in an expression;
12646 when appearing after it, the variable's value is used before the
12647 operation takes place.
12650 Pointer dereferencing. Defined on pointer types. Same precedence as
12654 Address operator. Defined on variables. Same precedence as @code{++}.
12656 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12657 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12658 to examine the address
12659 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12663 Negative. Defined on integral and floating-point types. Same
12664 precedence as @code{++}.
12667 Logical negation. Defined on integral types. Same precedence as
12671 Bitwise complement operator. Defined on integral types. Same precedence as
12676 Structure member, and pointer-to-structure member. For convenience,
12677 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12678 pointer based on the stored type information.
12679 Defined on @code{struct} and @code{union} data.
12682 Dereferences of pointers to members.
12685 Array indexing. @code{@var{a}[@var{i}]} is defined as
12686 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12689 Function parameter list. Same precedence as @code{->}.
12692 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12693 and @code{class} types.
12696 Doubled colons also represent the @value{GDBN} scope operator
12697 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12701 If an operator is redefined in the user code, @value{GDBN} usually
12702 attempts to invoke the redefined version instead of using the operator's
12703 predefined meaning.
12706 @subsubsection C and C@t{++} Constants
12708 @cindex C and C@t{++} constants
12710 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12715 Integer constants are a sequence of digits. Octal constants are
12716 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12717 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12718 @samp{l}, specifying that the constant should be treated as a
12722 Floating point constants are a sequence of digits, followed by a decimal
12723 point, followed by a sequence of digits, and optionally followed by an
12724 exponent. An exponent is of the form:
12725 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12726 sequence of digits. The @samp{+} is optional for positive exponents.
12727 A floating-point constant may also end with a letter @samp{f} or
12728 @samp{F}, specifying that the constant should be treated as being of
12729 the @code{float} (as opposed to the default @code{double}) type; or with
12730 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12734 Enumerated constants consist of enumerated identifiers, or their
12735 integral equivalents.
12738 Character constants are a single character surrounded by single quotes
12739 (@code{'}), or a number---the ordinal value of the corresponding character
12740 (usually its @sc{ascii} value). Within quotes, the single character may
12741 be represented by a letter or by @dfn{escape sequences}, which are of
12742 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12743 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12744 @samp{@var{x}} is a predefined special character---for example,
12745 @samp{\n} for newline.
12747 Wide character constants can be written by prefixing a character
12748 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12749 form of @samp{x}. The target wide character set is used when
12750 computing the value of this constant (@pxref{Character Sets}).
12753 String constants are a sequence of character constants surrounded by
12754 double quotes (@code{"}). Any valid character constant (as described
12755 above) may appear. Double quotes within the string must be preceded by
12756 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12759 Wide string constants can be written by prefixing a string constant
12760 with @samp{L}, as in C. The target wide character set is used when
12761 computing the value of this constant (@pxref{Character Sets}).
12764 Pointer constants are an integral value. You can also write pointers
12765 to constants using the C operator @samp{&}.
12768 Array constants are comma-separated lists surrounded by braces @samp{@{}
12769 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12770 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12771 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12774 @node C Plus Plus Expressions
12775 @subsubsection C@t{++} Expressions
12777 @cindex expressions in C@t{++}
12778 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12780 @cindex debugging C@t{++} programs
12781 @cindex C@t{++} compilers
12782 @cindex debug formats and C@t{++}
12783 @cindex @value{NGCC} and C@t{++}
12785 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12786 the proper compiler and the proper debug format. Currently,
12787 @value{GDBN} works best when debugging C@t{++} code that is compiled
12788 with the most recent version of @value{NGCC} possible. The DWARF
12789 debugging format is preferred; @value{NGCC} defaults to this on most
12790 popular platforms. Other compilers and/or debug formats are likely to
12791 work badly or not at all when using @value{GDBN} to debug C@t{++}
12792 code. @xref{Compilation}.
12797 @cindex member functions
12799 Member function calls are allowed; you can use expressions like
12802 count = aml->GetOriginal(x, y)
12805 @vindex this@r{, inside C@t{++} member functions}
12806 @cindex namespace in C@t{++}
12808 While a member function is active (in the selected stack frame), your
12809 expressions have the same namespace available as the member function;
12810 that is, @value{GDBN} allows implicit references to the class instance
12811 pointer @code{this} following the same rules as C@t{++}. @code{using}
12812 declarations in the current scope are also respected by @value{GDBN}.
12814 @cindex call overloaded functions
12815 @cindex overloaded functions, calling
12816 @cindex type conversions in C@t{++}
12818 You can call overloaded functions; @value{GDBN} resolves the function
12819 call to the right definition, with some restrictions. @value{GDBN} does not
12820 perform overload resolution involving user-defined type conversions,
12821 calls to constructors, or instantiations of templates that do not exist
12822 in the program. It also cannot handle ellipsis argument lists or
12825 It does perform integral conversions and promotions, floating-point
12826 promotions, arithmetic conversions, pointer conversions, conversions of
12827 class objects to base classes, and standard conversions such as those of
12828 functions or arrays to pointers; it requires an exact match on the
12829 number of function arguments.
12831 Overload resolution is always performed, unless you have specified
12832 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12833 ,@value{GDBN} Features for C@t{++}}.
12835 You must specify @code{set overload-resolution off} in order to use an
12836 explicit function signature to call an overloaded function, as in
12838 p 'foo(char,int)'('x', 13)
12841 The @value{GDBN} command-completion facility can simplify this;
12842 see @ref{Completion, ,Command Completion}.
12844 @cindex reference declarations
12846 @value{GDBN} understands variables declared as C@t{++} references; you can use
12847 them in expressions just as you do in C@t{++} source---they are automatically
12850 In the parameter list shown when @value{GDBN} displays a frame, the values of
12851 reference variables are not displayed (unlike other variables); this
12852 avoids clutter, since references are often used for large structures.
12853 The @emph{address} of a reference variable is always shown, unless
12854 you have specified @samp{set print address off}.
12857 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12858 expressions can use it just as expressions in your program do. Since
12859 one scope may be defined in another, you can use @code{::} repeatedly if
12860 necessary, for example in an expression like
12861 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12862 resolving name scope by reference to source files, in both C and C@t{++}
12863 debugging (@pxref{Variables, ,Program Variables}).
12866 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12871 @subsubsection C and C@t{++} Defaults
12873 @cindex C and C@t{++} defaults
12875 If you allow @value{GDBN} to set type and range checking automatically, they
12876 both default to @code{off} whenever the working language changes to
12877 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12878 selects the working language.
12880 If you allow @value{GDBN} to set the language automatically, it
12881 recognizes source files whose names end with @file{.c}, @file{.C}, or
12882 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12883 these files, it sets the working language to C or C@t{++}.
12884 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12885 for further details.
12887 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12888 @c unimplemented. If (b) changes, it might make sense to let this node
12889 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12892 @subsubsection C and C@t{++} Type and Range Checks
12894 @cindex C and C@t{++} checks
12896 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12897 is not used. However, if you turn type checking on, @value{GDBN}
12898 considers two variables type equivalent if:
12902 The two variables are structured and have the same structure, union, or
12906 The two variables have the same type name, or types that have been
12907 declared equivalent through @code{typedef}.
12910 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12913 The two @code{struct}, @code{union}, or @code{enum} variables are
12914 declared in the same declaration. (Note: this may not be true for all C
12919 Range checking, if turned on, is done on mathematical operations. Array
12920 indices are not checked, since they are often used to index a pointer
12921 that is not itself an array.
12924 @subsubsection @value{GDBN} and C
12926 The @code{set print union} and @code{show print union} commands apply to
12927 the @code{union} type. When set to @samp{on}, any @code{union} that is
12928 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12929 appears as @samp{@{...@}}.
12931 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12932 with pointers and a memory allocation function. @xref{Expressions,
12935 @node Debugging C Plus Plus
12936 @subsubsection @value{GDBN} Features for C@t{++}
12938 @cindex commands for C@t{++}
12940 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12941 designed specifically for use with C@t{++}. Here is a summary:
12944 @cindex break in overloaded functions
12945 @item @r{breakpoint menus}
12946 When you want a breakpoint in a function whose name is overloaded,
12947 @value{GDBN} has the capability to display a menu of possible breakpoint
12948 locations to help you specify which function definition you want.
12949 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12951 @cindex overloading in C@t{++}
12952 @item rbreak @var{regex}
12953 Setting breakpoints using regular expressions is helpful for setting
12954 breakpoints on overloaded functions that are not members of any special
12956 @xref{Set Breaks, ,Setting Breakpoints}.
12958 @cindex C@t{++} exception handling
12961 Debug C@t{++} exception handling using these commands. @xref{Set
12962 Catchpoints, , Setting Catchpoints}.
12964 @cindex inheritance
12965 @item ptype @var{typename}
12966 Print inheritance relationships as well as other information for type
12968 @xref{Symbols, ,Examining the Symbol Table}.
12970 @item info vtbl @var{expression}.
12971 The @code{info vtbl} command can be used to display the virtual
12972 method tables of the object computed by @var{expression}. This shows
12973 one entry per virtual table; there may be multiple virtual tables when
12974 multiple inheritance is in use.
12976 @cindex C@t{++} symbol display
12977 @item set print demangle
12978 @itemx show print demangle
12979 @itemx set print asm-demangle
12980 @itemx show print asm-demangle
12981 Control whether C@t{++} symbols display in their source form, both when
12982 displaying code as C@t{++} source and when displaying disassemblies.
12983 @xref{Print Settings, ,Print Settings}.
12985 @item set print object
12986 @itemx show print object
12987 Choose whether to print derived (actual) or declared types of objects.
12988 @xref{Print Settings, ,Print Settings}.
12990 @item set print vtbl
12991 @itemx show print vtbl
12992 Control the format for printing virtual function tables.
12993 @xref{Print Settings, ,Print Settings}.
12994 (The @code{vtbl} commands do not work on programs compiled with the HP
12995 ANSI C@t{++} compiler (@code{aCC}).)
12997 @kindex set overload-resolution
12998 @cindex overloaded functions, overload resolution
12999 @item set overload-resolution on
13000 Enable overload resolution for C@t{++} expression evaluation. The default
13001 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13002 and searches for a function whose signature matches the argument types,
13003 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13004 Expressions, ,C@t{++} Expressions}, for details).
13005 If it cannot find a match, it emits a message.
13007 @item set overload-resolution off
13008 Disable overload resolution for C@t{++} expression evaluation. For
13009 overloaded functions that are not class member functions, @value{GDBN}
13010 chooses the first function of the specified name that it finds in the
13011 symbol table, whether or not its arguments are of the correct type. For
13012 overloaded functions that are class member functions, @value{GDBN}
13013 searches for a function whose signature @emph{exactly} matches the
13016 @kindex show overload-resolution
13017 @item show overload-resolution
13018 Show the current setting of overload resolution.
13020 @item @r{Overloaded symbol names}
13021 You can specify a particular definition of an overloaded symbol, using
13022 the same notation that is used to declare such symbols in C@t{++}: type
13023 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13024 also use the @value{GDBN} command-line word completion facilities to list the
13025 available choices, or to finish the type list for you.
13026 @xref{Completion,, Command Completion}, for details on how to do this.
13029 @node Decimal Floating Point
13030 @subsubsection Decimal Floating Point format
13031 @cindex decimal floating point format
13033 @value{GDBN} can examine, set and perform computations with numbers in
13034 decimal floating point format, which in the C language correspond to the
13035 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13036 specified by the extension to support decimal floating-point arithmetic.
13038 There are two encodings in use, depending on the architecture: BID (Binary
13039 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13040 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13043 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13044 to manipulate decimal floating point numbers, it is not possible to convert
13045 (using a cast, for example) integers wider than 32-bit to decimal float.
13047 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13048 point computations, error checking in decimal float operations ignores
13049 underflow, overflow and divide by zero exceptions.
13051 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13052 to inspect @code{_Decimal128} values stored in floating point registers.
13053 See @ref{PowerPC,,PowerPC} for more details.
13059 @value{GDBN} can be used to debug programs written in D and compiled with
13060 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13061 specific feature --- dynamic arrays.
13066 @cindex Go (programming language)
13067 @value{GDBN} can be used to debug programs written in Go and compiled with
13068 @file{gccgo} or @file{6g} compilers.
13070 Here is a summary of the Go-specific features and restrictions:
13073 @cindex current Go package
13074 @item The current Go package
13075 The name of the current package does not need to be specified when
13076 specifying global variables and functions.
13078 For example, given the program:
13082 var myglob = "Shall we?"
13088 When stopped inside @code{main} either of these work:
13092 (gdb) p main.myglob
13095 @cindex builtin Go types
13096 @item Builtin Go types
13097 The @code{string} type is recognized by @value{GDBN} and is printed
13100 @cindex builtin Go functions
13101 @item Builtin Go functions
13102 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13103 function and handles it internally.
13106 @cindex restrictions on Go expressions
13107 @item Restrictions on Go expressions
13108 All Go operators are supported except @code{&^}.
13109 The Go @code{_} ``blank identifier'' is not supported.
13110 Automatic dereferencing of pointers is not supported.
13113 @subsection Objective-C
13115 @cindex Objective-C
13116 This section provides information about some commands and command
13117 options that are useful for debugging Objective-C code. See also
13118 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13119 few more commands specific to Objective-C support.
13122 * Method Names in Commands::
13123 * The Print Command with Objective-C::
13126 @node Method Names in Commands
13127 @subsubsection Method Names in Commands
13129 The following commands have been extended to accept Objective-C method
13130 names as line specifications:
13132 @kindex clear@r{, and Objective-C}
13133 @kindex break@r{, and Objective-C}
13134 @kindex info line@r{, and Objective-C}
13135 @kindex jump@r{, and Objective-C}
13136 @kindex list@r{, and Objective-C}
13140 @item @code{info line}
13145 A fully qualified Objective-C method name is specified as
13148 -[@var{Class} @var{methodName}]
13151 where the minus sign is used to indicate an instance method and a
13152 plus sign (not shown) is used to indicate a class method. The class
13153 name @var{Class} and method name @var{methodName} are enclosed in
13154 brackets, similar to the way messages are specified in Objective-C
13155 source code. For example, to set a breakpoint at the @code{create}
13156 instance method of class @code{Fruit} in the program currently being
13160 break -[Fruit create]
13163 To list ten program lines around the @code{initialize} class method,
13167 list +[NSText initialize]
13170 In the current version of @value{GDBN}, the plus or minus sign is
13171 required. In future versions of @value{GDBN}, the plus or minus
13172 sign will be optional, but you can use it to narrow the search. It
13173 is also possible to specify just a method name:
13179 You must specify the complete method name, including any colons. If
13180 your program's source files contain more than one @code{create} method,
13181 you'll be presented with a numbered list of classes that implement that
13182 method. Indicate your choice by number, or type @samp{0} to exit if
13185 As another example, to clear a breakpoint established at the
13186 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13189 clear -[NSWindow makeKeyAndOrderFront:]
13192 @node The Print Command with Objective-C
13193 @subsubsection The Print Command With Objective-C
13194 @cindex Objective-C, print objects
13195 @kindex print-object
13196 @kindex po @r{(@code{print-object})}
13198 The print command has also been extended to accept methods. For example:
13201 print -[@var{object} hash]
13204 @cindex print an Objective-C object description
13205 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13207 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13208 and print the result. Also, an additional command has been added,
13209 @code{print-object} or @code{po} for short, which is meant to print
13210 the description of an object. However, this command may only work
13211 with certain Objective-C libraries that have a particular hook
13212 function, @code{_NSPrintForDebugger}, defined.
13215 @subsection OpenCL C
13218 This section provides information about @value{GDBN}s OpenCL C support.
13221 * OpenCL C Datatypes::
13222 * OpenCL C Expressions::
13223 * OpenCL C Operators::
13226 @node OpenCL C Datatypes
13227 @subsubsection OpenCL C Datatypes
13229 @cindex OpenCL C Datatypes
13230 @value{GDBN} supports the builtin scalar and vector datatypes specified
13231 by OpenCL 1.1. In addition the half- and double-precision floating point
13232 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13233 extensions are also known to @value{GDBN}.
13235 @node OpenCL C Expressions
13236 @subsubsection OpenCL C Expressions
13238 @cindex OpenCL C Expressions
13239 @value{GDBN} supports accesses to vector components including the access as
13240 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13241 supported by @value{GDBN} can be used as well.
13243 @node OpenCL C Operators
13244 @subsubsection OpenCL C Operators
13246 @cindex OpenCL C Operators
13247 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13251 @subsection Fortran
13252 @cindex Fortran-specific support in @value{GDBN}
13254 @value{GDBN} can be used to debug programs written in Fortran, but it
13255 currently supports only the features of Fortran 77 language.
13257 @cindex trailing underscore, in Fortran symbols
13258 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13259 among them) append an underscore to the names of variables and
13260 functions. When you debug programs compiled by those compilers, you
13261 will need to refer to variables and functions with a trailing
13265 * Fortran Operators:: Fortran operators and expressions
13266 * Fortran Defaults:: Default settings for Fortran
13267 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13270 @node Fortran Operators
13271 @subsubsection Fortran Operators and Expressions
13273 @cindex Fortran operators and expressions
13275 Operators must be defined on values of specific types. For instance,
13276 @code{+} is defined on numbers, but not on characters or other non-
13277 arithmetic types. Operators are often defined on groups of types.
13281 The exponentiation operator. It raises the first operand to the power
13285 The range operator. Normally used in the form of array(low:high) to
13286 represent a section of array.
13289 The access component operator. Normally used to access elements in derived
13290 types. Also suitable for unions. As unions aren't part of regular Fortran,
13291 this can only happen when accessing a register that uses a gdbarch-defined
13295 @node Fortran Defaults
13296 @subsubsection Fortran Defaults
13298 @cindex Fortran Defaults
13300 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13301 default uses case-insensitive matches for Fortran symbols. You can
13302 change that with the @samp{set case-insensitive} command, see
13303 @ref{Symbols}, for the details.
13305 @node Special Fortran Commands
13306 @subsubsection Special Fortran Commands
13308 @cindex Special Fortran commands
13310 @value{GDBN} has some commands to support Fortran-specific features,
13311 such as displaying common blocks.
13314 @cindex @code{COMMON} blocks, Fortran
13315 @kindex info common
13316 @item info common @r{[}@var{common-name}@r{]}
13317 This command prints the values contained in the Fortran @code{COMMON}
13318 block whose name is @var{common-name}. With no argument, the names of
13319 all @code{COMMON} blocks visible at the current program location are
13326 @cindex Pascal support in @value{GDBN}, limitations
13327 Debugging Pascal programs which use sets, subranges, file variables, or
13328 nested functions does not currently work. @value{GDBN} does not support
13329 entering expressions, printing values, or similar features using Pascal
13332 The Pascal-specific command @code{set print pascal_static-members}
13333 controls whether static members of Pascal objects are displayed.
13334 @xref{Print Settings, pascal_static-members}.
13337 @subsection Modula-2
13339 @cindex Modula-2, @value{GDBN} support
13341 The extensions made to @value{GDBN} to support Modula-2 only support
13342 output from the @sc{gnu} Modula-2 compiler (which is currently being
13343 developed). Other Modula-2 compilers are not currently supported, and
13344 attempting to debug executables produced by them is most likely
13345 to give an error as @value{GDBN} reads in the executable's symbol
13348 @cindex expressions in Modula-2
13350 * M2 Operators:: Built-in operators
13351 * Built-In Func/Proc:: Built-in functions and procedures
13352 * M2 Constants:: Modula-2 constants
13353 * M2 Types:: Modula-2 types
13354 * M2 Defaults:: Default settings for Modula-2
13355 * Deviations:: Deviations from standard Modula-2
13356 * M2 Checks:: Modula-2 type and range checks
13357 * M2 Scope:: The scope operators @code{::} and @code{.}
13358 * GDB/M2:: @value{GDBN} and Modula-2
13362 @subsubsection Operators
13363 @cindex Modula-2 operators
13365 Operators must be defined on values of specific types. For instance,
13366 @code{+} is defined on numbers, but not on structures. Operators are
13367 often defined on groups of types. For the purposes of Modula-2, the
13368 following definitions hold:
13373 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13377 @emph{Character types} consist of @code{CHAR} and its subranges.
13380 @emph{Floating-point types} consist of @code{REAL}.
13383 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13387 @emph{Scalar types} consist of all of the above.
13390 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13393 @emph{Boolean types} consist of @code{BOOLEAN}.
13397 The following operators are supported, and appear in order of
13398 increasing precedence:
13402 Function argument or array index separator.
13405 Assignment. The value of @var{var} @code{:=} @var{value} is
13409 Less than, greater than on integral, floating-point, or enumerated
13413 Less than or equal to, greater than or equal to
13414 on integral, floating-point and enumerated types, or set inclusion on
13415 set types. Same precedence as @code{<}.
13417 @item =@r{, }<>@r{, }#
13418 Equality and two ways of expressing inequality, valid on scalar types.
13419 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13420 available for inequality, since @code{#} conflicts with the script
13424 Set membership. Defined on set types and the types of their members.
13425 Same precedence as @code{<}.
13428 Boolean disjunction. Defined on boolean types.
13431 Boolean conjunction. Defined on boolean types.
13434 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13437 Addition and subtraction on integral and floating-point types, or union
13438 and difference on set types.
13441 Multiplication on integral and floating-point types, or set intersection
13445 Division on floating-point types, or symmetric set difference on set
13446 types. Same precedence as @code{*}.
13449 Integer division and remainder. Defined on integral types. Same
13450 precedence as @code{*}.
13453 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13456 Pointer dereferencing. Defined on pointer types.
13459 Boolean negation. Defined on boolean types. Same precedence as
13463 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13464 precedence as @code{^}.
13467 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13470 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13474 @value{GDBN} and Modula-2 scope operators.
13478 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13479 treats the use of the operator @code{IN}, or the use of operators
13480 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13481 @code{<=}, and @code{>=} on sets as an error.
13485 @node Built-In Func/Proc
13486 @subsubsection Built-in Functions and Procedures
13487 @cindex Modula-2 built-ins
13489 Modula-2 also makes available several built-in procedures and functions.
13490 In describing these, the following metavariables are used:
13495 represents an @code{ARRAY} variable.
13498 represents a @code{CHAR} constant or variable.
13501 represents a variable or constant of integral type.
13504 represents an identifier that belongs to a set. Generally used in the
13505 same function with the metavariable @var{s}. The type of @var{s} should
13506 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13509 represents a variable or constant of integral or floating-point type.
13512 represents a variable or constant of floating-point type.
13518 represents a variable.
13521 represents a variable or constant of one of many types. See the
13522 explanation of the function for details.
13525 All Modula-2 built-in procedures also return a result, described below.
13529 Returns the absolute value of @var{n}.
13532 If @var{c} is a lower case letter, it returns its upper case
13533 equivalent, otherwise it returns its argument.
13536 Returns the character whose ordinal value is @var{i}.
13539 Decrements the value in the variable @var{v} by one. Returns the new value.
13541 @item DEC(@var{v},@var{i})
13542 Decrements the value in the variable @var{v} by @var{i}. Returns the
13545 @item EXCL(@var{m},@var{s})
13546 Removes the element @var{m} from the set @var{s}. Returns the new
13549 @item FLOAT(@var{i})
13550 Returns the floating point equivalent of the integer @var{i}.
13552 @item HIGH(@var{a})
13553 Returns the index of the last member of @var{a}.
13556 Increments the value in the variable @var{v} by one. Returns the new value.
13558 @item INC(@var{v},@var{i})
13559 Increments the value in the variable @var{v} by @var{i}. Returns the
13562 @item INCL(@var{m},@var{s})
13563 Adds the element @var{m} to the set @var{s} if it is not already
13564 there. Returns the new set.
13567 Returns the maximum value of the type @var{t}.
13570 Returns the minimum value of the type @var{t}.
13573 Returns boolean TRUE if @var{i} is an odd number.
13576 Returns the ordinal value of its argument. For example, the ordinal
13577 value of a character is its @sc{ascii} value (on machines supporting the
13578 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13579 integral, character and enumerated types.
13581 @item SIZE(@var{x})
13582 Returns the size of its argument. @var{x} can be a variable or a type.
13584 @item TRUNC(@var{r})
13585 Returns the integral part of @var{r}.
13587 @item TSIZE(@var{x})
13588 Returns the size of its argument. @var{x} can be a variable or a type.
13590 @item VAL(@var{t},@var{i})
13591 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13595 @emph{Warning:} Sets and their operations are not yet supported, so
13596 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13600 @cindex Modula-2 constants
13602 @subsubsection Constants
13604 @value{GDBN} allows you to express the constants of Modula-2 in the following
13610 Integer constants are simply a sequence of digits. When used in an
13611 expression, a constant is interpreted to be type-compatible with the
13612 rest of the expression. Hexadecimal integers are specified by a
13613 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13616 Floating point constants appear as a sequence of digits, followed by a
13617 decimal point and another sequence of digits. An optional exponent can
13618 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13619 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13620 digits of the floating point constant must be valid decimal (base 10)
13624 Character constants consist of a single character enclosed by a pair of
13625 like quotes, either single (@code{'}) or double (@code{"}). They may
13626 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13627 followed by a @samp{C}.
13630 String constants consist of a sequence of characters enclosed by a
13631 pair of like quotes, either single (@code{'}) or double (@code{"}).
13632 Escape sequences in the style of C are also allowed. @xref{C
13633 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13637 Enumerated constants consist of an enumerated identifier.
13640 Boolean constants consist of the identifiers @code{TRUE} and
13644 Pointer constants consist of integral values only.
13647 Set constants are not yet supported.
13651 @subsubsection Modula-2 Types
13652 @cindex Modula-2 types
13654 Currently @value{GDBN} can print the following data types in Modula-2
13655 syntax: array types, record types, set types, pointer types, procedure
13656 types, enumerated types, subrange types and base types. You can also
13657 print the contents of variables declared using these type.
13658 This section gives a number of simple source code examples together with
13659 sample @value{GDBN} sessions.
13661 The first example contains the following section of code:
13670 and you can request @value{GDBN} to interrogate the type and value of
13671 @code{r} and @code{s}.
13674 (@value{GDBP}) print s
13676 (@value{GDBP}) ptype s
13678 (@value{GDBP}) print r
13680 (@value{GDBP}) ptype r
13685 Likewise if your source code declares @code{s} as:
13689 s: SET ['A'..'Z'] ;
13693 then you may query the type of @code{s} by:
13696 (@value{GDBP}) ptype s
13697 type = SET ['A'..'Z']
13701 Note that at present you cannot interactively manipulate set
13702 expressions using the debugger.
13704 The following example shows how you might declare an array in Modula-2
13705 and how you can interact with @value{GDBN} to print its type and contents:
13709 s: ARRAY [-10..10] OF CHAR ;
13713 (@value{GDBP}) ptype s
13714 ARRAY [-10..10] OF CHAR
13717 Note that the array handling is not yet complete and although the type
13718 is printed correctly, expression handling still assumes that all
13719 arrays have a lower bound of zero and not @code{-10} as in the example
13722 Here are some more type related Modula-2 examples:
13726 colour = (blue, red, yellow, green) ;
13727 t = [blue..yellow] ;
13735 The @value{GDBN} interaction shows how you can query the data type
13736 and value of a variable.
13739 (@value{GDBP}) print s
13741 (@value{GDBP}) ptype t
13742 type = [blue..yellow]
13746 In this example a Modula-2 array is declared and its contents
13747 displayed. Observe that the contents are written in the same way as
13748 their @code{C} counterparts.
13752 s: ARRAY [1..5] OF CARDINAL ;
13758 (@value{GDBP}) print s
13759 $1 = @{1, 0, 0, 0, 0@}
13760 (@value{GDBP}) ptype s
13761 type = ARRAY [1..5] OF CARDINAL
13764 The Modula-2 language interface to @value{GDBN} also understands
13765 pointer types as shown in this example:
13769 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13776 and you can request that @value{GDBN} describes the type of @code{s}.
13779 (@value{GDBP}) ptype s
13780 type = POINTER TO ARRAY [1..5] OF CARDINAL
13783 @value{GDBN} handles compound types as we can see in this example.
13784 Here we combine array types, record types, pointer types and subrange
13795 myarray = ARRAY myrange OF CARDINAL ;
13796 myrange = [-2..2] ;
13798 s: POINTER TO ARRAY myrange OF foo ;
13802 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13806 (@value{GDBP}) ptype s
13807 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13810 f3 : ARRAY [-2..2] OF CARDINAL;
13815 @subsubsection Modula-2 Defaults
13816 @cindex Modula-2 defaults
13818 If type and range checking are set automatically by @value{GDBN}, they
13819 both default to @code{on} whenever the working language changes to
13820 Modula-2. This happens regardless of whether you or @value{GDBN}
13821 selected the working language.
13823 If you allow @value{GDBN} to set the language automatically, then entering
13824 code compiled from a file whose name ends with @file{.mod} sets the
13825 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13826 Infer the Source Language}, for further details.
13829 @subsubsection Deviations from Standard Modula-2
13830 @cindex Modula-2, deviations from
13832 A few changes have been made to make Modula-2 programs easier to debug.
13833 This is done primarily via loosening its type strictness:
13837 Unlike in standard Modula-2, pointer constants can be formed by
13838 integers. This allows you to modify pointer variables during
13839 debugging. (In standard Modula-2, the actual address contained in a
13840 pointer variable is hidden from you; it can only be modified
13841 through direct assignment to another pointer variable or expression that
13842 returned a pointer.)
13845 C escape sequences can be used in strings and characters to represent
13846 non-printable characters. @value{GDBN} prints out strings with these
13847 escape sequences embedded. Single non-printable characters are
13848 printed using the @samp{CHR(@var{nnn})} format.
13851 The assignment operator (@code{:=}) returns the value of its right-hand
13855 All built-in procedures both modify @emph{and} return their argument.
13859 @subsubsection Modula-2 Type and Range Checks
13860 @cindex Modula-2 checks
13863 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13866 @c FIXME remove warning when type/range checks added
13868 @value{GDBN} considers two Modula-2 variables type equivalent if:
13872 They are of types that have been declared equivalent via a @code{TYPE
13873 @var{t1} = @var{t2}} statement
13876 They have been declared on the same line. (Note: This is true of the
13877 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13880 As long as type checking is enabled, any attempt to combine variables
13881 whose types are not equivalent is an error.
13883 Range checking is done on all mathematical operations, assignment, array
13884 index bounds, and all built-in functions and procedures.
13887 @subsubsection The Scope Operators @code{::} and @code{.}
13889 @cindex @code{.}, Modula-2 scope operator
13890 @cindex colon, doubled as scope operator
13892 @vindex colon-colon@r{, in Modula-2}
13893 @c Info cannot handle :: but TeX can.
13896 @vindex ::@r{, in Modula-2}
13899 There are a few subtle differences between the Modula-2 scope operator
13900 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13905 @var{module} . @var{id}
13906 @var{scope} :: @var{id}
13910 where @var{scope} is the name of a module or a procedure,
13911 @var{module} the name of a module, and @var{id} is any declared
13912 identifier within your program, except another module.
13914 Using the @code{::} operator makes @value{GDBN} search the scope
13915 specified by @var{scope} for the identifier @var{id}. If it is not
13916 found in the specified scope, then @value{GDBN} searches all scopes
13917 enclosing the one specified by @var{scope}.
13919 Using the @code{.} operator makes @value{GDBN} search the current scope for
13920 the identifier specified by @var{id} that was imported from the
13921 definition module specified by @var{module}. With this operator, it is
13922 an error if the identifier @var{id} was not imported from definition
13923 module @var{module}, or if @var{id} is not an identifier in
13927 @subsubsection @value{GDBN} and Modula-2
13929 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13930 Five subcommands of @code{set print} and @code{show print} apply
13931 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13932 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13933 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13934 analogue in Modula-2.
13936 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13937 with any language, is not useful with Modula-2. Its
13938 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13939 created in Modula-2 as they can in C or C@t{++}. However, because an
13940 address can be specified by an integral constant, the construct
13941 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13943 @cindex @code{#} in Modula-2
13944 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13945 interpreted as the beginning of a comment. Use @code{<>} instead.
13951 The extensions made to @value{GDBN} for Ada only support
13952 output from the @sc{gnu} Ada (GNAT) compiler.
13953 Other Ada compilers are not currently supported, and
13954 attempting to debug executables produced by them is most likely
13958 @cindex expressions in Ada
13960 * Ada Mode Intro:: General remarks on the Ada syntax
13961 and semantics supported by Ada mode
13963 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13964 * Additions to Ada:: Extensions of the Ada expression syntax.
13965 * Stopping Before Main Program:: Debugging the program during elaboration.
13966 * Ada Tasks:: Listing and setting breakpoints in tasks.
13967 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13968 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13970 * Ada Glitches:: Known peculiarities of Ada mode.
13973 @node Ada Mode Intro
13974 @subsubsection Introduction
13975 @cindex Ada mode, general
13977 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13978 syntax, with some extensions.
13979 The philosophy behind the design of this subset is
13983 That @value{GDBN} should provide basic literals and access to operations for
13984 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13985 leaving more sophisticated computations to subprograms written into the
13986 program (which therefore may be called from @value{GDBN}).
13989 That type safety and strict adherence to Ada language restrictions
13990 are not particularly important to the @value{GDBN} user.
13993 That brevity is important to the @value{GDBN} user.
13996 Thus, for brevity, the debugger acts as if all names declared in
13997 user-written packages are directly visible, even if they are not visible
13998 according to Ada rules, thus making it unnecessary to fully qualify most
13999 names with their packages, regardless of context. Where this causes
14000 ambiguity, @value{GDBN} asks the user's intent.
14002 The debugger will start in Ada mode if it detects an Ada main program.
14003 As for other languages, it will enter Ada mode when stopped in a program that
14004 was translated from an Ada source file.
14006 While in Ada mode, you may use `@t{--}' for comments. This is useful
14007 mostly for documenting command files. The standard @value{GDBN} comment
14008 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14009 middle (to allow based literals).
14011 The debugger supports limited overloading. Given a subprogram call in which
14012 the function symbol has multiple definitions, it will use the number of
14013 actual parameters and some information about their types to attempt to narrow
14014 the set of definitions. It also makes very limited use of context, preferring
14015 procedures to functions in the context of the @code{call} command, and
14016 functions to procedures elsewhere.
14018 @node Omissions from Ada
14019 @subsubsection Omissions from Ada
14020 @cindex Ada, omissions from
14022 Here are the notable omissions from the subset:
14026 Only a subset of the attributes are supported:
14030 @t{'First}, @t{'Last}, and @t{'Length}
14031 on array objects (not on types and subtypes).
14034 @t{'Min} and @t{'Max}.
14037 @t{'Pos} and @t{'Val}.
14043 @t{'Range} on array objects (not subtypes), but only as the right
14044 operand of the membership (@code{in}) operator.
14047 @t{'Access}, @t{'Unchecked_Access}, and
14048 @t{'Unrestricted_Access} (a GNAT extension).
14056 @code{Characters.Latin_1} are not available and
14057 concatenation is not implemented. Thus, escape characters in strings are
14058 not currently available.
14061 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14062 equality of representations. They will generally work correctly
14063 for strings and arrays whose elements have integer or enumeration types.
14064 They may not work correctly for arrays whose element
14065 types have user-defined equality, for arrays of real values
14066 (in particular, IEEE-conformant floating point, because of negative
14067 zeroes and NaNs), and for arrays whose elements contain unused bits with
14068 indeterminate values.
14071 The other component-by-component array operations (@code{and}, @code{or},
14072 @code{xor}, @code{not}, and relational tests other than equality)
14073 are not implemented.
14076 @cindex array aggregates (Ada)
14077 @cindex record aggregates (Ada)
14078 @cindex aggregates (Ada)
14079 There is limited support for array and record aggregates. They are
14080 permitted only on the right sides of assignments, as in these examples:
14083 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14084 (@value{GDBP}) set An_Array := (1, others => 0)
14085 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14086 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14087 (@value{GDBP}) set A_Record := (1, "Peter", True);
14088 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14092 discriminant's value by assigning an aggregate has an
14093 undefined effect if that discriminant is used within the record.
14094 However, you can first modify discriminants by directly assigning to
14095 them (which normally would not be allowed in Ada), and then performing an
14096 aggregate assignment. For example, given a variable @code{A_Rec}
14097 declared to have a type such as:
14100 type Rec (Len : Small_Integer := 0) is record
14102 Vals : IntArray (1 .. Len);
14106 you can assign a value with a different size of @code{Vals} with two
14110 (@value{GDBP}) set A_Rec.Len := 4
14111 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14114 As this example also illustrates, @value{GDBN} is very loose about the usual
14115 rules concerning aggregates. You may leave out some of the
14116 components of an array or record aggregate (such as the @code{Len}
14117 component in the assignment to @code{A_Rec} above); they will retain their
14118 original values upon assignment. You may freely use dynamic values as
14119 indices in component associations. You may even use overlapping or
14120 redundant component associations, although which component values are
14121 assigned in such cases is not defined.
14124 Calls to dispatching subprograms are not implemented.
14127 The overloading algorithm is much more limited (i.e., less selective)
14128 than that of real Ada. It makes only limited use of the context in
14129 which a subexpression appears to resolve its meaning, and it is much
14130 looser in its rules for allowing type matches. As a result, some
14131 function calls will be ambiguous, and the user will be asked to choose
14132 the proper resolution.
14135 The @code{new} operator is not implemented.
14138 Entry calls are not implemented.
14141 Aside from printing, arithmetic operations on the native VAX floating-point
14142 formats are not supported.
14145 It is not possible to slice a packed array.
14148 The names @code{True} and @code{False}, when not part of a qualified name,
14149 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14151 Should your program
14152 redefine these names in a package or procedure (at best a dubious practice),
14153 you will have to use fully qualified names to access their new definitions.
14156 @node Additions to Ada
14157 @subsubsection Additions to Ada
14158 @cindex Ada, deviations from
14160 As it does for other languages, @value{GDBN} makes certain generic
14161 extensions to Ada (@pxref{Expressions}):
14165 If the expression @var{E} is a variable residing in memory (typically
14166 a local variable or array element) and @var{N} is a positive integer,
14167 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14168 @var{N}-1 adjacent variables following it in memory as an array. In
14169 Ada, this operator is generally not necessary, since its prime use is
14170 in displaying parts of an array, and slicing will usually do this in
14171 Ada. However, there are occasional uses when debugging programs in
14172 which certain debugging information has been optimized away.
14175 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14176 appears in function or file @var{B}.'' When @var{B} is a file name,
14177 you must typically surround it in single quotes.
14180 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14181 @var{type} that appears at address @var{addr}.''
14184 A name starting with @samp{$} is a convenience variable
14185 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14188 In addition, @value{GDBN} provides a few other shortcuts and outright
14189 additions specific to Ada:
14193 The assignment statement is allowed as an expression, returning
14194 its right-hand operand as its value. Thus, you may enter
14197 (@value{GDBP}) set x := y + 3
14198 (@value{GDBP}) print A(tmp := y + 1)
14202 The semicolon is allowed as an ``operator,'' returning as its value
14203 the value of its right-hand operand.
14204 This allows, for example,
14205 complex conditional breaks:
14208 (@value{GDBP}) break f
14209 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14213 Rather than use catenation and symbolic character names to introduce special
14214 characters into strings, one may instead use a special bracket notation,
14215 which is also used to print strings. A sequence of characters of the form
14216 @samp{["@var{XX}"]} within a string or character literal denotes the
14217 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14218 sequence of characters @samp{["""]} also denotes a single quotation mark
14219 in strings. For example,
14221 "One line.["0a"]Next line.["0a"]"
14224 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14228 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14229 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14233 (@value{GDBP}) print 'max(x, y)
14237 When printing arrays, @value{GDBN} uses positional notation when the
14238 array has a lower bound of 1, and uses a modified named notation otherwise.
14239 For example, a one-dimensional array of three integers with a lower bound
14240 of 3 might print as
14247 That is, in contrast to valid Ada, only the first component has a @code{=>}
14251 You may abbreviate attributes in expressions with any unique,
14252 multi-character subsequence of
14253 their names (an exact match gets preference).
14254 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14255 in place of @t{a'length}.
14258 @cindex quoting Ada internal identifiers
14259 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14260 to lower case. The GNAT compiler uses upper-case characters for
14261 some of its internal identifiers, which are normally of no interest to users.
14262 For the rare occasions when you actually have to look at them,
14263 enclose them in angle brackets to avoid the lower-case mapping.
14266 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14270 Printing an object of class-wide type or dereferencing an
14271 access-to-class-wide value will display all the components of the object's
14272 specific type (as indicated by its run-time tag). Likewise, component
14273 selection on such a value will operate on the specific type of the
14278 @node Stopping Before Main Program
14279 @subsubsection Stopping at the Very Beginning
14281 @cindex breakpointing Ada elaboration code
14282 It is sometimes necessary to debug the program during elaboration, and
14283 before reaching the main procedure.
14284 As defined in the Ada Reference
14285 Manual, the elaboration code is invoked from a procedure called
14286 @code{adainit}. To run your program up to the beginning of
14287 elaboration, simply use the following two commands:
14288 @code{tbreak adainit} and @code{run}.
14291 @subsubsection Extensions for Ada Tasks
14292 @cindex Ada, tasking
14294 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14295 @value{GDBN} provides the following task-related commands:
14300 This command shows a list of current Ada tasks, as in the following example:
14307 (@value{GDBP}) info tasks
14308 ID TID P-ID Pri State Name
14309 1 8088000 0 15 Child Activation Wait main_task
14310 2 80a4000 1 15 Accept Statement b
14311 3 809a800 1 15 Child Activation Wait a
14312 * 4 80ae800 3 15 Runnable c
14317 In this listing, the asterisk before the last task indicates it to be the
14318 task currently being inspected.
14322 Represents @value{GDBN}'s internal task number.
14328 The parent's task ID (@value{GDBN}'s internal task number).
14331 The base priority of the task.
14334 Current state of the task.
14338 The task has been created but has not been activated. It cannot be
14342 The task is not blocked for any reason known to Ada. (It may be waiting
14343 for a mutex, though.) It is conceptually "executing" in normal mode.
14346 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14347 that were waiting on terminate alternatives have been awakened and have
14348 terminated themselves.
14350 @item Child Activation Wait
14351 The task is waiting for created tasks to complete activation.
14353 @item Accept Statement
14354 The task is waiting on an accept or selective wait statement.
14356 @item Waiting on entry call
14357 The task is waiting on an entry call.
14359 @item Async Select Wait
14360 The task is waiting to start the abortable part of an asynchronous
14364 The task is waiting on a select statement with only a delay
14367 @item Child Termination Wait
14368 The task is sleeping having completed a master within itself, and is
14369 waiting for the tasks dependent on that master to become terminated or
14370 waiting on a terminate Phase.
14372 @item Wait Child in Term Alt
14373 The task is sleeping waiting for tasks on terminate alternatives to
14374 finish terminating.
14376 @item Accepting RV with @var{taskno}
14377 The task is accepting a rendez-vous with the task @var{taskno}.
14381 Name of the task in the program.
14385 @kindex info task @var{taskno}
14386 @item info task @var{taskno}
14387 This command shows detailled informations on the specified task, as in
14388 the following example:
14393 (@value{GDBP}) info tasks
14394 ID TID P-ID Pri State Name
14395 1 8077880 0 15 Child Activation Wait main_task
14396 * 2 807c468 1 15 Runnable task_1
14397 (@value{GDBP}) info task 2
14398 Ada Task: 0x807c468
14401 Parent: 1 (main_task)
14407 @kindex task@r{ (Ada)}
14408 @cindex current Ada task ID
14409 This command prints the ID of the current task.
14415 (@value{GDBP}) info tasks
14416 ID TID P-ID Pri State Name
14417 1 8077870 0 15 Child Activation Wait main_task
14418 * 2 807c458 1 15 Runnable t
14419 (@value{GDBP}) task
14420 [Current task is 2]
14423 @item task @var{taskno}
14424 @cindex Ada task switching
14425 This command is like the @code{thread @var{threadno}}
14426 command (@pxref{Threads}). It switches the context of debugging
14427 from the current task to the given task.
14433 (@value{GDBP}) info tasks
14434 ID TID P-ID Pri State Name
14435 1 8077870 0 15 Child Activation Wait main_task
14436 * 2 807c458 1 15 Runnable t
14437 (@value{GDBP}) task 1
14438 [Switching to task 1]
14439 #0 0x8067726 in pthread_cond_wait ()
14441 #0 0x8067726 in pthread_cond_wait ()
14442 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14443 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14444 #3 0x806153e in system.tasking.stages.activate_tasks ()
14445 #4 0x804aacc in un () at un.adb:5
14448 @item break @var{linespec} task @var{taskno}
14449 @itemx break @var{linespec} task @var{taskno} if @dots{}
14450 @cindex breakpoints and tasks, in Ada
14451 @cindex task breakpoints, in Ada
14452 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14453 These commands are like the @code{break @dots{} thread @dots{}}
14454 command (@pxref{Thread Stops}).
14455 @var{linespec} specifies source lines, as described
14456 in @ref{Specify Location}.
14458 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14459 to specify that you only want @value{GDBN} to stop the program when a
14460 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14461 numeric task identifiers assigned by @value{GDBN}, shown in the first
14462 column of the @samp{info tasks} display.
14464 If you do not specify @samp{task @var{taskno}} when you set a
14465 breakpoint, the breakpoint applies to @emph{all} tasks of your
14468 You can use the @code{task} qualifier on conditional breakpoints as
14469 well; in this case, place @samp{task @var{taskno}} before the
14470 breakpoint condition (before the @code{if}).
14478 (@value{GDBP}) info tasks
14479 ID TID P-ID Pri State Name
14480 1 140022020 0 15 Child Activation Wait main_task
14481 2 140045060 1 15 Accept/Select Wait t2
14482 3 140044840 1 15 Runnable t1
14483 * 4 140056040 1 15 Runnable t3
14484 (@value{GDBP}) b 15 task 2
14485 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14486 (@value{GDBP}) cont
14491 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14493 (@value{GDBP}) info tasks
14494 ID TID P-ID Pri State Name
14495 1 140022020 0 15 Child Activation Wait main_task
14496 * 2 140045060 1 15 Runnable t2
14497 3 140044840 1 15 Runnable t1
14498 4 140056040 1 15 Delay Sleep t3
14502 @node Ada Tasks and Core Files
14503 @subsubsection Tasking Support when Debugging Core Files
14504 @cindex Ada tasking and core file debugging
14506 When inspecting a core file, as opposed to debugging a live program,
14507 tasking support may be limited or even unavailable, depending on
14508 the platform being used.
14509 For instance, on x86-linux, the list of tasks is available, but task
14510 switching is not supported. On Tru64, however, task switching will work
14513 On certain platforms, including Tru64, the debugger needs to perform some
14514 memory writes in order to provide Ada tasking support. When inspecting
14515 a core file, this means that the core file must be opened with read-write
14516 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14517 Under these circumstances, you should make a backup copy of the core
14518 file before inspecting it with @value{GDBN}.
14520 @node Ravenscar Profile
14521 @subsubsection Tasking Support when using the Ravenscar Profile
14522 @cindex Ravenscar Profile
14524 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14525 specifically designed for systems with safety-critical real-time
14529 @kindex set ravenscar task-switching on
14530 @cindex task switching with program using Ravenscar Profile
14531 @item set ravenscar task-switching on
14532 Allows task switching when debugging a program that uses the Ravenscar
14533 Profile. This is the default.
14535 @kindex set ravenscar task-switching off
14536 @item set ravenscar task-switching off
14537 Turn off task switching when debugging a program that uses the Ravenscar
14538 Profile. This is mostly intended to disable the code that adds support
14539 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14540 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14541 To be effective, this command should be run before the program is started.
14543 @kindex show ravenscar task-switching
14544 @item show ravenscar task-switching
14545 Show whether it is possible to switch from task to task in a program
14546 using the Ravenscar Profile.
14551 @subsubsection Known Peculiarities of Ada Mode
14552 @cindex Ada, problems
14554 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14555 we know of several problems with and limitations of Ada mode in
14557 some of which will be fixed with planned future releases of the debugger
14558 and the GNU Ada compiler.
14562 Static constants that the compiler chooses not to materialize as objects in
14563 storage are invisible to the debugger.
14566 Named parameter associations in function argument lists are ignored (the
14567 argument lists are treated as positional).
14570 Many useful library packages are currently invisible to the debugger.
14573 Fixed-point arithmetic, conversions, input, and output is carried out using
14574 floating-point arithmetic, and may give results that only approximate those on
14578 The GNAT compiler never generates the prefix @code{Standard} for any of
14579 the standard symbols defined by the Ada language. @value{GDBN} knows about
14580 this: it will strip the prefix from names when you use it, and will never
14581 look for a name you have so qualified among local symbols, nor match against
14582 symbols in other packages or subprograms. If you have
14583 defined entities anywhere in your program other than parameters and
14584 local variables whose simple names match names in @code{Standard},
14585 GNAT's lack of qualification here can cause confusion. When this happens,
14586 you can usually resolve the confusion
14587 by qualifying the problematic names with package
14588 @code{Standard} explicitly.
14591 Older versions of the compiler sometimes generate erroneous debugging
14592 information, resulting in the debugger incorrectly printing the value
14593 of affected entities. In some cases, the debugger is able to work
14594 around an issue automatically. In other cases, the debugger is able
14595 to work around the issue, but the work-around has to be specifically
14598 @kindex set ada trust-PAD-over-XVS
14599 @kindex show ada trust-PAD-over-XVS
14602 @item set ada trust-PAD-over-XVS on
14603 Configure GDB to strictly follow the GNAT encoding when computing the
14604 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14605 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14606 a complete description of the encoding used by the GNAT compiler).
14607 This is the default.
14609 @item set ada trust-PAD-over-XVS off
14610 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14611 sometimes prints the wrong value for certain entities, changing @code{ada
14612 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14613 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14614 @code{off}, but this incurs a slight performance penalty, so it is
14615 recommended to leave this setting to @code{on} unless necessary.
14619 @node Unsupported Languages
14620 @section Unsupported Languages
14622 @cindex unsupported languages
14623 @cindex minimal language
14624 In addition to the other fully-supported programming languages,
14625 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14626 It does not represent a real programming language, but provides a set
14627 of capabilities close to what the C or assembly languages provide.
14628 This should allow most simple operations to be performed while debugging
14629 an application that uses a language currently not supported by @value{GDBN}.
14631 If the language is set to @code{auto}, @value{GDBN} will automatically
14632 select this language if the current frame corresponds to an unsupported
14636 @chapter Examining the Symbol Table
14638 The commands described in this chapter allow you to inquire about the
14639 symbols (names of variables, functions and types) defined in your
14640 program. This information is inherent in the text of your program and
14641 does not change as your program executes. @value{GDBN} finds it in your
14642 program's symbol table, in the file indicated when you started @value{GDBN}
14643 (@pxref{File Options, ,Choosing Files}), or by one of the
14644 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14646 @cindex symbol names
14647 @cindex names of symbols
14648 @cindex quoting names
14649 Occasionally, you may need to refer to symbols that contain unusual
14650 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14651 most frequent case is in referring to static variables in other
14652 source files (@pxref{Variables,,Program Variables}). File names
14653 are recorded in object files as debugging symbols, but @value{GDBN} would
14654 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14655 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14656 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14663 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14666 @cindex case-insensitive symbol names
14667 @cindex case sensitivity in symbol names
14668 @kindex set case-sensitive
14669 @item set case-sensitive on
14670 @itemx set case-sensitive off
14671 @itemx set case-sensitive auto
14672 Normally, when @value{GDBN} looks up symbols, it matches their names
14673 with case sensitivity determined by the current source language.
14674 Occasionally, you may wish to control that. The command @code{set
14675 case-sensitive} lets you do that by specifying @code{on} for
14676 case-sensitive matches or @code{off} for case-insensitive ones. If
14677 you specify @code{auto}, case sensitivity is reset to the default
14678 suitable for the source language. The default is case-sensitive
14679 matches for all languages except for Fortran, for which the default is
14680 case-insensitive matches.
14682 @kindex show case-sensitive
14683 @item show case-sensitive
14684 This command shows the current setting of case sensitivity for symbols
14687 @kindex info address
14688 @cindex address of a symbol
14689 @item info address @var{symbol}
14690 Describe where the data for @var{symbol} is stored. For a register
14691 variable, this says which register it is kept in. For a non-register
14692 local variable, this prints the stack-frame offset at which the variable
14695 Note the contrast with @samp{print &@var{symbol}}, which does not work
14696 at all for a register variable, and for a stack local variable prints
14697 the exact address of the current instantiation of the variable.
14699 @kindex info symbol
14700 @cindex symbol from address
14701 @cindex closest symbol and offset for an address
14702 @item info symbol @var{addr}
14703 Print the name of a symbol which is stored at the address @var{addr}.
14704 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14705 nearest symbol and an offset from it:
14708 (@value{GDBP}) info symbol 0x54320
14709 _initialize_vx + 396 in section .text
14713 This is the opposite of the @code{info address} command. You can use
14714 it to find out the name of a variable or a function given its address.
14716 For dynamically linked executables, the name of executable or shared
14717 library containing the symbol is also printed:
14720 (@value{GDBP}) info symbol 0x400225
14721 _start + 5 in section .text of /tmp/a.out
14722 (@value{GDBP}) info symbol 0x2aaaac2811cf
14723 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14727 @item whatis [@var{arg}]
14728 Print the data type of @var{arg}, which can be either an expression
14729 or a name of a data type. With no argument, print the data type of
14730 @code{$}, the last value in the value history.
14732 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14733 is not actually evaluated, and any side-effecting operations (such as
14734 assignments or function calls) inside it do not take place.
14736 If @var{arg} is a variable or an expression, @code{whatis} prints its
14737 literal type as it is used in the source code. If the type was
14738 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14739 the data type underlying the @code{typedef}. If the type of the
14740 variable or the expression is a compound data type, such as
14741 @code{struct} or @code{class}, @code{whatis} never prints their
14742 fields or methods. It just prints the @code{struct}/@code{class}
14743 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14744 such a compound data type, use @code{ptype}.
14746 If @var{arg} is a type name that was defined using @code{typedef},
14747 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14748 Unrolling means that @code{whatis} will show the underlying type used
14749 in the @code{typedef} declaration of @var{arg}. However, if that
14750 underlying type is also a @code{typedef}, @code{whatis} will not
14753 For C code, the type names may also have the form @samp{class
14754 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14755 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14758 @item ptype [@var{arg}]
14759 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14760 detailed description of the type, instead of just the name of the type.
14761 @xref{Expressions, ,Expressions}.
14763 Contrary to @code{whatis}, @code{ptype} always unrolls any
14764 @code{typedef}s in its argument declaration, whether the argument is
14765 a variable, expression, or a data type. This means that @code{ptype}
14766 of a variable or an expression will not print literally its type as
14767 present in the source code---use @code{whatis} for that. @code{typedef}s at
14768 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14769 fields, methods and inner @code{class typedef}s of @code{struct}s,
14770 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14772 For example, for this variable declaration:
14775 typedef double real_t;
14776 struct complex @{ real_t real; double imag; @};
14777 typedef struct complex complex_t;
14779 real_t *real_pointer_var;
14783 the two commands give this output:
14787 (@value{GDBP}) whatis var
14789 (@value{GDBP}) ptype var
14790 type = struct complex @{
14794 (@value{GDBP}) whatis complex_t
14795 type = struct complex
14796 (@value{GDBP}) whatis struct complex
14797 type = struct complex
14798 (@value{GDBP}) ptype struct complex
14799 type = struct complex @{
14803 (@value{GDBP}) whatis real_pointer_var
14805 (@value{GDBP}) ptype real_pointer_var
14811 As with @code{whatis}, using @code{ptype} without an argument refers to
14812 the type of @code{$}, the last value in the value history.
14814 @cindex incomplete type
14815 Sometimes, programs use opaque data types or incomplete specifications
14816 of complex data structure. If the debug information included in the
14817 program does not allow @value{GDBN} to display a full declaration of
14818 the data type, it will say @samp{<incomplete type>}. For example,
14819 given these declarations:
14823 struct foo *fooptr;
14827 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14830 (@value{GDBP}) ptype foo
14831 $1 = <incomplete type>
14835 ``Incomplete type'' is C terminology for data types that are not
14836 completely specified.
14839 @item info types @var{regexp}
14841 Print a brief description of all types whose names match the regular
14842 expression @var{regexp} (or all types in your program, if you supply
14843 no argument). Each complete typename is matched as though it were a
14844 complete line; thus, @samp{i type value} gives information on all
14845 types in your program whose names include the string @code{value}, but
14846 @samp{i type ^value$} gives information only on types whose complete
14847 name is @code{value}.
14849 This command differs from @code{ptype} in two ways: first, like
14850 @code{whatis}, it does not print a detailed description; second, it
14851 lists all source files where a type is defined.
14854 @cindex local variables
14855 @item info scope @var{location}
14856 List all the variables local to a particular scope. This command
14857 accepts a @var{location} argument---a function name, a source line, or
14858 an address preceded by a @samp{*}, and prints all the variables local
14859 to the scope defined by that location. (@xref{Specify Location}, for
14860 details about supported forms of @var{location}.) For example:
14863 (@value{GDBP}) @b{info scope command_line_handler}
14864 Scope for command_line_handler:
14865 Symbol rl is an argument at stack/frame offset 8, length 4.
14866 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14867 Symbol linelength is in static storage at address 0x150a1c, length 4.
14868 Symbol p is a local variable in register $esi, length 4.
14869 Symbol p1 is a local variable in register $ebx, length 4.
14870 Symbol nline is a local variable in register $edx, length 4.
14871 Symbol repeat is a local variable at frame offset -8, length 4.
14875 This command is especially useful for determining what data to collect
14876 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14879 @kindex info source
14881 Show information about the current source file---that is, the source file for
14882 the function containing the current point of execution:
14885 the name of the source file, and the directory containing it,
14887 the directory it was compiled in,
14889 its length, in lines,
14891 which programming language it is written in,
14893 whether the executable includes debugging information for that file, and
14894 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14896 whether the debugging information includes information about
14897 preprocessor macros.
14901 @kindex info sources
14903 Print the names of all source files in your program for which there is
14904 debugging information, organized into two lists: files whose symbols
14905 have already been read, and files whose symbols will be read when needed.
14907 @kindex info functions
14908 @item info functions
14909 Print the names and data types of all defined functions.
14911 @item info functions @var{regexp}
14912 Print the names and data types of all defined functions
14913 whose names contain a match for regular expression @var{regexp}.
14914 Thus, @samp{info fun step} finds all functions whose names
14915 include @code{step}; @samp{info fun ^step} finds those whose names
14916 start with @code{step}. If a function name contains characters
14917 that conflict with the regular expression language (e.g.@:
14918 @samp{operator*()}), they may be quoted with a backslash.
14920 @kindex info variables
14921 @item info variables
14922 Print the names and data types of all variables that are defined
14923 outside of functions (i.e.@: excluding local variables).
14925 @item info variables @var{regexp}
14926 Print the names and data types of all variables (except for local
14927 variables) whose names contain a match for regular expression
14930 @kindex info classes
14931 @cindex Objective-C, classes and selectors
14933 @itemx info classes @var{regexp}
14934 Display all Objective-C classes in your program, or
14935 (with the @var{regexp} argument) all those matching a particular regular
14938 @kindex info selectors
14939 @item info selectors
14940 @itemx info selectors @var{regexp}
14941 Display all Objective-C selectors in your program, or
14942 (with the @var{regexp} argument) all those matching a particular regular
14946 This was never implemented.
14947 @kindex info methods
14949 @itemx info methods @var{regexp}
14950 The @code{info methods} command permits the user to examine all defined
14951 methods within C@t{++} program, or (with the @var{regexp} argument) a
14952 specific set of methods found in the various C@t{++} classes. Many
14953 C@t{++} classes provide a large number of methods. Thus, the output
14954 from the @code{ptype} command can be overwhelming and hard to use. The
14955 @code{info-methods} command filters the methods, printing only those
14956 which match the regular-expression @var{regexp}.
14959 @cindex opaque data types
14960 @kindex set opaque-type-resolution
14961 @item set opaque-type-resolution on
14962 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14963 declared as a pointer to a @code{struct}, @code{class}, or
14964 @code{union}---for example, @code{struct MyType *}---that is used in one
14965 source file although the full declaration of @code{struct MyType} is in
14966 another source file. The default is on.
14968 A change in the setting of this subcommand will not take effect until
14969 the next time symbols for a file are loaded.
14971 @item set opaque-type-resolution off
14972 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14973 is printed as follows:
14975 @{<no data fields>@}
14978 @kindex show opaque-type-resolution
14979 @item show opaque-type-resolution
14980 Show whether opaque types are resolved or not.
14982 @kindex maint print symbols
14983 @cindex symbol dump
14984 @kindex maint print psymbols
14985 @cindex partial symbol dump
14986 @item maint print symbols @var{filename}
14987 @itemx maint print psymbols @var{filename}
14988 @itemx maint print msymbols @var{filename}
14989 Write a dump of debugging symbol data into the file @var{filename}.
14990 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14991 symbols with debugging data are included. If you use @samp{maint print
14992 symbols}, @value{GDBN} includes all the symbols for which it has already
14993 collected full details: that is, @var{filename} reflects symbols for
14994 only those files whose symbols @value{GDBN} has read. You can use the
14995 command @code{info sources} to find out which files these are. If you
14996 use @samp{maint print psymbols} instead, the dump shows information about
14997 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14998 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14999 @samp{maint print msymbols} dumps just the minimal symbol information
15000 required for each object file from which @value{GDBN} has read some symbols.
15001 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15002 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15004 @kindex maint info symtabs
15005 @kindex maint info psymtabs
15006 @cindex listing @value{GDBN}'s internal symbol tables
15007 @cindex symbol tables, listing @value{GDBN}'s internal
15008 @cindex full symbol tables, listing @value{GDBN}'s internal
15009 @cindex partial symbol tables, listing @value{GDBN}'s internal
15010 @item maint info symtabs @r{[} @var{regexp} @r{]}
15011 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15013 List the @code{struct symtab} or @code{struct partial_symtab}
15014 structures whose names match @var{regexp}. If @var{regexp} is not
15015 given, list them all. The output includes expressions which you can
15016 copy into a @value{GDBN} debugging this one to examine a particular
15017 structure in more detail. For example:
15020 (@value{GDBP}) maint info psymtabs dwarf2read
15021 @{ objfile /home/gnu/build/gdb/gdb
15022 ((struct objfile *) 0x82e69d0)
15023 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15024 ((struct partial_symtab *) 0x8474b10)
15027 text addresses 0x814d3c8 -- 0x8158074
15028 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15029 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15030 dependencies (none)
15033 (@value{GDBP}) maint info symtabs
15037 We see that there is one partial symbol table whose filename contains
15038 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15039 and we see that @value{GDBN} has not read in any symtabs yet at all.
15040 If we set a breakpoint on a function, that will cause @value{GDBN} to
15041 read the symtab for the compilation unit containing that function:
15044 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15045 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15047 (@value{GDBP}) maint info symtabs
15048 @{ objfile /home/gnu/build/gdb/gdb
15049 ((struct objfile *) 0x82e69d0)
15050 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15051 ((struct symtab *) 0x86c1f38)
15054 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15055 linetable ((struct linetable *) 0x8370fa0)
15056 debugformat DWARF 2
15065 @chapter Altering Execution
15067 Once you think you have found an error in your program, you might want to
15068 find out for certain whether correcting the apparent error would lead to
15069 correct results in the rest of the run. You can find the answer by
15070 experiment, using the @value{GDBN} features for altering execution of the
15073 For example, you can store new values into variables or memory
15074 locations, give your program a signal, restart it at a different
15075 address, or even return prematurely from a function.
15078 * Assignment:: Assignment to variables
15079 * Jumping:: Continuing at a different address
15080 * Signaling:: Giving your program a signal
15081 * Returning:: Returning from a function
15082 * Calling:: Calling your program's functions
15083 * Patching:: Patching your program
15087 @section Assignment to Variables
15090 @cindex setting variables
15091 To alter the value of a variable, evaluate an assignment expression.
15092 @xref{Expressions, ,Expressions}. For example,
15099 stores the value 4 into the variable @code{x}, and then prints the
15100 value of the assignment expression (which is 4).
15101 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15102 information on operators in supported languages.
15104 @kindex set variable
15105 @cindex variables, setting
15106 If you are not interested in seeing the value of the assignment, use the
15107 @code{set} command instead of the @code{print} command. @code{set} is
15108 really the same as @code{print} except that the expression's value is
15109 not printed and is not put in the value history (@pxref{Value History,
15110 ,Value History}). The expression is evaluated only for its effects.
15112 If the beginning of the argument string of the @code{set} command
15113 appears identical to a @code{set} subcommand, use the @code{set
15114 variable} command instead of just @code{set}. This command is identical
15115 to @code{set} except for its lack of subcommands. For example, if your
15116 program has a variable @code{width}, you get an error if you try to set
15117 a new value with just @samp{set width=13}, because @value{GDBN} has the
15118 command @code{set width}:
15121 (@value{GDBP}) whatis width
15123 (@value{GDBP}) p width
15125 (@value{GDBP}) set width=47
15126 Invalid syntax in expression.
15130 The invalid expression, of course, is @samp{=47}. In
15131 order to actually set the program's variable @code{width}, use
15134 (@value{GDBP}) set var width=47
15137 Because the @code{set} command has many subcommands that can conflict
15138 with the names of program variables, it is a good idea to use the
15139 @code{set variable} command instead of just @code{set}. For example, if
15140 your program has a variable @code{g}, you run into problems if you try
15141 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15142 the command @code{set gnutarget}, abbreviated @code{set g}:
15146 (@value{GDBP}) whatis g
15150 (@value{GDBP}) set g=4
15154 The program being debugged has been started already.
15155 Start it from the beginning? (y or n) y
15156 Starting program: /home/smith/cc_progs/a.out
15157 "/home/smith/cc_progs/a.out": can't open to read symbols:
15158 Invalid bfd target.
15159 (@value{GDBP}) show g
15160 The current BFD target is "=4".
15165 The program variable @code{g} did not change, and you silently set the
15166 @code{gnutarget} to an invalid value. In order to set the variable
15170 (@value{GDBP}) set var g=4
15173 @value{GDBN} allows more implicit conversions in assignments than C; you can
15174 freely store an integer value into a pointer variable or vice versa,
15175 and you can convert any structure to any other structure that is the
15176 same length or shorter.
15177 @comment FIXME: how do structs align/pad in these conversions?
15178 @comment /doc@cygnus.com 18dec1990
15180 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15181 construct to generate a value of specified type at a specified address
15182 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15183 to memory location @code{0x83040} as an integer (which implies a certain size
15184 and representation in memory), and
15187 set @{int@}0x83040 = 4
15191 stores the value 4 into that memory location.
15194 @section Continuing at a Different Address
15196 Ordinarily, when you continue your program, you do so at the place where
15197 it stopped, with the @code{continue} command. You can instead continue at
15198 an address of your own choosing, with the following commands:
15202 @item jump @var{linespec}
15203 @itemx jump @var{location}
15204 Resume execution at line @var{linespec} or at address given by
15205 @var{location}. Execution stops again immediately if there is a
15206 breakpoint there. @xref{Specify Location}, for a description of the
15207 different forms of @var{linespec} and @var{location}. It is common
15208 practice to use the @code{tbreak} command in conjunction with
15209 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15211 The @code{jump} command does not change the current stack frame, or
15212 the stack pointer, or the contents of any memory location or any
15213 register other than the program counter. If line @var{linespec} is in
15214 a different function from the one currently executing, the results may
15215 be bizarre if the two functions expect different patterns of arguments or
15216 of local variables. For this reason, the @code{jump} command requests
15217 confirmation if the specified line is not in the function currently
15218 executing. However, even bizarre results are predictable if you are
15219 well acquainted with the machine-language code of your program.
15222 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15223 On many systems, you can get much the same effect as the @code{jump}
15224 command by storing a new value into the register @code{$pc}. The
15225 difference is that this does not start your program running; it only
15226 changes the address of where it @emph{will} run when you continue. For
15234 makes the next @code{continue} command or stepping command execute at
15235 address @code{0x485}, rather than at the address where your program stopped.
15236 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15238 The most common occasion to use the @code{jump} command is to back
15239 up---perhaps with more breakpoints set---over a portion of a program
15240 that has already executed, in order to examine its execution in more
15245 @section Giving your Program a Signal
15246 @cindex deliver a signal to a program
15250 @item signal @var{signal}
15251 Resume execution where your program stopped, but immediately give it the
15252 signal @var{signal}. @var{signal} can be the name or the number of a
15253 signal. For example, on many systems @code{signal 2} and @code{signal
15254 SIGINT} are both ways of sending an interrupt signal.
15256 Alternatively, if @var{signal} is zero, continue execution without
15257 giving a signal. This is useful when your program stopped on account of
15258 a signal and would ordinary see the signal when resumed with the
15259 @code{continue} command; @samp{signal 0} causes it to resume without a
15262 @code{signal} does not repeat when you press @key{RET} a second time
15263 after executing the command.
15267 Invoking the @code{signal} command is not the same as invoking the
15268 @code{kill} utility from the shell. Sending a signal with @code{kill}
15269 causes @value{GDBN} to decide what to do with the signal depending on
15270 the signal handling tables (@pxref{Signals}). The @code{signal} command
15271 passes the signal directly to your program.
15275 @section Returning from a Function
15278 @cindex returning from a function
15281 @itemx return @var{expression}
15282 You can cancel execution of a function call with the @code{return}
15283 command. If you give an
15284 @var{expression} argument, its value is used as the function's return
15288 When you use @code{return}, @value{GDBN} discards the selected stack frame
15289 (and all frames within it). You can think of this as making the
15290 discarded frame return prematurely. If you wish to specify a value to
15291 be returned, give that value as the argument to @code{return}.
15293 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15294 Frame}), and any other frames inside of it, leaving its caller as the
15295 innermost remaining frame. That frame becomes selected. The
15296 specified value is stored in the registers used for returning values
15299 The @code{return} command does not resume execution; it leaves the
15300 program stopped in the state that would exist if the function had just
15301 returned. In contrast, the @code{finish} command (@pxref{Continuing
15302 and Stepping, ,Continuing and Stepping}) resumes execution until the
15303 selected stack frame returns naturally.
15305 @value{GDBN} needs to know how the @var{expression} argument should be set for
15306 the inferior. The concrete registers assignment depends on the OS ABI and the
15307 type being returned by the selected stack frame. For example it is common for
15308 OS ABI to return floating point values in FPU registers while integer values in
15309 CPU registers. Still some ABIs return even floating point values in CPU
15310 registers. Larger integer widths (such as @code{long long int}) also have
15311 specific placement rules. @value{GDBN} already knows the OS ABI from its
15312 current target so it needs to find out also the type being returned to make the
15313 assignment into the right register(s).
15315 Normally, the selected stack frame has debug info. @value{GDBN} will always
15316 use the debug info instead of the implicit type of @var{expression} when the
15317 debug info is available. For example, if you type @kbd{return -1}, and the
15318 function in the current stack frame is declared to return a @code{long long
15319 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15320 into a @code{long long int}:
15323 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15325 (@value{GDBP}) return -1
15326 Make func return now? (y or n) y
15327 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15328 43 printf ("result=%lld\n", func ());
15332 However, if the selected stack frame does not have a debug info, e.g., if the
15333 function was compiled without debug info, @value{GDBN} has to find out the type
15334 to return from user. Specifying a different type by mistake may set the value
15335 in different inferior registers than the caller code expects. For example,
15336 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15337 of a @code{long long int} result for a debug info less function (on 32-bit
15338 architectures). Therefore the user is required to specify the return type by
15339 an appropriate cast explicitly:
15342 Breakpoint 2, 0x0040050b in func ()
15343 (@value{GDBP}) return -1
15344 Return value type not available for selected stack frame.
15345 Please use an explicit cast of the value to return.
15346 (@value{GDBP}) return (long long int) -1
15347 Make selected stack frame return now? (y or n) y
15348 #0 0x00400526 in main ()
15353 @section Calling Program Functions
15356 @cindex calling functions
15357 @cindex inferior functions, calling
15358 @item print @var{expr}
15359 Evaluate the expression @var{expr} and display the resulting value.
15360 @var{expr} may include calls to functions in the program being
15364 @item call @var{expr}
15365 Evaluate the expression @var{expr} without displaying @code{void}
15368 You can use this variant of the @code{print} command if you want to
15369 execute a function from your program that does not return anything
15370 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15371 with @code{void} returned values that @value{GDBN} will otherwise
15372 print. If the result is not void, it is printed and saved in the
15376 It is possible for the function you call via the @code{print} or
15377 @code{call} command to generate a signal (e.g., if there's a bug in
15378 the function, or if you passed it incorrect arguments). What happens
15379 in that case is controlled by the @code{set unwindonsignal} command.
15381 Similarly, with a C@t{++} program it is possible for the function you
15382 call via the @code{print} or @code{call} command to generate an
15383 exception that is not handled due to the constraints of the dummy
15384 frame. In this case, any exception that is raised in the frame, but has
15385 an out-of-frame exception handler will not be found. GDB builds a
15386 dummy-frame for the inferior function call, and the unwinder cannot
15387 seek for exception handlers outside of this dummy-frame. What happens
15388 in that case is controlled by the
15389 @code{set unwind-on-terminating-exception} command.
15392 @item set unwindonsignal
15393 @kindex set unwindonsignal
15394 @cindex unwind stack in called functions
15395 @cindex call dummy stack unwinding
15396 Set unwinding of the stack if a signal is received while in a function
15397 that @value{GDBN} called in the program being debugged. If set to on,
15398 @value{GDBN} unwinds the stack it created for the call and restores
15399 the context to what it was before the call. If set to off (the
15400 default), @value{GDBN} stops in the frame where the signal was
15403 @item show unwindonsignal
15404 @kindex show unwindonsignal
15405 Show the current setting of stack unwinding in the functions called by
15408 @item set unwind-on-terminating-exception
15409 @kindex set unwind-on-terminating-exception
15410 @cindex unwind stack in called functions with unhandled exceptions
15411 @cindex call dummy stack unwinding on unhandled exception.
15412 Set unwinding of the stack if a C@t{++} exception is raised, but left
15413 unhandled while in a function that @value{GDBN} called in the program being
15414 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15415 it created for the call and restores the context to what it was before
15416 the call. If set to off, @value{GDBN} the exception is delivered to
15417 the default C@t{++} exception handler and the inferior terminated.
15419 @item show unwind-on-terminating-exception
15420 @kindex show unwind-on-terminating-exception
15421 Show the current setting of stack unwinding in the functions called by
15426 @cindex weak alias functions
15427 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15428 for another function. In such case, @value{GDBN} might not pick up
15429 the type information, including the types of the function arguments,
15430 which causes @value{GDBN} to call the inferior function incorrectly.
15431 As a result, the called function will function erroneously and may
15432 even crash. A solution to that is to use the name of the aliased
15436 @section Patching Programs
15438 @cindex patching binaries
15439 @cindex writing into executables
15440 @cindex writing into corefiles
15442 By default, @value{GDBN} opens the file containing your program's
15443 executable code (or the corefile) read-only. This prevents accidental
15444 alterations to machine code; but it also prevents you from intentionally
15445 patching your program's binary.
15447 If you'd like to be able to patch the binary, you can specify that
15448 explicitly with the @code{set write} command. For example, you might
15449 want to turn on internal debugging flags, or even to make emergency
15455 @itemx set write off
15456 If you specify @samp{set write on}, @value{GDBN} opens executable and
15457 core files for both reading and writing; if you specify @kbd{set write
15458 off} (the default), @value{GDBN} opens them read-only.
15460 If you have already loaded a file, you must load it again (using the
15461 @code{exec-file} or @code{core-file} command) after changing @code{set
15462 write}, for your new setting to take effect.
15466 Display whether executable files and core files are opened for writing
15467 as well as reading.
15471 @chapter @value{GDBN} Files
15473 @value{GDBN} needs to know the file name of the program to be debugged,
15474 both in order to read its symbol table and in order to start your
15475 program. To debug a core dump of a previous run, you must also tell
15476 @value{GDBN} the name of the core dump file.
15479 * Files:: Commands to specify files
15480 * Separate Debug Files:: Debugging information in separate files
15481 * Index Files:: Index files speed up GDB
15482 * Symbol Errors:: Errors reading symbol files
15483 * Data Files:: GDB data files
15487 @section Commands to Specify Files
15489 @cindex symbol table
15490 @cindex core dump file
15492 You may want to specify executable and core dump file names. The usual
15493 way to do this is at start-up time, using the arguments to
15494 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15495 Out of @value{GDBN}}).
15497 Occasionally it is necessary to change to a different file during a
15498 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15499 specify a file you want to use. Or you are debugging a remote target
15500 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15501 Program}). In these situations the @value{GDBN} commands to specify
15502 new files are useful.
15505 @cindex executable file
15507 @item file @var{filename}
15508 Use @var{filename} as the program to be debugged. It is read for its
15509 symbols and for the contents of pure memory. It is also the program
15510 executed when you use the @code{run} command. If you do not specify a
15511 directory and the file is not found in the @value{GDBN} working directory,
15512 @value{GDBN} uses the environment variable @code{PATH} as a list of
15513 directories to search, just as the shell does when looking for a program
15514 to run. You can change the value of this variable, for both @value{GDBN}
15515 and your program, using the @code{path} command.
15517 @cindex unlinked object files
15518 @cindex patching object files
15519 You can load unlinked object @file{.o} files into @value{GDBN} using
15520 the @code{file} command. You will not be able to ``run'' an object
15521 file, but you can disassemble functions and inspect variables. Also,
15522 if the underlying BFD functionality supports it, you could use
15523 @kbd{gdb -write} to patch object files using this technique. Note
15524 that @value{GDBN} can neither interpret nor modify relocations in this
15525 case, so branches and some initialized variables will appear to go to
15526 the wrong place. But this feature is still handy from time to time.
15529 @code{file} with no argument makes @value{GDBN} discard any information it
15530 has on both executable file and the symbol table.
15533 @item exec-file @r{[} @var{filename} @r{]}
15534 Specify that the program to be run (but not the symbol table) is found
15535 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15536 if necessary to locate your program. Omitting @var{filename} means to
15537 discard information on the executable file.
15539 @kindex symbol-file
15540 @item symbol-file @r{[} @var{filename} @r{]}
15541 Read symbol table information from file @var{filename}. @code{PATH} is
15542 searched when necessary. Use the @code{file} command to get both symbol
15543 table and program to run from the same file.
15545 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15546 program's symbol table.
15548 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15549 some breakpoints and auto-display expressions. This is because they may
15550 contain pointers to the internal data recording symbols and data types,
15551 which are part of the old symbol table data being discarded inside
15554 @code{symbol-file} does not repeat if you press @key{RET} again after
15557 When @value{GDBN} is configured for a particular environment, it
15558 understands debugging information in whatever format is the standard
15559 generated for that environment; you may use either a @sc{gnu} compiler, or
15560 other compilers that adhere to the local conventions.
15561 Best results are usually obtained from @sc{gnu} compilers; for example,
15562 using @code{@value{NGCC}} you can generate debugging information for
15565 For most kinds of object files, with the exception of old SVR3 systems
15566 using COFF, the @code{symbol-file} command does not normally read the
15567 symbol table in full right away. Instead, it scans the symbol table
15568 quickly to find which source files and which symbols are present. The
15569 details are read later, one source file at a time, as they are needed.
15571 The purpose of this two-stage reading strategy is to make @value{GDBN}
15572 start up faster. For the most part, it is invisible except for
15573 occasional pauses while the symbol table details for a particular source
15574 file are being read. (The @code{set verbose} command can turn these
15575 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15576 Warnings and Messages}.)
15578 We have not implemented the two-stage strategy for COFF yet. When the
15579 symbol table is stored in COFF format, @code{symbol-file} reads the
15580 symbol table data in full right away. Note that ``stabs-in-COFF''
15581 still does the two-stage strategy, since the debug info is actually
15585 @cindex reading symbols immediately
15586 @cindex symbols, reading immediately
15587 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15588 @itemx file @r{[} -readnow @r{]} @var{filename}
15589 You can override the @value{GDBN} two-stage strategy for reading symbol
15590 tables by using the @samp{-readnow} option with any of the commands that
15591 load symbol table information, if you want to be sure @value{GDBN} has the
15592 entire symbol table available.
15594 @c FIXME: for now no mention of directories, since this seems to be in
15595 @c flux. 13mar1992 status is that in theory GDB would look either in
15596 @c current dir or in same dir as myprog; but issues like competing
15597 @c GDB's, or clutter in system dirs, mean that in practice right now
15598 @c only current dir is used. FFish says maybe a special GDB hierarchy
15599 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15603 @item core-file @r{[}@var{filename}@r{]}
15605 Specify the whereabouts of a core dump file to be used as the ``contents
15606 of memory''. Traditionally, core files contain only some parts of the
15607 address space of the process that generated them; @value{GDBN} can access the
15608 executable file itself for other parts.
15610 @code{core-file} with no argument specifies that no core file is
15613 Note that the core file is ignored when your program is actually running
15614 under @value{GDBN}. So, if you have been running your program and you
15615 wish to debug a core file instead, you must kill the subprocess in which
15616 the program is running. To do this, use the @code{kill} command
15617 (@pxref{Kill Process, ,Killing the Child Process}).
15619 @kindex add-symbol-file
15620 @cindex dynamic linking
15621 @item add-symbol-file @var{filename} @var{address}
15622 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15623 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15624 The @code{add-symbol-file} command reads additional symbol table
15625 information from the file @var{filename}. You would use this command
15626 when @var{filename} has been dynamically loaded (by some other means)
15627 into the program that is running. @var{address} should be the memory
15628 address at which the file has been loaded; @value{GDBN} cannot figure
15629 this out for itself. You can additionally specify an arbitrary number
15630 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15631 section name and base address for that section. You can specify any
15632 @var{address} as an expression.
15634 The symbol table of the file @var{filename} is added to the symbol table
15635 originally read with the @code{symbol-file} command. You can use the
15636 @code{add-symbol-file} command any number of times; the new symbol data
15637 thus read keeps adding to the old. To discard all old symbol data
15638 instead, use the @code{symbol-file} command without any arguments.
15640 @cindex relocatable object files, reading symbols from
15641 @cindex object files, relocatable, reading symbols from
15642 @cindex reading symbols from relocatable object files
15643 @cindex symbols, reading from relocatable object files
15644 @cindex @file{.o} files, reading symbols from
15645 Although @var{filename} is typically a shared library file, an
15646 executable file, or some other object file which has been fully
15647 relocated for loading into a process, you can also load symbolic
15648 information from relocatable @file{.o} files, as long as:
15652 the file's symbolic information refers only to linker symbols defined in
15653 that file, not to symbols defined by other object files,
15655 every section the file's symbolic information refers to has actually
15656 been loaded into the inferior, as it appears in the file, and
15658 you can determine the address at which every section was loaded, and
15659 provide these to the @code{add-symbol-file} command.
15663 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15664 relocatable files into an already running program; such systems
15665 typically make the requirements above easy to meet. However, it's
15666 important to recognize that many native systems use complex link
15667 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15668 assembly, for example) that make the requirements difficult to meet. In
15669 general, one cannot assume that using @code{add-symbol-file} to read a
15670 relocatable object file's symbolic information will have the same effect
15671 as linking the relocatable object file into the program in the normal
15674 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15676 @kindex add-symbol-file-from-memory
15677 @cindex @code{syscall DSO}
15678 @cindex load symbols from memory
15679 @item add-symbol-file-from-memory @var{address}
15680 Load symbols from the given @var{address} in a dynamically loaded
15681 object file whose image is mapped directly into the inferior's memory.
15682 For example, the Linux kernel maps a @code{syscall DSO} into each
15683 process's address space; this DSO provides kernel-specific code for
15684 some system calls. The argument can be any expression whose
15685 evaluation yields the address of the file's shared object file header.
15686 For this command to work, you must have used @code{symbol-file} or
15687 @code{exec-file} commands in advance.
15689 @kindex add-shared-symbol-files
15691 @item add-shared-symbol-files @var{library-file}
15692 @itemx assf @var{library-file}
15693 The @code{add-shared-symbol-files} command can currently be used only
15694 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15695 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15696 @value{GDBN} automatically looks for shared libraries, however if
15697 @value{GDBN} does not find yours, you can invoke
15698 @code{add-shared-symbol-files}. It takes one argument: the shared
15699 library's file name. @code{assf} is a shorthand alias for
15700 @code{add-shared-symbol-files}.
15703 @item section @var{section} @var{addr}
15704 The @code{section} command changes the base address of the named
15705 @var{section} of the exec file to @var{addr}. This can be used if the
15706 exec file does not contain section addresses, (such as in the
15707 @code{a.out} format), or when the addresses specified in the file
15708 itself are wrong. Each section must be changed separately. The
15709 @code{info files} command, described below, lists all the sections and
15713 @kindex info target
15716 @code{info files} and @code{info target} are synonymous; both print the
15717 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15718 including the names of the executable and core dump files currently in
15719 use by @value{GDBN}, and the files from which symbols were loaded. The
15720 command @code{help target} lists all possible targets rather than
15723 @kindex maint info sections
15724 @item maint info sections
15725 Another command that can give you extra information about program sections
15726 is @code{maint info sections}. In addition to the section information
15727 displayed by @code{info files}, this command displays the flags and file
15728 offset of each section in the executable and core dump files. In addition,
15729 @code{maint info sections} provides the following command options (which
15730 may be arbitrarily combined):
15734 Display sections for all loaded object files, including shared libraries.
15735 @item @var{sections}
15736 Display info only for named @var{sections}.
15737 @item @var{section-flags}
15738 Display info only for sections for which @var{section-flags} are true.
15739 The section flags that @value{GDBN} currently knows about are:
15742 Section will have space allocated in the process when loaded.
15743 Set for all sections except those containing debug information.
15745 Section will be loaded from the file into the child process memory.
15746 Set for pre-initialized code and data, clear for @code{.bss} sections.
15748 Section needs to be relocated before loading.
15750 Section cannot be modified by the child process.
15752 Section contains executable code only.
15754 Section contains data only (no executable code).
15756 Section will reside in ROM.
15758 Section contains data for constructor/destructor lists.
15760 Section is not empty.
15762 An instruction to the linker to not output the section.
15763 @item COFF_SHARED_LIBRARY
15764 A notification to the linker that the section contains
15765 COFF shared library information.
15767 Section contains common symbols.
15770 @kindex set trust-readonly-sections
15771 @cindex read-only sections
15772 @item set trust-readonly-sections on
15773 Tell @value{GDBN} that readonly sections in your object file
15774 really are read-only (i.e.@: that their contents will not change).
15775 In that case, @value{GDBN} can fetch values from these sections
15776 out of the object file, rather than from the target program.
15777 For some targets (notably embedded ones), this can be a significant
15778 enhancement to debugging performance.
15780 The default is off.
15782 @item set trust-readonly-sections off
15783 Tell @value{GDBN} not to trust readonly sections. This means that
15784 the contents of the section might change while the program is running,
15785 and must therefore be fetched from the target when needed.
15787 @item show trust-readonly-sections
15788 Show the current setting of trusting readonly sections.
15791 All file-specifying commands allow both absolute and relative file names
15792 as arguments. @value{GDBN} always converts the file name to an absolute file
15793 name and remembers it that way.
15795 @cindex shared libraries
15796 @anchor{Shared Libraries}
15797 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15798 and IBM RS/6000 AIX shared libraries.
15800 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15801 shared libraries. @xref{Expat}.
15803 @value{GDBN} automatically loads symbol definitions from shared libraries
15804 when you use the @code{run} command, or when you examine a core file.
15805 (Before you issue the @code{run} command, @value{GDBN} does not understand
15806 references to a function in a shared library, however---unless you are
15807 debugging a core file).
15809 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15810 automatically loads the symbols at the time of the @code{shl_load} call.
15812 @c FIXME: some @value{GDBN} release may permit some refs to undef
15813 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15814 @c FIXME...lib; check this from time to time when updating manual
15816 There are times, however, when you may wish to not automatically load
15817 symbol definitions from shared libraries, such as when they are
15818 particularly large or there are many of them.
15820 To control the automatic loading of shared library symbols, use the
15824 @kindex set auto-solib-add
15825 @item set auto-solib-add @var{mode}
15826 If @var{mode} is @code{on}, symbols from all shared object libraries
15827 will be loaded automatically when the inferior begins execution, you
15828 attach to an independently started inferior, or when the dynamic linker
15829 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15830 is @code{off}, symbols must be loaded manually, using the
15831 @code{sharedlibrary} command. The default value is @code{on}.
15833 @cindex memory used for symbol tables
15834 If your program uses lots of shared libraries with debug info that
15835 takes large amounts of memory, you can decrease the @value{GDBN}
15836 memory footprint by preventing it from automatically loading the
15837 symbols from shared libraries. To that end, type @kbd{set
15838 auto-solib-add off} before running the inferior, then load each
15839 library whose debug symbols you do need with @kbd{sharedlibrary
15840 @var{regexp}}, where @var{regexp} is a regular expression that matches
15841 the libraries whose symbols you want to be loaded.
15843 @kindex show auto-solib-add
15844 @item show auto-solib-add
15845 Display the current autoloading mode.
15848 @cindex load shared library
15849 To explicitly load shared library symbols, use the @code{sharedlibrary}
15853 @kindex info sharedlibrary
15855 @item info share @var{regex}
15856 @itemx info sharedlibrary @var{regex}
15857 Print the names of the shared libraries which are currently loaded
15858 that match @var{regex}. If @var{regex} is omitted then print
15859 all shared libraries that are loaded.
15861 @kindex sharedlibrary
15863 @item sharedlibrary @var{regex}
15864 @itemx share @var{regex}
15865 Load shared object library symbols for files matching a
15866 Unix regular expression.
15867 As with files loaded automatically, it only loads shared libraries
15868 required by your program for a core file or after typing @code{run}. If
15869 @var{regex} is omitted all shared libraries required by your program are
15872 @item nosharedlibrary
15873 @kindex nosharedlibrary
15874 @cindex unload symbols from shared libraries
15875 Unload all shared object library symbols. This discards all symbols
15876 that have been loaded from all shared libraries. Symbols from shared
15877 libraries that were loaded by explicit user requests are not
15881 Sometimes you may wish that @value{GDBN} stops and gives you control
15882 when any of shared library events happen. The best way to do this is
15883 to use @code{catch load} and @code{catch unload} (@pxref{Set
15886 @value{GDBN} also supports the the @code{set stop-on-solib-events}
15887 command for this. This command exists for historical reasons. It is
15888 less useful than setting a catchpoint, because it does not allow for
15889 conditions or commands as a catchpoint does.
15892 @item set stop-on-solib-events
15893 @kindex set stop-on-solib-events
15894 This command controls whether @value{GDBN} should give you control
15895 when the dynamic linker notifies it about some shared library event.
15896 The most common event of interest is loading or unloading of a new
15899 @item show stop-on-solib-events
15900 @kindex show stop-on-solib-events
15901 Show whether @value{GDBN} stops and gives you control when shared
15902 library events happen.
15905 Shared libraries are also supported in many cross or remote debugging
15906 configurations. @value{GDBN} needs to have access to the target's libraries;
15907 this can be accomplished either by providing copies of the libraries
15908 on the host system, or by asking @value{GDBN} to automatically retrieve the
15909 libraries from the target. If copies of the target libraries are
15910 provided, they need to be the same as the target libraries, although the
15911 copies on the target can be stripped as long as the copies on the host are
15914 @cindex where to look for shared libraries
15915 For remote debugging, you need to tell @value{GDBN} where the target
15916 libraries are, so that it can load the correct copies---otherwise, it
15917 may try to load the host's libraries. @value{GDBN} has two variables
15918 to specify the search directories for target libraries.
15921 @cindex prefix for shared library file names
15922 @cindex system root, alternate
15923 @kindex set solib-absolute-prefix
15924 @kindex set sysroot
15925 @item set sysroot @var{path}
15926 Use @var{path} as the system root for the program being debugged. Any
15927 absolute shared library paths will be prefixed with @var{path}; many
15928 runtime loaders store the absolute paths to the shared library in the
15929 target program's memory. If you use @code{set sysroot} to find shared
15930 libraries, they need to be laid out in the same way that they are on
15931 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15934 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15935 retrieve the target libraries from the remote system. This is only
15936 supported when using a remote target that supports the @code{remote get}
15937 command (@pxref{File Transfer,,Sending files to a remote system}).
15938 The part of @var{path} following the initial @file{remote:}
15939 (if present) is used as system root prefix on the remote file system.
15940 @footnote{If you want to specify a local system root using a directory
15941 that happens to be named @file{remote:}, you need to use some equivalent
15942 variant of the name like @file{./remote:}.}
15944 For targets with an MS-DOS based filesystem, such as MS-Windows and
15945 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15946 absolute file name with @var{path}. But first, on Unix hosts,
15947 @value{GDBN} converts all backslash directory separators into forward
15948 slashes, because the backslash is not a directory separator on Unix:
15951 c:\foo\bar.dll @result{} c:/foo/bar.dll
15954 Then, @value{GDBN} attempts prefixing the target file name with
15955 @var{path}, and looks for the resulting file name in the host file
15959 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15962 If that does not find the shared library, @value{GDBN} tries removing
15963 the @samp{:} character from the drive spec, both for convenience, and,
15964 for the case of the host file system not supporting file names with
15968 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15971 This makes it possible to have a system root that mirrors a target
15972 with more than one drive. E.g., you may want to setup your local
15973 copies of the target system shared libraries like so (note @samp{c} vs
15977 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15978 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15979 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15983 and point the system root at @file{/path/to/sysroot}, so that
15984 @value{GDBN} can find the correct copies of both
15985 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15987 If that still does not find the shared library, @value{GDBN} tries
15988 removing the whole drive spec from the target file name:
15991 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15994 This last lookup makes it possible to not care about the drive name,
15995 if you don't want or need to.
15997 The @code{set solib-absolute-prefix} command is an alias for @code{set
16000 @cindex default system root
16001 @cindex @samp{--with-sysroot}
16002 You can set the default system root by using the configure-time
16003 @samp{--with-sysroot} option. If the system root is inside
16004 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16005 @samp{--exec-prefix}), then the default system root will be updated
16006 automatically if the installed @value{GDBN} is moved to a new
16009 @kindex show sysroot
16011 Display the current shared library prefix.
16013 @kindex set solib-search-path
16014 @item set solib-search-path @var{path}
16015 If this variable is set, @var{path} is a colon-separated list of
16016 directories to search for shared libraries. @samp{solib-search-path}
16017 is used after @samp{sysroot} fails to locate the library, or if the
16018 path to the library is relative instead of absolute. If you want to
16019 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16020 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16021 finding your host's libraries. @samp{sysroot} is preferred; setting
16022 it to a nonexistent directory may interfere with automatic loading
16023 of shared library symbols.
16025 @kindex show solib-search-path
16026 @item show solib-search-path
16027 Display the current shared library search path.
16029 @cindex DOS file-name semantics of file names.
16030 @kindex set target-file-system-kind (unix|dos-based|auto)
16031 @kindex show target-file-system-kind
16032 @item set target-file-system-kind @var{kind}
16033 Set assumed file system kind for target reported file names.
16035 Shared library file names as reported by the target system may not
16036 make sense as is on the system @value{GDBN} is running on. For
16037 example, when remote debugging a target that has MS-DOS based file
16038 system semantics, from a Unix host, the target may be reporting to
16039 @value{GDBN} a list of loaded shared libraries with file names such as
16040 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16041 drive letters, so the @samp{c:\} prefix is not normally understood as
16042 indicating an absolute file name, and neither is the backslash
16043 normally considered a directory separator character. In that case,
16044 the native file system would interpret this whole absolute file name
16045 as a relative file name with no directory components. This would make
16046 it impossible to point @value{GDBN} at a copy of the remote target's
16047 shared libraries on the host using @code{set sysroot}, and impractical
16048 with @code{set solib-search-path}. Setting
16049 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16050 to interpret such file names similarly to how the target would, and to
16051 map them to file names valid on @value{GDBN}'s native file system
16052 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16053 to one of the supported file system kinds. In that case, @value{GDBN}
16054 tries to determine the appropriate file system variant based on the
16055 current target's operating system (@pxref{ABI, ,Configuring the
16056 Current ABI}). The supported file system settings are:
16060 Instruct @value{GDBN} to assume the target file system is of Unix
16061 kind. Only file names starting the forward slash (@samp{/}) character
16062 are considered absolute, and the directory separator character is also
16066 Instruct @value{GDBN} to assume the target file system is DOS based.
16067 File names starting with either a forward slash, or a drive letter
16068 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16069 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16070 considered directory separators.
16073 Instruct @value{GDBN} to use the file system kind associated with the
16074 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16075 This is the default.
16079 @cindex file name canonicalization
16080 @cindex base name differences
16081 When processing file names provided by the user, @value{GDBN}
16082 frequently needs to compare them to the file names recorded in the
16083 program's debug info. Normally, @value{GDBN} compares just the
16084 @dfn{base names} of the files as strings, which is reasonably fast
16085 even for very large programs. (The base name of a file is the last
16086 portion of its name, after stripping all the leading directories.)
16087 This shortcut in comparison is based upon the assumption that files
16088 cannot have more than one base name. This is usually true, but
16089 references to files that use symlinks or similar filesystem
16090 facilities violate that assumption. If your program records files
16091 using such facilities, or if you provide file names to @value{GDBN}
16092 using symlinks etc., you can set @code{basenames-may-differ} to
16093 @code{true} to instruct @value{GDBN} to completely canonicalize each
16094 pair of file names it needs to compare. This will make file-name
16095 comparisons accurate, but at a price of a significant slowdown.
16098 @item set basenames-may-differ
16099 @kindex set basenames-may-differ
16100 Set whether a source file may have multiple base names.
16102 @item show basenames-may-differ
16103 @kindex show basenames-may-differ
16104 Show whether a source file may have multiple base names.
16107 @node Separate Debug Files
16108 @section Debugging Information in Separate Files
16109 @cindex separate debugging information files
16110 @cindex debugging information in separate files
16111 @cindex @file{.debug} subdirectories
16112 @cindex debugging information directory, global
16113 @cindex global debugging information directory
16114 @cindex build ID, and separate debugging files
16115 @cindex @file{.build-id} directory
16117 @value{GDBN} allows you to put a program's debugging information in a
16118 file separate from the executable itself, in a way that allows
16119 @value{GDBN} to find and load the debugging information automatically.
16120 Since debugging information can be very large---sometimes larger
16121 than the executable code itself---some systems distribute debugging
16122 information for their executables in separate files, which users can
16123 install only when they need to debug a problem.
16125 @value{GDBN} supports two ways of specifying the separate debug info
16130 The executable contains a @dfn{debug link} that specifies the name of
16131 the separate debug info file. The separate debug file's name is
16132 usually @file{@var{executable}.debug}, where @var{executable} is the
16133 name of the corresponding executable file without leading directories
16134 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16135 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16136 checksum for the debug file, which @value{GDBN} uses to validate that
16137 the executable and the debug file came from the same build.
16140 The executable contains a @dfn{build ID}, a unique bit string that is
16141 also present in the corresponding debug info file. (This is supported
16142 only on some operating systems, notably those which use the ELF format
16143 for binary files and the @sc{gnu} Binutils.) For more details about
16144 this feature, see the description of the @option{--build-id}
16145 command-line option in @ref{Options, , Command Line Options, ld.info,
16146 The GNU Linker}. The debug info file's name is not specified
16147 explicitly by the build ID, but can be computed from the build ID, see
16151 Depending on the way the debug info file is specified, @value{GDBN}
16152 uses two different methods of looking for the debug file:
16156 For the ``debug link'' method, @value{GDBN} looks up the named file in
16157 the directory of the executable file, then in a subdirectory of that
16158 directory named @file{.debug}, and finally under the global debug
16159 directory, in a subdirectory whose name is identical to the leading
16160 directories of the executable's absolute file name.
16163 For the ``build ID'' method, @value{GDBN} looks in the
16164 @file{.build-id} subdirectory of the global debug directory for a file
16165 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16166 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16167 are the rest of the bit string. (Real build ID strings are 32 or more
16168 hex characters, not 10.)
16171 So, for example, suppose you ask @value{GDBN} to debug
16172 @file{/usr/bin/ls}, which has a debug link that specifies the
16173 file @file{ls.debug}, and a build ID whose value in hex is
16174 @code{abcdef1234}. If the global debug directory is
16175 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16176 debug information files, in the indicated order:
16180 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16182 @file{/usr/bin/ls.debug}
16184 @file{/usr/bin/.debug/ls.debug}
16186 @file{/usr/lib/debug/usr/bin/ls.debug}.
16189 You can set the global debugging info directory's name, and view the
16190 name @value{GDBN} is currently using.
16194 @kindex set debug-file-directory
16195 @item set debug-file-directory @var{directories}
16196 Set the directories which @value{GDBN} searches for separate debugging
16197 information files to @var{directory}. Multiple directory components can be set
16198 concatenating them by a directory separator.
16200 @kindex show debug-file-directory
16201 @item show debug-file-directory
16202 Show the directories @value{GDBN} searches for separate debugging
16207 @cindex @code{.gnu_debuglink} sections
16208 @cindex debug link sections
16209 A debug link is a special section of the executable file named
16210 @code{.gnu_debuglink}. The section must contain:
16214 A filename, with any leading directory components removed, followed by
16217 zero to three bytes of padding, as needed to reach the next four-byte
16218 boundary within the section, and
16220 a four-byte CRC checksum, stored in the same endianness used for the
16221 executable file itself. The checksum is computed on the debugging
16222 information file's full contents by the function given below, passing
16223 zero as the @var{crc} argument.
16226 Any executable file format can carry a debug link, as long as it can
16227 contain a section named @code{.gnu_debuglink} with the contents
16230 @cindex @code{.note.gnu.build-id} sections
16231 @cindex build ID sections
16232 The build ID is a special section in the executable file (and in other
16233 ELF binary files that @value{GDBN} may consider). This section is
16234 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16235 It contains unique identification for the built files---the ID remains
16236 the same across multiple builds of the same build tree. The default
16237 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16238 content for the build ID string. The same section with an identical
16239 value is present in the original built binary with symbols, in its
16240 stripped variant, and in the separate debugging information file.
16242 The debugging information file itself should be an ordinary
16243 executable, containing a full set of linker symbols, sections, and
16244 debugging information. The sections of the debugging information file
16245 should have the same names, addresses, and sizes as the original file,
16246 but they need not contain any data---much like a @code{.bss} section
16247 in an ordinary executable.
16249 The @sc{gnu} binary utilities (Binutils) package includes the
16250 @samp{objcopy} utility that can produce
16251 the separated executable / debugging information file pairs using the
16252 following commands:
16255 @kbd{objcopy --only-keep-debug foo foo.debug}
16260 These commands remove the debugging
16261 information from the executable file @file{foo} and place it in the file
16262 @file{foo.debug}. You can use the first, second or both methods to link the
16267 The debug link method needs the following additional command to also leave
16268 behind a debug link in @file{foo}:
16271 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16274 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16275 a version of the @code{strip} command such that the command @kbd{strip foo -f
16276 foo.debug} has the same functionality as the two @code{objcopy} commands and
16277 the @code{ln -s} command above, together.
16280 Build ID gets embedded into the main executable using @code{ld --build-id} or
16281 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16282 compatibility fixes for debug files separation are present in @sc{gnu} binary
16283 utilities (Binutils) package since version 2.18.
16288 @cindex CRC algorithm definition
16289 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16290 IEEE 802.3 using the polynomial:
16292 @c TexInfo requires naked braces for multi-digit exponents for Tex
16293 @c output, but this causes HTML output to barf. HTML has to be set using
16294 @c raw commands. So we end up having to specify this equation in 2
16299 <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>
16300 + <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
16306 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16307 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16311 The function is computed byte at a time, taking the least
16312 significant bit of each byte first. The initial pattern
16313 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16314 the final result is inverted to ensure trailing zeros also affect the
16317 @emph{Note:} This is the same CRC polynomial as used in handling the
16318 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16319 , @value{GDBN} Remote Serial Protocol}). However in the
16320 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16321 significant bit first, and the result is not inverted, so trailing
16322 zeros have no effect on the CRC value.
16324 To complete the description, we show below the code of the function
16325 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16326 initially supplied @code{crc} argument means that an initial call to
16327 this function passing in zero will start computing the CRC using
16330 @kindex gnu_debuglink_crc32
16333 gnu_debuglink_crc32 (unsigned long crc,
16334 unsigned char *buf, size_t len)
16336 static const unsigned long crc32_table[256] =
16338 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16339 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16340 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16341 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16342 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16343 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16344 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16345 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16346 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16347 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16348 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16349 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16350 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16351 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16352 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16353 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16354 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16355 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16356 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16357 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16358 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16359 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16360 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16361 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16362 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16363 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16364 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16365 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16366 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16367 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16368 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16369 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16370 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16371 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16372 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16373 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16374 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16375 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16376 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16377 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16378 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16379 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16380 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16381 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16382 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16383 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16384 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16385 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16386 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16387 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16388 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16391 unsigned char *end;
16393 crc = ~crc & 0xffffffff;
16394 for (end = buf + len; buf < end; ++buf)
16395 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16396 return ~crc & 0xffffffff;
16401 This computation does not apply to the ``build ID'' method.
16405 @section Index Files Speed Up @value{GDBN}
16406 @cindex index files
16407 @cindex @samp{.gdb_index} section
16409 When @value{GDBN} finds a symbol file, it scans the symbols in the
16410 file in order to construct an internal symbol table. This lets most
16411 @value{GDBN} operations work quickly---at the cost of a delay early
16412 on. For large programs, this delay can be quite lengthy, so
16413 @value{GDBN} provides a way to build an index, which speeds up
16416 The index is stored as a section in the symbol file. @value{GDBN} can
16417 write the index to a file, then you can put it into the symbol file
16418 using @command{objcopy}.
16420 To create an index file, use the @code{save gdb-index} command:
16423 @item save gdb-index @var{directory}
16424 @kindex save gdb-index
16425 Create an index file for each symbol file currently known by
16426 @value{GDBN}. Each file is named after its corresponding symbol file,
16427 with @samp{.gdb-index} appended, and is written into the given
16431 Once you have created an index file you can merge it into your symbol
16432 file, here named @file{symfile}, using @command{objcopy}:
16435 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16436 --set-section-flags .gdb_index=readonly symfile symfile
16439 There are currently some limitation on indices. They only work when
16440 for DWARF debugging information, not stabs. And, they do not
16441 currently work for programs using Ada.
16443 @node Symbol Errors
16444 @section Errors Reading Symbol Files
16446 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16447 such as symbol types it does not recognize, or known bugs in compiler
16448 output. By default, @value{GDBN} does not notify you of such problems, since
16449 they are relatively common and primarily of interest to people
16450 debugging compilers. If you are interested in seeing information
16451 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16452 only one message about each such type of problem, no matter how many
16453 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16454 to see how many times the problems occur, with the @code{set
16455 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16458 The messages currently printed, and their meanings, include:
16461 @item inner block not inside outer block in @var{symbol}
16463 The symbol information shows where symbol scopes begin and end
16464 (such as at the start of a function or a block of statements). This
16465 error indicates that an inner scope block is not fully contained
16466 in its outer scope blocks.
16468 @value{GDBN} circumvents the problem by treating the inner block as if it had
16469 the same scope as the outer block. In the error message, @var{symbol}
16470 may be shown as ``@code{(don't know)}'' if the outer block is not a
16473 @item block at @var{address} out of order
16475 The symbol information for symbol scope blocks should occur in
16476 order of increasing addresses. This error indicates that it does not
16479 @value{GDBN} does not circumvent this problem, and has trouble
16480 locating symbols in the source file whose symbols it is reading. (You
16481 can often determine what source file is affected by specifying
16482 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16485 @item bad block start address patched
16487 The symbol information for a symbol scope block has a start address
16488 smaller than the address of the preceding source line. This is known
16489 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16491 @value{GDBN} circumvents the problem by treating the symbol scope block as
16492 starting on the previous source line.
16494 @item bad string table offset in symbol @var{n}
16497 Symbol number @var{n} contains a pointer into the string table which is
16498 larger than the size of the string table.
16500 @value{GDBN} circumvents the problem by considering the symbol to have the
16501 name @code{foo}, which may cause other problems if many symbols end up
16504 @item unknown symbol type @code{0x@var{nn}}
16506 The symbol information contains new data types that @value{GDBN} does
16507 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16508 uncomprehended information, in hexadecimal.
16510 @value{GDBN} circumvents the error by ignoring this symbol information.
16511 This usually allows you to debug your program, though certain symbols
16512 are not accessible. If you encounter such a problem and feel like
16513 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16514 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16515 and examine @code{*bufp} to see the symbol.
16517 @item stub type has NULL name
16519 @value{GDBN} could not find the full definition for a struct or class.
16521 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16522 The symbol information for a C@t{++} member function is missing some
16523 information that recent versions of the compiler should have output for
16526 @item info mismatch between compiler and debugger
16528 @value{GDBN} could not parse a type specification output by the compiler.
16533 @section GDB Data Files
16535 @cindex prefix for data files
16536 @value{GDBN} will sometimes read an auxiliary data file. These files
16537 are kept in a directory known as the @dfn{data directory}.
16539 You can set the data directory's name, and view the name @value{GDBN}
16540 is currently using.
16543 @kindex set data-directory
16544 @item set data-directory @var{directory}
16545 Set the directory which @value{GDBN} searches for auxiliary data files
16546 to @var{directory}.
16548 @kindex show data-directory
16549 @item show data-directory
16550 Show the directory @value{GDBN} searches for auxiliary data files.
16553 @cindex default data directory
16554 @cindex @samp{--with-gdb-datadir}
16555 You can set the default data directory by using the configure-time
16556 @samp{--with-gdb-datadir} option. If the data directory is inside
16557 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16558 @samp{--exec-prefix}), then the default data directory will be updated
16559 automatically if the installed @value{GDBN} is moved to a new
16562 The data directory may also be specified with the
16563 @code{--data-directory} command line option.
16564 @xref{Mode Options}.
16567 @chapter Specifying a Debugging Target
16569 @cindex debugging target
16570 A @dfn{target} is the execution environment occupied by your program.
16572 Often, @value{GDBN} runs in the same host environment as your program;
16573 in that case, the debugging target is specified as a side effect when
16574 you use the @code{file} or @code{core} commands. When you need more
16575 flexibility---for example, running @value{GDBN} on a physically separate
16576 host, or controlling a standalone system over a serial port or a
16577 realtime system over a TCP/IP connection---you can use the @code{target}
16578 command to specify one of the target types configured for @value{GDBN}
16579 (@pxref{Target Commands, ,Commands for Managing Targets}).
16581 @cindex target architecture
16582 It is possible to build @value{GDBN} for several different @dfn{target
16583 architectures}. When @value{GDBN} is built like that, you can choose
16584 one of the available architectures with the @kbd{set architecture}
16588 @kindex set architecture
16589 @kindex show architecture
16590 @item set architecture @var{arch}
16591 This command sets the current target architecture to @var{arch}. The
16592 value of @var{arch} can be @code{"auto"}, in addition to one of the
16593 supported architectures.
16595 @item show architecture
16596 Show the current target architecture.
16598 @item set processor
16600 @kindex set processor
16601 @kindex show processor
16602 These are alias commands for, respectively, @code{set architecture}
16603 and @code{show architecture}.
16607 * Active Targets:: Active targets
16608 * Target Commands:: Commands for managing targets
16609 * Byte Order:: Choosing target byte order
16612 @node Active Targets
16613 @section Active Targets
16615 @cindex stacking targets
16616 @cindex active targets
16617 @cindex multiple targets
16619 There are multiple classes of targets such as: processes, executable files or
16620 recording sessions. Core files belong to the process class, making core file
16621 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16622 on multiple active targets, one in each class. This allows you to (for
16623 example) start a process and inspect its activity, while still having access to
16624 the executable file after the process finishes. Or if you start process
16625 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16626 presented a virtual layer of the recording target, while the process target
16627 remains stopped at the chronologically last point of the process execution.
16629 Use the @code{core-file} and @code{exec-file} commands to select a new core
16630 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16631 specify as a target a process that is already running, use the @code{attach}
16632 command (@pxref{Attach, ,Debugging an Already-running Process}).
16634 @node Target Commands
16635 @section Commands for Managing Targets
16638 @item target @var{type} @var{parameters}
16639 Connects the @value{GDBN} host environment to a target machine or
16640 process. A target is typically a protocol for talking to debugging
16641 facilities. You use the argument @var{type} to specify the type or
16642 protocol of the target machine.
16644 Further @var{parameters} are interpreted by the target protocol, but
16645 typically include things like device names or host names to connect
16646 with, process numbers, and baud rates.
16648 The @code{target} command does not repeat if you press @key{RET} again
16649 after executing the command.
16651 @kindex help target
16653 Displays the names of all targets available. To display targets
16654 currently selected, use either @code{info target} or @code{info files}
16655 (@pxref{Files, ,Commands to Specify Files}).
16657 @item help target @var{name}
16658 Describe a particular target, including any parameters necessary to
16661 @kindex set gnutarget
16662 @item set gnutarget @var{args}
16663 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16664 knows whether it is reading an @dfn{executable},
16665 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16666 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16667 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16670 @emph{Warning:} To specify a file format with @code{set gnutarget},
16671 you must know the actual BFD name.
16675 @xref{Files, , Commands to Specify Files}.
16677 @kindex show gnutarget
16678 @item show gnutarget
16679 Use the @code{show gnutarget} command to display what file format
16680 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16681 @value{GDBN} will determine the file format for each file automatically,
16682 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16685 @cindex common targets
16686 Here are some common targets (available, or not, depending on the GDB
16691 @item target exec @var{program}
16692 @cindex executable file target
16693 An executable file. @samp{target exec @var{program}} is the same as
16694 @samp{exec-file @var{program}}.
16696 @item target core @var{filename}
16697 @cindex core dump file target
16698 A core dump file. @samp{target core @var{filename}} is the same as
16699 @samp{core-file @var{filename}}.
16701 @item target remote @var{medium}
16702 @cindex remote target
16703 A remote system connected to @value{GDBN} via a serial line or network
16704 connection. This command tells @value{GDBN} to use its own remote
16705 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16707 For example, if you have a board connected to @file{/dev/ttya} on the
16708 machine running @value{GDBN}, you could say:
16711 target remote /dev/ttya
16714 @code{target remote} supports the @code{load} command. This is only
16715 useful if you have some other way of getting the stub to the target
16716 system, and you can put it somewhere in memory where it won't get
16717 clobbered by the download.
16719 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16720 @cindex built-in simulator target
16721 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16729 works; however, you cannot assume that a specific memory map, device
16730 drivers, or even basic I/O is available, although some simulators do
16731 provide these. For info about any processor-specific simulator details,
16732 see the appropriate section in @ref{Embedded Processors, ,Embedded
16737 Some configurations may include these targets as well:
16741 @item target nrom @var{dev}
16742 @cindex NetROM ROM emulator target
16743 NetROM ROM emulator. This target only supports downloading.
16747 Different targets are available on different configurations of @value{GDBN};
16748 your configuration may have more or fewer targets.
16750 Many remote targets require you to download the executable's code once
16751 you've successfully established a connection. You may wish to control
16752 various aspects of this process.
16757 @kindex set hash@r{, for remote monitors}
16758 @cindex hash mark while downloading
16759 This command controls whether a hash mark @samp{#} is displayed while
16760 downloading a file to the remote monitor. If on, a hash mark is
16761 displayed after each S-record is successfully downloaded to the
16765 @kindex show hash@r{, for remote monitors}
16766 Show the current status of displaying the hash mark.
16768 @item set debug monitor
16769 @kindex set debug monitor
16770 @cindex display remote monitor communications
16771 Enable or disable display of communications messages between
16772 @value{GDBN} and the remote monitor.
16774 @item show debug monitor
16775 @kindex show debug monitor
16776 Show the current status of displaying communications between
16777 @value{GDBN} and the remote monitor.
16782 @kindex load @var{filename}
16783 @item load @var{filename}
16785 Depending on what remote debugging facilities are configured into
16786 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16787 is meant to make @var{filename} (an executable) available for debugging
16788 on the remote system---by downloading, or dynamic linking, for example.
16789 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16790 the @code{add-symbol-file} command.
16792 If your @value{GDBN} does not have a @code{load} command, attempting to
16793 execute it gets the error message ``@code{You can't do that when your
16794 target is @dots{}}''
16796 The file is loaded at whatever address is specified in the executable.
16797 For some object file formats, you can specify the load address when you
16798 link the program; for other formats, like a.out, the object file format
16799 specifies a fixed address.
16800 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16802 Depending on the remote side capabilities, @value{GDBN} may be able to
16803 load programs into flash memory.
16805 @code{load} does not repeat if you press @key{RET} again after using it.
16809 @section Choosing Target Byte Order
16811 @cindex choosing target byte order
16812 @cindex target byte order
16814 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16815 offer the ability to run either big-endian or little-endian byte
16816 orders. Usually the executable or symbol will include a bit to
16817 designate the endian-ness, and you will not need to worry about
16818 which to use. However, you may still find it useful to adjust
16819 @value{GDBN}'s idea of processor endian-ness manually.
16823 @item set endian big
16824 Instruct @value{GDBN} to assume the target is big-endian.
16826 @item set endian little
16827 Instruct @value{GDBN} to assume the target is little-endian.
16829 @item set endian auto
16830 Instruct @value{GDBN} to use the byte order associated with the
16834 Display @value{GDBN}'s current idea of the target byte order.
16838 Note that these commands merely adjust interpretation of symbolic
16839 data on the host, and that they have absolutely no effect on the
16843 @node Remote Debugging
16844 @chapter Debugging Remote Programs
16845 @cindex remote debugging
16847 If you are trying to debug a program running on a machine that cannot run
16848 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16849 For example, you might use remote debugging on an operating system kernel,
16850 or on a small system which does not have a general purpose operating system
16851 powerful enough to run a full-featured debugger.
16853 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16854 to make this work with particular debugging targets. In addition,
16855 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16856 but not specific to any particular target system) which you can use if you
16857 write the remote stubs---the code that runs on the remote system to
16858 communicate with @value{GDBN}.
16860 Other remote targets may be available in your
16861 configuration of @value{GDBN}; use @code{help target} to list them.
16864 * Connecting:: Connecting to a remote target
16865 * File Transfer:: Sending files to a remote system
16866 * Server:: Using the gdbserver program
16867 * Remote Configuration:: Remote configuration
16868 * Remote Stub:: Implementing a remote stub
16872 @section Connecting to a Remote Target
16874 On the @value{GDBN} host machine, you will need an unstripped copy of
16875 your program, since @value{GDBN} needs symbol and debugging information.
16876 Start up @value{GDBN} as usual, using the name of the local copy of your
16877 program as the first argument.
16879 @cindex @code{target remote}
16880 @value{GDBN} can communicate with the target over a serial line, or
16881 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16882 each case, @value{GDBN} uses the same protocol for debugging your
16883 program; only the medium carrying the debugging packets varies. The
16884 @code{target remote} command establishes a connection to the target.
16885 Its arguments indicate which medium to use:
16889 @item target remote @var{serial-device}
16890 @cindex serial line, @code{target remote}
16891 Use @var{serial-device} to communicate with the target. For example,
16892 to use a serial line connected to the device named @file{/dev/ttyb}:
16895 target remote /dev/ttyb
16898 If you're using a serial line, you may want to give @value{GDBN} the
16899 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16900 (@pxref{Remote Configuration, set remotebaud}) before the
16901 @code{target} command.
16903 @item target remote @code{@var{host}:@var{port}}
16904 @itemx target remote @code{tcp:@var{host}:@var{port}}
16905 @cindex @acronym{TCP} port, @code{target remote}
16906 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16907 The @var{host} may be either a host name or a numeric @acronym{IP}
16908 address; @var{port} must be a decimal number. The @var{host} could be
16909 the target machine itself, if it is directly connected to the net, or
16910 it might be a terminal server which in turn has a serial line to the
16913 For example, to connect to port 2828 on a terminal server named
16917 target remote manyfarms:2828
16920 If your remote target is actually running on the same machine as your
16921 debugger session (e.g.@: a simulator for your target running on the
16922 same host), you can omit the hostname. For example, to connect to
16923 port 1234 on your local machine:
16926 target remote :1234
16930 Note that the colon is still required here.
16932 @item target remote @code{udp:@var{host}:@var{port}}
16933 @cindex @acronym{UDP} port, @code{target remote}
16934 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16935 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16938 target remote udp:manyfarms:2828
16941 When using a @acronym{UDP} connection for remote debugging, you should
16942 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16943 can silently drop packets on busy or unreliable networks, which will
16944 cause havoc with your debugging session.
16946 @item target remote | @var{command}
16947 @cindex pipe, @code{target remote} to
16948 Run @var{command} in the background and communicate with it using a
16949 pipe. The @var{command} is a shell command, to be parsed and expanded
16950 by the system's command shell, @code{/bin/sh}; it should expect remote
16951 protocol packets on its standard input, and send replies on its
16952 standard output. You could use this to run a stand-alone simulator
16953 that speaks the remote debugging protocol, to make net connections
16954 using programs like @code{ssh}, or for other similar tricks.
16956 If @var{command} closes its standard output (perhaps by exiting),
16957 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16958 program has already exited, this will have no effect.)
16962 Once the connection has been established, you can use all the usual
16963 commands to examine and change data. The remote program is already
16964 running; you can use @kbd{step} and @kbd{continue}, and you do not
16965 need to use @kbd{run}.
16967 @cindex interrupting remote programs
16968 @cindex remote programs, interrupting
16969 Whenever @value{GDBN} is waiting for the remote program, if you type the
16970 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16971 program. This may or may not succeed, depending in part on the hardware
16972 and the serial drivers the remote system uses. If you type the
16973 interrupt character once again, @value{GDBN} displays this prompt:
16976 Interrupted while waiting for the program.
16977 Give up (and stop debugging it)? (y or n)
16980 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16981 (If you decide you want to try again later, you can use @samp{target
16982 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16983 goes back to waiting.
16986 @kindex detach (remote)
16988 When you have finished debugging the remote program, you can use the
16989 @code{detach} command to release it from @value{GDBN} control.
16990 Detaching from the target normally resumes its execution, but the results
16991 will depend on your particular remote stub. After the @code{detach}
16992 command, @value{GDBN} is free to connect to another target.
16996 The @code{disconnect} command behaves like @code{detach}, except that
16997 the target is generally not resumed. It will wait for @value{GDBN}
16998 (this instance or another one) to connect and continue debugging. After
16999 the @code{disconnect} command, @value{GDBN} is again free to connect to
17002 @cindex send command to remote monitor
17003 @cindex extend @value{GDBN} for remote targets
17004 @cindex add new commands for external monitor
17006 @item monitor @var{cmd}
17007 This command allows you to send arbitrary commands directly to the
17008 remote monitor. Since @value{GDBN} doesn't care about the commands it
17009 sends like this, this command is the way to extend @value{GDBN}---you
17010 can add new commands that only the external monitor will understand
17014 @node File Transfer
17015 @section Sending files to a remote system
17016 @cindex remote target, file transfer
17017 @cindex file transfer
17018 @cindex sending files to remote systems
17020 Some remote targets offer the ability to transfer files over the same
17021 connection used to communicate with @value{GDBN}. This is convenient
17022 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17023 running @code{gdbserver} over a network interface. For other targets,
17024 e.g.@: embedded devices with only a single serial port, this may be
17025 the only way to upload or download files.
17027 Not all remote targets support these commands.
17031 @item remote put @var{hostfile} @var{targetfile}
17032 Copy file @var{hostfile} from the host system (the machine running
17033 @value{GDBN}) to @var{targetfile} on the target system.
17036 @item remote get @var{targetfile} @var{hostfile}
17037 Copy file @var{targetfile} from the target system to @var{hostfile}
17038 on the host system.
17040 @kindex remote delete
17041 @item remote delete @var{targetfile}
17042 Delete @var{targetfile} from the target system.
17047 @section Using the @code{gdbserver} Program
17050 @cindex remote connection without stubs
17051 @code{gdbserver} is a control program for Unix-like systems, which
17052 allows you to connect your program with a remote @value{GDBN} via
17053 @code{target remote}---but without linking in the usual debugging stub.
17055 @code{gdbserver} is not a complete replacement for the debugging stubs,
17056 because it requires essentially the same operating-system facilities
17057 that @value{GDBN} itself does. In fact, a system that can run
17058 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17059 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17060 because it is a much smaller program than @value{GDBN} itself. It is
17061 also easier to port than all of @value{GDBN}, so you may be able to get
17062 started more quickly on a new system by using @code{gdbserver}.
17063 Finally, if you develop code for real-time systems, you may find that
17064 the tradeoffs involved in real-time operation make it more convenient to
17065 do as much development work as possible on another system, for example
17066 by cross-compiling. You can use @code{gdbserver} to make a similar
17067 choice for debugging.
17069 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17070 or a TCP connection, using the standard @value{GDBN} remote serial
17074 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17075 Do not run @code{gdbserver} connected to any public network; a
17076 @value{GDBN} connection to @code{gdbserver} provides access to the
17077 target system with the same privileges as the user running
17081 @subsection Running @code{gdbserver}
17082 @cindex arguments, to @code{gdbserver}
17083 @cindex @code{gdbserver}, command-line arguments
17085 Run @code{gdbserver} on the target system. You need a copy of the
17086 program you want to debug, including any libraries it requires.
17087 @code{gdbserver} does not need your program's symbol table, so you can
17088 strip the program if necessary to save space. @value{GDBN} on the host
17089 system does all the symbol handling.
17091 To use the server, you must tell it how to communicate with @value{GDBN};
17092 the name of your program; and the arguments for your program. The usual
17096 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17099 @var{comm} is either a device name (to use a serial line), or a TCP
17100 hostname and portnumber, or @code{-} or @code{stdio} to use
17101 stdin/stdout of @code{gdbserver}.
17102 For example, to debug Emacs with the argument
17103 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17107 target> gdbserver /dev/com1 emacs foo.txt
17110 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17113 To use a TCP connection instead of a serial line:
17116 target> gdbserver host:2345 emacs foo.txt
17119 The only difference from the previous example is the first argument,
17120 specifying that you are communicating with the host @value{GDBN} via
17121 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17122 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17123 (Currently, the @samp{host} part is ignored.) You can choose any number
17124 you want for the port number as long as it does not conflict with any
17125 TCP ports already in use on the target system (for example, @code{23} is
17126 reserved for @code{telnet}).@footnote{If you choose a port number that
17127 conflicts with another service, @code{gdbserver} prints an error message
17128 and exits.} You must use the same port number with the host @value{GDBN}
17129 @code{target remote} command.
17131 The @code{stdio} connection is useful when starting @code{gdbserver}
17135 (gdb) target remote | ssh -T hostname gdbserver - hello
17138 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17139 and we don't want escape-character handling. Ssh does this by default when
17140 a command is provided, the flag is provided to make it explicit.
17141 You could elide it if you want to.
17143 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17144 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17145 display through a pipe connected to gdbserver.
17146 Both @code{stdout} and @code{stderr} use the same pipe.
17148 @subsubsection Attaching to a Running Program
17149 @cindex attach to a program, @code{gdbserver}
17150 @cindex @option{--attach}, @code{gdbserver} option
17152 On some targets, @code{gdbserver} can also attach to running programs.
17153 This is accomplished via the @code{--attach} argument. The syntax is:
17156 target> gdbserver --attach @var{comm} @var{pid}
17159 @var{pid} is the process ID of a currently running process. It isn't necessary
17160 to point @code{gdbserver} at a binary for the running process.
17163 You can debug processes by name instead of process ID if your target has the
17164 @code{pidof} utility:
17167 target> gdbserver --attach @var{comm} `pidof @var{program}`
17170 In case more than one copy of @var{program} is running, or @var{program}
17171 has multiple threads, most versions of @code{pidof} support the
17172 @code{-s} option to only return the first process ID.
17174 @subsubsection Multi-Process Mode for @code{gdbserver}
17175 @cindex @code{gdbserver}, multiple processes
17176 @cindex multiple processes with @code{gdbserver}
17178 When you connect to @code{gdbserver} using @code{target remote},
17179 @code{gdbserver} debugs the specified program only once. When the
17180 program exits, or you detach from it, @value{GDBN} closes the connection
17181 and @code{gdbserver} exits.
17183 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17184 enters multi-process mode. When the debugged program exits, or you
17185 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17186 though no program is running. The @code{run} and @code{attach}
17187 commands instruct @code{gdbserver} to run or attach to a new program.
17188 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17189 remote exec-file}) to select the program to run. Command line
17190 arguments are supported, except for wildcard expansion and I/O
17191 redirection (@pxref{Arguments}).
17193 @cindex @option{--multi}, @code{gdbserver} option
17194 To start @code{gdbserver} without supplying an initial command to run
17195 or process ID to attach, use the @option{--multi} command line option.
17196 Then you can connect using @kbd{target extended-remote} and start
17197 the program you want to debug.
17199 In multi-process mode @code{gdbserver} does not automatically exit unless you
17200 use the option @option{--once}. You can terminate it by using
17201 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17202 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17203 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17204 @option{--multi} option to @code{gdbserver} has no influence on that.
17206 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17208 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17210 @code{gdbserver} normally terminates after all of its debugged processes have
17211 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17212 extended-remote}, @code{gdbserver} stays running even with no processes left.
17213 @value{GDBN} normally terminates the spawned debugged process on its exit,
17214 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17215 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17216 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17217 stays running even in the @kbd{target remote} mode.
17219 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17220 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17221 completeness, at most one @value{GDBN} can be connected at a time.
17223 @cindex @option{--once}, @code{gdbserver} option
17224 By default, @code{gdbserver} keeps the listening TCP port open, so that
17225 additional connections are possible. However, if you start @code{gdbserver}
17226 with the @option{--once} option, it will stop listening for any further
17227 connection attempts after connecting to the first @value{GDBN} session. This
17228 means no further connections to @code{gdbserver} will be possible after the
17229 first one. It also means @code{gdbserver} will terminate after the first
17230 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17231 connections and even in the @kbd{target extended-remote} mode. The
17232 @option{--once} option allows reusing the same port number for connecting to
17233 multiple instances of @code{gdbserver} running on the same host, since each
17234 instance closes its port after the first connection.
17236 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17238 @cindex @option{--debug}, @code{gdbserver} option
17239 The @option{--debug} option tells @code{gdbserver} to display extra
17240 status information about the debugging process.
17241 @cindex @option{--remote-debug}, @code{gdbserver} option
17242 The @option{--remote-debug} option tells @code{gdbserver} to display
17243 remote protocol debug output. These options are intended for
17244 @code{gdbserver} development and for bug reports to the developers.
17246 @cindex @option{--wrapper}, @code{gdbserver} option
17247 The @option{--wrapper} option specifies a wrapper to launch programs
17248 for debugging. The option should be followed by the name of the
17249 wrapper, then any command-line arguments to pass to the wrapper, then
17250 @kbd{--} indicating the end of the wrapper arguments.
17252 @code{gdbserver} runs the specified wrapper program with a combined
17253 command line including the wrapper arguments, then the name of the
17254 program to debug, then any arguments to the program. The wrapper
17255 runs until it executes your program, and then @value{GDBN} gains control.
17257 You can use any program that eventually calls @code{execve} with
17258 its arguments as a wrapper. Several standard Unix utilities do
17259 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17260 with @code{exec "$@@"} will also work.
17262 For example, you can use @code{env} to pass an environment variable to
17263 the debugged program, without setting the variable in @code{gdbserver}'s
17267 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17270 @subsection Connecting to @code{gdbserver}
17272 Run @value{GDBN} on the host system.
17274 First make sure you have the necessary symbol files. Load symbols for
17275 your application using the @code{file} command before you connect. Use
17276 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17277 was compiled with the correct sysroot using @code{--with-sysroot}).
17279 The symbol file and target libraries must exactly match the executable
17280 and libraries on the target, with one exception: the files on the host
17281 system should not be stripped, even if the files on the target system
17282 are. Mismatched or missing files will lead to confusing results
17283 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17284 files may also prevent @code{gdbserver} from debugging multi-threaded
17287 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17288 For TCP connections, you must start up @code{gdbserver} prior to using
17289 the @code{target remote} command. Otherwise you may get an error whose
17290 text depends on the host system, but which usually looks something like
17291 @samp{Connection refused}. Don't use the @code{load}
17292 command in @value{GDBN} when using @code{gdbserver}, since the program is
17293 already on the target.
17295 @subsection Monitor Commands for @code{gdbserver}
17296 @cindex monitor commands, for @code{gdbserver}
17297 @anchor{Monitor Commands for gdbserver}
17299 During a @value{GDBN} session using @code{gdbserver}, you can use the
17300 @code{monitor} command to send special requests to @code{gdbserver}.
17301 Here are the available commands.
17305 List the available monitor commands.
17307 @item monitor set debug 0
17308 @itemx monitor set debug 1
17309 Disable or enable general debugging messages.
17311 @item monitor set remote-debug 0
17312 @itemx monitor set remote-debug 1
17313 Disable or enable specific debugging messages associated with the remote
17314 protocol (@pxref{Remote Protocol}).
17316 @item monitor set libthread-db-search-path [PATH]
17317 @cindex gdbserver, search path for @code{libthread_db}
17318 When this command is issued, @var{path} is a colon-separated list of
17319 directories to search for @code{libthread_db} (@pxref{Threads,,set
17320 libthread-db-search-path}). If you omit @var{path},
17321 @samp{libthread-db-search-path} will be reset to its default value.
17323 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17324 not supported in @code{gdbserver}.
17327 Tell gdbserver to exit immediately. This command should be followed by
17328 @code{disconnect} to close the debugging session. @code{gdbserver} will
17329 detach from any attached processes and kill any processes it created.
17330 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17331 of a multi-process mode debug session.
17335 @subsection Tracepoints support in @code{gdbserver}
17336 @cindex tracepoints support in @code{gdbserver}
17338 On some targets, @code{gdbserver} supports tracepoints, fast
17339 tracepoints and static tracepoints.
17341 For fast or static tracepoints to work, a special library called the
17342 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17343 This library is built and distributed as an integral part of
17344 @code{gdbserver}. In addition, support for static tracepoints
17345 requires building the in-process agent library with static tracepoints
17346 support. At present, the UST (LTTng Userspace Tracer,
17347 @url{http://lttng.org/ust}) tracing engine is supported. This support
17348 is automatically available if UST development headers are found in the
17349 standard include path when @code{gdbserver} is built, or if
17350 @code{gdbserver} was explicitly configured using @option{--with-ust}
17351 to point at such headers. You can explicitly disable the support
17352 using @option{--with-ust=no}.
17354 There are several ways to load the in-process agent in your program:
17357 @item Specifying it as dependency at link time
17359 You can link your program dynamically with the in-process agent
17360 library. On most systems, this is accomplished by adding
17361 @code{-linproctrace} to the link command.
17363 @item Using the system's preloading mechanisms
17365 You can force loading the in-process agent at startup time by using
17366 your system's support for preloading shared libraries. Many Unixes
17367 support the concept of preloading user defined libraries. In most
17368 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17369 in the environment. See also the description of @code{gdbserver}'s
17370 @option{--wrapper} command line option.
17372 @item Using @value{GDBN} to force loading the agent at run time
17374 On some systems, you can force the inferior to load a shared library,
17375 by calling a dynamic loader function in the inferior that takes care
17376 of dynamically looking up and loading a shared library. On most Unix
17377 systems, the function is @code{dlopen}. You'll use the @code{call}
17378 command for that. For example:
17381 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17384 Note that on most Unix systems, for the @code{dlopen} function to be
17385 available, the program needs to be linked with @code{-ldl}.
17388 On systems that have a userspace dynamic loader, like most Unix
17389 systems, when you connect to @code{gdbserver} using @code{target
17390 remote}, you'll find that the program is stopped at the dynamic
17391 loader's entry point, and no shared library has been loaded in the
17392 program's address space yet, including the in-process agent. In that
17393 case, before being able to use any of the fast or static tracepoints
17394 features, you need to let the loader run and load the shared
17395 libraries. The simplest way to do that is to run the program to the
17396 main procedure. E.g., if debugging a C or C@t{++} program, start
17397 @code{gdbserver} like so:
17400 $ gdbserver :9999 myprogram
17403 Start GDB and connect to @code{gdbserver} like so, and run to main:
17407 (@value{GDBP}) target remote myhost:9999
17408 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17409 (@value{GDBP}) b main
17410 (@value{GDBP}) continue
17413 The in-process tracing agent library should now be loaded into the
17414 process; you can confirm it with the @code{info sharedlibrary}
17415 command, which will list @file{libinproctrace.so} as loaded in the
17416 process. You are now ready to install fast tracepoints, list static
17417 tracepoint markers, probe static tracepoints markers, and start
17420 @node Remote Configuration
17421 @section Remote Configuration
17424 @kindex show remote
17425 This section documents the configuration options available when
17426 debugging remote programs. For the options related to the File I/O
17427 extensions of the remote protocol, see @ref{system,
17428 system-call-allowed}.
17431 @item set remoteaddresssize @var{bits}
17432 @cindex address size for remote targets
17433 @cindex bits in remote address
17434 Set the maximum size of address in a memory packet to the specified
17435 number of bits. @value{GDBN} will mask off the address bits above
17436 that number, when it passes addresses to the remote target. The
17437 default value is the number of bits in the target's address.
17439 @item show remoteaddresssize
17440 Show the current value of remote address size in bits.
17442 @item set remotebaud @var{n}
17443 @cindex baud rate for remote targets
17444 Set the baud rate for the remote serial I/O to @var{n} baud. The
17445 value is used to set the speed of the serial port used for debugging
17448 @item show remotebaud
17449 Show the current speed of the remote connection.
17451 @item set remotebreak
17452 @cindex interrupt remote programs
17453 @cindex BREAK signal instead of Ctrl-C
17454 @anchor{set remotebreak}
17455 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17456 when you type @kbd{Ctrl-c} to interrupt the program running
17457 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17458 character instead. The default is off, since most remote systems
17459 expect to see @samp{Ctrl-C} as the interrupt signal.
17461 @item show remotebreak
17462 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17463 interrupt the remote program.
17465 @item set remoteflow on
17466 @itemx set remoteflow off
17467 @kindex set remoteflow
17468 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17469 on the serial port used to communicate to the remote target.
17471 @item show remoteflow
17472 @kindex show remoteflow
17473 Show the current setting of hardware flow control.
17475 @item set remotelogbase @var{base}
17476 Set the base (a.k.a.@: radix) of logging serial protocol
17477 communications to @var{base}. Supported values of @var{base} are:
17478 @code{ascii}, @code{octal}, and @code{hex}. The default is
17481 @item show remotelogbase
17482 Show the current setting of the radix for logging remote serial
17485 @item set remotelogfile @var{file}
17486 @cindex record serial communications on file
17487 Record remote serial communications on the named @var{file}. The
17488 default is not to record at all.
17490 @item show remotelogfile.
17491 Show the current setting of the file name on which to record the
17492 serial communications.
17494 @item set remotetimeout @var{num}
17495 @cindex timeout for serial communications
17496 @cindex remote timeout
17497 Set the timeout limit to wait for the remote target to respond to
17498 @var{num} seconds. The default is 2 seconds.
17500 @item show remotetimeout
17501 Show the current number of seconds to wait for the remote target
17504 @cindex limit hardware breakpoints and watchpoints
17505 @cindex remote target, limit break- and watchpoints
17506 @anchor{set remote hardware-watchpoint-limit}
17507 @anchor{set remote hardware-breakpoint-limit}
17508 @item set remote hardware-watchpoint-limit @var{limit}
17509 @itemx set remote hardware-breakpoint-limit @var{limit}
17510 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17511 watchpoints. A limit of -1, the default, is treated as unlimited.
17513 @cindex limit hardware watchpoints length
17514 @cindex remote target, limit watchpoints length
17515 @anchor{set remote hardware-watchpoint-length-limit}
17516 @item set remote hardware-watchpoint-length-limit @var{limit}
17517 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17518 a remote hardware watchpoint. A limit of -1, the default, is treated
17521 @item show remote hardware-watchpoint-length-limit
17522 Show the current limit (in bytes) of the maximum length of
17523 a remote hardware watchpoint.
17525 @item set remote exec-file @var{filename}
17526 @itemx show remote exec-file
17527 @anchor{set remote exec-file}
17528 @cindex executable file, for remote target
17529 Select the file used for @code{run} with @code{target
17530 extended-remote}. This should be set to a filename valid on the
17531 target system. If it is not set, the target will use a default
17532 filename (e.g.@: the last program run).
17534 @item set remote interrupt-sequence
17535 @cindex interrupt remote programs
17536 @cindex select Ctrl-C, BREAK or BREAK-g
17537 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17538 @samp{BREAK-g} as the
17539 sequence to the remote target in order to interrupt the execution.
17540 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17541 is high level of serial line for some certain time.
17542 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17543 It is @code{BREAK} signal followed by character @code{g}.
17545 @item show interrupt-sequence
17546 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17547 is sent by @value{GDBN} to interrupt the remote program.
17548 @code{BREAK-g} is BREAK signal followed by @code{g} and
17549 also known as Magic SysRq g.
17551 @item set remote interrupt-on-connect
17552 @cindex send interrupt-sequence on start
17553 Specify whether interrupt-sequence is sent to remote target when
17554 @value{GDBN} connects to it. This is mostly needed when you debug
17555 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17556 which is known as Magic SysRq g in order to connect @value{GDBN}.
17558 @item show interrupt-on-connect
17559 Show whether interrupt-sequence is sent
17560 to remote target when @value{GDBN} connects to it.
17564 @item set tcp auto-retry on
17565 @cindex auto-retry, for remote TCP target
17566 Enable auto-retry for remote TCP connections. This is useful if the remote
17567 debugging agent is launched in parallel with @value{GDBN}; there is a race
17568 condition because the agent may not become ready to accept the connection
17569 before @value{GDBN} attempts to connect. When auto-retry is
17570 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17571 to establish the connection using the timeout specified by
17572 @code{set tcp connect-timeout}.
17574 @item set tcp auto-retry off
17575 Do not auto-retry failed TCP connections.
17577 @item show tcp auto-retry
17578 Show the current auto-retry setting.
17580 @item set tcp connect-timeout @var{seconds}
17581 @cindex connection timeout, for remote TCP target
17582 @cindex timeout, for remote target connection
17583 Set the timeout for establishing a TCP connection to the remote target to
17584 @var{seconds}. The timeout affects both polling to retry failed connections
17585 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17586 that are merely slow to complete, and represents an approximate cumulative
17589 @item show tcp connect-timeout
17590 Show the current connection timeout setting.
17593 @cindex remote packets, enabling and disabling
17594 The @value{GDBN} remote protocol autodetects the packets supported by
17595 your debugging stub. If you need to override the autodetection, you
17596 can use these commands to enable or disable individual packets. Each
17597 packet can be set to @samp{on} (the remote target supports this
17598 packet), @samp{off} (the remote target does not support this packet),
17599 or @samp{auto} (detect remote target support for this packet). They
17600 all default to @samp{auto}. For more information about each packet,
17601 see @ref{Remote Protocol}.
17603 During normal use, you should not have to use any of these commands.
17604 If you do, that may be a bug in your remote debugging stub, or a bug
17605 in @value{GDBN}. You may want to report the problem to the
17606 @value{GDBN} developers.
17608 For each packet @var{name}, the command to enable or disable the
17609 packet is @code{set remote @var{name}-packet}. The available settings
17612 @multitable @columnfractions 0.28 0.32 0.25
17615 @tab Related Features
17617 @item @code{fetch-register}
17619 @tab @code{info registers}
17621 @item @code{set-register}
17625 @item @code{binary-download}
17627 @tab @code{load}, @code{set}
17629 @item @code{read-aux-vector}
17630 @tab @code{qXfer:auxv:read}
17631 @tab @code{info auxv}
17633 @item @code{symbol-lookup}
17634 @tab @code{qSymbol}
17635 @tab Detecting multiple threads
17637 @item @code{attach}
17638 @tab @code{vAttach}
17641 @item @code{verbose-resume}
17643 @tab Stepping or resuming multiple threads
17649 @item @code{software-breakpoint}
17653 @item @code{hardware-breakpoint}
17657 @item @code{write-watchpoint}
17661 @item @code{read-watchpoint}
17665 @item @code{access-watchpoint}
17669 @item @code{target-features}
17670 @tab @code{qXfer:features:read}
17671 @tab @code{set architecture}
17673 @item @code{library-info}
17674 @tab @code{qXfer:libraries:read}
17675 @tab @code{info sharedlibrary}
17677 @item @code{memory-map}
17678 @tab @code{qXfer:memory-map:read}
17679 @tab @code{info mem}
17681 @item @code{read-sdata-object}
17682 @tab @code{qXfer:sdata:read}
17683 @tab @code{print $_sdata}
17685 @item @code{read-spu-object}
17686 @tab @code{qXfer:spu:read}
17687 @tab @code{info spu}
17689 @item @code{write-spu-object}
17690 @tab @code{qXfer:spu:write}
17691 @tab @code{info spu}
17693 @item @code{read-siginfo-object}
17694 @tab @code{qXfer:siginfo:read}
17695 @tab @code{print $_siginfo}
17697 @item @code{write-siginfo-object}
17698 @tab @code{qXfer:siginfo:write}
17699 @tab @code{set $_siginfo}
17701 @item @code{threads}
17702 @tab @code{qXfer:threads:read}
17703 @tab @code{info threads}
17705 @item @code{get-thread-local-@*storage-address}
17706 @tab @code{qGetTLSAddr}
17707 @tab Displaying @code{__thread} variables
17709 @item @code{get-thread-information-block-address}
17710 @tab @code{qGetTIBAddr}
17711 @tab Display MS-Windows Thread Information Block.
17713 @item @code{search-memory}
17714 @tab @code{qSearch:memory}
17717 @item @code{supported-packets}
17718 @tab @code{qSupported}
17719 @tab Remote communications parameters
17721 @item @code{pass-signals}
17722 @tab @code{QPassSignals}
17723 @tab @code{handle @var{signal}}
17725 @item @code{program-signals}
17726 @tab @code{QProgramSignals}
17727 @tab @code{handle @var{signal}}
17729 @item @code{hostio-close-packet}
17730 @tab @code{vFile:close}
17731 @tab @code{remote get}, @code{remote put}
17733 @item @code{hostio-open-packet}
17734 @tab @code{vFile:open}
17735 @tab @code{remote get}, @code{remote put}
17737 @item @code{hostio-pread-packet}
17738 @tab @code{vFile:pread}
17739 @tab @code{remote get}, @code{remote put}
17741 @item @code{hostio-pwrite-packet}
17742 @tab @code{vFile:pwrite}
17743 @tab @code{remote get}, @code{remote put}
17745 @item @code{hostio-unlink-packet}
17746 @tab @code{vFile:unlink}
17747 @tab @code{remote delete}
17749 @item @code{hostio-readlink-packet}
17750 @tab @code{vFile:readlink}
17753 @item @code{noack-packet}
17754 @tab @code{QStartNoAckMode}
17755 @tab Packet acknowledgment
17757 @item @code{osdata}
17758 @tab @code{qXfer:osdata:read}
17759 @tab @code{info os}
17761 @item @code{query-attached}
17762 @tab @code{qAttached}
17763 @tab Querying remote process attach state.
17765 @item @code{traceframe-info}
17766 @tab @code{qXfer:traceframe-info:read}
17767 @tab Traceframe info
17769 @item @code{install-in-trace}
17770 @tab @code{InstallInTrace}
17771 @tab Install tracepoint in tracing
17773 @item @code{disable-randomization}
17774 @tab @code{QDisableRandomization}
17775 @tab @code{set disable-randomization}
17777 @item @code{conditional-breakpoints-packet}
17778 @tab @code{Z0 and Z1}
17779 @tab @code{Support for target-side breakpoint condition evaluation}
17783 @section Implementing a Remote Stub
17785 @cindex debugging stub, example
17786 @cindex remote stub, example
17787 @cindex stub example, remote debugging
17788 The stub files provided with @value{GDBN} implement the target side of the
17789 communication protocol, and the @value{GDBN} side is implemented in the
17790 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17791 these subroutines to communicate, and ignore the details. (If you're
17792 implementing your own stub file, you can still ignore the details: start
17793 with one of the existing stub files. @file{sparc-stub.c} is the best
17794 organized, and therefore the easiest to read.)
17796 @cindex remote serial debugging, overview
17797 To debug a program running on another machine (the debugging
17798 @dfn{target} machine), you must first arrange for all the usual
17799 prerequisites for the program to run by itself. For example, for a C
17804 A startup routine to set up the C runtime environment; these usually
17805 have a name like @file{crt0}. The startup routine may be supplied by
17806 your hardware supplier, or you may have to write your own.
17809 A C subroutine library to support your program's
17810 subroutine calls, notably managing input and output.
17813 A way of getting your program to the other machine---for example, a
17814 download program. These are often supplied by the hardware
17815 manufacturer, but you may have to write your own from hardware
17819 The next step is to arrange for your program to use a serial port to
17820 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17821 machine). In general terms, the scheme looks like this:
17825 @value{GDBN} already understands how to use this protocol; when everything
17826 else is set up, you can simply use the @samp{target remote} command
17827 (@pxref{Targets,,Specifying a Debugging Target}).
17829 @item On the target,
17830 you must link with your program a few special-purpose subroutines that
17831 implement the @value{GDBN} remote serial protocol. The file containing these
17832 subroutines is called a @dfn{debugging stub}.
17834 On certain remote targets, you can use an auxiliary program
17835 @code{gdbserver} instead of linking a stub into your program.
17836 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17839 The debugging stub is specific to the architecture of the remote
17840 machine; for example, use @file{sparc-stub.c} to debug programs on
17843 @cindex remote serial stub list
17844 These working remote stubs are distributed with @value{GDBN}:
17849 @cindex @file{i386-stub.c}
17852 For Intel 386 and compatible architectures.
17855 @cindex @file{m68k-stub.c}
17856 @cindex Motorola 680x0
17858 For Motorola 680x0 architectures.
17861 @cindex @file{sh-stub.c}
17864 For Renesas SH architectures.
17867 @cindex @file{sparc-stub.c}
17869 For @sc{sparc} architectures.
17871 @item sparcl-stub.c
17872 @cindex @file{sparcl-stub.c}
17875 For Fujitsu @sc{sparclite} architectures.
17879 The @file{README} file in the @value{GDBN} distribution may list other
17880 recently added stubs.
17883 * Stub Contents:: What the stub can do for you
17884 * Bootstrapping:: What you must do for the stub
17885 * Debug Session:: Putting it all together
17888 @node Stub Contents
17889 @subsection What the Stub Can Do for You
17891 @cindex remote serial stub
17892 The debugging stub for your architecture supplies these three
17896 @item set_debug_traps
17897 @findex set_debug_traps
17898 @cindex remote serial stub, initialization
17899 This routine arranges for @code{handle_exception} to run when your
17900 program stops. You must call this subroutine explicitly in your
17901 program's startup code.
17903 @item handle_exception
17904 @findex handle_exception
17905 @cindex remote serial stub, main routine
17906 This is the central workhorse, but your program never calls it
17907 explicitly---the setup code arranges for @code{handle_exception} to
17908 run when a trap is triggered.
17910 @code{handle_exception} takes control when your program stops during
17911 execution (for example, on a breakpoint), and mediates communications
17912 with @value{GDBN} on the host machine. This is where the communications
17913 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17914 representative on the target machine. It begins by sending summary
17915 information on the state of your program, then continues to execute,
17916 retrieving and transmitting any information @value{GDBN} needs, until you
17917 execute a @value{GDBN} command that makes your program resume; at that point,
17918 @code{handle_exception} returns control to your own code on the target
17922 @cindex @code{breakpoint} subroutine, remote
17923 Use this auxiliary subroutine to make your program contain a
17924 breakpoint. Depending on the particular situation, this may be the only
17925 way for @value{GDBN} to get control. For instance, if your target
17926 machine has some sort of interrupt button, you won't need to call this;
17927 pressing the interrupt button transfers control to
17928 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17929 simply receiving characters on the serial port may also trigger a trap;
17930 again, in that situation, you don't need to call @code{breakpoint} from
17931 your own program---simply running @samp{target remote} from the host
17932 @value{GDBN} session gets control.
17934 Call @code{breakpoint} if none of these is true, or if you simply want
17935 to make certain your program stops at a predetermined point for the
17936 start of your debugging session.
17939 @node Bootstrapping
17940 @subsection What You Must Do for the Stub
17942 @cindex remote stub, support routines
17943 The debugging stubs that come with @value{GDBN} are set up for a particular
17944 chip architecture, but they have no information about the rest of your
17945 debugging target machine.
17947 First of all you need to tell the stub how to communicate with the
17951 @item int getDebugChar()
17952 @findex getDebugChar
17953 Write this subroutine to read a single character from the serial port.
17954 It may be identical to @code{getchar} for your target system; a
17955 different name is used to allow you to distinguish the two if you wish.
17957 @item void putDebugChar(int)
17958 @findex putDebugChar
17959 Write this subroutine to write a single character to the serial port.
17960 It may be identical to @code{putchar} for your target system; a
17961 different name is used to allow you to distinguish the two if you wish.
17964 @cindex control C, and remote debugging
17965 @cindex interrupting remote targets
17966 If you want @value{GDBN} to be able to stop your program while it is
17967 running, you need to use an interrupt-driven serial driver, and arrange
17968 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17969 character). That is the character which @value{GDBN} uses to tell the
17970 remote system to stop.
17972 Getting the debugging target to return the proper status to @value{GDBN}
17973 probably requires changes to the standard stub; one quick and dirty way
17974 is to just execute a breakpoint instruction (the ``dirty'' part is that
17975 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17977 Other routines you need to supply are:
17980 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17981 @findex exceptionHandler
17982 Write this function to install @var{exception_address} in the exception
17983 handling tables. You need to do this because the stub does not have any
17984 way of knowing what the exception handling tables on your target system
17985 are like (for example, the processor's table might be in @sc{rom},
17986 containing entries which point to a table in @sc{ram}).
17987 @var{exception_number} is the exception number which should be changed;
17988 its meaning is architecture-dependent (for example, different numbers
17989 might represent divide by zero, misaligned access, etc). When this
17990 exception occurs, control should be transferred directly to
17991 @var{exception_address}, and the processor state (stack, registers,
17992 and so on) should be just as it is when a processor exception occurs. So if
17993 you want to use a jump instruction to reach @var{exception_address}, it
17994 should be a simple jump, not a jump to subroutine.
17996 For the 386, @var{exception_address} should be installed as an interrupt
17997 gate so that interrupts are masked while the handler runs. The gate
17998 should be at privilege level 0 (the most privileged level). The
17999 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18000 help from @code{exceptionHandler}.
18002 @item void flush_i_cache()
18003 @findex flush_i_cache
18004 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18005 instruction cache, if any, on your target machine. If there is no
18006 instruction cache, this subroutine may be a no-op.
18008 On target machines that have instruction caches, @value{GDBN} requires this
18009 function to make certain that the state of your program is stable.
18013 You must also make sure this library routine is available:
18016 @item void *memset(void *, int, int)
18018 This is the standard library function @code{memset} that sets an area of
18019 memory to a known value. If you have one of the free versions of
18020 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18021 either obtain it from your hardware manufacturer, or write your own.
18024 If you do not use the GNU C compiler, you may need other standard
18025 library subroutines as well; this varies from one stub to another,
18026 but in general the stubs are likely to use any of the common library
18027 subroutines which @code{@value{NGCC}} generates as inline code.
18030 @node Debug Session
18031 @subsection Putting it All Together
18033 @cindex remote serial debugging summary
18034 In summary, when your program is ready to debug, you must follow these
18039 Make sure you have defined the supporting low-level routines
18040 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18042 @code{getDebugChar}, @code{putDebugChar},
18043 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18047 Insert these lines in your program's startup code, before the main
18048 procedure is called:
18055 On some machines, when a breakpoint trap is raised, the hardware
18056 automatically makes the PC point to the instruction after the
18057 breakpoint. If your machine doesn't do that, you may need to adjust
18058 @code{handle_exception} to arrange for it to return to the instruction
18059 after the breakpoint on this first invocation, so that your program
18060 doesn't keep hitting the initial breakpoint instead of making
18064 For the 680x0 stub only, you need to provide a variable called
18065 @code{exceptionHook}. Normally you just use:
18068 void (*exceptionHook)() = 0;
18072 but if before calling @code{set_debug_traps}, you set it to point to a
18073 function in your program, that function is called when
18074 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18075 error). The function indicated by @code{exceptionHook} is called with
18076 one parameter: an @code{int} which is the exception number.
18079 Compile and link together: your program, the @value{GDBN} debugging stub for
18080 your target architecture, and the supporting subroutines.
18083 Make sure you have a serial connection between your target machine and
18084 the @value{GDBN} host, and identify the serial port on the host.
18087 @c The "remote" target now provides a `load' command, so we should
18088 @c document that. FIXME.
18089 Download your program to your target machine (or get it there by
18090 whatever means the manufacturer provides), and start it.
18093 Start @value{GDBN} on the host, and connect to the target
18094 (@pxref{Connecting,,Connecting to a Remote Target}).
18098 @node Configurations
18099 @chapter Configuration-Specific Information
18101 While nearly all @value{GDBN} commands are available for all native and
18102 cross versions of the debugger, there are some exceptions. This chapter
18103 describes things that are only available in certain configurations.
18105 There are three major categories of configurations: native
18106 configurations, where the host and target are the same, embedded
18107 operating system configurations, which are usually the same for several
18108 different processor architectures, and bare embedded processors, which
18109 are quite different from each other.
18114 * Embedded Processors::
18121 This section describes details specific to particular native
18126 * BSD libkvm Interface:: Debugging BSD kernel memory images
18127 * SVR4 Process Information:: SVR4 process information
18128 * DJGPP Native:: Features specific to the DJGPP port
18129 * Cygwin Native:: Features specific to the Cygwin port
18130 * Hurd Native:: Features specific to @sc{gnu} Hurd
18131 * Neutrino:: Features specific to QNX Neutrino
18132 * Darwin:: Features specific to Darwin
18138 On HP-UX systems, if you refer to a function or variable name that
18139 begins with a dollar sign, @value{GDBN} searches for a user or system
18140 name first, before it searches for a convenience variable.
18143 @node BSD libkvm Interface
18144 @subsection BSD libkvm Interface
18147 @cindex kernel memory image
18148 @cindex kernel crash dump
18150 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18151 interface that provides a uniform interface for accessing kernel virtual
18152 memory images, including live systems and crash dumps. @value{GDBN}
18153 uses this interface to allow you to debug live kernels and kernel crash
18154 dumps on many native BSD configurations. This is implemented as a
18155 special @code{kvm} debugging target. For debugging a live system, load
18156 the currently running kernel into @value{GDBN} and connect to the
18160 (@value{GDBP}) @b{target kvm}
18163 For debugging crash dumps, provide the file name of the crash dump as an
18167 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18170 Once connected to the @code{kvm} target, the following commands are
18176 Set current context from the @dfn{Process Control Block} (PCB) address.
18179 Set current context from proc address. This command isn't available on
18180 modern FreeBSD systems.
18183 @node SVR4 Process Information
18184 @subsection SVR4 Process Information
18186 @cindex examine process image
18187 @cindex process info via @file{/proc}
18189 Many versions of SVR4 and compatible systems provide a facility called
18190 @samp{/proc} that can be used to examine the image of a running
18191 process using file-system subroutines. If @value{GDBN} is configured
18192 for an operating system with this facility, the command @code{info
18193 proc} is available to report information about the process running
18194 your program, or about any process running on your system. @code{info
18195 proc} works only on SVR4 systems that include the @code{procfs} code.
18196 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
18197 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
18203 @itemx info proc @var{process-id}
18204 Summarize available information about any running process. If a
18205 process ID is specified by @var{process-id}, display information about
18206 that process; otherwise display information about the program being
18207 debugged. The summary includes the debugged process ID, the command
18208 line used to invoke it, its current working directory, and its
18209 executable file's absolute file name.
18211 On some systems, @var{process-id} can be of the form
18212 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18213 within a process. If the optional @var{pid} part is missing, it means
18214 a thread from the process being debugged (the leading @samp{/} still
18215 needs to be present, or else @value{GDBN} will interpret the number as
18216 a process ID rather than a thread ID).
18218 @item info proc mappings
18219 @cindex memory address space mappings
18220 Report the memory address space ranges accessible in the program, with
18221 information on whether the process has read, write, or execute access
18222 rights to each range. On @sc{gnu}/Linux systems, each memory range
18223 includes the object file which is mapped to that range, instead of the
18224 memory access rights to that range.
18226 @item info proc stat
18227 @itemx info proc status
18228 @cindex process detailed status information
18229 These subcommands are specific to @sc{gnu}/Linux systems. They show
18230 the process-related information, including the user ID and group ID;
18231 how many threads are there in the process; its virtual memory usage;
18232 the signals that are pending, blocked, and ignored; its TTY; its
18233 consumption of system and user time; its stack size; its @samp{nice}
18234 value; etc. For more information, see the @samp{proc} man page
18235 (type @kbd{man 5 proc} from your shell prompt).
18237 @item info proc all
18238 Show all the information about the process described under all of the
18239 above @code{info proc} subcommands.
18242 @comment These sub-options of 'info proc' were not included when
18243 @comment procfs.c was re-written. Keep their descriptions around
18244 @comment against the day when someone finds the time to put them back in.
18245 @kindex info proc times
18246 @item info proc times
18247 Starting time, user CPU time, and system CPU time for your program and
18250 @kindex info proc id
18252 Report on the process IDs related to your program: its own process ID,
18253 the ID of its parent, the process group ID, and the session ID.
18256 @item set procfs-trace
18257 @kindex set procfs-trace
18258 @cindex @code{procfs} API calls
18259 This command enables and disables tracing of @code{procfs} API calls.
18261 @item show procfs-trace
18262 @kindex show procfs-trace
18263 Show the current state of @code{procfs} API call tracing.
18265 @item set procfs-file @var{file}
18266 @kindex set procfs-file
18267 Tell @value{GDBN} to write @code{procfs} API trace to the named
18268 @var{file}. @value{GDBN} appends the trace info to the previous
18269 contents of the file. The default is to display the trace on the
18272 @item show procfs-file
18273 @kindex show procfs-file
18274 Show the file to which @code{procfs} API trace is written.
18276 @item proc-trace-entry
18277 @itemx proc-trace-exit
18278 @itemx proc-untrace-entry
18279 @itemx proc-untrace-exit
18280 @kindex proc-trace-entry
18281 @kindex proc-trace-exit
18282 @kindex proc-untrace-entry
18283 @kindex proc-untrace-exit
18284 These commands enable and disable tracing of entries into and exits
18285 from the @code{syscall} interface.
18288 @kindex info pidlist
18289 @cindex process list, QNX Neutrino
18290 For QNX Neutrino only, this command displays the list of all the
18291 processes and all the threads within each process.
18294 @kindex info meminfo
18295 @cindex mapinfo list, QNX Neutrino
18296 For QNX Neutrino only, this command displays the list of all mapinfos.
18300 @subsection Features for Debugging @sc{djgpp} Programs
18301 @cindex @sc{djgpp} debugging
18302 @cindex native @sc{djgpp} debugging
18303 @cindex MS-DOS-specific commands
18306 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18307 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18308 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18309 top of real-mode DOS systems and their emulations.
18311 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18312 defines a few commands specific to the @sc{djgpp} port. This
18313 subsection describes those commands.
18318 This is a prefix of @sc{djgpp}-specific commands which print
18319 information about the target system and important OS structures.
18322 @cindex MS-DOS system info
18323 @cindex free memory information (MS-DOS)
18324 @item info dos sysinfo
18325 This command displays assorted information about the underlying
18326 platform: the CPU type and features, the OS version and flavor, the
18327 DPMI version, and the available conventional and DPMI memory.
18332 @cindex segment descriptor tables
18333 @cindex descriptor tables display
18335 @itemx info dos ldt
18336 @itemx info dos idt
18337 These 3 commands display entries from, respectively, Global, Local,
18338 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18339 tables are data structures which store a descriptor for each segment
18340 that is currently in use. The segment's selector is an index into a
18341 descriptor table; the table entry for that index holds the
18342 descriptor's base address and limit, and its attributes and access
18345 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18346 segment (used for both data and the stack), and a DOS segment (which
18347 allows access to DOS/BIOS data structures and absolute addresses in
18348 conventional memory). However, the DPMI host will usually define
18349 additional segments in order to support the DPMI environment.
18351 @cindex garbled pointers
18352 These commands allow to display entries from the descriptor tables.
18353 Without an argument, all entries from the specified table are
18354 displayed. An argument, which should be an integer expression, means
18355 display a single entry whose index is given by the argument. For
18356 example, here's a convenient way to display information about the
18357 debugged program's data segment:
18360 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18361 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18365 This comes in handy when you want to see whether a pointer is outside
18366 the data segment's limit (i.e.@: @dfn{garbled}).
18368 @cindex page tables display (MS-DOS)
18370 @itemx info dos pte
18371 These two commands display entries from, respectively, the Page
18372 Directory and the Page Tables. Page Directories and Page Tables are
18373 data structures which control how virtual memory addresses are mapped
18374 into physical addresses. A Page Table includes an entry for every
18375 page of memory that is mapped into the program's address space; there
18376 may be several Page Tables, each one holding up to 4096 entries. A
18377 Page Directory has up to 4096 entries, one each for every Page Table
18378 that is currently in use.
18380 Without an argument, @kbd{info dos pde} displays the entire Page
18381 Directory, and @kbd{info dos pte} displays all the entries in all of
18382 the Page Tables. An argument, an integer expression, given to the
18383 @kbd{info dos pde} command means display only that entry from the Page
18384 Directory table. An argument given to the @kbd{info dos pte} command
18385 means display entries from a single Page Table, the one pointed to by
18386 the specified entry in the Page Directory.
18388 @cindex direct memory access (DMA) on MS-DOS
18389 These commands are useful when your program uses @dfn{DMA} (Direct
18390 Memory Access), which needs physical addresses to program the DMA
18393 These commands are supported only with some DPMI servers.
18395 @cindex physical address from linear address
18396 @item info dos address-pte @var{addr}
18397 This command displays the Page Table entry for a specified linear
18398 address. The argument @var{addr} is a linear address which should
18399 already have the appropriate segment's base address added to it,
18400 because this command accepts addresses which may belong to @emph{any}
18401 segment. For example, here's how to display the Page Table entry for
18402 the page where a variable @code{i} is stored:
18405 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18406 @exdent @code{Page Table entry for address 0x11a00d30:}
18407 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18411 This says that @code{i} is stored at offset @code{0xd30} from the page
18412 whose physical base address is @code{0x02698000}, and shows all the
18413 attributes of that page.
18415 Note that you must cast the addresses of variables to a @code{char *},
18416 since otherwise the value of @code{__djgpp_base_address}, the base
18417 address of all variables and functions in a @sc{djgpp} program, will
18418 be added using the rules of C pointer arithmetics: if @code{i} is
18419 declared an @code{int}, @value{GDBN} will add 4 times the value of
18420 @code{__djgpp_base_address} to the address of @code{i}.
18422 Here's another example, it displays the Page Table entry for the
18426 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18427 @exdent @code{Page Table entry for address 0x29110:}
18428 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18432 (The @code{+ 3} offset is because the transfer buffer's address is the
18433 3rd member of the @code{_go32_info_block} structure.) The output
18434 clearly shows that this DPMI server maps the addresses in conventional
18435 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18436 linear (@code{0x29110}) addresses are identical.
18438 This command is supported only with some DPMI servers.
18441 @cindex DOS serial data link, remote debugging
18442 In addition to native debugging, the DJGPP port supports remote
18443 debugging via a serial data link. The following commands are specific
18444 to remote serial debugging in the DJGPP port of @value{GDBN}.
18447 @kindex set com1base
18448 @kindex set com1irq
18449 @kindex set com2base
18450 @kindex set com2irq
18451 @kindex set com3base
18452 @kindex set com3irq
18453 @kindex set com4base
18454 @kindex set com4irq
18455 @item set com1base @var{addr}
18456 This command sets the base I/O port address of the @file{COM1} serial
18459 @item set com1irq @var{irq}
18460 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18461 for the @file{COM1} serial port.
18463 There are similar commands @samp{set com2base}, @samp{set com3irq},
18464 etc.@: for setting the port address and the @code{IRQ} lines for the
18467 @kindex show com1base
18468 @kindex show com1irq
18469 @kindex show com2base
18470 @kindex show com2irq
18471 @kindex show com3base
18472 @kindex show com3irq
18473 @kindex show com4base
18474 @kindex show com4irq
18475 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18476 display the current settings of the base address and the @code{IRQ}
18477 lines used by the COM ports.
18480 @kindex info serial
18481 @cindex DOS serial port status
18482 This command prints the status of the 4 DOS serial ports. For each
18483 port, it prints whether it's active or not, its I/O base address and
18484 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18485 counts of various errors encountered so far.
18489 @node Cygwin Native
18490 @subsection Features for Debugging MS Windows PE Executables
18491 @cindex MS Windows debugging
18492 @cindex native Cygwin debugging
18493 @cindex Cygwin-specific commands
18495 @value{GDBN} supports native debugging of MS Windows programs, including
18496 DLLs with and without symbolic debugging information.
18498 @cindex Ctrl-BREAK, MS-Windows
18499 @cindex interrupt debuggee on MS-Windows
18500 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18501 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18502 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18503 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18504 sequence, which can be used to interrupt the debuggee even if it
18507 There are various additional Cygwin-specific commands, described in
18508 this section. Working with DLLs that have no debugging symbols is
18509 described in @ref{Non-debug DLL Symbols}.
18514 This is a prefix of MS Windows-specific commands which print
18515 information about the target system and important OS structures.
18517 @item info w32 selector
18518 This command displays information returned by
18519 the Win32 API @code{GetThreadSelectorEntry} function.
18520 It takes an optional argument that is evaluated to
18521 a long value to give the information about this given selector.
18522 Without argument, this command displays information
18523 about the six segment registers.
18525 @item info w32 thread-information-block
18526 This command displays thread specific information stored in the
18527 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18528 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18532 This is a Cygwin-specific alias of @code{info shared}.
18534 @kindex dll-symbols
18536 This command loads symbols from a dll similarly to
18537 add-sym command but without the need to specify a base address.
18539 @kindex set cygwin-exceptions
18540 @cindex debugging the Cygwin DLL
18541 @cindex Cygwin DLL, debugging
18542 @item set cygwin-exceptions @var{mode}
18543 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18544 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18545 @value{GDBN} will delay recognition of exceptions, and may ignore some
18546 exceptions which seem to be caused by internal Cygwin DLL
18547 ``bookkeeping''. This option is meant primarily for debugging the
18548 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18549 @value{GDBN} users with false @code{SIGSEGV} signals.
18551 @kindex show cygwin-exceptions
18552 @item show cygwin-exceptions
18553 Displays whether @value{GDBN} will break on exceptions that happen
18554 inside the Cygwin DLL itself.
18556 @kindex set new-console
18557 @item set new-console @var{mode}
18558 If @var{mode} is @code{on} the debuggee will
18559 be started in a new console on next start.
18560 If @var{mode} is @code{off}, the debuggee will
18561 be started in the same console as the debugger.
18563 @kindex show new-console
18564 @item show new-console
18565 Displays whether a new console is used
18566 when the debuggee is started.
18568 @kindex set new-group
18569 @item set new-group @var{mode}
18570 This boolean value controls whether the debuggee should
18571 start a new group or stay in the same group as the debugger.
18572 This affects the way the Windows OS handles
18575 @kindex show new-group
18576 @item show new-group
18577 Displays current value of new-group boolean.
18579 @kindex set debugevents
18580 @item set debugevents
18581 This boolean value adds debug output concerning kernel events related
18582 to the debuggee seen by the debugger. This includes events that
18583 signal thread and process creation and exit, DLL loading and
18584 unloading, console interrupts, and debugging messages produced by the
18585 Windows @code{OutputDebugString} API call.
18587 @kindex set debugexec
18588 @item set debugexec
18589 This boolean value adds debug output concerning execute events
18590 (such as resume thread) seen by the debugger.
18592 @kindex set debugexceptions
18593 @item set debugexceptions
18594 This boolean value adds debug output concerning exceptions in the
18595 debuggee seen by the debugger.
18597 @kindex set debugmemory
18598 @item set debugmemory
18599 This boolean value adds debug output concerning debuggee memory reads
18600 and writes by the debugger.
18604 This boolean values specifies whether the debuggee is called
18605 via a shell or directly (default value is on).
18609 Displays if the debuggee will be started with a shell.
18614 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18617 @node Non-debug DLL Symbols
18618 @subsubsection Support for DLLs without Debugging Symbols
18619 @cindex DLLs with no debugging symbols
18620 @cindex Minimal symbols and DLLs
18622 Very often on windows, some of the DLLs that your program relies on do
18623 not include symbolic debugging information (for example,
18624 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18625 symbols in a DLL, it relies on the minimal amount of symbolic
18626 information contained in the DLL's export table. This section
18627 describes working with such symbols, known internally to @value{GDBN} as
18628 ``minimal symbols''.
18630 Note that before the debugged program has started execution, no DLLs
18631 will have been loaded. The easiest way around this problem is simply to
18632 start the program --- either by setting a breakpoint or letting the
18633 program run once to completion. It is also possible to force
18634 @value{GDBN} to load a particular DLL before starting the executable ---
18635 see the shared library information in @ref{Files}, or the
18636 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18637 explicitly loading symbols from a DLL with no debugging information will
18638 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18639 which may adversely affect symbol lookup performance.
18641 @subsubsection DLL Name Prefixes
18643 In keeping with the naming conventions used by the Microsoft debugging
18644 tools, DLL export symbols are made available with a prefix based on the
18645 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18646 also entered into the symbol table, so @code{CreateFileA} is often
18647 sufficient. In some cases there will be name clashes within a program
18648 (particularly if the executable itself includes full debugging symbols)
18649 necessitating the use of the fully qualified name when referring to the
18650 contents of the DLL. Use single-quotes around the name to avoid the
18651 exclamation mark (``!'') being interpreted as a language operator.
18653 Note that the internal name of the DLL may be all upper-case, even
18654 though the file name of the DLL is lower-case, or vice-versa. Since
18655 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18656 some confusion. If in doubt, try the @code{info functions} and
18657 @code{info variables} commands or even @code{maint print msymbols}
18658 (@pxref{Symbols}). Here's an example:
18661 (@value{GDBP}) info function CreateFileA
18662 All functions matching regular expression "CreateFileA":
18664 Non-debugging symbols:
18665 0x77e885f4 CreateFileA
18666 0x77e885f4 KERNEL32!CreateFileA
18670 (@value{GDBP}) info function !
18671 All functions matching regular expression "!":
18673 Non-debugging symbols:
18674 0x6100114c cygwin1!__assert
18675 0x61004034 cygwin1!_dll_crt0@@0
18676 0x61004240 cygwin1!dll_crt0(per_process *)
18680 @subsubsection Working with Minimal Symbols
18682 Symbols extracted from a DLL's export table do not contain very much
18683 type information. All that @value{GDBN} can do is guess whether a symbol
18684 refers to a function or variable depending on the linker section that
18685 contains the symbol. Also note that the actual contents of the memory
18686 contained in a DLL are not available unless the program is running. This
18687 means that you cannot examine the contents of a variable or disassemble
18688 a function within a DLL without a running program.
18690 Variables are generally treated as pointers and dereferenced
18691 automatically. For this reason, it is often necessary to prefix a
18692 variable name with the address-of operator (``&'') and provide explicit
18693 type information in the command. Here's an example of the type of
18697 (@value{GDBP}) print 'cygwin1!__argv'
18702 (@value{GDBP}) x 'cygwin1!__argv'
18703 0x10021610: "\230y\""
18706 And two possible solutions:
18709 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18710 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18714 (@value{GDBP}) x/2x &'cygwin1!__argv'
18715 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18716 (@value{GDBP}) x/x 0x10021608
18717 0x10021608: 0x0022fd98
18718 (@value{GDBP}) x/s 0x0022fd98
18719 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18722 Setting a break point within a DLL is possible even before the program
18723 starts execution. However, under these circumstances, @value{GDBN} can't
18724 examine the initial instructions of the function in order to skip the
18725 function's frame set-up code. You can work around this by using ``*&''
18726 to set the breakpoint at a raw memory address:
18729 (@value{GDBP}) break *&'python22!PyOS_Readline'
18730 Breakpoint 1 at 0x1e04eff0
18733 The author of these extensions is not entirely convinced that setting a
18734 break point within a shared DLL like @file{kernel32.dll} is completely
18738 @subsection Commands Specific to @sc{gnu} Hurd Systems
18739 @cindex @sc{gnu} Hurd debugging
18741 This subsection describes @value{GDBN} commands specific to the
18742 @sc{gnu} Hurd native debugging.
18747 @kindex set signals@r{, Hurd command}
18748 @kindex set sigs@r{, Hurd command}
18749 This command toggles the state of inferior signal interception by
18750 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18751 affected by this command. @code{sigs} is a shorthand alias for
18756 @kindex show signals@r{, Hurd command}
18757 @kindex show sigs@r{, Hurd command}
18758 Show the current state of intercepting inferior's signals.
18760 @item set signal-thread
18761 @itemx set sigthread
18762 @kindex set signal-thread
18763 @kindex set sigthread
18764 This command tells @value{GDBN} which thread is the @code{libc} signal
18765 thread. That thread is run when a signal is delivered to a running
18766 process. @code{set sigthread} is the shorthand alias of @code{set
18769 @item show signal-thread
18770 @itemx show sigthread
18771 @kindex show signal-thread
18772 @kindex show sigthread
18773 These two commands show which thread will run when the inferior is
18774 delivered a signal.
18777 @kindex set stopped@r{, Hurd command}
18778 This commands tells @value{GDBN} that the inferior process is stopped,
18779 as with the @code{SIGSTOP} signal. The stopped process can be
18780 continued by delivering a signal to it.
18783 @kindex show stopped@r{, Hurd command}
18784 This command shows whether @value{GDBN} thinks the debuggee is
18787 @item set exceptions
18788 @kindex set exceptions@r{, Hurd command}
18789 Use this command to turn off trapping of exceptions in the inferior.
18790 When exception trapping is off, neither breakpoints nor
18791 single-stepping will work. To restore the default, set exception
18794 @item show exceptions
18795 @kindex show exceptions@r{, Hurd command}
18796 Show the current state of trapping exceptions in the inferior.
18798 @item set task pause
18799 @kindex set task@r{, Hurd commands}
18800 @cindex task attributes (@sc{gnu} Hurd)
18801 @cindex pause current task (@sc{gnu} Hurd)
18802 This command toggles task suspension when @value{GDBN} has control.
18803 Setting it to on takes effect immediately, and the task is suspended
18804 whenever @value{GDBN} gets control. Setting it to off will take
18805 effect the next time the inferior is continued. If this option is set
18806 to off, you can use @code{set thread default pause on} or @code{set
18807 thread pause on} (see below) to pause individual threads.
18809 @item show task pause
18810 @kindex show task@r{, Hurd commands}
18811 Show the current state of task suspension.
18813 @item set task detach-suspend-count
18814 @cindex task suspend count
18815 @cindex detach from task, @sc{gnu} Hurd
18816 This command sets the suspend count the task will be left with when
18817 @value{GDBN} detaches from it.
18819 @item show task detach-suspend-count
18820 Show the suspend count the task will be left with when detaching.
18822 @item set task exception-port
18823 @itemx set task excp
18824 @cindex task exception port, @sc{gnu} Hurd
18825 This command sets the task exception port to which @value{GDBN} will
18826 forward exceptions. The argument should be the value of the @dfn{send
18827 rights} of the task. @code{set task excp} is a shorthand alias.
18829 @item set noninvasive
18830 @cindex noninvasive task options
18831 This command switches @value{GDBN} to a mode that is the least
18832 invasive as far as interfering with the inferior is concerned. This
18833 is the same as using @code{set task pause}, @code{set exceptions}, and
18834 @code{set signals} to values opposite to the defaults.
18836 @item info send-rights
18837 @itemx info receive-rights
18838 @itemx info port-rights
18839 @itemx info port-sets
18840 @itemx info dead-names
18843 @cindex send rights, @sc{gnu} Hurd
18844 @cindex receive rights, @sc{gnu} Hurd
18845 @cindex port rights, @sc{gnu} Hurd
18846 @cindex port sets, @sc{gnu} Hurd
18847 @cindex dead names, @sc{gnu} Hurd
18848 These commands display information about, respectively, send rights,
18849 receive rights, port rights, port sets, and dead names of a task.
18850 There are also shorthand aliases: @code{info ports} for @code{info
18851 port-rights} and @code{info psets} for @code{info port-sets}.
18853 @item set thread pause
18854 @kindex set thread@r{, Hurd command}
18855 @cindex thread properties, @sc{gnu} Hurd
18856 @cindex pause current thread (@sc{gnu} Hurd)
18857 This command toggles current thread suspension when @value{GDBN} has
18858 control. Setting it to on takes effect immediately, and the current
18859 thread is suspended whenever @value{GDBN} gets control. Setting it to
18860 off will take effect the next time the inferior is continued.
18861 Normally, this command has no effect, since when @value{GDBN} has
18862 control, the whole task is suspended. However, if you used @code{set
18863 task pause off} (see above), this command comes in handy to suspend
18864 only the current thread.
18866 @item show thread pause
18867 @kindex show thread@r{, Hurd command}
18868 This command shows the state of current thread suspension.
18870 @item set thread run
18871 This command sets whether the current thread is allowed to run.
18873 @item show thread run
18874 Show whether the current thread is allowed to run.
18876 @item set thread detach-suspend-count
18877 @cindex thread suspend count, @sc{gnu} Hurd
18878 @cindex detach from thread, @sc{gnu} Hurd
18879 This command sets the suspend count @value{GDBN} will leave on a
18880 thread when detaching. This number is relative to the suspend count
18881 found by @value{GDBN} when it notices the thread; use @code{set thread
18882 takeover-suspend-count} to force it to an absolute value.
18884 @item show thread detach-suspend-count
18885 Show the suspend count @value{GDBN} will leave on the thread when
18888 @item set thread exception-port
18889 @itemx set thread excp
18890 Set the thread exception port to which to forward exceptions. This
18891 overrides the port set by @code{set task exception-port} (see above).
18892 @code{set thread excp} is the shorthand alias.
18894 @item set thread takeover-suspend-count
18895 Normally, @value{GDBN}'s thread suspend counts are relative to the
18896 value @value{GDBN} finds when it notices each thread. This command
18897 changes the suspend counts to be absolute instead.
18899 @item set thread default
18900 @itemx show thread default
18901 @cindex thread default settings, @sc{gnu} Hurd
18902 Each of the above @code{set thread} commands has a @code{set thread
18903 default} counterpart (e.g., @code{set thread default pause}, @code{set
18904 thread default exception-port}, etc.). The @code{thread default}
18905 variety of commands sets the default thread properties for all
18906 threads; you can then change the properties of individual threads with
18907 the non-default commands.
18912 @subsection QNX Neutrino
18913 @cindex QNX Neutrino
18915 @value{GDBN} provides the following commands specific to the QNX
18919 @item set debug nto-debug
18920 @kindex set debug nto-debug
18921 When set to on, enables debugging messages specific to the QNX
18924 @item show debug nto-debug
18925 @kindex show debug nto-debug
18926 Show the current state of QNX Neutrino messages.
18933 @value{GDBN} provides the following commands specific to the Darwin target:
18936 @item set debug darwin @var{num}
18937 @kindex set debug darwin
18938 When set to a non zero value, enables debugging messages specific to
18939 the Darwin support. Higher values produce more verbose output.
18941 @item show debug darwin
18942 @kindex show debug darwin
18943 Show the current state of Darwin messages.
18945 @item set debug mach-o @var{num}
18946 @kindex set debug mach-o
18947 When set to a non zero value, enables debugging messages while
18948 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18949 file format used on Darwin for object and executable files.) Higher
18950 values produce more verbose output. This is a command to diagnose
18951 problems internal to @value{GDBN} and should not be needed in normal
18954 @item show debug mach-o
18955 @kindex show debug mach-o
18956 Show the current state of Mach-O file messages.
18958 @item set mach-exceptions on
18959 @itemx set mach-exceptions off
18960 @kindex set mach-exceptions
18961 On Darwin, faults are first reported as a Mach exception and are then
18962 mapped to a Posix signal. Use this command to turn on trapping of
18963 Mach exceptions in the inferior. This might be sometimes useful to
18964 better understand the cause of a fault. The default is off.
18966 @item show mach-exceptions
18967 @kindex show mach-exceptions
18968 Show the current state of exceptions trapping.
18973 @section Embedded Operating Systems
18975 This section describes configurations involving the debugging of
18976 embedded operating systems that are available for several different
18980 * VxWorks:: Using @value{GDBN} with VxWorks
18983 @value{GDBN} includes the ability to debug programs running on
18984 various real-time operating systems.
18987 @subsection Using @value{GDBN} with VxWorks
18993 @kindex target vxworks
18994 @item target vxworks @var{machinename}
18995 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18996 is the target system's machine name or IP address.
19000 On VxWorks, @code{load} links @var{filename} dynamically on the
19001 current target system as well as adding its symbols in @value{GDBN}.
19003 @value{GDBN} enables developers to spawn and debug tasks running on networked
19004 VxWorks targets from a Unix host. Already-running tasks spawned from
19005 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19006 both the Unix host and on the VxWorks target. The program
19007 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19008 installed with the name @code{vxgdb}, to distinguish it from a
19009 @value{GDBN} for debugging programs on the host itself.)
19012 @item VxWorks-timeout @var{args}
19013 @kindex vxworks-timeout
19014 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19015 This option is set by the user, and @var{args} represents the number of
19016 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19017 your VxWorks target is a slow software simulator or is on the far side
19018 of a thin network line.
19021 The following information on connecting to VxWorks was current when
19022 this manual was produced; newer releases of VxWorks may use revised
19025 @findex INCLUDE_RDB
19026 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19027 to include the remote debugging interface routines in the VxWorks
19028 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19029 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19030 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19031 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19032 information on configuring and remaking VxWorks, see the manufacturer's
19034 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19036 Once you have included @file{rdb.a} in your VxWorks system image and set
19037 your Unix execution search path to find @value{GDBN}, you are ready to
19038 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19039 @code{vxgdb}, depending on your installation).
19041 @value{GDBN} comes up showing the prompt:
19048 * VxWorks Connection:: Connecting to VxWorks
19049 * VxWorks Download:: VxWorks download
19050 * VxWorks Attach:: Running tasks
19053 @node VxWorks Connection
19054 @subsubsection Connecting to VxWorks
19056 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19057 network. To connect to a target whose host name is ``@code{tt}'', type:
19060 (vxgdb) target vxworks tt
19064 @value{GDBN} displays messages like these:
19067 Attaching remote machine across net...
19072 @value{GDBN} then attempts to read the symbol tables of any object modules
19073 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19074 these files by searching the directories listed in the command search
19075 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19076 to find an object file, it displays a message such as:
19079 prog.o: No such file or directory.
19082 When this happens, add the appropriate directory to the search path with
19083 the @value{GDBN} command @code{path}, and execute the @code{target}
19086 @node VxWorks Download
19087 @subsubsection VxWorks Download
19089 @cindex download to VxWorks
19090 If you have connected to the VxWorks target and you want to debug an
19091 object that has not yet been loaded, you can use the @value{GDBN}
19092 @code{load} command to download a file from Unix to VxWorks
19093 incrementally. The object file given as an argument to the @code{load}
19094 command is actually opened twice: first by the VxWorks target in order
19095 to download the code, then by @value{GDBN} in order to read the symbol
19096 table. This can lead to problems if the current working directories on
19097 the two systems differ. If both systems have NFS mounted the same
19098 filesystems, you can avoid these problems by using absolute paths.
19099 Otherwise, it is simplest to set the working directory on both systems
19100 to the directory in which the object file resides, and then to reference
19101 the file by its name, without any path. For instance, a program
19102 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19103 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19104 program, type this on VxWorks:
19107 -> cd "@var{vxpath}/vw/demo/rdb"
19111 Then, in @value{GDBN}, type:
19114 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19115 (vxgdb) load prog.o
19118 @value{GDBN} displays a response similar to this:
19121 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19124 You can also use the @code{load} command to reload an object module
19125 after editing and recompiling the corresponding source file. Note that
19126 this makes @value{GDBN} delete all currently-defined breakpoints,
19127 auto-displays, and convenience variables, and to clear the value
19128 history. (This is necessary in order to preserve the integrity of
19129 debugger's data structures that reference the target system's symbol
19132 @node VxWorks Attach
19133 @subsubsection Running Tasks
19135 @cindex running VxWorks tasks
19136 You can also attach to an existing task using the @code{attach} command as
19140 (vxgdb) attach @var{task}
19144 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19145 or suspended when you attach to it. Running tasks are suspended at
19146 the time of attachment.
19148 @node Embedded Processors
19149 @section Embedded Processors
19151 This section goes into details specific to particular embedded
19154 @cindex send command to simulator
19155 Whenever a specific embedded processor has a simulator, @value{GDBN}
19156 allows to send an arbitrary command to the simulator.
19159 @item sim @var{command}
19160 @kindex sim@r{, a command}
19161 Send an arbitrary @var{command} string to the simulator. Consult the
19162 documentation for the specific simulator in use for information about
19163 acceptable commands.
19169 * M32R/D:: Renesas M32R/D
19170 * M68K:: Motorola M68K
19171 * MicroBlaze:: Xilinx MicroBlaze
19172 * MIPS Embedded:: MIPS Embedded
19173 * OpenRISC 1000:: OpenRisc 1000
19174 * PA:: HP PA Embedded
19175 * PowerPC Embedded:: PowerPC Embedded
19176 * Sparclet:: Tsqware Sparclet
19177 * Sparclite:: Fujitsu Sparclite
19178 * Z8000:: Zilog Z8000
19181 * Super-H:: Renesas Super-H
19190 @item target rdi @var{dev}
19191 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19192 use this target to communicate with both boards running the Angel
19193 monitor, or with the EmbeddedICE JTAG debug device.
19196 @item target rdp @var{dev}
19201 @value{GDBN} provides the following ARM-specific commands:
19204 @item set arm disassembler
19206 This commands selects from a list of disassembly styles. The
19207 @code{"std"} style is the standard style.
19209 @item show arm disassembler
19211 Show the current disassembly style.
19213 @item set arm apcs32
19214 @cindex ARM 32-bit mode
19215 This command toggles ARM operation mode between 32-bit and 26-bit.
19217 @item show arm apcs32
19218 Display the current usage of the ARM 32-bit mode.
19220 @item set arm fpu @var{fputype}
19221 This command sets the ARM floating-point unit (FPU) type. The
19222 argument @var{fputype} can be one of these:
19226 Determine the FPU type by querying the OS ABI.
19228 Software FPU, with mixed-endian doubles on little-endian ARM
19231 GCC-compiled FPA co-processor.
19233 Software FPU with pure-endian doubles.
19239 Show the current type of the FPU.
19242 This command forces @value{GDBN} to use the specified ABI.
19245 Show the currently used ABI.
19247 @item set arm fallback-mode (arm|thumb|auto)
19248 @value{GDBN} uses the symbol table, when available, to determine
19249 whether instructions are ARM or Thumb. This command controls
19250 @value{GDBN}'s default behavior when the symbol table is not
19251 available. The default is @samp{auto}, which causes @value{GDBN} to
19252 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19255 @item show arm fallback-mode
19256 Show the current fallback instruction mode.
19258 @item set arm force-mode (arm|thumb|auto)
19259 This command overrides use of the symbol table to determine whether
19260 instructions are ARM or Thumb. The default is @samp{auto}, which
19261 causes @value{GDBN} to use the symbol table and then the setting
19262 of @samp{set arm fallback-mode}.
19264 @item show arm force-mode
19265 Show the current forced instruction mode.
19267 @item set debug arm
19268 Toggle whether to display ARM-specific debugging messages from the ARM
19269 target support subsystem.
19271 @item show debug arm
19272 Show whether ARM-specific debugging messages are enabled.
19275 The following commands are available when an ARM target is debugged
19276 using the RDI interface:
19279 @item rdilogfile @r{[}@var{file}@r{]}
19281 @cindex ADP (Angel Debugger Protocol) logging
19282 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19283 With an argument, sets the log file to the specified @var{file}. With
19284 no argument, show the current log file name. The default log file is
19287 @item rdilogenable @r{[}@var{arg}@r{]}
19288 @kindex rdilogenable
19289 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19290 enables logging, with an argument 0 or @code{"no"} disables it. With
19291 no arguments displays the current setting. When logging is enabled,
19292 ADP packets exchanged between @value{GDBN} and the RDI target device
19293 are logged to a file.
19295 @item set rdiromatzero
19296 @kindex set rdiromatzero
19297 @cindex ROM at zero address, RDI
19298 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19299 vector catching is disabled, so that zero address can be used. If off
19300 (the default), vector catching is enabled. For this command to take
19301 effect, it needs to be invoked prior to the @code{target rdi} command.
19303 @item show rdiromatzero
19304 @kindex show rdiromatzero
19305 Show the current setting of ROM at zero address.
19307 @item set rdiheartbeat
19308 @kindex set rdiheartbeat
19309 @cindex RDI heartbeat
19310 Enable or disable RDI heartbeat packets. It is not recommended to
19311 turn on this option, since it confuses ARM and EPI JTAG interface, as
19312 well as the Angel monitor.
19314 @item show rdiheartbeat
19315 @kindex show rdiheartbeat
19316 Show the setting of RDI heartbeat packets.
19320 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19321 The @value{GDBN} ARM simulator accepts the following optional arguments.
19324 @item --swi-support=@var{type}
19325 Tell the simulator which SWI interfaces to support.
19326 @var{type} may be a comma separated list of the following values.
19327 The default value is @code{all}.
19340 @subsection Renesas M32R/D and M32R/SDI
19343 @kindex target m32r
19344 @item target m32r @var{dev}
19345 Renesas M32R/D ROM monitor.
19347 @kindex target m32rsdi
19348 @item target m32rsdi @var{dev}
19349 Renesas M32R SDI server, connected via parallel port to the board.
19352 The following @value{GDBN} commands are specific to the M32R monitor:
19355 @item set download-path @var{path}
19356 @kindex set download-path
19357 @cindex find downloadable @sc{srec} files (M32R)
19358 Set the default path for finding downloadable @sc{srec} files.
19360 @item show download-path
19361 @kindex show download-path
19362 Show the default path for downloadable @sc{srec} files.
19364 @item set board-address @var{addr}
19365 @kindex set board-address
19366 @cindex M32-EVA target board address
19367 Set the IP address for the M32R-EVA target board.
19369 @item show board-address
19370 @kindex show board-address
19371 Show the current IP address of the target board.
19373 @item set server-address @var{addr}
19374 @kindex set server-address
19375 @cindex download server address (M32R)
19376 Set the IP address for the download server, which is the @value{GDBN}'s
19379 @item show server-address
19380 @kindex show server-address
19381 Display the IP address of the download server.
19383 @item upload @r{[}@var{file}@r{]}
19384 @kindex upload@r{, M32R}
19385 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19386 upload capability. If no @var{file} argument is given, the current
19387 executable file is uploaded.
19389 @item tload @r{[}@var{file}@r{]}
19390 @kindex tload@r{, M32R}
19391 Test the @code{upload} command.
19394 The following commands are available for M32R/SDI:
19399 @cindex reset SDI connection, M32R
19400 This command resets the SDI connection.
19404 This command shows the SDI connection status.
19407 @kindex debug_chaos
19408 @cindex M32R/Chaos debugging
19409 Instructs the remote that M32R/Chaos debugging is to be used.
19411 @item use_debug_dma
19412 @kindex use_debug_dma
19413 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19416 @kindex use_mon_code
19417 Instructs the remote to use the MON_CODE method of accessing memory.
19420 @kindex use_ib_break
19421 Instructs the remote to set breakpoints by IB break.
19423 @item use_dbt_break
19424 @kindex use_dbt_break
19425 Instructs the remote to set breakpoints by DBT.
19431 The Motorola m68k configuration includes ColdFire support, and a
19432 target command for the following ROM monitor.
19436 @kindex target dbug
19437 @item target dbug @var{dev}
19438 dBUG ROM monitor for Motorola ColdFire.
19443 @subsection MicroBlaze
19444 @cindex Xilinx MicroBlaze
19445 @cindex XMD, Xilinx Microprocessor Debugger
19447 The MicroBlaze is a soft-core processor supported on various Xilinx
19448 FPGAs, such as Spartan or Virtex series. Boards with these processors
19449 usually have JTAG ports which connect to a host system running the Xilinx
19450 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19451 This host system is used to download the configuration bitstream to
19452 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19453 communicates with the target board using the JTAG interface and
19454 presents a @code{gdbserver} interface to the board. By default
19455 @code{xmd} uses port @code{1234}. (While it is possible to change
19456 this default port, it requires the use of undocumented @code{xmd}
19457 commands. Contact Xilinx support if you need to do this.)
19459 Use these GDB commands to connect to the MicroBlaze target processor.
19462 @item target remote :1234
19463 Use this command to connect to the target if you are running @value{GDBN}
19464 on the same system as @code{xmd}.
19466 @item target remote @var{xmd-host}:1234
19467 Use this command to connect to the target if it is connected to @code{xmd}
19468 running on a different system named @var{xmd-host}.
19471 Use this command to download a program to the MicroBlaze target.
19473 @item set debug microblaze @var{n}
19474 Enable MicroBlaze-specific debugging messages if non-zero.
19476 @item show debug microblaze @var{n}
19477 Show MicroBlaze-specific debugging level.
19480 @node MIPS Embedded
19481 @subsection MIPS Embedded
19483 @cindex MIPS boards
19484 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19485 MIPS board attached to a serial line. This is available when
19486 you configure @value{GDBN} with @samp{--target=mips-elf}.
19489 Use these @value{GDBN} commands to specify the connection to your target board:
19492 @item target mips @var{port}
19493 @kindex target mips @var{port}
19494 To run a program on the board, start up @code{@value{GDBP}} with the
19495 name of your program as the argument. To connect to the board, use the
19496 command @samp{target mips @var{port}}, where @var{port} is the name of
19497 the serial port connected to the board. If the program has not already
19498 been downloaded to the board, you may use the @code{load} command to
19499 download it. You can then use all the usual @value{GDBN} commands.
19501 For example, this sequence connects to the target board through a serial
19502 port, and loads and runs a program called @var{prog} through the
19506 host$ @value{GDBP} @var{prog}
19507 @value{GDBN} is free software and @dots{}
19508 (@value{GDBP}) target mips /dev/ttyb
19509 (@value{GDBP}) load @var{prog}
19513 @item target mips @var{hostname}:@var{portnumber}
19514 On some @value{GDBN} host configurations, you can specify a TCP
19515 connection (for instance, to a serial line managed by a terminal
19516 concentrator) instead of a serial port, using the syntax
19517 @samp{@var{hostname}:@var{portnumber}}.
19519 @item target pmon @var{port}
19520 @kindex target pmon @var{port}
19523 @item target ddb @var{port}
19524 @kindex target ddb @var{port}
19525 NEC's DDB variant of PMON for Vr4300.
19527 @item target lsi @var{port}
19528 @kindex target lsi @var{port}
19529 LSI variant of PMON.
19531 @kindex target r3900
19532 @item target r3900 @var{dev}
19533 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19535 @kindex target array
19536 @item target array @var{dev}
19537 Array Tech LSI33K RAID controller board.
19543 @value{GDBN} also supports these special commands for MIPS targets:
19546 @item set mipsfpu double
19547 @itemx set mipsfpu single
19548 @itemx set mipsfpu none
19549 @itemx set mipsfpu auto
19550 @itemx show mipsfpu
19551 @kindex set mipsfpu
19552 @kindex show mipsfpu
19553 @cindex MIPS remote floating point
19554 @cindex floating point, MIPS remote
19555 If your target board does not support the MIPS floating point
19556 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19557 need this, you may wish to put the command in your @value{GDBN} init
19558 file). This tells @value{GDBN} how to find the return value of
19559 functions which return floating point values. It also allows
19560 @value{GDBN} to avoid saving the floating point registers when calling
19561 functions on the board. If you are using a floating point coprocessor
19562 with only single precision floating point support, as on the @sc{r4650}
19563 processor, use the command @samp{set mipsfpu single}. The default
19564 double precision floating point coprocessor may be selected using
19565 @samp{set mipsfpu double}.
19567 In previous versions the only choices were double precision or no
19568 floating point, so @samp{set mipsfpu on} will select double precision
19569 and @samp{set mipsfpu off} will select no floating point.
19571 As usual, you can inquire about the @code{mipsfpu} variable with
19572 @samp{show mipsfpu}.
19574 @item set timeout @var{seconds}
19575 @itemx set retransmit-timeout @var{seconds}
19576 @itemx show timeout
19577 @itemx show retransmit-timeout
19578 @cindex @code{timeout}, MIPS protocol
19579 @cindex @code{retransmit-timeout}, MIPS protocol
19580 @kindex set timeout
19581 @kindex show timeout
19582 @kindex set retransmit-timeout
19583 @kindex show retransmit-timeout
19584 You can control the timeout used while waiting for a packet, in the MIPS
19585 remote protocol, with the @code{set timeout @var{seconds}} command. The
19586 default is 5 seconds. Similarly, you can control the timeout used while
19587 waiting for an acknowledgment of a packet with the @code{set
19588 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19589 You can inspect both values with @code{show timeout} and @code{show
19590 retransmit-timeout}. (These commands are @emph{only} available when
19591 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19593 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19594 is waiting for your program to stop. In that case, @value{GDBN} waits
19595 forever because it has no way of knowing how long the program is going
19596 to run before stopping.
19598 @item set syn-garbage-limit @var{num}
19599 @kindex set syn-garbage-limit@r{, MIPS remote}
19600 @cindex synchronize with remote MIPS target
19601 Limit the maximum number of characters @value{GDBN} should ignore when
19602 it tries to synchronize with the remote target. The default is 10
19603 characters. Setting the limit to -1 means there's no limit.
19605 @item show syn-garbage-limit
19606 @kindex show syn-garbage-limit@r{, MIPS remote}
19607 Show the current limit on the number of characters to ignore when
19608 trying to synchronize with the remote system.
19610 @item set monitor-prompt @var{prompt}
19611 @kindex set monitor-prompt@r{, MIPS remote}
19612 @cindex remote monitor prompt
19613 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19614 remote monitor. The default depends on the target:
19624 @item show monitor-prompt
19625 @kindex show monitor-prompt@r{, MIPS remote}
19626 Show the current strings @value{GDBN} expects as the prompt from the
19629 @item set monitor-warnings
19630 @kindex set monitor-warnings@r{, MIPS remote}
19631 Enable or disable monitor warnings about hardware breakpoints. This
19632 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19633 display warning messages whose codes are returned by the @code{lsi}
19634 PMON monitor for breakpoint commands.
19636 @item show monitor-warnings
19637 @kindex show monitor-warnings@r{, MIPS remote}
19638 Show the current setting of printing monitor warnings.
19640 @item pmon @var{command}
19641 @kindex pmon@r{, MIPS remote}
19642 @cindex send PMON command
19643 This command allows sending an arbitrary @var{command} string to the
19644 monitor. The monitor must be in debug mode for this to work.
19647 @node OpenRISC 1000
19648 @subsection OpenRISC 1000
19649 @cindex OpenRISC 1000
19651 @cindex or1k boards
19652 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19653 about platform and commands.
19657 @kindex target jtag
19658 @item target jtag jtag://@var{host}:@var{port}
19660 Connects to remote JTAG server.
19661 JTAG remote server can be either an or1ksim or JTAG server,
19662 connected via parallel port to the board.
19664 Example: @code{target jtag jtag://localhost:9999}
19667 @item or1ksim @var{command}
19668 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19669 Simulator, proprietary commands can be executed.
19671 @kindex info or1k spr
19672 @item info or1k spr
19673 Displays spr groups.
19675 @item info or1k spr @var{group}
19676 @itemx info or1k spr @var{groupno}
19677 Displays register names in selected group.
19679 @item info or1k spr @var{group} @var{register}
19680 @itemx info or1k spr @var{register}
19681 @itemx info or1k spr @var{groupno} @var{registerno}
19682 @itemx info or1k spr @var{registerno}
19683 Shows information about specified spr register.
19686 @item spr @var{group} @var{register} @var{value}
19687 @itemx spr @var{register @var{value}}
19688 @itemx spr @var{groupno} @var{registerno @var{value}}
19689 @itemx spr @var{registerno @var{value}}
19690 Writes @var{value} to specified spr register.
19693 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19694 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19695 program execution and is thus much faster. Hardware breakpoints/watchpoint
19696 triggers can be set using:
19699 Load effective address/data
19701 Store effective address/data
19703 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19708 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19709 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19711 @code{htrace} commands:
19712 @cindex OpenRISC 1000 htrace
19715 @item hwatch @var{conditional}
19716 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19717 or Data. For example:
19719 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19721 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19725 Display information about current HW trace configuration.
19727 @item htrace trigger @var{conditional}
19728 Set starting criteria for HW trace.
19730 @item htrace qualifier @var{conditional}
19731 Set acquisition qualifier for HW trace.
19733 @item htrace stop @var{conditional}
19734 Set HW trace stopping criteria.
19736 @item htrace record [@var{data}]*
19737 Selects the data to be recorded, when qualifier is met and HW trace was
19740 @item htrace enable
19741 @itemx htrace disable
19742 Enables/disables the HW trace.
19744 @item htrace rewind [@var{filename}]
19745 Clears currently recorded trace data.
19747 If filename is specified, new trace file is made and any newly collected data
19748 will be written there.
19750 @item htrace print [@var{start} [@var{len}]]
19751 Prints trace buffer, using current record configuration.
19753 @item htrace mode continuous
19754 Set continuous trace mode.
19756 @item htrace mode suspend
19757 Set suspend trace mode.
19761 @node PowerPC Embedded
19762 @subsection PowerPC Embedded
19764 @cindex DVC register
19765 @value{GDBN} supports using the DVC (Data Value Compare) register to
19766 implement in hardware simple hardware watchpoint conditions of the form:
19769 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19770 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19773 The DVC register will be automatically used when @value{GDBN} detects
19774 such pattern in a condition expression, and the created watchpoint uses one
19775 debug register (either the @code{exact-watchpoints} option is on and the
19776 variable is scalar, or the variable has a length of one byte). This feature
19777 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19780 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19781 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19782 in which case watchpoints using only one debug register are created when
19783 watching variables of scalar types.
19785 You can create an artificial array to watch an arbitrary memory
19786 region using one of the following commands (@pxref{Expressions}):
19789 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19790 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19793 PowerPC embedded processors support masked watchpoints. See the discussion
19794 about the @code{mask} argument in @ref{Set Watchpoints}.
19796 @cindex ranged breakpoint
19797 PowerPC embedded processors support hardware accelerated
19798 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19799 the inferior whenever it executes an instruction at any address within
19800 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19801 use the @code{break-range} command.
19803 @value{GDBN} provides the following PowerPC-specific commands:
19806 @kindex break-range
19807 @item break-range @var{start-location}, @var{end-location}
19808 Set a breakpoint for an address range.
19809 @var{start-location} and @var{end-location} can specify a function name,
19810 a line number, an offset of lines from the current line or from the start
19811 location, or an address of an instruction (see @ref{Specify Location},
19812 for a list of all the possible ways to specify a @var{location}.)
19813 The breakpoint will stop execution of the inferior whenever it
19814 executes an instruction at any address within the specified range,
19815 (including @var{start-location} and @var{end-location}.)
19817 @kindex set powerpc
19818 @item set powerpc soft-float
19819 @itemx show powerpc soft-float
19820 Force @value{GDBN} to use (or not use) a software floating point calling
19821 convention. By default, @value{GDBN} selects the calling convention based
19822 on the selected architecture and the provided executable file.
19824 @item set powerpc vector-abi
19825 @itemx show powerpc vector-abi
19826 Force @value{GDBN} to use the specified calling convention for vector
19827 arguments and return values. The valid options are @samp{auto};
19828 @samp{generic}, to avoid vector registers even if they are present;
19829 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19830 registers. By default, @value{GDBN} selects the calling convention
19831 based on the selected architecture and the provided executable file.
19833 @item set powerpc exact-watchpoints
19834 @itemx show powerpc exact-watchpoints
19835 Allow @value{GDBN} to use only one debug register when watching a variable
19836 of scalar type, thus assuming that the variable is accessed through the
19837 address of its first byte.
19839 @kindex target dink32
19840 @item target dink32 @var{dev}
19841 DINK32 ROM monitor.
19843 @kindex target ppcbug
19844 @item target ppcbug @var{dev}
19845 @kindex target ppcbug1
19846 @item target ppcbug1 @var{dev}
19847 PPCBUG ROM monitor for PowerPC.
19850 @item target sds @var{dev}
19851 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19854 @cindex SDS protocol
19855 The following commands specific to the SDS protocol are supported
19859 @item set sdstimeout @var{nsec}
19860 @kindex set sdstimeout
19861 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19862 default is 2 seconds.
19864 @item show sdstimeout
19865 @kindex show sdstimeout
19866 Show the current value of the SDS timeout.
19868 @item sds @var{command}
19869 @kindex sds@r{, a command}
19870 Send the specified @var{command} string to the SDS monitor.
19875 @subsection HP PA Embedded
19879 @kindex target op50n
19880 @item target op50n @var{dev}
19881 OP50N monitor, running on an OKI HPPA board.
19883 @kindex target w89k
19884 @item target w89k @var{dev}
19885 W89K monitor, running on a Winbond HPPA board.
19890 @subsection Tsqware Sparclet
19894 @value{GDBN} enables developers to debug tasks running on
19895 Sparclet targets from a Unix host.
19896 @value{GDBN} uses code that runs on
19897 both the Unix host and on the Sparclet target. The program
19898 @code{@value{GDBP}} is installed and executed on the Unix host.
19901 @item remotetimeout @var{args}
19902 @kindex remotetimeout
19903 @value{GDBN} supports the option @code{remotetimeout}.
19904 This option is set by the user, and @var{args} represents the number of
19905 seconds @value{GDBN} waits for responses.
19908 @cindex compiling, on Sparclet
19909 When compiling for debugging, include the options @samp{-g} to get debug
19910 information and @samp{-Ttext} to relocate the program to where you wish to
19911 load it on the target. You may also want to add the options @samp{-n} or
19912 @samp{-N} in order to reduce the size of the sections. Example:
19915 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19918 You can use @code{objdump} to verify that the addresses are what you intended:
19921 sparclet-aout-objdump --headers --syms prog
19924 @cindex running, on Sparclet
19926 your Unix execution search path to find @value{GDBN}, you are ready to
19927 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19928 (or @code{sparclet-aout-gdb}, depending on your installation).
19930 @value{GDBN} comes up showing the prompt:
19937 * Sparclet File:: Setting the file to debug
19938 * Sparclet Connection:: Connecting to Sparclet
19939 * Sparclet Download:: Sparclet download
19940 * Sparclet Execution:: Running and debugging
19943 @node Sparclet File
19944 @subsubsection Setting File to Debug
19946 The @value{GDBN} command @code{file} lets you choose with program to debug.
19949 (gdbslet) file prog
19953 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19954 @value{GDBN} locates
19955 the file by searching the directories listed in the command search
19957 If the file was compiled with debug information (option @samp{-g}), source
19958 files will be searched as well.
19959 @value{GDBN} locates
19960 the source files by searching the directories listed in the directory search
19961 path (@pxref{Environment, ,Your Program's Environment}).
19963 to find a file, it displays a message such as:
19966 prog: No such file or directory.
19969 When this happens, add the appropriate directories to the search paths with
19970 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19971 @code{target} command again.
19973 @node Sparclet Connection
19974 @subsubsection Connecting to Sparclet
19976 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19977 To connect to a target on serial port ``@code{ttya}'', type:
19980 (gdbslet) target sparclet /dev/ttya
19981 Remote target sparclet connected to /dev/ttya
19982 main () at ../prog.c:3
19986 @value{GDBN} displays messages like these:
19992 @node Sparclet Download
19993 @subsubsection Sparclet Download
19995 @cindex download to Sparclet
19996 Once connected to the Sparclet target,
19997 you can use the @value{GDBN}
19998 @code{load} command to download the file from the host to the target.
19999 The file name and load offset should be given as arguments to the @code{load}
20001 Since the file format is aout, the program must be loaded to the starting
20002 address. You can use @code{objdump} to find out what this value is. The load
20003 offset is an offset which is added to the VMA (virtual memory address)
20004 of each of the file's sections.
20005 For instance, if the program
20006 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20007 and bss at 0x12010170, in @value{GDBN}, type:
20010 (gdbslet) load prog 0x12010000
20011 Loading section .text, size 0xdb0 vma 0x12010000
20014 If the code is loaded at a different address then what the program was linked
20015 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20016 to tell @value{GDBN} where to map the symbol table.
20018 @node Sparclet Execution
20019 @subsubsection Running and Debugging
20021 @cindex running and debugging Sparclet programs
20022 You can now begin debugging the task using @value{GDBN}'s execution control
20023 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20024 manual for the list of commands.
20028 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20030 Starting program: prog
20031 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20032 3 char *symarg = 0;
20034 4 char *execarg = "hello!";
20039 @subsection Fujitsu Sparclite
20043 @kindex target sparclite
20044 @item target sparclite @var{dev}
20045 Fujitsu sparclite boards, used only for the purpose of loading.
20046 You must use an additional command to debug the program.
20047 For example: target remote @var{dev} using @value{GDBN} standard
20053 @subsection Zilog Z8000
20056 @cindex simulator, Z8000
20057 @cindex Zilog Z8000 simulator
20059 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20062 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20063 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20064 segmented variant). The simulator recognizes which architecture is
20065 appropriate by inspecting the object code.
20068 @item target sim @var{args}
20070 @kindex target sim@r{, with Z8000}
20071 Debug programs on a simulated CPU. If the simulator supports setup
20072 options, specify them via @var{args}.
20076 After specifying this target, you can debug programs for the simulated
20077 CPU in the same style as programs for your host computer; use the
20078 @code{file} command to load a new program image, the @code{run} command
20079 to run your program, and so on.
20081 As well as making available all the usual machine registers
20082 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20083 additional items of information as specially named registers:
20088 Counts clock-ticks in the simulator.
20091 Counts instructions run in the simulator.
20094 Execution time in 60ths of a second.
20098 You can refer to these values in @value{GDBN} expressions with the usual
20099 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20100 conditional breakpoint that suspends only after at least 5000
20101 simulated clock ticks.
20104 @subsection Atmel AVR
20107 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20108 following AVR-specific commands:
20111 @item info io_registers
20112 @kindex info io_registers@r{, AVR}
20113 @cindex I/O registers (Atmel AVR)
20114 This command displays information about the AVR I/O registers. For
20115 each register, @value{GDBN} prints its number and value.
20122 When configured for debugging CRIS, @value{GDBN} provides the
20123 following CRIS-specific commands:
20126 @item set cris-version @var{ver}
20127 @cindex CRIS version
20128 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20129 The CRIS version affects register names and sizes. This command is useful in
20130 case autodetection of the CRIS version fails.
20132 @item show cris-version
20133 Show the current CRIS version.
20135 @item set cris-dwarf2-cfi
20136 @cindex DWARF-2 CFI and CRIS
20137 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20138 Change to @samp{off} when using @code{gcc-cris} whose version is below
20141 @item show cris-dwarf2-cfi
20142 Show the current state of using DWARF-2 CFI.
20144 @item set cris-mode @var{mode}
20146 Set the current CRIS mode to @var{mode}. It should only be changed when
20147 debugging in guru mode, in which case it should be set to
20148 @samp{guru} (the default is @samp{normal}).
20150 @item show cris-mode
20151 Show the current CRIS mode.
20155 @subsection Renesas Super-H
20158 For the Renesas Super-H processor, @value{GDBN} provides these
20163 @kindex regs@r{, Super-H}
20164 Show the values of all Super-H registers.
20166 @item set sh calling-convention @var{convention}
20167 @kindex set sh calling-convention
20168 Set the calling-convention used when calling functions from @value{GDBN}.
20169 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20170 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20171 convention. If the DWARF-2 information of the called function specifies
20172 that the function follows the Renesas calling convention, the function
20173 is called using the Renesas calling convention. If the calling convention
20174 is set to @samp{renesas}, the Renesas calling convention is always used,
20175 regardless of the DWARF-2 information. This can be used to override the
20176 default of @samp{gcc} if debug information is missing, or the compiler
20177 does not emit the DWARF-2 calling convention entry for a function.
20179 @item show sh calling-convention
20180 @kindex show sh calling-convention
20181 Show the current calling convention setting.
20186 @node Architectures
20187 @section Architectures
20189 This section describes characteristics of architectures that affect
20190 all uses of @value{GDBN} with the architecture, both native and cross.
20197 * HPPA:: HP PA architecture
20198 * SPU:: Cell Broadband Engine SPU architecture
20203 @subsection x86 Architecture-specific Issues
20206 @item set struct-convention @var{mode}
20207 @kindex set struct-convention
20208 @cindex struct return convention
20209 @cindex struct/union returned in registers
20210 Set the convention used by the inferior to return @code{struct}s and
20211 @code{union}s from functions to @var{mode}. Possible values of
20212 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20213 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20214 are returned on the stack, while @code{"reg"} means that a
20215 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20216 be returned in a register.
20218 @item show struct-convention
20219 @kindex show struct-convention
20220 Show the current setting of the convention to return @code{struct}s
20229 @kindex set rstack_high_address
20230 @cindex AMD 29K register stack
20231 @cindex register stack, AMD29K
20232 @item set rstack_high_address @var{address}
20233 On AMD 29000 family processors, registers are saved in a separate
20234 @dfn{register stack}. There is no way for @value{GDBN} to determine the
20235 extent of this stack. Normally, @value{GDBN} just assumes that the
20236 stack is ``large enough''. This may result in @value{GDBN} referencing
20237 memory locations that do not exist. If necessary, you can get around
20238 this problem by specifying the ending address of the register stack with
20239 the @code{set rstack_high_address} command. The argument should be an
20240 address, which you probably want to precede with @samp{0x} to specify in
20243 @kindex show rstack_high_address
20244 @item show rstack_high_address
20245 Display the current limit of the register stack, on AMD 29000 family
20253 See the following section.
20258 @cindex stack on Alpha
20259 @cindex stack on MIPS
20260 @cindex Alpha stack
20262 Alpha- and MIPS-based computers use an unusual stack frame, which
20263 sometimes requires @value{GDBN} to search backward in the object code to
20264 find the beginning of a function.
20266 @cindex response time, MIPS debugging
20267 To improve response time (especially for embedded applications, where
20268 @value{GDBN} may be restricted to a slow serial line for this search)
20269 you may want to limit the size of this search, using one of these
20273 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
20274 @item set heuristic-fence-post @var{limit}
20275 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20276 search for the beginning of a function. A value of @var{0} (the
20277 default) means there is no limit. However, except for @var{0}, the
20278 larger the limit the more bytes @code{heuristic-fence-post} must search
20279 and therefore the longer it takes to run. You should only need to use
20280 this command when debugging a stripped executable.
20282 @item show heuristic-fence-post
20283 Display the current limit.
20287 These commands are available @emph{only} when @value{GDBN} is configured
20288 for debugging programs on Alpha or MIPS processors.
20290 Several MIPS-specific commands are available when debugging MIPS
20294 @item set mips abi @var{arg}
20295 @kindex set mips abi
20296 @cindex set ABI for MIPS
20297 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
20298 values of @var{arg} are:
20302 The default ABI associated with the current binary (this is the
20312 @item show mips abi
20313 @kindex show mips abi
20314 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20317 @itemx show mipsfpu
20318 @xref{MIPS Embedded, set mipsfpu}.
20320 @item set mips mask-address @var{arg}
20321 @kindex set mips mask-address
20322 @cindex MIPS addresses, masking
20323 This command determines whether the most-significant 32 bits of 64-bit
20324 MIPS addresses are masked off. The argument @var{arg} can be
20325 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20326 setting, which lets @value{GDBN} determine the correct value.
20328 @item show mips mask-address
20329 @kindex show mips mask-address
20330 Show whether the upper 32 bits of MIPS addresses are masked off or
20333 @item set remote-mips64-transfers-32bit-regs
20334 @kindex set remote-mips64-transfers-32bit-regs
20335 This command controls compatibility with 64-bit MIPS targets that
20336 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20337 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20338 and 64 bits for other registers, set this option to @samp{on}.
20340 @item show remote-mips64-transfers-32bit-regs
20341 @kindex show remote-mips64-transfers-32bit-regs
20342 Show the current setting of compatibility with older MIPS 64 targets.
20344 @item set debug mips
20345 @kindex set debug mips
20346 This command turns on and off debugging messages for the MIPS-specific
20347 target code in @value{GDBN}.
20349 @item show debug mips
20350 @kindex show debug mips
20351 Show the current setting of MIPS debugging messages.
20357 @cindex HPPA support
20359 When @value{GDBN} is debugging the HP PA architecture, it provides the
20360 following special commands:
20363 @item set debug hppa
20364 @kindex set debug hppa
20365 This command determines whether HPPA architecture-specific debugging
20366 messages are to be displayed.
20368 @item show debug hppa
20369 Show whether HPPA debugging messages are displayed.
20371 @item maint print unwind @var{address}
20372 @kindex maint print unwind@r{, HPPA}
20373 This command displays the contents of the unwind table entry at the
20374 given @var{address}.
20380 @subsection Cell Broadband Engine SPU architecture
20381 @cindex Cell Broadband Engine
20384 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20385 it provides the following special commands:
20388 @item info spu event
20390 Display SPU event facility status. Shows current event mask
20391 and pending event status.
20393 @item info spu signal
20394 Display SPU signal notification facility status. Shows pending
20395 signal-control word and signal notification mode of both signal
20396 notification channels.
20398 @item info spu mailbox
20399 Display SPU mailbox facility status. Shows all pending entries,
20400 in order of processing, in each of the SPU Write Outbound,
20401 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20404 Display MFC DMA status. Shows all pending commands in the MFC
20405 DMA queue. For each entry, opcode, tag, class IDs, effective
20406 and local store addresses and transfer size are shown.
20408 @item info spu proxydma
20409 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20410 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20411 and local store addresses and transfer size are shown.
20415 When @value{GDBN} is debugging a combined PowerPC/SPU application
20416 on the Cell Broadband Engine, it provides in addition the following
20420 @item set spu stop-on-load @var{arg}
20422 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20423 will give control to the user when a new SPE thread enters its @code{main}
20424 function. The default is @code{off}.
20426 @item show spu stop-on-load
20428 Show whether to stop for new SPE threads.
20430 @item set spu auto-flush-cache @var{arg}
20431 Set whether to automatically flush the software-managed cache. When set to
20432 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20433 cache to be flushed whenever SPE execution stops. This provides a consistent
20434 view of PowerPC memory that is accessed via the cache. If an application
20435 does not use the software-managed cache, this option has no effect.
20437 @item show spu auto-flush-cache
20438 Show whether to automatically flush the software-managed cache.
20443 @subsection PowerPC
20444 @cindex PowerPC architecture
20446 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20447 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20448 numbers stored in the floating point registers. These values must be stored
20449 in two consecutive registers, always starting at an even register like
20450 @code{f0} or @code{f2}.
20452 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20453 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20454 @code{f2} and @code{f3} for @code{$dl1} and so on.
20456 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20457 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20460 @node Controlling GDB
20461 @chapter Controlling @value{GDBN}
20463 You can alter the way @value{GDBN} interacts with you by using the
20464 @code{set} command. For commands controlling how @value{GDBN} displays
20465 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20470 * Editing:: Command editing
20471 * Command History:: Command history
20472 * Screen Size:: Screen size
20473 * Numbers:: Numbers
20474 * ABI:: Configuring the current ABI
20475 * Auto-loading:: Automatically loading associated files
20476 * Messages/Warnings:: Optional warnings and messages
20477 * Debugging Output:: Optional messages about internal happenings
20478 * Other Misc Settings:: Other Miscellaneous Settings
20486 @value{GDBN} indicates its readiness to read a command by printing a string
20487 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20488 can change the prompt string with the @code{set prompt} command. For
20489 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20490 the prompt in one of the @value{GDBN} sessions so that you can always tell
20491 which one you are talking to.
20493 @emph{Note:} @code{set prompt} does not add a space for you after the
20494 prompt you set. This allows you to set a prompt which ends in a space
20495 or a prompt that does not.
20499 @item set prompt @var{newprompt}
20500 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20502 @kindex show prompt
20504 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20507 Versions of @value{GDBN} that ship with Python scripting enabled have
20508 prompt extensions. The commands for interacting with these extensions
20512 @kindex set extended-prompt
20513 @item set extended-prompt @var{prompt}
20514 Set an extended prompt that allows for substitutions.
20515 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20516 substitution. Any escape sequences specified as part of the prompt
20517 string are replaced with the corresponding strings each time the prompt
20523 set extended-prompt Current working directory: \w (gdb)
20526 Note that when an extended-prompt is set, it takes control of the
20527 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20529 @kindex show extended-prompt
20530 @item show extended-prompt
20531 Prints the extended prompt. Any escape sequences specified as part of
20532 the prompt string with @code{set extended-prompt}, are replaced with the
20533 corresponding strings each time the prompt is displayed.
20537 @section Command Editing
20539 @cindex command line editing
20541 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20542 @sc{gnu} library provides consistent behavior for programs which provide a
20543 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20544 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20545 substitution, and a storage and recall of command history across
20546 debugging sessions.
20548 You may control the behavior of command line editing in @value{GDBN} with the
20549 command @code{set}.
20552 @kindex set editing
20555 @itemx set editing on
20556 Enable command line editing (enabled by default).
20558 @item set editing off
20559 Disable command line editing.
20561 @kindex show editing
20563 Show whether command line editing is enabled.
20566 @ifset SYSTEM_READLINE
20567 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20569 @ifclear SYSTEM_READLINE
20570 @xref{Command Line Editing},
20572 for more details about the Readline
20573 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20574 encouraged to read that chapter.
20576 @node Command History
20577 @section Command History
20578 @cindex command history
20580 @value{GDBN} can keep track of the commands you type during your
20581 debugging sessions, so that you can be certain of precisely what
20582 happened. Use these commands to manage the @value{GDBN} command
20585 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20586 package, to provide the history facility.
20587 @ifset SYSTEM_READLINE
20588 @xref{Using History Interactively, , , history, GNU History Library},
20590 @ifclear SYSTEM_READLINE
20591 @xref{Using History Interactively},
20593 for the detailed description of the History library.
20595 To issue a command to @value{GDBN} without affecting certain aspects of
20596 the state which is seen by users, prefix it with @samp{server }
20597 (@pxref{Server Prefix}). This
20598 means that this command will not affect the command history, nor will it
20599 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20600 pressed on a line by itself.
20602 @cindex @code{server}, command prefix
20603 The server prefix does not affect the recording of values into the value
20604 history; to print a value without recording it into the value history,
20605 use the @code{output} command instead of the @code{print} command.
20607 Here is the description of @value{GDBN} commands related to command
20611 @cindex history substitution
20612 @cindex history file
20613 @kindex set history filename
20614 @cindex @env{GDBHISTFILE}, environment variable
20615 @item set history filename @var{fname}
20616 Set the name of the @value{GDBN} command history file to @var{fname}.
20617 This is the file where @value{GDBN} reads an initial command history
20618 list, and where it writes the command history from this session when it
20619 exits. You can access this list through history expansion or through
20620 the history command editing characters listed below. This file defaults
20621 to the value of the environment variable @code{GDBHISTFILE}, or to
20622 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20625 @cindex save command history
20626 @kindex set history save
20627 @item set history save
20628 @itemx set history save on
20629 Record command history in a file, whose name may be specified with the
20630 @code{set history filename} command. By default, this option is disabled.
20632 @item set history save off
20633 Stop recording command history in a file.
20635 @cindex history size
20636 @kindex set history size
20637 @cindex @env{HISTSIZE}, environment variable
20638 @item set history size @var{size}
20639 Set the number of commands which @value{GDBN} keeps in its history list.
20640 This defaults to the value of the environment variable
20641 @code{HISTSIZE}, or to 256 if this variable is not set.
20644 History expansion assigns special meaning to the character @kbd{!}.
20645 @ifset SYSTEM_READLINE
20646 @xref{Event Designators, , , history, GNU History Library},
20648 @ifclear SYSTEM_READLINE
20649 @xref{Event Designators},
20653 @cindex history expansion, turn on/off
20654 Since @kbd{!} is also the logical not operator in C, history expansion
20655 is off by default. If you decide to enable history expansion with the
20656 @code{set history expansion on} command, you may sometimes need to
20657 follow @kbd{!} (when it is used as logical not, in an expression) with
20658 a space or a tab to prevent it from being expanded. The readline
20659 history facilities do not attempt substitution on the strings
20660 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20662 The commands to control history expansion are:
20665 @item set history expansion on
20666 @itemx set history expansion
20667 @kindex set history expansion
20668 Enable history expansion. History expansion is off by default.
20670 @item set history expansion off
20671 Disable history expansion.
20674 @kindex show history
20676 @itemx show history filename
20677 @itemx show history save
20678 @itemx show history size
20679 @itemx show history expansion
20680 These commands display the state of the @value{GDBN} history parameters.
20681 @code{show history} by itself displays all four states.
20686 @kindex show commands
20687 @cindex show last commands
20688 @cindex display command history
20689 @item show commands
20690 Display the last ten commands in the command history.
20692 @item show commands @var{n}
20693 Print ten commands centered on command number @var{n}.
20695 @item show commands +
20696 Print ten commands just after the commands last printed.
20700 @section Screen Size
20701 @cindex size of screen
20702 @cindex pauses in output
20704 Certain commands to @value{GDBN} may produce large amounts of
20705 information output to the screen. To help you read all of it,
20706 @value{GDBN} pauses and asks you for input at the end of each page of
20707 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20708 to discard the remaining output. Also, the screen width setting
20709 determines when to wrap lines of output. Depending on what is being
20710 printed, @value{GDBN} tries to break the line at a readable place,
20711 rather than simply letting it overflow onto the following line.
20713 Normally @value{GDBN} knows the size of the screen from the terminal
20714 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20715 together with the value of the @code{TERM} environment variable and the
20716 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20717 you can override it with the @code{set height} and @code{set
20724 @kindex show height
20725 @item set height @var{lpp}
20727 @itemx set width @var{cpl}
20729 These @code{set} commands specify a screen height of @var{lpp} lines and
20730 a screen width of @var{cpl} characters. The associated @code{show}
20731 commands display the current settings.
20733 If you specify a height of zero lines, @value{GDBN} does not pause during
20734 output no matter how long the output is. This is useful if output is to a
20735 file or to an editor buffer.
20737 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20738 from wrapping its output.
20740 @item set pagination on
20741 @itemx set pagination off
20742 @kindex set pagination
20743 Turn the output pagination on or off; the default is on. Turning
20744 pagination off is the alternative to @code{set height 0}. Note that
20745 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20746 Options, -batch}) also automatically disables pagination.
20748 @item show pagination
20749 @kindex show pagination
20750 Show the current pagination mode.
20755 @cindex number representation
20756 @cindex entering numbers
20758 You can always enter numbers in octal, decimal, or hexadecimal in
20759 @value{GDBN} by the usual conventions: octal numbers begin with
20760 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20761 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20762 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20763 10; likewise, the default display for numbers---when no particular
20764 format is specified---is base 10. You can change the default base for
20765 both input and output with the commands described below.
20768 @kindex set input-radix
20769 @item set input-radix @var{base}
20770 Set the default base for numeric input. Supported choices
20771 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20772 specified either unambiguously or using the current input radix; for
20776 set input-radix 012
20777 set input-radix 10.
20778 set input-radix 0xa
20782 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20783 leaves the input radix unchanged, no matter what it was, since
20784 @samp{10}, being without any leading or trailing signs of its base, is
20785 interpreted in the current radix. Thus, if the current radix is 16,
20786 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20789 @kindex set output-radix
20790 @item set output-radix @var{base}
20791 Set the default base for numeric display. Supported choices
20792 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20793 specified either unambiguously or using the current input radix.
20795 @kindex show input-radix
20796 @item show input-radix
20797 Display the current default base for numeric input.
20799 @kindex show output-radix
20800 @item show output-radix
20801 Display the current default base for numeric display.
20803 @item set radix @r{[}@var{base}@r{]}
20807 These commands set and show the default base for both input and output
20808 of numbers. @code{set radix} sets the radix of input and output to
20809 the same base; without an argument, it resets the radix back to its
20810 default value of 10.
20815 @section Configuring the Current ABI
20817 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20818 application automatically. However, sometimes you need to override its
20819 conclusions. Use these commands to manage @value{GDBN}'s view of the
20826 One @value{GDBN} configuration can debug binaries for multiple operating
20827 system targets, either via remote debugging or native emulation.
20828 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20829 but you can override its conclusion using the @code{set osabi} command.
20830 One example where this is useful is in debugging of binaries which use
20831 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20832 not have the same identifying marks that the standard C library for your
20837 Show the OS ABI currently in use.
20840 With no argument, show the list of registered available OS ABI's.
20842 @item set osabi @var{abi}
20843 Set the current OS ABI to @var{abi}.
20846 @cindex float promotion
20848 Generally, the way that an argument of type @code{float} is passed to a
20849 function depends on whether the function is prototyped. For a prototyped
20850 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20851 according to the architecture's convention for @code{float}. For unprototyped
20852 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20853 @code{double} and then passed.
20855 Unfortunately, some forms of debug information do not reliably indicate whether
20856 a function is prototyped. If @value{GDBN} calls a function that is not marked
20857 as prototyped, it consults @kbd{set coerce-float-to-double}.
20860 @kindex set coerce-float-to-double
20861 @item set coerce-float-to-double
20862 @itemx set coerce-float-to-double on
20863 Arguments of type @code{float} will be promoted to @code{double} when passed
20864 to an unprototyped function. This is the default setting.
20866 @item set coerce-float-to-double off
20867 Arguments of type @code{float} will be passed directly to unprototyped
20870 @kindex show coerce-float-to-double
20871 @item show coerce-float-to-double
20872 Show the current setting of promoting @code{float} to @code{double}.
20876 @kindex show cp-abi
20877 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20878 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20879 used to build your application. @value{GDBN} only fully supports
20880 programs with a single C@t{++} ABI; if your program contains code using
20881 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20882 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20883 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20884 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20885 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20886 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20891 Show the C@t{++} ABI currently in use.
20894 With no argument, show the list of supported C@t{++} ABI's.
20896 @item set cp-abi @var{abi}
20897 @itemx set cp-abi auto
20898 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20902 @section Automatically loading associated files
20903 @cindex auto-loading
20905 @value{GDBN} sometimes reads files with commands and settings automatically,
20906 without being explicitly told so by the user. We call this feature
20907 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
20908 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
20909 results or introduce security risks (e.g., if the file comes from untrusted
20912 For these reasons, @value{GDBN} includes commands and options to let you
20913 control when to auto-load files and which files should be auto-loaded.
20916 @anchor{set auto-load off}
20917 @kindex set auto-load off
20918 @item set auto-load off
20919 Globally disable loading of all auto-loaded files.
20920 You may want to use this command with the @samp{-iex} option
20921 (@pxref{Option -init-eval-command}) such as:
20923 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
20926 Be aware that system init file (@pxref{System-wide configuration})
20927 and init files from your home directory (@pxref{Home Directory Init File})
20928 still get read (as they come from generally trusted directories).
20929 To prevent @value{GDBN} from auto-loading even those init files, use the
20930 @option{-nx} option (@pxref{Mode Options}), in addition to
20931 @code{set auto-load no}.
20933 @anchor{show auto-load}
20934 @kindex show auto-load
20935 @item show auto-load
20936 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
20940 (gdb) show auto-load
20941 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
20942 libthread-db: Auto-loading of inferior specific libthread_db is on.
20943 local-gdbinit: Auto-loading of .gdbinit script from current directory is on.
20944 python-scripts: Auto-loading of Python scripts is on.
20945 safe-path: List of directories from which it is safe to auto-load files
20949 @anchor{info auto-load}
20950 @kindex info auto-load
20951 @item info auto-load
20952 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
20956 (gdb) info auto-load
20959 Yes /home/user/gdb/gdb-gdb.gdb
20960 libthread-db: No auto-loaded libthread-db.
20961 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been loaded.
20964 Yes /home/user/gdb/gdb-gdb.py
20968 These are various kinds of files @value{GDBN} can automatically load:
20972 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
20974 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
20976 @xref{dotdebug_gdb_scripts section},
20977 controlled by @ref{set auto-load python-scripts}.
20979 @xref{Init File in the Current Directory},
20980 controlled by @ref{set auto-load local-gdbinit}.
20982 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
20985 These are @value{GDBN} control commands for the auto-loading:
20987 @multitable @columnfractions .5 .5
20988 @item @xref{set auto-load off}.
20989 @tab Disable auto-loading globally.
20990 @item @xref{show auto-load}.
20991 @tab Show setting of all kinds of files.
20992 @item @xref{info auto-load}.
20993 @tab Show state of all kinds of files.
20994 @item @xref{set auto-load gdb-scripts}.
20995 @tab Control for @value{GDBN} command scripts.
20996 @item @xref{show auto-load gdb-scripts}.
20997 @tab Show setting of @value{GDBN} command scripts.
20998 @item @xref{info auto-load gdb-scripts}.
20999 @tab Show state of @value{GDBN} command scripts.
21000 @item @xref{set auto-load python-scripts}.
21001 @tab Control for @value{GDBN} Python scripts.
21002 @item @xref{show auto-load python-scripts}.
21003 @tab Show setting of @value{GDBN} Python scripts.
21004 @item @xref{info auto-load python-scripts}.
21005 @tab Show state of @value{GDBN} Python scripts.
21006 @item @xref{set auto-load local-gdbinit}.
21007 @tab Control for init file in the current directory.
21008 @item @xref{show auto-load local-gdbinit}.
21009 @tab Show setting of init file in the current directory.
21010 @item @xref{info auto-load local-gdbinit}.
21011 @tab Show state of init file in the current directory.
21012 @item @xref{set auto-load libthread-db}.
21013 @tab Control for thread debugging library.
21014 @item @xref{show auto-load libthread-db}.
21015 @tab Show setting of thread debugging library.
21016 @item @xref{info auto-load libthread-db}.
21017 @tab Show state of thread debugging library.
21018 @item @xref{set auto-load safe-path}.
21019 @tab Control directories trusted for automatic loading.
21020 @item @xref{show auto-load safe-path}.
21021 @tab Show directories trusted for automatic loading.
21022 @item @xref{add-auto-load-safe-path}.
21023 @tab Add directory trusted for automatic loading.
21027 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21028 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21029 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21030 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21031 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21032 @xref{Python Auto-loading}.
21035 @node Init File in the Current Directory
21036 @subsection Automatically loading init file in the current directory
21037 @cindex auto-loading init file in the current directory
21039 By default, @value{GDBN} reads and executes the canned sequences of commands
21040 from init file (if any) in the current working directory,
21041 see @ref{Init File in the Current Directory during Startup}.
21044 @anchor{set auto-load local-gdbinit}
21045 @kindex set auto-load local-gdbinit
21046 @item set auto-load local-gdbinit [on|off]
21047 Enable or disable the auto-loading of canned sequences of commands
21048 (@pxref{Sequences}) found in init file in the current directory.
21050 @anchor{show auto-load local-gdbinit}
21051 @kindex show auto-load local-gdbinit
21052 @item show auto-load local-gdbinit
21053 Show whether auto-loading of canned sequences of commands from init file in the
21054 current directory is enabled or disabled.
21056 @anchor{info auto-load local-gdbinit}
21057 @kindex info auto-load local-gdbinit
21058 @item info auto-load local-gdbinit
21059 Print whether canned sequences of commands from init file in the
21060 current directory have been auto-loaded.
21063 @node libthread_db.so.1 file
21064 @subsection Automatically loading thread debugging library
21065 @cindex auto-loading libthread_db.so.1
21067 This feature is currently present only on @sc{gnu}/Linux native hosts.
21069 @value{GDBN} reads in some cases thread debugging library from places specific
21070 to the inferior (@pxref{set libthread-db-search-path}).
21072 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21073 without checking this @samp{set auto-load libthread-db} switch as system
21074 libraries have to be trusted in general. In all other cases of
21075 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21076 auto-load libthread-db} is enabled before trying to open such thread debugging
21080 @anchor{set auto-load libthread-db}
21081 @kindex set auto-load libthread-db
21082 @item set auto-load libthread-db [on|off]
21083 Enable or disable the auto-loading of inferior specific thread debugging library.
21085 @anchor{show auto-load libthread-db}
21086 @kindex show auto-load libthread-db
21087 @item show auto-load libthread-db
21088 Show whether auto-loading of inferior specific thread debugging library is
21089 enabled or disabled.
21091 @anchor{info auto-load libthread-db}
21092 @kindex info auto-load libthread-db
21093 @item info auto-load libthread-db
21094 Print the list of all loaded inferior specific thread debugging libraries and
21095 for each such library print list of inferior @var{pid}s using it.
21098 @node objfile-gdb.gdb file
21099 @subsection The @file{@var{objfile}-gdb.gdb} file
21100 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21102 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21103 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21104 auto-load gdb-scripts} is set to @samp{on}.
21106 For more background refer to the similar Python scripts auto-loading
21107 description (@pxref{objfile-gdb.py file}).
21110 @anchor{set auto-load gdb-scripts}
21111 @kindex set auto-load gdb-scripts
21112 @item set auto-load gdb-scripts [on|off]
21113 Enable or disable the auto-loading of canned sequences of commands scripts.
21115 @anchor{show auto-load gdb-scripts}
21116 @kindex show auto-load gdb-scripts
21117 @item show auto-load gdb-scripts
21118 Show whether auto-loading of canned sequences of commands scripts is enabled or
21121 @anchor{info auto-load gdb-scripts}
21122 @kindex info auto-load gdb-scripts
21123 @cindex print list of auto-loaded canned sequences of commands scripts
21124 @item info auto-load gdb-scripts [@var{regexp}]
21125 Print the list of all canned sequences of commands scripts that @value{GDBN}
21129 If @var{regexp} is supplied only canned sequences of commands scripts with
21130 matching names are printed.
21132 @node Auto-loading safe path
21133 @subsection Security restriction for auto-loading
21134 @cindex auto-loading safe-path
21136 As the files of inferior can come from untrusted source (such as submitted by
21137 an application user) @value{GDBN} does not always load any files automatically.
21138 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21139 directories trusted for loading files not explicitly requested by user.
21141 If the path is not set properly you will see a warning and the file will not
21146 Reading symbols from /home/user/gdb/gdb...done.
21147 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21148 declined by your `auto-load safe-path' set to "/usr/local".
21149 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21150 declined by your `auto-load safe-path' set to "/usr/local".
21153 The list of trusted directories is controlled by the following commands:
21156 @anchor{set auto-load safe-path}
21157 @kindex set auto-load safe-path
21158 @item set auto-load safe-path @var{directories}
21159 Set the list of directories (and their subdirectories) trusted for automatic
21160 loading and execution of scripts. You can also enter a specific trusted file.
21161 The list of directories uses directory separator (@samp{:} on GNU and Unix
21162 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21163 to the @env{PATH} environment variable.
21165 @anchor{show auto-load safe-path}
21166 @kindex show auto-load safe-path
21167 @item show auto-load safe-path
21168 Show the list of directories trusted for automatic loading and execution of
21171 @anchor{add-auto-load-safe-path}
21172 @kindex add-auto-load-safe-path
21173 @item add-auto-load-safe-path
21174 Add an entry (or list of entries) the list of directories trusted for automatic
21175 loading and execution of scripts. Multiple entries may be delimited by the
21176 host platform directory separator in use.
21179 Setting this variable to an empty string disables this security protection.
21180 This variable is supposed to be set to the system directories writable by the
21181 system superuser only. Users can add their source directories in init files in
21182 their home directories (@pxref{Home Directory Init File}). See also deprecated
21183 init file in the current directory
21184 (@pxref{Init File in the Current Directory during Startup}).
21186 To force @value{GDBN} to load the files it declined to load in the previous
21187 example, you could use one of the following ways:
21190 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21191 Specify this trusted directory (or a file) as additional component of the list.
21192 You have to specify also any existing directories displayed by
21193 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21195 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21196 Specify this directory as in the previous case but just for a single
21197 @value{GDBN} session.
21199 @item @kbd{gdb -iex "set auto-load safe-path" @dots{}}
21200 Disable auto-loading safety for a single @value{GDBN} session.
21201 This assumes all the files you debug during this @value{GDBN} session will come
21202 from trusted sources.
21204 @item @kbd{./configure --without-auto-load-safe-path}
21205 During compilation of @value{GDBN} you may disable any auto-loading safety.
21206 This assumes all the files you will ever debug with this @value{GDBN} come from
21210 On the other hand you can also explicitly forbid automatic files loading which
21211 also suppresses any such warning messages:
21214 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21215 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21217 @item @file{~/.gdbinit}: @samp{set auto-load no}
21218 Disable auto-loading globally for the user
21219 (@pxref{Home Directory Init File}). While it is improbable, you could also
21220 use system init file instead (@pxref{System-wide configuration}).
21223 This setting applies to the file names as entered by user. If no entry matches
21224 @value{GDBN} tries as a last resort to also resolve all the file names into
21225 their canonical form (typically resolving symbolic links) and compare the
21226 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21227 own before starting the comparison so a canonical form of directories is
21228 recommended to be entered.
21230 @node Auto-loading verbose mode
21231 @subsection Displaying files tried for auto-load
21232 @cindex auto-loading verbose mode
21234 For better visibility of all the file locations where you can place scripts to
21235 be auto-loaded with inferior --- or to protect yourself against accidental
21236 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21237 all the files attempted to be loaded. Both existing and non-existing files may
21240 For example the list of directories from which it is safe to auto-load files
21241 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21242 may not be too obvious while setting it up.
21245 (gdb) set debug auto-load on
21246 (gdb) file ~/src/t/true
21247 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21248 for objfile "/tmp/true".
21249 auto-load: Updating directories of "/usr:/opt".
21250 auto-load: Using directory "/usr".
21251 auto-load: Using directory "/opt".
21252 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21253 by your `auto-load safe-path' set to "/usr:/opt".
21257 @anchor{set debug auto-load}
21258 @kindex set debug auto-load
21259 @item set debug auto-load [on|off]
21260 Set whether to print the filenames attempted to be auto-loaded.
21262 @anchor{show debug auto-load}
21263 @kindex show debug auto-load
21264 @item show debug auto-load
21265 Show whether printing of the filenames attempted to be auto-loaded is turned
21269 @node Messages/Warnings
21270 @section Optional Warnings and Messages
21272 @cindex verbose operation
21273 @cindex optional warnings
21274 By default, @value{GDBN} is silent about its inner workings. If you are
21275 running on a slow machine, you may want to use the @code{set verbose}
21276 command. This makes @value{GDBN} tell you when it does a lengthy
21277 internal operation, so you will not think it has crashed.
21279 Currently, the messages controlled by @code{set verbose} are those
21280 which announce that the symbol table for a source file is being read;
21281 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21284 @kindex set verbose
21285 @item set verbose on
21286 Enables @value{GDBN} output of certain informational messages.
21288 @item set verbose off
21289 Disables @value{GDBN} output of certain informational messages.
21291 @kindex show verbose
21293 Displays whether @code{set verbose} is on or off.
21296 By default, if @value{GDBN} encounters bugs in the symbol table of an
21297 object file, it is silent; but if you are debugging a compiler, you may
21298 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21303 @kindex set complaints
21304 @item set complaints @var{limit}
21305 Permits @value{GDBN} to output @var{limit} complaints about each type of
21306 unusual symbols before becoming silent about the problem. Set
21307 @var{limit} to zero to suppress all complaints; set it to a large number
21308 to prevent complaints from being suppressed.
21310 @kindex show complaints
21311 @item show complaints
21312 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21316 @anchor{confirmation requests}
21317 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21318 lot of stupid questions to confirm certain commands. For example, if
21319 you try to run a program which is already running:
21323 The program being debugged has been started already.
21324 Start it from the beginning? (y or n)
21327 If you are willing to unflinchingly face the consequences of your own
21328 commands, you can disable this ``feature'':
21332 @kindex set confirm
21334 @cindex confirmation
21335 @cindex stupid questions
21336 @item set confirm off
21337 Disables confirmation requests. Note that running @value{GDBN} with
21338 the @option{--batch} option (@pxref{Mode Options, -batch}) also
21339 automatically disables confirmation requests.
21341 @item set confirm on
21342 Enables confirmation requests (the default).
21344 @kindex show confirm
21346 Displays state of confirmation requests.
21350 @cindex command tracing
21351 If you need to debug user-defined commands or sourced files you may find it
21352 useful to enable @dfn{command tracing}. In this mode each command will be
21353 printed as it is executed, prefixed with one or more @samp{+} symbols, the
21354 quantity denoting the call depth of each command.
21357 @kindex set trace-commands
21358 @cindex command scripts, debugging
21359 @item set trace-commands on
21360 Enable command tracing.
21361 @item set trace-commands off
21362 Disable command tracing.
21363 @item show trace-commands
21364 Display the current state of command tracing.
21367 @node Debugging Output
21368 @section Optional Messages about Internal Happenings
21369 @cindex optional debugging messages
21371 @value{GDBN} has commands that enable optional debugging messages from
21372 various @value{GDBN} subsystems; normally these commands are of
21373 interest to @value{GDBN} maintainers, or when reporting a bug. This
21374 section documents those commands.
21377 @kindex set exec-done-display
21378 @item set exec-done-display
21379 Turns on or off the notification of asynchronous commands'
21380 completion. When on, @value{GDBN} will print a message when an
21381 asynchronous command finishes its execution. The default is off.
21382 @kindex show exec-done-display
21383 @item show exec-done-display
21384 Displays the current setting of asynchronous command completion
21387 @cindex gdbarch debugging info
21388 @cindex architecture debugging info
21389 @item set debug arch
21390 Turns on or off display of gdbarch debugging info. The default is off
21392 @item show debug arch
21393 Displays the current state of displaying gdbarch debugging info.
21394 @item set debug aix-thread
21395 @cindex AIX threads
21396 Display debugging messages about inner workings of the AIX thread
21398 @item show debug aix-thread
21399 Show the current state of AIX thread debugging info display.
21400 @item set debug check-physname
21402 Check the results of the ``physname'' computation. When reading DWARF
21403 debugging information for C@t{++}, @value{GDBN} attempts to compute
21404 each entity's name. @value{GDBN} can do this computation in two
21405 different ways, depending on exactly what information is present.
21406 When enabled, this setting causes @value{GDBN} to compute the names
21407 both ways and display any discrepancies.
21408 @item show debug check-physname
21409 Show the current state of ``physname'' checking.
21410 @item set debug dwarf2-die
21411 @cindex DWARF2 DIEs
21412 Dump DWARF2 DIEs after they are read in.
21413 The value is the number of nesting levels to print.
21414 A value of zero turns off the display.
21415 @item show debug dwarf2-die
21416 Show the current state of DWARF2 DIE debugging.
21417 @item set debug displaced
21418 @cindex displaced stepping debugging info
21419 Turns on or off display of @value{GDBN} debugging info for the
21420 displaced stepping support. The default is off.
21421 @item show debug displaced
21422 Displays the current state of displaying @value{GDBN} debugging info
21423 related to displaced stepping.
21424 @item set debug event
21425 @cindex event debugging info
21426 Turns on or off display of @value{GDBN} event debugging info. The
21428 @item show debug event
21429 Displays the current state of displaying @value{GDBN} event debugging
21431 @item set debug expression
21432 @cindex expression debugging info
21433 Turns on or off display of debugging info about @value{GDBN}
21434 expression parsing. The default is off.
21435 @item show debug expression
21436 Displays the current state of displaying debugging info about
21437 @value{GDBN} expression parsing.
21438 @item set debug frame
21439 @cindex frame debugging info
21440 Turns on or off display of @value{GDBN} frame debugging info. The
21442 @item show debug frame
21443 Displays the current state of displaying @value{GDBN} frame debugging
21445 @item set debug gnu-nat
21446 @cindex @sc{gnu}/Hurd debug messages
21447 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
21448 @item show debug gnu-nat
21449 Show the current state of @sc{gnu}/Hurd debugging messages.
21450 @item set debug infrun
21451 @cindex inferior debugging info
21452 Turns on or off display of @value{GDBN} debugging info for running the inferior.
21453 The default is off. @file{infrun.c} contains GDB's runtime state machine used
21454 for implementing operations such as single-stepping the inferior.
21455 @item show debug infrun
21456 Displays the current state of @value{GDBN} inferior debugging.
21457 @item set debug jit
21458 @cindex just-in-time compilation, debugging messages
21459 Turns on or off debugging messages from JIT debug support.
21460 @item show debug jit
21461 Displays the current state of @value{GDBN} JIT debugging.
21462 @item set debug lin-lwp
21463 @cindex @sc{gnu}/Linux LWP debug messages
21464 @cindex Linux lightweight processes
21465 Turns on or off debugging messages from the Linux LWP debug support.
21466 @item show debug lin-lwp
21467 Show the current state of Linux LWP debugging messages.
21468 @item set debug observer
21469 @cindex observer debugging info
21470 Turns on or off display of @value{GDBN} observer debugging. This
21471 includes info such as the notification of observable events.
21472 @item show debug observer
21473 Displays the current state of observer debugging.
21474 @item set debug overload
21475 @cindex C@t{++} overload debugging info
21476 Turns on or off display of @value{GDBN} C@t{++} overload debugging
21477 info. This includes info such as ranking of functions, etc. The default
21479 @item show debug overload
21480 Displays the current state of displaying @value{GDBN} C@t{++} overload
21482 @cindex expression parser, debugging info
21483 @cindex debug expression parser
21484 @item set debug parser
21485 Turns on or off the display of expression parser debugging output.
21486 Internally, this sets the @code{yydebug} variable in the expression
21487 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
21488 details. The default is off.
21489 @item show debug parser
21490 Show the current state of expression parser debugging.
21491 @cindex packets, reporting on stdout
21492 @cindex serial connections, debugging
21493 @cindex debug remote protocol
21494 @cindex remote protocol debugging
21495 @cindex display remote packets
21496 @item set debug remote
21497 Turns on or off display of reports on all packets sent back and forth across
21498 the serial line to the remote machine. The info is printed on the
21499 @value{GDBN} standard output stream. The default is off.
21500 @item show debug remote
21501 Displays the state of display of remote packets.
21502 @item set debug serial
21503 Turns on or off display of @value{GDBN} serial debugging info. The
21505 @item show debug serial
21506 Displays the current state of displaying @value{GDBN} serial debugging
21508 @item set debug solib-frv
21509 @cindex FR-V shared-library debugging
21510 Turns on or off debugging messages for FR-V shared-library code.
21511 @item show debug solib-frv
21512 Display the current state of FR-V shared-library code debugging
21514 @item set debug target
21515 @cindex target debugging info
21516 Turns on or off display of @value{GDBN} target debugging info. This info
21517 includes what is going on at the target level of GDB, as it happens. The
21518 default is 0. Set it to 1 to track events, and to 2 to also track the
21519 value of large memory transfers. Changes to this flag do not take effect
21520 until the next time you connect to a target or use the @code{run} command.
21521 @item show debug target
21522 Displays the current state of displaying @value{GDBN} target debugging
21524 @item set debug timestamp
21525 @cindex timestampping debugging info
21526 Turns on or off display of timestamps with @value{GDBN} debugging info.
21527 When enabled, seconds and microseconds are displayed before each debugging
21529 @item show debug timestamp
21530 Displays the current state of displaying timestamps with @value{GDBN}
21532 @item set debugvarobj
21533 @cindex variable object debugging info
21534 Turns on or off display of @value{GDBN} variable object debugging
21535 info. The default is off.
21536 @item show debugvarobj
21537 Displays the current state of displaying @value{GDBN} variable object
21539 @item set debug xml
21540 @cindex XML parser debugging
21541 Turns on or off debugging messages for built-in XML parsers.
21542 @item show debug xml
21543 Displays the current state of XML debugging messages.
21546 @node Other Misc Settings
21547 @section Other Miscellaneous Settings
21548 @cindex miscellaneous settings
21551 @kindex set interactive-mode
21552 @item set interactive-mode
21553 If @code{on}, forces @value{GDBN} to assume that GDB was started
21554 in a terminal. In practice, this means that @value{GDBN} should wait
21555 for the user to answer queries generated by commands entered at
21556 the command prompt. If @code{off}, forces @value{GDBN} to operate
21557 in the opposite mode, and it uses the default answers to all queries.
21558 If @code{auto} (the default), @value{GDBN} tries to determine whether
21559 its standard input is a terminal, and works in interactive-mode if it
21560 is, non-interactively otherwise.
21562 In the vast majority of cases, the debugger should be able to guess
21563 correctly which mode should be used. But this setting can be useful
21564 in certain specific cases, such as running a MinGW @value{GDBN}
21565 inside a cygwin window.
21567 @kindex show interactive-mode
21568 @item show interactive-mode
21569 Displays whether the debugger is operating in interactive mode or not.
21572 @node Extending GDB
21573 @chapter Extending @value{GDBN}
21574 @cindex extending GDB
21576 @value{GDBN} provides three mechanisms for extension. The first is based
21577 on composition of @value{GDBN} commands, the second is based on the
21578 Python scripting language, and the third is for defining new aliases of
21581 To facilitate the use of the first two extensions, @value{GDBN} is capable
21582 of evaluating the contents of a file. When doing so, @value{GDBN}
21583 can recognize which scripting language is being used by looking at
21584 the filename extension. Files with an unrecognized filename extension
21585 are always treated as a @value{GDBN} Command Files.
21586 @xref{Command Files,, Command files}.
21588 You can control how @value{GDBN} evaluates these files with the following
21592 @kindex set script-extension
21593 @kindex show script-extension
21594 @item set script-extension off
21595 All scripts are always evaluated as @value{GDBN} Command Files.
21597 @item set script-extension soft
21598 The debugger determines the scripting language based on filename
21599 extension. If this scripting language is supported, @value{GDBN}
21600 evaluates the script using that language. Otherwise, it evaluates
21601 the file as a @value{GDBN} Command File.
21603 @item set script-extension strict
21604 The debugger determines the scripting language based on filename
21605 extension, and evaluates the script using that language. If the
21606 language is not supported, then the evaluation fails.
21608 @item show script-extension
21609 Display the current value of the @code{script-extension} option.
21614 * Sequences:: Canned Sequences of Commands
21615 * Python:: Scripting @value{GDBN} using Python
21616 * Aliases:: Creating new spellings of existing commands
21620 @section Canned Sequences of Commands
21622 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
21623 Command Lists}), @value{GDBN} provides two ways to store sequences of
21624 commands for execution as a unit: user-defined commands and command
21628 * Define:: How to define your own commands
21629 * Hooks:: Hooks for user-defined commands
21630 * Command Files:: How to write scripts of commands to be stored in a file
21631 * Output:: Commands for controlled output
21635 @subsection User-defined Commands
21637 @cindex user-defined command
21638 @cindex arguments, to user-defined commands
21639 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
21640 which you assign a new name as a command. This is done with the
21641 @code{define} command. User commands may accept up to 10 arguments
21642 separated by whitespace. Arguments are accessed within the user command
21643 via @code{$arg0@dots{}$arg9}. A trivial example:
21647 print $arg0 + $arg1 + $arg2
21652 To execute the command use:
21659 This defines the command @code{adder}, which prints the sum of
21660 its three arguments. Note the arguments are text substitutions, so they may
21661 reference variables, use complex expressions, or even perform inferior
21664 @cindex argument count in user-defined commands
21665 @cindex how many arguments (user-defined commands)
21666 In addition, @code{$argc} may be used to find out how many arguments have
21667 been passed. This expands to a number in the range 0@dots{}10.
21672 print $arg0 + $arg1
21675 print $arg0 + $arg1 + $arg2
21683 @item define @var{commandname}
21684 Define a command named @var{commandname}. If there is already a command
21685 by that name, you are asked to confirm that you want to redefine it.
21686 @var{commandname} may be a bare command name consisting of letters,
21687 numbers, dashes, and underscores. It may also start with any predefined
21688 prefix command. For example, @samp{define target my-target} creates
21689 a user-defined @samp{target my-target} command.
21691 The definition of the command is made up of other @value{GDBN} command lines,
21692 which are given following the @code{define} command. The end of these
21693 commands is marked by a line containing @code{end}.
21696 @kindex end@r{ (user-defined commands)}
21697 @item document @var{commandname}
21698 Document the user-defined command @var{commandname}, so that it can be
21699 accessed by @code{help}. The command @var{commandname} must already be
21700 defined. This command reads lines of documentation just as @code{define}
21701 reads the lines of the command definition, ending with @code{end}.
21702 After the @code{document} command is finished, @code{help} on command
21703 @var{commandname} displays the documentation you have written.
21705 You may use the @code{document} command again to change the
21706 documentation of a command. Redefining the command with @code{define}
21707 does not change the documentation.
21709 @kindex dont-repeat
21710 @cindex don't repeat command
21712 Used inside a user-defined command, this tells @value{GDBN} that this
21713 command should not be repeated when the user hits @key{RET}
21714 (@pxref{Command Syntax, repeat last command}).
21716 @kindex help user-defined
21717 @item help user-defined
21718 List all user-defined commands and all python commands defined in class
21719 COMAND_USER. The first line of the documentation or docstring is
21724 @itemx show user @var{commandname}
21725 Display the @value{GDBN} commands used to define @var{commandname} (but
21726 not its documentation). If no @var{commandname} is given, display the
21727 definitions for all user-defined commands.
21728 This does not work for user-defined python commands.
21730 @cindex infinite recursion in user-defined commands
21731 @kindex show max-user-call-depth
21732 @kindex set max-user-call-depth
21733 @item show max-user-call-depth
21734 @itemx set max-user-call-depth
21735 The value of @code{max-user-call-depth} controls how many recursion
21736 levels are allowed in user-defined commands before @value{GDBN} suspects an
21737 infinite recursion and aborts the command.
21738 This does not apply to user-defined python commands.
21741 In addition to the above commands, user-defined commands frequently
21742 use control flow commands, described in @ref{Command Files}.
21744 When user-defined commands are executed, the
21745 commands of the definition are not printed. An error in any command
21746 stops execution of the user-defined command.
21748 If used interactively, commands that would ask for confirmation proceed
21749 without asking when used inside a user-defined command. Many @value{GDBN}
21750 commands that normally print messages to say what they are doing omit the
21751 messages when used in a user-defined command.
21754 @subsection User-defined Command Hooks
21755 @cindex command hooks
21756 @cindex hooks, for commands
21757 @cindex hooks, pre-command
21760 You may define @dfn{hooks}, which are a special kind of user-defined
21761 command. Whenever you run the command @samp{foo}, if the user-defined
21762 command @samp{hook-foo} exists, it is executed (with no arguments)
21763 before that command.
21765 @cindex hooks, post-command
21767 A hook may also be defined which is run after the command you executed.
21768 Whenever you run the command @samp{foo}, if the user-defined command
21769 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21770 that command. Post-execution hooks may exist simultaneously with
21771 pre-execution hooks, for the same command.
21773 It is valid for a hook to call the command which it hooks. If this
21774 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21776 @c It would be nice if hookpost could be passed a parameter indicating
21777 @c if the command it hooks executed properly or not. FIXME!
21779 @kindex stop@r{, a pseudo-command}
21780 In addition, a pseudo-command, @samp{stop} exists. Defining
21781 (@samp{hook-stop}) makes the associated commands execute every time
21782 execution stops in your program: before breakpoint commands are run,
21783 displays are printed, or the stack frame is printed.
21785 For example, to ignore @code{SIGALRM} signals while
21786 single-stepping, but treat them normally during normal execution,
21791 handle SIGALRM nopass
21795 handle SIGALRM pass
21798 define hook-continue
21799 handle SIGALRM pass
21803 As a further example, to hook at the beginning and end of the @code{echo}
21804 command, and to add extra text to the beginning and end of the message,
21812 define hookpost-echo
21816 (@value{GDBP}) echo Hello World
21817 <<<---Hello World--->>>
21822 You can define a hook for any single-word command in @value{GDBN}, but
21823 not for command aliases; you should define a hook for the basic command
21824 name, e.g.@: @code{backtrace} rather than @code{bt}.
21825 @c FIXME! So how does Joe User discover whether a command is an alias
21827 You can hook a multi-word command by adding @code{hook-} or
21828 @code{hookpost-} to the last word of the command, e.g.@:
21829 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21831 If an error occurs during the execution of your hook, execution of
21832 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21833 (before the command that you actually typed had a chance to run).
21835 If you try to define a hook which does not match any known command, you
21836 get a warning from the @code{define} command.
21838 @node Command Files
21839 @subsection Command Files
21841 @cindex command files
21842 @cindex scripting commands
21843 A command file for @value{GDBN} is a text file made of lines that are
21844 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21845 also be included. An empty line in a command file does nothing; it
21846 does not mean to repeat the last command, as it would from the
21849 You can request the execution of a command file with the @code{source}
21850 command. Note that the @code{source} command is also used to evaluate
21851 scripts that are not Command Files. The exact behavior can be configured
21852 using the @code{script-extension} setting.
21853 @xref{Extending GDB,, Extending GDB}.
21857 @cindex execute commands from a file
21858 @item source [-s] [-v] @var{filename}
21859 Execute the command file @var{filename}.
21862 The lines in a command file are generally executed sequentially,
21863 unless the order of execution is changed by one of the
21864 @emph{flow-control commands} described below. The commands are not
21865 printed as they are executed. An error in any command terminates
21866 execution of the command file and control is returned to the console.
21868 @value{GDBN} first searches for @var{filename} in the current directory.
21869 If the file is not found there, and @var{filename} does not specify a
21870 directory, then @value{GDBN} also looks for the file on the source search path
21871 (specified with the @samp{directory} command);
21872 except that @file{$cdir} is not searched because the compilation directory
21873 is not relevant to scripts.
21875 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21876 on the search path even if @var{filename} specifies a directory.
21877 The search is done by appending @var{filename} to each element of the
21878 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21879 and the search path contains @file{/home/user} then @value{GDBN} will
21880 look for the script @file{/home/user/mylib/myscript}.
21881 The search is also done if @var{filename} is an absolute path.
21882 For example, if @var{filename} is @file{/tmp/myscript} and
21883 the search path contains @file{/home/user} then @value{GDBN} will
21884 look for the script @file{/home/user/tmp/myscript}.
21885 For DOS-like systems, if @var{filename} contains a drive specification,
21886 it is stripped before concatenation. For example, if @var{filename} is
21887 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21888 will look for the script @file{c:/tmp/myscript}.
21890 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21891 each command as it is executed. The option must be given before
21892 @var{filename}, and is interpreted as part of the filename anywhere else.
21894 Commands that would ask for confirmation if used interactively proceed
21895 without asking when used in a command file. Many @value{GDBN} commands that
21896 normally print messages to say what they are doing omit the messages
21897 when called from command files.
21899 @value{GDBN} also accepts command input from standard input. In this
21900 mode, normal output goes to standard output and error output goes to
21901 standard error. Errors in a command file supplied on standard input do
21902 not terminate execution of the command file---execution continues with
21906 gdb < cmds > log 2>&1
21909 (The syntax above will vary depending on the shell used.) This example
21910 will execute commands from the file @file{cmds}. All output and errors
21911 would be directed to @file{log}.
21913 Since commands stored on command files tend to be more general than
21914 commands typed interactively, they frequently need to deal with
21915 complicated situations, such as different or unexpected values of
21916 variables and symbols, changes in how the program being debugged is
21917 built, etc. @value{GDBN} provides a set of flow-control commands to
21918 deal with these complexities. Using these commands, you can write
21919 complex scripts that loop over data structures, execute commands
21920 conditionally, etc.
21927 This command allows to include in your script conditionally executed
21928 commands. The @code{if} command takes a single argument, which is an
21929 expression to evaluate. It is followed by a series of commands that
21930 are executed only if the expression is true (its value is nonzero).
21931 There can then optionally be an @code{else} line, followed by a series
21932 of commands that are only executed if the expression was false. The
21933 end of the list is marked by a line containing @code{end}.
21937 This command allows to write loops. Its syntax is similar to
21938 @code{if}: the command takes a single argument, which is an expression
21939 to evaluate, and must be followed by the commands to execute, one per
21940 line, terminated by an @code{end}. These commands are called the
21941 @dfn{body} of the loop. The commands in the body of @code{while} are
21942 executed repeatedly as long as the expression evaluates to true.
21946 This command exits the @code{while} loop in whose body it is included.
21947 Execution of the script continues after that @code{while}s @code{end}
21950 @kindex loop_continue
21951 @item loop_continue
21952 This command skips the execution of the rest of the body of commands
21953 in the @code{while} loop in whose body it is included. Execution
21954 branches to the beginning of the @code{while} loop, where it evaluates
21955 the controlling expression.
21957 @kindex end@r{ (if/else/while commands)}
21959 Terminate the block of commands that are the body of @code{if},
21960 @code{else}, or @code{while} flow-control commands.
21965 @subsection Commands for Controlled Output
21967 During the execution of a command file or a user-defined command, normal
21968 @value{GDBN} output is suppressed; the only output that appears is what is
21969 explicitly printed by the commands in the definition. This section
21970 describes three commands useful for generating exactly the output you
21975 @item echo @var{text}
21976 @c I do not consider backslash-space a standard C escape sequence
21977 @c because it is not in ANSI.
21978 Print @var{text}. Nonprinting characters can be included in
21979 @var{text} using C escape sequences, such as @samp{\n} to print a
21980 newline. @strong{No newline is printed unless you specify one.}
21981 In addition to the standard C escape sequences, a backslash followed
21982 by a space stands for a space. This is useful for displaying a
21983 string with spaces at the beginning or the end, since leading and
21984 trailing spaces are otherwise trimmed from all arguments.
21985 To print @samp{@w{ }and foo =@w{ }}, use the command
21986 @samp{echo \@w{ }and foo = \@w{ }}.
21988 A backslash at the end of @var{text} can be used, as in C, to continue
21989 the command onto subsequent lines. For example,
21992 echo This is some text\n\
21993 which is continued\n\
21994 onto several lines.\n
21997 produces the same output as
22000 echo This is some text\n
22001 echo which is continued\n
22002 echo onto several lines.\n
22006 @item output @var{expression}
22007 Print the value of @var{expression} and nothing but that value: no
22008 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22009 value history either. @xref{Expressions, ,Expressions}, for more information
22012 @item output/@var{fmt} @var{expression}
22013 Print the value of @var{expression} in format @var{fmt}. You can use
22014 the same formats as for @code{print}. @xref{Output Formats,,Output
22015 Formats}, for more information.
22018 @item printf @var{template}, @var{expressions}@dots{}
22019 Print the values of one or more @var{expressions} under the control of
22020 the string @var{template}. To print several values, make
22021 @var{expressions} be a comma-separated list of individual expressions,
22022 which may be either numbers or pointers. Their values are printed as
22023 specified by @var{template}, exactly as a C program would do by
22024 executing the code below:
22027 printf (@var{template}, @var{expressions}@dots{});
22030 As in @code{C} @code{printf}, ordinary characters in @var{template}
22031 are printed verbatim, while @dfn{conversion specification} introduced
22032 by the @samp{%} character cause subsequent @var{expressions} to be
22033 evaluated, their values converted and formatted according to type and
22034 style information encoded in the conversion specifications, and then
22037 For example, you can print two values in hex like this:
22040 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22043 @code{printf} supports all the standard @code{C} conversion
22044 specifications, including the flags and modifiers between the @samp{%}
22045 character and the conversion letter, with the following exceptions:
22049 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22052 The modifier @samp{*} is not supported for specifying precision or
22056 The @samp{'} flag (for separation of digits into groups according to
22057 @code{LC_NUMERIC'}) is not supported.
22060 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22064 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22067 The conversion letters @samp{a} and @samp{A} are not supported.
22071 Note that the @samp{ll} type modifier is supported only if the
22072 underlying @code{C} implementation used to build @value{GDBN} supports
22073 the @code{long long int} type, and the @samp{L} type modifier is
22074 supported only if @code{long double} type is available.
22076 As in @code{C}, @code{printf} supports simple backslash-escape
22077 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22078 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22079 single character. Octal and hexadecimal escape sequences are not
22082 Additionally, @code{printf} supports conversion specifications for DFP
22083 (@dfn{Decimal Floating Point}) types using the following length modifiers
22084 together with a floating point specifier.
22089 @samp{H} for printing @code{Decimal32} types.
22092 @samp{D} for printing @code{Decimal64} types.
22095 @samp{DD} for printing @code{Decimal128} types.
22098 If the underlying @code{C} implementation used to build @value{GDBN} has
22099 support for the three length modifiers for DFP types, other modifiers
22100 such as width and precision will also be available for @value{GDBN} to use.
22102 In case there is no such @code{C} support, no additional modifiers will be
22103 available and the value will be printed in the standard way.
22105 Here's an example of printing DFP types using the above conversion letters:
22107 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22111 @item eval @var{template}, @var{expressions}@dots{}
22112 Convert the values of one or more @var{expressions} under the control of
22113 the string @var{template} to a command line, and call it.
22118 @section Scripting @value{GDBN} using Python
22119 @cindex python scripting
22120 @cindex scripting with python
22122 You can script @value{GDBN} using the @uref{http://www.python.org/,
22123 Python programming language}. This feature is available only if
22124 @value{GDBN} was configured using @option{--with-python}.
22126 @cindex python directory
22127 Python scripts used by @value{GDBN} should be installed in
22128 @file{@var{data-directory}/python}, where @var{data-directory} is
22129 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22130 This directory, known as the @dfn{python directory},
22131 is automatically added to the Python Search Path in order to allow
22132 the Python interpreter to locate all scripts installed at this location.
22134 Additionally, @value{GDBN} commands and convenience functions which
22135 are written in Python and are located in the
22136 @file{@var{data-directory}/python/gdb/command} or
22137 @file{@var{data-directory}/python/gdb/function} directories are
22138 automatically imported when @value{GDBN} starts.
22141 * Python Commands:: Accessing Python from @value{GDBN}.
22142 * Python API:: Accessing @value{GDBN} from Python.
22143 * Python Auto-loading:: Automatically loading Python code.
22144 * Python modules:: Python modules provided by @value{GDBN}.
22147 @node Python Commands
22148 @subsection Python Commands
22149 @cindex python commands
22150 @cindex commands to access python
22152 @value{GDBN} provides one command for accessing the Python interpreter,
22153 and one related setting:
22157 @item python @r{[}@var{code}@r{]}
22158 The @code{python} command can be used to evaluate Python code.
22160 If given an argument, the @code{python} command will evaluate the
22161 argument as a Python command. For example:
22164 (@value{GDBP}) python print 23
22168 If you do not provide an argument to @code{python}, it will act as a
22169 multi-line command, like @code{define}. In this case, the Python
22170 script is made up of subsequent command lines, given after the
22171 @code{python} command. This command list is terminated using a line
22172 containing @code{end}. For example:
22175 (@value{GDBP}) python
22177 End with a line saying just "end".
22183 @kindex set python print-stack
22184 @item set python print-stack
22185 By default, @value{GDBN} will print only the message component of a
22186 Python exception when an error occurs in a Python script. This can be
22187 controlled using @code{set python print-stack}: if @code{full}, then
22188 full Python stack printing is enabled; if @code{none}, then Python stack
22189 and message printing is disabled; if @code{message}, the default, only
22190 the message component of the error is printed.
22193 It is also possible to execute a Python script from the @value{GDBN}
22197 @item source @file{script-name}
22198 The script name must end with @samp{.py} and @value{GDBN} must be configured
22199 to recognize the script language based on filename extension using
22200 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22202 @item python execfile ("script-name")
22203 This method is based on the @code{execfile} Python built-in function,
22204 and thus is always available.
22208 @subsection Python API
22210 @cindex programming in python
22212 @cindex python stdout
22213 @cindex python pagination
22214 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22215 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22216 A Python program which outputs to one of these streams may have its
22217 output interrupted by the user (@pxref{Screen Size}). In this
22218 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22221 * Basic Python:: Basic Python Functions.
22222 * Exception Handling:: How Python exceptions are translated.
22223 * Values From Inferior:: Python representation of values.
22224 * Types In Python:: Python representation of types.
22225 * Pretty Printing API:: Pretty-printing values.
22226 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22227 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22228 * Inferiors In Python:: Python representation of inferiors (processes)
22229 * Events In Python:: Listening for events from @value{GDBN}.
22230 * Threads In Python:: Accessing inferior threads from Python.
22231 * Commands In Python:: Implementing new commands in Python.
22232 * Parameters In Python:: Adding new @value{GDBN} parameters.
22233 * Functions In Python:: Writing new convenience functions.
22234 * Progspaces In Python:: Program spaces.
22235 * Objfiles In Python:: Object files.
22236 * Frames In Python:: Accessing inferior stack frames from Python.
22237 * Blocks In Python:: Accessing frame blocks from Python.
22238 * Symbols In Python:: Python representation of symbols.
22239 * Symbol Tables In Python:: Python representation of symbol tables.
22240 * Lazy Strings In Python:: Python representation of lazy strings.
22241 * Breakpoints In Python:: Manipulating breakpoints using Python.
22242 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22247 @subsubsection Basic Python
22249 @cindex python functions
22250 @cindex python module
22252 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22253 methods and classes added by @value{GDBN} are placed in this module.
22254 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22255 use in all scripts evaluated by the @code{python} command.
22257 @findex gdb.PYTHONDIR
22258 @defvar gdb.PYTHONDIR
22259 A string containing the python directory (@pxref{Python}).
22262 @findex gdb.execute
22263 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
22264 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
22265 If a GDB exception happens while @var{command} runs, it is
22266 translated as described in @ref{Exception Handling,,Exception Handling}.
22268 @var{from_tty} specifies whether @value{GDBN} ought to consider this
22269 command as having originated from the user invoking it interactively.
22270 It must be a boolean value. If omitted, it defaults to @code{False}.
22272 By default, any output produced by @var{command} is sent to
22273 @value{GDBN}'s standard output. If the @var{to_string} parameter is
22274 @code{True}, then output will be collected by @code{gdb.execute} and
22275 returned as a string. The default is @code{False}, in which case the
22276 return value is @code{None}. If @var{to_string} is @code{True}, the
22277 @value{GDBN} virtual terminal will be temporarily set to unlimited width
22278 and height, and its pagination will be disabled; @pxref{Screen Size}.
22281 @findex gdb.breakpoints
22282 @defun gdb.breakpoints ()
22283 Return a sequence holding all of @value{GDBN}'s breakpoints.
22284 @xref{Breakpoints In Python}, for more information.
22287 @findex gdb.parameter
22288 @defun gdb.parameter (parameter)
22289 Return the value of a @value{GDBN} parameter. @var{parameter} is a
22290 string naming the parameter to look up; @var{parameter} may contain
22291 spaces if the parameter has a multi-part name. For example,
22292 @samp{print object} is a valid parameter name.
22294 If the named parameter does not exist, this function throws a
22295 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
22296 parameter's value is converted to a Python value of the appropriate
22297 type, and returned.
22300 @findex gdb.history
22301 @defun gdb.history (number)
22302 Return a value from @value{GDBN}'s value history (@pxref{Value
22303 History}). @var{number} indicates which history element to return.
22304 If @var{number} is negative, then @value{GDBN} will take its absolute value
22305 and count backward from the last element (i.e., the most recent element) to
22306 find the value to return. If @var{number} is zero, then @value{GDBN} will
22307 return the most recent element. If the element specified by @var{number}
22308 doesn't exist in the value history, a @code{gdb.error} exception will be
22311 If no exception is raised, the return value is always an instance of
22312 @code{gdb.Value} (@pxref{Values From Inferior}).
22315 @findex gdb.parse_and_eval
22316 @defun gdb.parse_and_eval (expression)
22317 Parse @var{expression} as an expression in the current language,
22318 evaluate it, and return the result as a @code{gdb.Value}.
22319 @var{expression} must be a string.
22321 This function can be useful when implementing a new command
22322 (@pxref{Commands In Python}), as it provides a way to parse the
22323 command's argument as an expression. It is also useful simply to
22324 compute values, for example, it is the only way to get the value of a
22325 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
22328 @findex gdb.post_event
22329 @defun gdb.post_event (event)
22330 Put @var{event}, a callable object taking no arguments, into
22331 @value{GDBN}'s internal event queue. This callable will be invoked at
22332 some later point, during @value{GDBN}'s event processing. Events
22333 posted using @code{post_event} will be run in the order in which they
22334 were posted; however, there is no way to know when they will be
22335 processed relative to other events inside @value{GDBN}.
22337 @value{GDBN} is not thread-safe. If your Python program uses multiple
22338 threads, you must be careful to only call @value{GDBN}-specific
22339 functions in the main @value{GDBN} thread. @code{post_event} ensures
22343 (@value{GDBP}) python
22347 > def __init__(self, message):
22348 > self.message = message;
22349 > def __call__(self):
22350 > gdb.write(self.message)
22352 >class MyThread1 (threading.Thread):
22354 > gdb.post_event(Writer("Hello "))
22356 >class MyThread2 (threading.Thread):
22358 > gdb.post_event(Writer("World\n"))
22360 >MyThread1().start()
22361 >MyThread2().start()
22363 (@value{GDBP}) Hello World
22368 @defun gdb.write (string @r{[}, stream{]})
22369 Print a string to @value{GDBN}'s paginated output stream. The
22370 optional @var{stream} determines the stream to print to. The default
22371 stream is @value{GDBN}'s standard output stream. Possible stream
22378 @value{GDBN}'s standard output stream.
22383 @value{GDBN}'s standard error stream.
22388 @value{GDBN}'s log stream (@pxref{Logging Output}).
22391 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
22392 call this function and will automatically direct the output to the
22397 @defun gdb.flush ()
22398 Flush the buffer of a @value{GDBN} paginated stream so that the
22399 contents are displayed immediately. @value{GDBN} will flush the
22400 contents of a stream automatically when it encounters a newline in the
22401 buffer. The optional @var{stream} determines the stream to flush. The
22402 default stream is @value{GDBN}'s standard output stream. Possible
22409 @value{GDBN}'s standard output stream.
22414 @value{GDBN}'s standard error stream.
22419 @value{GDBN}'s log stream (@pxref{Logging Output}).
22423 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
22424 call this function for the relevant stream.
22427 @findex gdb.target_charset
22428 @defun gdb.target_charset ()
22429 Return the name of the current target character set (@pxref{Character
22430 Sets}). This differs from @code{gdb.parameter('target-charset')} in
22431 that @samp{auto} is never returned.
22434 @findex gdb.target_wide_charset
22435 @defun gdb.target_wide_charset ()
22436 Return the name of the current target wide character set
22437 (@pxref{Character Sets}). This differs from
22438 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
22442 @findex gdb.solib_name
22443 @defun gdb.solib_name (address)
22444 Return the name of the shared library holding the given @var{address}
22445 as a string, or @code{None}.
22448 @findex gdb.decode_line
22449 @defun gdb.decode_line @r{[}expression@r{]}
22450 Return locations of the line specified by @var{expression}, or of the
22451 current line if no argument was given. This function returns a Python
22452 tuple containing two elements. The first element contains a string
22453 holding any unparsed section of @var{expression} (or @code{None} if
22454 the expression has been fully parsed). The second element contains
22455 either @code{None} or another tuple that contains all the locations
22456 that match the expression represented as @code{gdb.Symtab_and_line}
22457 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
22458 provided, it is decoded the way that @value{GDBN}'s inbuilt
22459 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
22462 @defun gdb.prompt_hook (current_prompt)
22463 @anchor{prompt_hook}
22465 If @var{prompt_hook} is callable, @value{GDBN} will call the method
22466 assigned to this operation before a prompt is displayed by
22469 The parameter @code{current_prompt} contains the current @value{GDBN}
22470 prompt. This method must return a Python string, or @code{None}. If
22471 a string is returned, the @value{GDBN} prompt will be set to that
22472 string. If @code{None} is returned, @value{GDBN} will continue to use
22473 the current prompt.
22475 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
22476 such as those used by readline for command input, and annotation
22477 related prompts are prohibited from being changed.
22480 @node Exception Handling
22481 @subsubsection Exception Handling
22482 @cindex python exceptions
22483 @cindex exceptions, python
22485 When executing the @code{python} command, Python exceptions
22486 uncaught within the Python code are translated to calls to
22487 @value{GDBN} error-reporting mechanism. If the command that called
22488 @code{python} does not handle the error, @value{GDBN} will
22489 terminate it and print an error message containing the Python
22490 exception name, the associated value, and the Python call stack
22491 backtrace at the point where the exception was raised. Example:
22494 (@value{GDBP}) python print foo
22495 Traceback (most recent call last):
22496 File "<string>", line 1, in <module>
22497 NameError: name 'foo' is not defined
22500 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
22501 Python code are converted to Python exceptions. The type of the
22502 Python exception depends on the error.
22506 This is the base class for most exceptions generated by @value{GDBN}.
22507 It is derived from @code{RuntimeError}, for compatibility with earlier
22508 versions of @value{GDBN}.
22510 If an error occurring in @value{GDBN} does not fit into some more
22511 specific category, then the generated exception will have this type.
22513 @item gdb.MemoryError
22514 This is a subclass of @code{gdb.error} which is thrown when an
22515 operation tried to access invalid memory in the inferior.
22517 @item KeyboardInterrupt
22518 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
22519 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
22522 In all cases, your exception handler will see the @value{GDBN} error
22523 message as its value and the Python call stack backtrace at the Python
22524 statement closest to where the @value{GDBN} error occured as the
22527 @findex gdb.GdbError
22528 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
22529 it is useful to be able to throw an exception that doesn't cause a
22530 traceback to be printed. For example, the user may have invoked the
22531 command incorrectly. Use the @code{gdb.GdbError} exception
22532 to handle this case. Example:
22536 >class HelloWorld (gdb.Command):
22537 > """Greet the whole world."""
22538 > def __init__ (self):
22539 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
22540 > def invoke (self, args, from_tty):
22541 > argv = gdb.string_to_argv (args)
22542 > if len (argv) != 0:
22543 > raise gdb.GdbError ("hello-world takes no arguments")
22544 > print "Hello, World!"
22547 (gdb) hello-world 42
22548 hello-world takes no arguments
22551 @node Values From Inferior
22552 @subsubsection Values From Inferior
22553 @cindex values from inferior, with Python
22554 @cindex python, working with values from inferior
22556 @cindex @code{gdb.Value}
22557 @value{GDBN} provides values it obtains from the inferior program in
22558 an object of type @code{gdb.Value}. @value{GDBN} uses this object
22559 for its internal bookkeeping of the inferior's values, and for
22560 fetching values when necessary.
22562 Inferior values that are simple scalars can be used directly in
22563 Python expressions that are valid for the value's data type. Here's
22564 an example for an integer or floating-point value @code{some_val}:
22571 As result of this, @code{bar} will also be a @code{gdb.Value} object
22572 whose values are of the same type as those of @code{some_val}.
22574 Inferior values that are structures or instances of some class can
22575 be accessed using the Python @dfn{dictionary syntax}. For example, if
22576 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
22577 can access its @code{foo} element with:
22580 bar = some_val['foo']
22583 Again, @code{bar} will also be a @code{gdb.Value} object.
22585 A @code{gdb.Value} that represents a function can be executed via
22586 inferior function call. Any arguments provided to the call must match
22587 the function's prototype, and must be provided in the order specified
22590 For example, @code{some_val} is a @code{gdb.Value} instance
22591 representing a function that takes two integers as arguments. To
22592 execute this function, call it like so:
22595 result = some_val (10,20)
22598 Any values returned from a function call will be stored as a
22601 The following attributes are provided:
22604 @defvar Value.address
22605 If this object is addressable, this read-only attribute holds a
22606 @code{gdb.Value} object representing the address. Otherwise,
22607 this attribute holds @code{None}.
22610 @cindex optimized out value in Python
22611 @defvar Value.is_optimized_out
22612 This read-only boolean attribute is true if the compiler optimized out
22613 this value, thus it is not available for fetching from the inferior.
22617 The type of this @code{gdb.Value}. The value of this attribute is a
22618 @code{gdb.Type} object (@pxref{Types In Python}).
22621 @defvar Value.dynamic_type
22622 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
22623 type information (@acronym{RTTI}) to determine the dynamic type of the
22624 value. If this value is of class type, it will return the class in
22625 which the value is embedded, if any. If this value is of pointer or
22626 reference to a class type, it will compute the dynamic type of the
22627 referenced object, and return a pointer or reference to that type,
22628 respectively. In all other cases, it will return the value's static
22631 Note that this feature will only work when debugging a C@t{++} program
22632 that includes @acronym{RTTI} for the object in question. Otherwise,
22633 it will just return the static type of the value as in @kbd{ptype foo}
22634 (@pxref{Symbols, ptype}).
22637 @defvar Value.is_lazy
22638 The value of this read-only boolean attribute is @code{True} if this
22639 @code{gdb.Value} has not yet been fetched from the inferior.
22640 @value{GDBN} does not fetch values until necessary, for efficiency.
22644 myval = gdb.parse_and_eval ('somevar')
22647 The value of @code{somevar} is not fetched at this time. It will be
22648 fetched when the value is needed, or when the @code{fetch_lazy}
22653 The following methods are provided:
22656 @defun Value.__init__ (@var{val})
22657 Many Python values can be converted directly to a @code{gdb.Value} via
22658 this object initializer. Specifically:
22661 @item Python boolean
22662 A Python boolean is converted to the boolean type from the current
22665 @item Python integer
22666 A Python integer is converted to the C @code{long} type for the
22667 current architecture.
22670 A Python long is converted to the C @code{long long} type for the
22671 current architecture.
22674 A Python float is converted to the C @code{double} type for the
22675 current architecture.
22677 @item Python string
22678 A Python string is converted to a target string, using the current
22681 @item @code{gdb.Value}
22682 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22684 @item @code{gdb.LazyString}
22685 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22686 Python}), then the lazy string's @code{value} method is called, and
22687 its result is used.
22691 @defun Value.cast (type)
22692 Return a new instance of @code{gdb.Value} that is the result of
22693 casting this instance to the type described by @var{type}, which must
22694 be a @code{gdb.Type} object. If the cast cannot be performed for some
22695 reason, this method throws an exception.
22698 @defun Value.dereference ()
22699 For pointer data types, this method returns a new @code{gdb.Value} object
22700 whose contents is the object pointed to by the pointer. For example, if
22701 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22708 then you can use the corresponding @code{gdb.Value} to access what
22709 @code{foo} points to like this:
22712 bar = foo.dereference ()
22715 The result @code{bar} will be a @code{gdb.Value} object holding the
22716 value pointed to by @code{foo}.
22718 A similar function @code{Value.referenced_value} exists which also
22719 returns @code{gdb.Value} objects corresonding to the values pointed to
22720 by pointer values (and additionally, values referenced by reference
22721 values). However, the behavior of @code{Value.dereference}
22722 differs from @code{Value.referenced_value} by the fact that the
22723 behavior of @code{Value.dereference} is identical to applying the C
22724 unary operator @code{*} on a given value. For example, consider a
22725 reference to a pointer @code{ptrref}, declared in your C@t{++} program
22729 typedef int *intptr;
22733 intptr &ptrref = ptr;
22736 Though @code{ptrref} is a reference value, one can apply the method
22737 @code{Value.dereference} to the @code{gdb.Value} object corresponding
22738 to it and obtain a @code{gdb.Value} which is identical to that
22739 corresponding to @code{val}. However, if you apply the method
22740 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
22741 object identical to that corresponding to @code{ptr}.
22744 py_ptrref = gdb.parse_and_eval ("ptrref")
22745 py_val = py_ptrref.dereference ()
22746 py_ptr = py_ptrref.referenced_value ()
22749 The @code{gdb.Value} object @code{py_val} is identical to that
22750 corresponding to @code{val}, and @code{py_ptr} is identical to that
22751 corresponding to @code{ptr}. In general, @code{Value.dereference} can
22752 be applied whenever the C unary operator @code{*} can be applied
22753 to the corresponding C value. For those cases where applying both
22754 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
22755 the results obtained need not be identical (as we have seen in the above
22756 example). The results are however identical when applied on
22757 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
22758 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
22761 @defun Value.referenced_value ()
22762 For pointer or reference data types, this method returns a new
22763 @code{gdb.Value} object corresponding to the value referenced by the
22764 pointer/reference value. For pointer data types,
22765 @code{Value.dereference} and @code{Value.referenced_value} produce
22766 identical results. The difference between these methods is that
22767 @code{Value.dereference} cannot get the values referenced by reference
22768 values. For example, consider a reference to an @code{int}, declared
22769 in your C@t{++} program as
22777 then applying @code{Value.dereference} to the @code{gdb.Value} object
22778 corresponding to @code{ref} will result in an error, while applying
22779 @code{Value.referenced_value} will result in a @code{gdb.Value} object
22780 identical to that corresponding to @code{val}.
22783 py_ref = gdb.parse_and_eval ("ref")
22784 er_ref = py_ref.dereference () # Results in error
22785 py_val = py_ref.referenced_value () # Returns the referenced value
22788 The @code{gdb.Value} object @code{py_val} is identical to that
22789 corresponding to @code{val}.
22792 @defun Value.dynamic_cast (type)
22793 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22794 operator were used. Consult a C@t{++} reference for details.
22797 @defun Value.reinterpret_cast (type)
22798 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22799 operator were used. Consult a C@t{++} reference for details.
22802 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22803 If this @code{gdb.Value} represents a string, then this method
22804 converts the contents to a Python string. Otherwise, this method will
22805 throw an exception.
22807 Strings are recognized in a language-specific way; whether a given
22808 @code{gdb.Value} represents a string is determined by the current
22811 For C-like languages, a value is a string if it is a pointer to or an
22812 array of characters or ints. The string is assumed to be terminated
22813 by a zero of the appropriate width. However if the optional length
22814 argument is given, the string will be converted to that given length,
22815 ignoring any embedded zeros that the string may contain.
22817 If the optional @var{encoding} argument is given, it must be a string
22818 naming the encoding of the string in the @code{gdb.Value}, such as
22819 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22820 the same encodings as the corresponding argument to Python's
22821 @code{string.decode} method, and the Python codec machinery will be used
22822 to convert the string. If @var{encoding} is not given, or if
22823 @var{encoding} is the empty string, then either the @code{target-charset}
22824 (@pxref{Character Sets}) will be used, or a language-specific encoding
22825 will be used, if the current language is able to supply one.
22827 The optional @var{errors} argument is the same as the corresponding
22828 argument to Python's @code{string.decode} method.
22830 If the optional @var{length} argument is given, the string will be
22831 fetched and converted to the given length.
22834 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22835 If this @code{gdb.Value} represents a string, then this method
22836 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22837 In Python}). Otherwise, this method will throw an exception.
22839 If the optional @var{encoding} argument is given, it must be a string
22840 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22841 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22842 @var{encoding} argument is an encoding that @value{GDBN} does
22843 recognize, @value{GDBN} will raise an error.
22845 When a lazy string is printed, the @value{GDBN} encoding machinery is
22846 used to convert the string during printing. If the optional
22847 @var{encoding} argument is not provided, or is an empty string,
22848 @value{GDBN} will automatically select the encoding most suitable for
22849 the string type. For further information on encoding in @value{GDBN}
22850 please see @ref{Character Sets}.
22852 If the optional @var{length} argument is given, the string will be
22853 fetched and encoded to the length of characters specified. If
22854 the @var{length} argument is not provided, the string will be fetched
22855 and encoded until a null of appropriate width is found.
22858 @defun Value.fetch_lazy ()
22859 If the @code{gdb.Value} object is currently a lazy value
22860 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22861 fetched from the inferior. Any errors that occur in the process
22862 will produce a Python exception.
22864 If the @code{gdb.Value} object is not a lazy value, this method
22867 This method does not return a value.
22872 @node Types In Python
22873 @subsubsection Types In Python
22874 @cindex types in Python
22875 @cindex Python, working with types
22878 @value{GDBN} represents types from the inferior using the class
22881 The following type-related functions are available in the @code{gdb}
22884 @findex gdb.lookup_type
22885 @defun gdb.lookup_type (name @r{[}, block@r{]})
22886 This function looks up a type by name. @var{name} is the name of the
22887 type to look up. It must be a string.
22889 If @var{block} is given, then @var{name} is looked up in that scope.
22890 Otherwise, it is searched for globally.
22892 Ordinarily, this function will return an instance of @code{gdb.Type}.
22893 If the named type cannot be found, it will throw an exception.
22896 If the type is a structure or class type, or an enum type, the fields
22897 of that type can be accessed using the Python @dfn{dictionary syntax}.
22898 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22899 a structure type, you can access its @code{foo} field with:
22902 bar = some_type['foo']
22905 @code{bar} will be a @code{gdb.Field} object; see below under the
22906 description of the @code{Type.fields} method for a description of the
22907 @code{gdb.Field} class.
22909 An instance of @code{Type} has the following attributes:
22913 The type code for this type. The type code will be one of the
22914 @code{TYPE_CODE_} constants defined below.
22917 @defvar Type.sizeof
22918 The size of this type, in target @code{char} units. Usually, a
22919 target's @code{char} type will be an 8-bit byte. However, on some
22920 unusual platforms, this type may have a different size.
22924 The tag name for this type. The tag name is the name after
22925 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22926 languages have this concept. If this type has no tag name, then
22927 @code{None} is returned.
22931 The following methods are provided:
22934 @defun Type.fields ()
22935 For structure and union types, this method returns the fields. Range
22936 types have two fields, the minimum and maximum values. Enum types
22937 have one field per enum constant. Function and method types have one
22938 field per parameter. The base types of C@t{++} classes are also
22939 represented as fields. If the type has no fields, or does not fit
22940 into one of these categories, an empty sequence will be returned.
22942 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22945 This attribute is not available for @code{static} fields (as in
22946 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22947 position of the field. For @code{enum} fields, the value is the
22948 enumeration member's integer representation.
22951 The name of the field, or @code{None} for anonymous fields.
22954 This is @code{True} if the field is artificial, usually meaning that
22955 it was provided by the compiler and not the user. This attribute is
22956 always provided, and is @code{False} if the field is not artificial.
22958 @item is_base_class
22959 This is @code{True} if the field represents a base class of a C@t{++}
22960 structure. This attribute is always provided, and is @code{False}
22961 if the field is not a base class of the type that is the argument of
22962 @code{fields}, or if that type was not a C@t{++} class.
22965 If the field is packed, or is a bitfield, then this will have a
22966 non-zero value, which is the size of the field in bits. Otherwise,
22967 this will be zero; in this case the field's size is given by its type.
22970 The type of the field. This is usually an instance of @code{Type},
22971 but it can be @code{None} in some situations.
22975 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22976 Return a new @code{gdb.Type} object which represents an array of this
22977 type. If one argument is given, it is the inclusive upper bound of
22978 the array; in this case the lower bound is zero. If two arguments are
22979 given, the first argument is the lower bound of the array, and the
22980 second argument is the upper bound of the array. An array's length
22981 must not be negative, but the bounds can be.
22984 @defun Type.const ()
22985 Return a new @code{gdb.Type} object which represents a
22986 @code{const}-qualified variant of this type.
22989 @defun Type.volatile ()
22990 Return a new @code{gdb.Type} object which represents a
22991 @code{volatile}-qualified variant of this type.
22994 @defun Type.unqualified ()
22995 Return a new @code{gdb.Type} object which represents an unqualified
22996 variant of this type. That is, the result is neither @code{const} nor
23000 @defun Type.range ()
23001 Return a Python @code{Tuple} object that contains two elements: the
23002 low bound of the argument type and the high bound of that type. If
23003 the type does not have a range, @value{GDBN} will raise a
23004 @code{gdb.error} exception (@pxref{Exception Handling}).
23007 @defun Type.reference ()
23008 Return a new @code{gdb.Type} object which represents a reference to this
23012 @defun Type.pointer ()
23013 Return a new @code{gdb.Type} object which represents a pointer to this
23017 @defun Type.strip_typedefs ()
23018 Return a new @code{gdb.Type} that represents the real type,
23019 after removing all layers of typedefs.
23022 @defun Type.target ()
23023 Return a new @code{gdb.Type} object which represents the target type
23026 For a pointer type, the target type is the type of the pointed-to
23027 object. For an array type (meaning C-like arrays), the target type is
23028 the type of the elements of the array. For a function or method type,
23029 the target type is the type of the return value. For a complex type,
23030 the target type is the type of the elements. For a typedef, the
23031 target type is the aliased type.
23033 If the type does not have a target, this method will throw an
23037 @defun Type.template_argument (n @r{[}, block@r{]})
23038 If this @code{gdb.Type} is an instantiation of a template, this will
23039 return a new @code{gdb.Type} which represents the type of the
23040 @var{n}th template argument.
23042 If this @code{gdb.Type} is not a template type, this will throw an
23043 exception. Ordinarily, only C@t{++} code will have template types.
23045 If @var{block} is given, then @var{name} is looked up in that scope.
23046 Otherwise, it is searched for globally.
23051 Each type has a code, which indicates what category this type falls
23052 into. The available type categories are represented by constants
23053 defined in the @code{gdb} module:
23056 @findex TYPE_CODE_PTR
23057 @findex gdb.TYPE_CODE_PTR
23058 @item gdb.TYPE_CODE_PTR
23059 The type is a pointer.
23061 @findex TYPE_CODE_ARRAY
23062 @findex gdb.TYPE_CODE_ARRAY
23063 @item gdb.TYPE_CODE_ARRAY
23064 The type is an array.
23066 @findex TYPE_CODE_STRUCT
23067 @findex gdb.TYPE_CODE_STRUCT
23068 @item gdb.TYPE_CODE_STRUCT
23069 The type is a structure.
23071 @findex TYPE_CODE_UNION
23072 @findex gdb.TYPE_CODE_UNION
23073 @item gdb.TYPE_CODE_UNION
23074 The type is a union.
23076 @findex TYPE_CODE_ENUM
23077 @findex gdb.TYPE_CODE_ENUM
23078 @item gdb.TYPE_CODE_ENUM
23079 The type is an enum.
23081 @findex TYPE_CODE_FLAGS
23082 @findex gdb.TYPE_CODE_FLAGS
23083 @item gdb.TYPE_CODE_FLAGS
23084 A bit flags type, used for things such as status registers.
23086 @findex TYPE_CODE_FUNC
23087 @findex gdb.TYPE_CODE_FUNC
23088 @item gdb.TYPE_CODE_FUNC
23089 The type is a function.
23091 @findex TYPE_CODE_INT
23092 @findex gdb.TYPE_CODE_INT
23093 @item gdb.TYPE_CODE_INT
23094 The type is an integer type.
23096 @findex TYPE_CODE_FLT
23097 @findex gdb.TYPE_CODE_FLT
23098 @item gdb.TYPE_CODE_FLT
23099 A floating point type.
23101 @findex TYPE_CODE_VOID
23102 @findex gdb.TYPE_CODE_VOID
23103 @item gdb.TYPE_CODE_VOID
23104 The special type @code{void}.
23106 @findex TYPE_CODE_SET
23107 @findex gdb.TYPE_CODE_SET
23108 @item gdb.TYPE_CODE_SET
23111 @findex TYPE_CODE_RANGE
23112 @findex gdb.TYPE_CODE_RANGE
23113 @item gdb.TYPE_CODE_RANGE
23114 A range type, that is, an integer type with bounds.
23116 @findex TYPE_CODE_STRING
23117 @findex gdb.TYPE_CODE_STRING
23118 @item gdb.TYPE_CODE_STRING
23119 A string type. Note that this is only used for certain languages with
23120 language-defined string types; C strings are not represented this way.
23122 @findex TYPE_CODE_BITSTRING
23123 @findex gdb.TYPE_CODE_BITSTRING
23124 @item gdb.TYPE_CODE_BITSTRING
23127 @findex TYPE_CODE_ERROR
23128 @findex gdb.TYPE_CODE_ERROR
23129 @item gdb.TYPE_CODE_ERROR
23130 An unknown or erroneous type.
23132 @findex TYPE_CODE_METHOD
23133 @findex gdb.TYPE_CODE_METHOD
23134 @item gdb.TYPE_CODE_METHOD
23135 A method type, as found in C@t{++} or Java.
23137 @findex TYPE_CODE_METHODPTR
23138 @findex gdb.TYPE_CODE_METHODPTR
23139 @item gdb.TYPE_CODE_METHODPTR
23140 A pointer-to-member-function.
23142 @findex TYPE_CODE_MEMBERPTR
23143 @findex gdb.TYPE_CODE_MEMBERPTR
23144 @item gdb.TYPE_CODE_MEMBERPTR
23145 A pointer-to-member.
23147 @findex TYPE_CODE_REF
23148 @findex gdb.TYPE_CODE_REF
23149 @item gdb.TYPE_CODE_REF
23152 @findex TYPE_CODE_CHAR
23153 @findex gdb.TYPE_CODE_CHAR
23154 @item gdb.TYPE_CODE_CHAR
23157 @findex TYPE_CODE_BOOL
23158 @findex gdb.TYPE_CODE_BOOL
23159 @item gdb.TYPE_CODE_BOOL
23162 @findex TYPE_CODE_COMPLEX
23163 @findex gdb.TYPE_CODE_COMPLEX
23164 @item gdb.TYPE_CODE_COMPLEX
23165 A complex float type.
23167 @findex TYPE_CODE_TYPEDEF
23168 @findex gdb.TYPE_CODE_TYPEDEF
23169 @item gdb.TYPE_CODE_TYPEDEF
23170 A typedef to some other type.
23172 @findex TYPE_CODE_NAMESPACE
23173 @findex gdb.TYPE_CODE_NAMESPACE
23174 @item gdb.TYPE_CODE_NAMESPACE
23175 A C@t{++} namespace.
23177 @findex TYPE_CODE_DECFLOAT
23178 @findex gdb.TYPE_CODE_DECFLOAT
23179 @item gdb.TYPE_CODE_DECFLOAT
23180 A decimal floating point type.
23182 @findex TYPE_CODE_INTERNAL_FUNCTION
23183 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23184 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23185 A function internal to @value{GDBN}. This is the type used to represent
23186 convenience functions.
23189 Further support for types is provided in the @code{gdb.types}
23190 Python module (@pxref{gdb.types}).
23192 @node Pretty Printing API
23193 @subsubsection Pretty Printing API
23195 An example output is provided (@pxref{Pretty Printing}).
23197 A pretty-printer is just an object that holds a value and implements a
23198 specific interface, defined here.
23200 @defun pretty_printer.children (self)
23201 @value{GDBN} will call this method on a pretty-printer to compute the
23202 children of the pretty-printer's value.
23204 This method must return an object conforming to the Python iterator
23205 protocol. Each item returned by the iterator must be a tuple holding
23206 two elements. The first element is the ``name'' of the child; the
23207 second element is the child's value. The value can be any Python
23208 object which is convertible to a @value{GDBN} value.
23210 This method is optional. If it does not exist, @value{GDBN} will act
23211 as though the value has no children.
23214 @defun pretty_printer.display_hint (self)
23215 The CLI may call this method and use its result to change the
23216 formatting of a value. The result will also be supplied to an MI
23217 consumer as a @samp{displayhint} attribute of the variable being
23220 This method is optional. If it does exist, this method must return a
23223 Some display hints are predefined by @value{GDBN}:
23227 Indicate that the object being printed is ``array-like''. The CLI
23228 uses this to respect parameters such as @code{set print elements} and
23229 @code{set print array}.
23232 Indicate that the object being printed is ``map-like'', and that the
23233 children of this value can be assumed to alternate between keys and
23237 Indicate that the object being printed is ``string-like''. If the
23238 printer's @code{to_string} method returns a Python string of some
23239 kind, then @value{GDBN} will call its internal language-specific
23240 string-printing function to format the string. For the CLI this means
23241 adding quotation marks, possibly escaping some characters, respecting
23242 @code{set print elements}, and the like.
23246 @defun pretty_printer.to_string (self)
23247 @value{GDBN} will call this method to display the string
23248 representation of the value passed to the object's constructor.
23250 When printing from the CLI, if the @code{to_string} method exists,
23251 then @value{GDBN} will prepend its result to the values returned by
23252 @code{children}. Exactly how this formatting is done is dependent on
23253 the display hint, and may change as more hints are added. Also,
23254 depending on the print settings (@pxref{Print Settings}), the CLI may
23255 print just the result of @code{to_string} in a stack trace, omitting
23256 the result of @code{children}.
23258 If this method returns a string, it is printed verbatim.
23260 Otherwise, if this method returns an instance of @code{gdb.Value},
23261 then @value{GDBN} prints this value. This may result in a call to
23262 another pretty-printer.
23264 If instead the method returns a Python value which is convertible to a
23265 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
23266 the resulting value. Again, this may result in a call to another
23267 pretty-printer. Python scalars (integers, floats, and booleans) and
23268 strings are convertible to @code{gdb.Value}; other types are not.
23270 Finally, if this method returns @code{None} then no further operations
23271 are peformed in this method and nothing is printed.
23273 If the result is not one of these types, an exception is raised.
23276 @value{GDBN} provides a function which can be used to look up the
23277 default pretty-printer for a @code{gdb.Value}:
23279 @findex gdb.default_visualizer
23280 @defun gdb.default_visualizer (value)
23281 This function takes a @code{gdb.Value} object as an argument. If a
23282 pretty-printer for this value exists, then it is returned. If no such
23283 printer exists, then this returns @code{None}.
23286 @node Selecting Pretty-Printers
23287 @subsubsection Selecting Pretty-Printers
23289 The Python list @code{gdb.pretty_printers} contains an array of
23290 functions or callable objects that have been registered via addition
23291 as a pretty-printer. Printers in this list are called @code{global}
23292 printers, they're available when debugging all inferiors.
23293 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
23294 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
23297 Each function on these lists is passed a single @code{gdb.Value}
23298 argument and should return a pretty-printer object conforming to the
23299 interface definition above (@pxref{Pretty Printing API}). If a function
23300 cannot create a pretty-printer for the value, it should return
23303 @value{GDBN} first checks the @code{pretty_printers} attribute of each
23304 @code{gdb.Objfile} in the current program space and iteratively calls
23305 each enabled lookup routine in the list for that @code{gdb.Objfile}
23306 until it receives a pretty-printer object.
23307 If no pretty-printer is found in the objfile lists, @value{GDBN} then
23308 searches the pretty-printer list of the current program space,
23309 calling each enabled function until an object is returned.
23310 After these lists have been exhausted, it tries the global
23311 @code{gdb.pretty_printers} list, again calling each enabled function until an
23312 object is returned.
23314 The order in which the objfiles are searched is not specified. For a
23315 given list, functions are always invoked from the head of the list,
23316 and iterated over sequentially until the end of the list, or a printer
23317 object is returned.
23319 For various reasons a pretty-printer may not work.
23320 For example, the underlying data structure may have changed and
23321 the pretty-printer is out of date.
23323 The consequences of a broken pretty-printer are severe enough that
23324 @value{GDBN} provides support for enabling and disabling individual
23325 printers. For example, if @code{print frame-arguments} is on,
23326 a backtrace can become highly illegible if any argument is printed
23327 with a broken printer.
23329 Pretty-printers are enabled and disabled by attaching an @code{enabled}
23330 attribute to the registered function or callable object. If this attribute
23331 is present and its value is @code{False}, the printer is disabled, otherwise
23332 the printer is enabled.
23334 @node Writing a Pretty-Printer
23335 @subsubsection Writing a Pretty-Printer
23336 @cindex writing a pretty-printer
23338 A pretty-printer consists of two parts: a lookup function to detect
23339 if the type is supported, and the printer itself.
23341 Here is an example showing how a @code{std::string} printer might be
23342 written. @xref{Pretty Printing API}, for details on the API this class
23346 class StdStringPrinter(object):
23347 "Print a std::string"
23349 def __init__(self, val):
23352 def to_string(self):
23353 return self.val['_M_dataplus']['_M_p']
23355 def display_hint(self):
23359 And here is an example showing how a lookup function for the printer
23360 example above might be written.
23363 def str_lookup_function(val):
23364 lookup_tag = val.type.tag
23365 if lookup_tag == None:
23367 regex = re.compile("^std::basic_string<char,.*>$")
23368 if regex.match(lookup_tag):
23369 return StdStringPrinter(val)
23373 The example lookup function extracts the value's type, and attempts to
23374 match it to a type that it can pretty-print. If it is a type the
23375 printer can pretty-print, it will return a printer object. If not, it
23376 returns @code{None}.
23378 We recommend that you put your core pretty-printers into a Python
23379 package. If your pretty-printers are for use with a library, we
23380 further recommend embedding a version number into the package name.
23381 This practice will enable @value{GDBN} to load multiple versions of
23382 your pretty-printers at the same time, because they will have
23385 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
23386 can be evaluated multiple times without changing its meaning. An
23387 ideal auto-load file will consist solely of @code{import}s of your
23388 printer modules, followed by a call to a register pretty-printers with
23389 the current objfile.
23391 Taken as a whole, this approach will scale nicely to multiple
23392 inferiors, each potentially using a different library version.
23393 Embedding a version number in the Python package name will ensure that
23394 @value{GDBN} is able to load both sets of printers simultaneously.
23395 Then, because the search for pretty-printers is done by objfile, and
23396 because your auto-loaded code took care to register your library's
23397 printers with a specific objfile, @value{GDBN} will find the correct
23398 printers for the specific version of the library used by each
23401 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
23402 this code might appear in @code{gdb.libstdcxx.v6}:
23405 def register_printers(objfile):
23406 objfile.pretty_printers.append(str_lookup_function)
23410 And then the corresponding contents of the auto-load file would be:
23413 import gdb.libstdcxx.v6
23414 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
23417 The previous example illustrates a basic pretty-printer.
23418 There are a few things that can be improved on.
23419 The printer doesn't have a name, making it hard to identify in a
23420 list of installed printers. The lookup function has a name, but
23421 lookup functions can have arbitrary, even identical, names.
23423 Second, the printer only handles one type, whereas a library typically has
23424 several types. One could install a lookup function for each desired type
23425 in the library, but one could also have a single lookup function recognize
23426 several types. The latter is the conventional way this is handled.
23427 If a pretty-printer can handle multiple data types, then its
23428 @dfn{subprinters} are the printers for the individual data types.
23430 The @code{gdb.printing} module provides a formal way of solving these
23431 problems (@pxref{gdb.printing}).
23432 Here is another example that handles multiple types.
23434 These are the types we are going to pretty-print:
23437 struct foo @{ int a, b; @};
23438 struct bar @{ struct foo x, y; @};
23441 Here are the printers:
23445 """Print a foo object."""
23447 def __init__(self, val):
23450 def to_string(self):
23451 return ("a=<" + str(self.val["a"]) +
23452 "> b=<" + str(self.val["b"]) + ">")
23455 """Print a bar object."""
23457 def __init__(self, val):
23460 def to_string(self):
23461 return ("x=<" + str(self.val["x"]) +
23462 "> y=<" + str(self.val["y"]) + ">")
23465 This example doesn't need a lookup function, that is handled by the
23466 @code{gdb.printing} module. Instead a function is provided to build up
23467 the object that handles the lookup.
23470 import gdb.printing
23472 def build_pretty_printer():
23473 pp = gdb.printing.RegexpCollectionPrettyPrinter(
23475 pp.add_printer('foo', '^foo$', fooPrinter)
23476 pp.add_printer('bar', '^bar$', barPrinter)
23480 And here is the autoload support:
23483 import gdb.printing
23485 gdb.printing.register_pretty_printer(
23486 gdb.current_objfile(),
23487 my_library.build_pretty_printer())
23490 Finally, when this printer is loaded into @value{GDBN}, here is the
23491 corresponding output of @samp{info pretty-printer}:
23494 (gdb) info pretty-printer
23501 @node Inferiors In Python
23502 @subsubsection Inferiors In Python
23503 @cindex inferiors in Python
23505 @findex gdb.Inferior
23506 Programs which are being run under @value{GDBN} are called inferiors
23507 (@pxref{Inferiors and Programs}). Python scripts can access
23508 information about and manipulate inferiors controlled by @value{GDBN}
23509 via objects of the @code{gdb.Inferior} class.
23511 The following inferior-related functions are available in the @code{gdb}
23514 @defun gdb.inferiors ()
23515 Return a tuple containing all inferior objects.
23518 @defun gdb.selected_inferior ()
23519 Return an object representing the current inferior.
23522 A @code{gdb.Inferior} object has the following attributes:
23525 @defvar Inferior.num
23526 ID of inferior, as assigned by GDB.
23529 @defvar Inferior.pid
23530 Process ID of the inferior, as assigned by the underlying operating
23534 @defvar Inferior.was_attached
23535 Boolean signaling whether the inferior was created using `attach', or
23536 started by @value{GDBN} itself.
23540 A @code{gdb.Inferior} object has the following methods:
23543 @defun Inferior.is_valid ()
23544 Returns @code{True} if the @code{gdb.Inferior} object is valid,
23545 @code{False} if not. A @code{gdb.Inferior} object will become invalid
23546 if the inferior no longer exists within @value{GDBN}. All other
23547 @code{gdb.Inferior} methods will throw an exception if it is invalid
23548 at the time the method is called.
23551 @defun Inferior.threads ()
23552 This method returns a tuple holding all the threads which are valid
23553 when it is called. If there are no valid threads, the method will
23554 return an empty tuple.
23557 @findex gdb.read_memory
23558 @defun Inferior.read_memory (address, length)
23559 Read @var{length} bytes of memory from the inferior, starting at
23560 @var{address}. Returns a buffer object, which behaves much like an array
23561 or a string. It can be modified and given to the @code{gdb.write_memory}
23565 @findex gdb.write_memory
23566 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
23567 Write the contents of @var{buffer} to the inferior, starting at
23568 @var{address}. The @var{buffer} parameter must be a Python object
23569 which supports the buffer protocol, i.e., a string, an array or the
23570 object returned from @code{gdb.read_memory}. If given, @var{length}
23571 determines the number of bytes from @var{buffer} to be written.
23574 @findex gdb.search_memory
23575 @defun Inferior.search_memory (address, length, pattern)
23576 Search a region of the inferior memory starting at @var{address} with
23577 the given @var{length} using the search pattern supplied in
23578 @var{pattern}. The @var{pattern} parameter must be a Python object
23579 which supports the buffer protocol, i.e., a string, an array or the
23580 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
23581 containing the address where the pattern was found, or @code{None} if
23582 the pattern could not be found.
23586 @node Events In Python
23587 @subsubsection Events In Python
23588 @cindex inferior events in Python
23590 @value{GDBN} provides a general event facility so that Python code can be
23591 notified of various state changes, particularly changes that occur in
23594 An @dfn{event} is just an object that describes some state change. The
23595 type of the object and its attributes will vary depending on the details
23596 of the change. All the existing events are described below.
23598 In order to be notified of an event, you must register an event handler
23599 with an @dfn{event registry}. An event registry is an object in the
23600 @code{gdb.events} module which dispatches particular events. A registry
23601 provides methods to register and unregister event handlers:
23604 @defun EventRegistry.connect (object)
23605 Add the given callable @var{object} to the registry. This object will be
23606 called when an event corresponding to this registry occurs.
23609 @defun EventRegistry.disconnect (object)
23610 Remove the given @var{object} from the registry. Once removed, the object
23611 will no longer receive notifications of events.
23615 Here is an example:
23618 def exit_handler (event):
23619 print "event type: exit"
23620 print "exit code: %d" % (event.exit_code)
23622 gdb.events.exited.connect (exit_handler)
23625 In the above example we connect our handler @code{exit_handler} to the
23626 registry @code{events.exited}. Once connected, @code{exit_handler} gets
23627 called when the inferior exits. The argument @dfn{event} in this example is
23628 of type @code{gdb.ExitedEvent}. As you can see in the example the
23629 @code{ExitedEvent} object has an attribute which indicates the exit code of
23632 The following is a listing of the event registries that are available and
23633 details of the events they emit:
23638 Emits @code{gdb.ThreadEvent}.
23640 Some events can be thread specific when @value{GDBN} is running in non-stop
23641 mode. When represented in Python, these events all extend
23642 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
23643 events which are emitted by this or other modules might extend this event.
23644 Examples of these events are @code{gdb.BreakpointEvent} and
23645 @code{gdb.ContinueEvent}.
23648 @defvar ThreadEvent.inferior_thread
23649 In non-stop mode this attribute will be set to the specific thread which was
23650 involved in the emitted event. Otherwise, it will be set to @code{None}.
23654 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
23656 This event indicates that the inferior has been continued after a stop. For
23657 inherited attribute refer to @code{gdb.ThreadEvent} above.
23659 @item events.exited
23660 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
23661 @code{events.ExitedEvent} has two attributes:
23663 @defvar ExitedEvent.exit_code
23664 An integer representing the exit code, if available, which the inferior
23665 has returned. (The exit code could be unavailable if, for example,
23666 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
23667 the attribute does not exist.
23669 @defvar ExitedEvent inferior
23670 A reference to the inferior which triggered the @code{exited} event.
23675 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
23677 Indicates that the inferior has stopped. All events emitted by this registry
23678 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
23679 will indicate the stopped thread when @value{GDBN} is running in non-stop
23680 mode. Refer to @code{gdb.ThreadEvent} above for more details.
23682 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
23684 This event indicates that the inferior or one of its threads has received as
23685 signal. @code{gdb.SignalEvent} has the following attributes:
23688 @defvar SignalEvent.stop_signal
23689 A string representing the signal received by the inferior. A list of possible
23690 signal values can be obtained by running the command @code{info signals} in
23691 the @value{GDBN} command prompt.
23695 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
23697 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
23698 been hit, and has the following attributes:
23701 @defvar BreakpointEvent.breakpoints
23702 A sequence containing references to all the breakpoints (type
23703 @code{gdb.Breakpoint}) that were hit.
23704 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
23706 @defvar BreakpointEvent.breakpoint
23707 A reference to the first breakpoint that was hit.
23708 This function is maintained for backward compatibility and is now deprecated
23709 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
23713 @item events.new_objfile
23714 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
23715 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
23718 @defvar NewObjFileEvent.new_objfile
23719 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
23720 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
23726 @node Threads In Python
23727 @subsubsection Threads In Python
23728 @cindex threads in python
23730 @findex gdb.InferiorThread
23731 Python scripts can access information about, and manipulate inferior threads
23732 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
23734 The following thread-related functions are available in the @code{gdb}
23737 @findex gdb.selected_thread
23738 @defun gdb.selected_thread ()
23739 This function returns the thread object for the selected thread. If there
23740 is no selected thread, this will return @code{None}.
23743 A @code{gdb.InferiorThread} object has the following attributes:
23746 @defvar InferiorThread.name
23747 The name of the thread. If the user specified a name using
23748 @code{thread name}, then this returns that name. Otherwise, if an
23749 OS-supplied name is available, then it is returned. Otherwise, this
23750 returns @code{None}.
23752 This attribute can be assigned to. The new value must be a string
23753 object, which sets the new name, or @code{None}, which removes any
23754 user-specified thread name.
23757 @defvar InferiorThread.num
23758 ID of the thread, as assigned by GDB.
23761 @defvar InferiorThread.ptid
23762 ID of the thread, as assigned by the operating system. This attribute is a
23763 tuple containing three integers. The first is the Process ID (PID); the second
23764 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23765 Either the LWPID or TID may be 0, which indicates that the operating system
23766 does not use that identifier.
23770 A @code{gdb.InferiorThread} object has the following methods:
23773 @defun InferiorThread.is_valid ()
23774 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23775 @code{False} if not. A @code{gdb.InferiorThread} object will become
23776 invalid if the thread exits, or the inferior that the thread belongs
23777 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23778 exception if it is invalid at the time the method is called.
23781 @defun InferiorThread.switch ()
23782 This changes @value{GDBN}'s currently selected thread to the one represented
23786 @defun InferiorThread.is_stopped ()
23787 Return a Boolean indicating whether the thread is stopped.
23790 @defun InferiorThread.is_running ()
23791 Return a Boolean indicating whether the thread is running.
23794 @defun InferiorThread.is_exited ()
23795 Return a Boolean indicating whether the thread is exited.
23799 @node Commands In Python
23800 @subsubsection Commands In Python
23802 @cindex commands in python
23803 @cindex python commands
23804 You can implement new @value{GDBN} CLI commands in Python. A CLI
23805 command is implemented using an instance of the @code{gdb.Command}
23806 class, most commonly using a subclass.
23808 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23809 The object initializer for @code{Command} registers the new command
23810 with @value{GDBN}. This initializer is normally invoked from the
23811 subclass' own @code{__init__} method.
23813 @var{name} is the name of the command. If @var{name} consists of
23814 multiple words, then the initial words are looked for as prefix
23815 commands. In this case, if one of the prefix commands does not exist,
23816 an exception is raised.
23818 There is no support for multi-line commands.
23820 @var{command_class} should be one of the @samp{COMMAND_} constants
23821 defined below. This argument tells @value{GDBN} how to categorize the
23822 new command in the help system.
23824 @var{completer_class} is an optional argument. If given, it should be
23825 one of the @samp{COMPLETE_} constants defined below. This argument
23826 tells @value{GDBN} how to perform completion for this command. If not
23827 given, @value{GDBN} will attempt to complete using the object's
23828 @code{complete} method (see below); if no such method is found, an
23829 error will occur when completion is attempted.
23831 @var{prefix} is an optional argument. If @code{True}, then the new
23832 command is a prefix command; sub-commands of this command may be
23835 The help text for the new command is taken from the Python
23836 documentation string for the command's class, if there is one. If no
23837 documentation string is provided, the default value ``This command is
23838 not documented.'' is used.
23841 @cindex don't repeat Python command
23842 @defun Command.dont_repeat ()
23843 By default, a @value{GDBN} command is repeated when the user enters a
23844 blank line at the command prompt. A command can suppress this
23845 behavior by invoking the @code{dont_repeat} method. This is similar
23846 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23849 @defun Command.invoke (argument, from_tty)
23850 This method is called by @value{GDBN} when this command is invoked.
23852 @var{argument} is a string. It is the argument to the command, after
23853 leading and trailing whitespace has been stripped.
23855 @var{from_tty} is a boolean argument. When true, this means that the
23856 command was entered by the user at the terminal; when false it means
23857 that the command came from elsewhere.
23859 If this method throws an exception, it is turned into a @value{GDBN}
23860 @code{error} call. Otherwise, the return value is ignored.
23862 @findex gdb.string_to_argv
23863 To break @var{argument} up into an argv-like string use
23864 @code{gdb.string_to_argv}. This function behaves identically to
23865 @value{GDBN}'s internal argument lexer @code{buildargv}.
23866 It is recommended to use this for consistency.
23867 Arguments are separated by spaces and may be quoted.
23871 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23872 ['1', '2 "3', '4 "5', "6 '7"]
23877 @cindex completion of Python commands
23878 @defun Command.complete (text, word)
23879 This method is called by @value{GDBN} when the user attempts
23880 completion on this command. All forms of completion are handled by
23881 this method, that is, the @key{TAB} and @key{M-?} key bindings
23882 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23885 The arguments @var{text} and @var{word} are both strings. @var{text}
23886 holds the complete command line up to the cursor's location.
23887 @var{word} holds the last word of the command line; this is computed
23888 using a word-breaking heuristic.
23890 The @code{complete} method can return several values:
23893 If the return value is a sequence, the contents of the sequence are
23894 used as the completions. It is up to @code{complete} to ensure that the
23895 contents actually do complete the word. A zero-length sequence is
23896 allowed, it means that there were no completions available. Only
23897 string elements of the sequence are used; other elements in the
23898 sequence are ignored.
23901 If the return value is one of the @samp{COMPLETE_} constants defined
23902 below, then the corresponding @value{GDBN}-internal completion
23903 function is invoked, and its result is used.
23906 All other results are treated as though there were no available
23911 When a new command is registered, it must be declared as a member of
23912 some general class of commands. This is used to classify top-level
23913 commands in the on-line help system; note that prefix commands are not
23914 listed under their own category but rather that of their top-level
23915 command. The available classifications are represented by constants
23916 defined in the @code{gdb} module:
23919 @findex COMMAND_NONE
23920 @findex gdb.COMMAND_NONE
23921 @item gdb.COMMAND_NONE
23922 The command does not belong to any particular class. A command in
23923 this category will not be displayed in any of the help categories.
23925 @findex COMMAND_RUNNING
23926 @findex gdb.COMMAND_RUNNING
23927 @item gdb.COMMAND_RUNNING
23928 The command is related to running the inferior. For example,
23929 @code{start}, @code{step}, and @code{continue} are in this category.
23930 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23931 commands in this category.
23933 @findex COMMAND_DATA
23934 @findex gdb.COMMAND_DATA
23935 @item gdb.COMMAND_DATA
23936 The command is related to data or variables. For example,
23937 @code{call}, @code{find}, and @code{print} are in this category. Type
23938 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23941 @findex COMMAND_STACK
23942 @findex gdb.COMMAND_STACK
23943 @item gdb.COMMAND_STACK
23944 The command has to do with manipulation of the stack. For example,
23945 @code{backtrace}, @code{frame}, and @code{return} are in this
23946 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23947 list of commands in this category.
23949 @findex COMMAND_FILES
23950 @findex gdb.COMMAND_FILES
23951 @item gdb.COMMAND_FILES
23952 This class is used for file-related commands. For example,
23953 @code{file}, @code{list} and @code{section} are in this category.
23954 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23955 commands in this category.
23957 @findex COMMAND_SUPPORT
23958 @findex gdb.COMMAND_SUPPORT
23959 @item gdb.COMMAND_SUPPORT
23960 This should be used for ``support facilities'', generally meaning
23961 things that are useful to the user when interacting with @value{GDBN},
23962 but not related to the state of the inferior. For example,
23963 @code{help}, @code{make}, and @code{shell} are in this category. Type
23964 @kbd{help support} at the @value{GDBN} prompt to see a list of
23965 commands in this category.
23967 @findex COMMAND_STATUS
23968 @findex gdb.COMMAND_STATUS
23969 @item gdb.COMMAND_STATUS
23970 The command is an @samp{info}-related command, that is, related to the
23971 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23972 and @code{show} are in this category. Type @kbd{help status} at the
23973 @value{GDBN} prompt to see a list of commands in this category.
23975 @findex COMMAND_BREAKPOINTS
23976 @findex gdb.COMMAND_BREAKPOINTS
23977 @item gdb.COMMAND_BREAKPOINTS
23978 The command has to do with breakpoints. For example, @code{break},
23979 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23980 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23983 @findex COMMAND_TRACEPOINTS
23984 @findex gdb.COMMAND_TRACEPOINTS
23985 @item gdb.COMMAND_TRACEPOINTS
23986 The command has to do with tracepoints. For example, @code{trace},
23987 @code{actions}, and @code{tfind} are in this category. Type
23988 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23989 commands in this category.
23991 @findex COMMAND_USER
23992 @findex gdb.COMMAND_USER
23993 @item gdb.COMMAND_USER
23994 The command is a general purpose command for the user, and typically
23995 does not fit in one of the other categories.
23996 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
23997 a list of commands in this category, as well as the list of gdb macros
23998 (@pxref{Sequences}).
24000 @findex COMMAND_OBSCURE
24001 @findex gdb.COMMAND_OBSCURE
24002 @item gdb.COMMAND_OBSCURE
24003 The command is only used in unusual circumstances, or is not of
24004 general interest to users. For example, @code{checkpoint},
24005 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24006 obscure} at the @value{GDBN} prompt to see a list of commands in this
24009 @findex COMMAND_MAINTENANCE
24010 @findex gdb.COMMAND_MAINTENANCE
24011 @item gdb.COMMAND_MAINTENANCE
24012 The command is only useful to @value{GDBN} maintainers. The
24013 @code{maintenance} and @code{flushregs} commands are in this category.
24014 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24015 commands in this category.
24018 A new command can use a predefined completion function, either by
24019 specifying it via an argument at initialization, or by returning it
24020 from the @code{complete} method. These predefined completion
24021 constants are all defined in the @code{gdb} module:
24024 @findex COMPLETE_NONE
24025 @findex gdb.COMPLETE_NONE
24026 @item gdb.COMPLETE_NONE
24027 This constant means that no completion should be done.
24029 @findex COMPLETE_FILENAME
24030 @findex gdb.COMPLETE_FILENAME
24031 @item gdb.COMPLETE_FILENAME
24032 This constant means that filename completion should be performed.
24034 @findex COMPLETE_LOCATION
24035 @findex gdb.COMPLETE_LOCATION
24036 @item gdb.COMPLETE_LOCATION
24037 This constant means that location completion should be done.
24038 @xref{Specify Location}.
24040 @findex COMPLETE_COMMAND
24041 @findex gdb.COMPLETE_COMMAND
24042 @item gdb.COMPLETE_COMMAND
24043 This constant means that completion should examine @value{GDBN}
24046 @findex COMPLETE_SYMBOL
24047 @findex gdb.COMPLETE_SYMBOL
24048 @item gdb.COMPLETE_SYMBOL
24049 This constant means that completion should be done using symbol names
24053 The following code snippet shows how a trivial CLI command can be
24054 implemented in Python:
24057 class HelloWorld (gdb.Command):
24058 """Greet the whole world."""
24060 def __init__ (self):
24061 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24063 def invoke (self, arg, from_tty):
24064 print "Hello, World!"
24069 The last line instantiates the class, and is necessary to trigger the
24070 registration of the command with @value{GDBN}. Depending on how the
24071 Python code is read into @value{GDBN}, you may need to import the
24072 @code{gdb} module explicitly.
24074 @node Parameters In Python
24075 @subsubsection Parameters In Python
24077 @cindex parameters in python
24078 @cindex python parameters
24079 @tindex gdb.Parameter
24081 You can implement new @value{GDBN} parameters using Python. A new
24082 parameter is implemented as an instance of the @code{gdb.Parameter}
24085 Parameters are exposed to the user via the @code{set} and
24086 @code{show} commands. @xref{Help}.
24088 There are many parameters that already exist and can be set in
24089 @value{GDBN}. Two examples are: @code{set follow fork} and
24090 @code{set charset}. Setting these parameters influences certain
24091 behavior in @value{GDBN}. Similarly, you can define parameters that
24092 can be used to influence behavior in custom Python scripts and commands.
24094 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24095 The object initializer for @code{Parameter} registers the new
24096 parameter with @value{GDBN}. This initializer is normally invoked
24097 from the subclass' own @code{__init__} method.
24099 @var{name} is the name of the new parameter. If @var{name} consists
24100 of multiple words, then the initial words are looked for as prefix
24101 parameters. An example of this can be illustrated with the
24102 @code{set print} set of parameters. If @var{name} is
24103 @code{print foo}, then @code{print} will be searched as the prefix
24104 parameter. In this case the parameter can subsequently be accessed in
24105 @value{GDBN} as @code{set print foo}.
24107 If @var{name} consists of multiple words, and no prefix parameter group
24108 can be found, an exception is raised.
24110 @var{command-class} should be one of the @samp{COMMAND_} constants
24111 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24112 categorize the new parameter in the help system.
24114 @var{parameter-class} should be one of the @samp{PARAM_} constants
24115 defined below. This argument tells @value{GDBN} the type of the new
24116 parameter; this information is used for input validation and
24119 If @var{parameter-class} is @code{PARAM_ENUM}, then
24120 @var{enum-sequence} must be a sequence of strings. These strings
24121 represent the possible values for the parameter.
24123 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24124 of a fourth argument will cause an exception to be thrown.
24126 The help text for the new parameter is taken from the Python
24127 documentation string for the parameter's class, if there is one. If
24128 there is no documentation string, a default value is used.
24131 @defvar Parameter.set_doc
24132 If this attribute exists, and is a string, then its value is used as
24133 the help text for this parameter's @code{set} command. The value is
24134 examined when @code{Parameter.__init__} is invoked; subsequent changes
24138 @defvar Parameter.show_doc
24139 If this attribute exists, and is a string, then its value is used as
24140 the help text for this parameter's @code{show} command. The value is
24141 examined when @code{Parameter.__init__} is invoked; subsequent changes
24145 @defvar Parameter.value
24146 The @code{value} attribute holds the underlying value of the
24147 parameter. It can be read and assigned to just as any other
24148 attribute. @value{GDBN} does validation when assignments are made.
24151 There are two methods that should be implemented in any
24152 @code{Parameter} class. These are:
24154 @defun Parameter.get_set_string (self)
24155 @value{GDBN} will call this method when a @var{parameter}'s value has
24156 been changed via the @code{set} API (for example, @kbd{set foo off}).
24157 The @code{value} attribute has already been populated with the new
24158 value and may be used in output. This method must return a string.
24161 @defun Parameter.get_show_string (self, svalue)
24162 @value{GDBN} will call this method when a @var{parameter}'s
24163 @code{show} API has been invoked (for example, @kbd{show foo}). The
24164 argument @code{svalue} receives the string representation of the
24165 current value. This method must return a string.
24168 When a new parameter is defined, its type must be specified. The
24169 available types are represented by constants defined in the @code{gdb}
24173 @findex PARAM_BOOLEAN
24174 @findex gdb.PARAM_BOOLEAN
24175 @item gdb.PARAM_BOOLEAN
24176 The value is a plain boolean. The Python boolean values, @code{True}
24177 and @code{False} are the only valid values.
24179 @findex PARAM_AUTO_BOOLEAN
24180 @findex gdb.PARAM_AUTO_BOOLEAN
24181 @item gdb.PARAM_AUTO_BOOLEAN
24182 The value has three possible states: true, false, and @samp{auto}. In
24183 Python, true and false are represented using boolean constants, and
24184 @samp{auto} is represented using @code{None}.
24186 @findex PARAM_UINTEGER
24187 @findex gdb.PARAM_UINTEGER
24188 @item gdb.PARAM_UINTEGER
24189 The value is an unsigned integer. The value of 0 should be
24190 interpreted to mean ``unlimited''.
24192 @findex PARAM_INTEGER
24193 @findex gdb.PARAM_INTEGER
24194 @item gdb.PARAM_INTEGER
24195 The value is a signed integer. The value of 0 should be interpreted
24196 to mean ``unlimited''.
24198 @findex PARAM_STRING
24199 @findex gdb.PARAM_STRING
24200 @item gdb.PARAM_STRING
24201 The value is a string. When the user modifies the string, any escape
24202 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
24203 translated into corresponding characters and encoded into the current
24206 @findex PARAM_STRING_NOESCAPE
24207 @findex gdb.PARAM_STRING_NOESCAPE
24208 @item gdb.PARAM_STRING_NOESCAPE
24209 The value is a string. When the user modifies the string, escapes are
24210 passed through untranslated.
24212 @findex PARAM_OPTIONAL_FILENAME
24213 @findex gdb.PARAM_OPTIONAL_FILENAME
24214 @item gdb.PARAM_OPTIONAL_FILENAME
24215 The value is a either a filename (a string), or @code{None}.
24217 @findex PARAM_FILENAME
24218 @findex gdb.PARAM_FILENAME
24219 @item gdb.PARAM_FILENAME
24220 The value is a filename. This is just like
24221 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
24223 @findex PARAM_ZINTEGER
24224 @findex gdb.PARAM_ZINTEGER
24225 @item gdb.PARAM_ZINTEGER
24226 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
24227 is interpreted as itself.
24230 @findex gdb.PARAM_ENUM
24231 @item gdb.PARAM_ENUM
24232 The value is a string, which must be one of a collection string
24233 constants provided when the parameter is created.
24236 @node Functions In Python
24237 @subsubsection Writing new convenience functions
24239 @cindex writing convenience functions
24240 @cindex convenience functions in python
24241 @cindex python convenience functions
24242 @tindex gdb.Function
24244 You can implement new convenience functions (@pxref{Convenience Vars})
24245 in Python. A convenience function is an instance of a subclass of the
24246 class @code{gdb.Function}.
24248 @defun Function.__init__ (name)
24249 The initializer for @code{Function} registers the new function with
24250 @value{GDBN}. The argument @var{name} is the name of the function,
24251 a string. The function will be visible to the user as a convenience
24252 variable of type @code{internal function}, whose name is the same as
24253 the given @var{name}.
24255 The documentation for the new function is taken from the documentation
24256 string for the new class.
24259 @defun Function.invoke (@var{*args})
24260 When a convenience function is evaluated, its arguments are converted
24261 to instances of @code{gdb.Value}, and then the function's
24262 @code{invoke} method is called. Note that @value{GDBN} does not
24263 predetermine the arity of convenience functions. Instead, all
24264 available arguments are passed to @code{invoke}, following the
24265 standard Python calling convention. In particular, a convenience
24266 function can have default values for parameters without ill effect.
24268 The return value of this method is used as its value in the enclosing
24269 expression. If an ordinary Python value is returned, it is converted
24270 to a @code{gdb.Value} following the usual rules.
24273 The following code snippet shows how a trivial convenience function can
24274 be implemented in Python:
24277 class Greet (gdb.Function):
24278 """Return string to greet someone.
24279 Takes a name as argument."""
24281 def __init__ (self):
24282 super (Greet, self).__init__ ("greet")
24284 def invoke (self, name):
24285 return "Hello, %s!" % name.string ()
24290 The last line instantiates the class, and is necessary to trigger the
24291 registration of the function with @value{GDBN}. Depending on how the
24292 Python code is read into @value{GDBN}, you may need to import the
24293 @code{gdb} module explicitly.
24295 @node Progspaces In Python
24296 @subsubsection Program Spaces In Python
24298 @cindex progspaces in python
24299 @tindex gdb.Progspace
24301 A program space, or @dfn{progspace}, represents a symbolic view
24302 of an address space.
24303 It consists of all of the objfiles of the program.
24304 @xref{Objfiles In Python}.
24305 @xref{Inferiors and Programs, program spaces}, for more details
24306 about program spaces.
24308 The following progspace-related functions are available in the
24311 @findex gdb.current_progspace
24312 @defun gdb.current_progspace ()
24313 This function returns the program space of the currently selected inferior.
24314 @xref{Inferiors and Programs}.
24317 @findex gdb.progspaces
24318 @defun gdb.progspaces ()
24319 Return a sequence of all the progspaces currently known to @value{GDBN}.
24322 Each progspace is represented by an instance of the @code{gdb.Progspace}
24325 @defvar Progspace.filename
24326 The file name of the progspace as a string.
24329 @defvar Progspace.pretty_printers
24330 The @code{pretty_printers} attribute is a list of functions. It is
24331 used to look up pretty-printers. A @code{Value} is passed to each
24332 function in order; if the function returns @code{None}, then the
24333 search continues. Otherwise, the return value should be an object
24334 which is used to format the value. @xref{Pretty Printing API}, for more
24338 @node Objfiles In Python
24339 @subsubsection Objfiles In Python
24341 @cindex objfiles in python
24342 @tindex gdb.Objfile
24344 @value{GDBN} loads symbols for an inferior from various
24345 symbol-containing files (@pxref{Files}). These include the primary
24346 executable file, any shared libraries used by the inferior, and any
24347 separate debug info files (@pxref{Separate Debug Files}).
24348 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
24350 The following objfile-related functions are available in the
24353 @findex gdb.current_objfile
24354 @defun gdb.current_objfile ()
24355 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
24356 sets the ``current objfile'' to the corresponding objfile. This
24357 function returns the current objfile. If there is no current objfile,
24358 this function returns @code{None}.
24361 @findex gdb.objfiles
24362 @defun gdb.objfiles ()
24363 Return a sequence of all the objfiles current known to @value{GDBN}.
24364 @xref{Objfiles In Python}.
24367 Each objfile is represented by an instance of the @code{gdb.Objfile}
24370 @defvar Objfile.filename
24371 The file name of the objfile as a string.
24374 @defvar Objfile.pretty_printers
24375 The @code{pretty_printers} attribute is a list of functions. It is
24376 used to look up pretty-printers. A @code{Value} is passed to each
24377 function in order; if the function returns @code{None}, then the
24378 search continues. Otherwise, the return value should be an object
24379 which is used to format the value. @xref{Pretty Printing API}, for more
24383 A @code{gdb.Objfile} object has the following methods:
24385 @defun Objfile.is_valid ()
24386 Returns @code{True} if the @code{gdb.Objfile} object is valid,
24387 @code{False} if not. A @code{gdb.Objfile} object can become invalid
24388 if the object file it refers to is not loaded in @value{GDBN} any
24389 longer. All other @code{gdb.Objfile} methods will throw an exception
24390 if it is invalid at the time the method is called.
24393 @node Frames In Python
24394 @subsubsection Accessing inferior stack frames from Python.
24396 @cindex frames in python
24397 When the debugged program stops, @value{GDBN} is able to analyze its call
24398 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
24399 represents a frame in the stack. A @code{gdb.Frame} object is only valid
24400 while its corresponding frame exists in the inferior's stack. If you try
24401 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
24402 exception (@pxref{Exception Handling}).
24404 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
24408 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
24412 The following frame-related functions are available in the @code{gdb} module:
24414 @findex gdb.selected_frame
24415 @defun gdb.selected_frame ()
24416 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
24419 @findex gdb.newest_frame
24420 @defun gdb.newest_frame ()
24421 Return the newest frame object for the selected thread.
24424 @defun gdb.frame_stop_reason_string (reason)
24425 Return a string explaining the reason why @value{GDBN} stopped unwinding
24426 frames, as expressed by the given @var{reason} code (an integer, see the
24427 @code{unwind_stop_reason} method further down in this section).
24430 A @code{gdb.Frame} object has the following methods:
24433 @defun Frame.is_valid ()
24434 Returns true if the @code{gdb.Frame} object is valid, false if not.
24435 A frame object can become invalid if the frame it refers to doesn't
24436 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
24437 an exception if it is invalid at the time the method is called.
24440 @defun Frame.name ()
24441 Returns the function name of the frame, or @code{None} if it can't be
24445 @defun Frame.type ()
24446 Returns the type of the frame. The value can be one of:
24448 @item gdb.NORMAL_FRAME
24449 An ordinary stack frame.
24451 @item gdb.DUMMY_FRAME
24452 A fake stack frame that was created by @value{GDBN} when performing an
24453 inferior function call.
24455 @item gdb.INLINE_FRAME
24456 A frame representing an inlined function. The function was inlined
24457 into a @code{gdb.NORMAL_FRAME} that is older than this one.
24459 @item gdb.TAILCALL_FRAME
24460 A frame representing a tail call. @xref{Tail Call Frames}.
24462 @item gdb.SIGTRAMP_FRAME
24463 A signal trampoline frame. This is the frame created by the OS when
24464 it calls into a signal handler.
24466 @item gdb.ARCH_FRAME
24467 A fake stack frame representing a cross-architecture call.
24469 @item gdb.SENTINEL_FRAME
24470 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
24475 @defun Frame.unwind_stop_reason ()
24476 Return an integer representing the reason why it's not possible to find
24477 more frames toward the outermost frame. Use
24478 @code{gdb.frame_stop_reason_string} to convert the value returned by this
24479 function to a string. The value can be one of:
24482 @item gdb.FRAME_UNWIND_NO_REASON
24483 No particular reason (older frames should be available).
24485 @item gdb.FRAME_UNWIND_NULL_ID
24486 The previous frame's analyzer returns an invalid result.
24488 @item gdb.FRAME_UNWIND_OUTERMOST
24489 This frame is the outermost.
24491 @item gdb.FRAME_UNWIND_UNAVAILABLE
24492 Cannot unwind further, because that would require knowing the
24493 values of registers or memory that have not been collected.
24495 @item gdb.FRAME_UNWIND_INNER_ID
24496 This frame ID looks like it ought to belong to a NEXT frame,
24497 but we got it for a PREV frame. Normally, this is a sign of
24498 unwinder failure. It could also indicate stack corruption.
24500 @item gdb.FRAME_UNWIND_SAME_ID
24501 This frame has the same ID as the previous one. That means
24502 that unwinding further would almost certainly give us another
24503 frame with exactly the same ID, so break the chain. Normally,
24504 this is a sign of unwinder failure. It could also indicate
24507 @item gdb.FRAME_UNWIND_NO_SAVED_PC
24508 The frame unwinder did not find any saved PC, but we needed
24509 one to unwind further.
24511 @item gdb.FRAME_UNWIND_FIRST_ERROR
24512 Any stop reason greater or equal to this value indicates some kind
24513 of error. This special value facilitates writing code that tests
24514 for errors in unwinding in a way that will work correctly even if
24515 the list of the other values is modified in future @value{GDBN}
24516 versions. Using it, you could write:
24518 reason = gdb.selected_frame().unwind_stop_reason ()
24519 reason_str = gdb.frame_stop_reason_string (reason)
24520 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
24521 print "An error occured: %s" % reason_str
24528 Returns the frame's resume address.
24531 @defun Frame.block ()
24532 Return the frame's code block. @xref{Blocks In Python}.
24535 @defun Frame.function ()
24536 Return the symbol for the function corresponding to this frame.
24537 @xref{Symbols In Python}.
24540 @defun Frame.older ()
24541 Return the frame that called this frame.
24544 @defun Frame.newer ()
24545 Return the frame called by this frame.
24548 @defun Frame.find_sal ()
24549 Return the frame's symtab and line object.
24550 @xref{Symbol Tables In Python}.
24553 @defun Frame.read_var (variable @r{[}, block@r{]})
24554 Return the value of @var{variable} in this frame. If the optional
24555 argument @var{block} is provided, search for the variable from that
24556 block; otherwise start at the frame's current block (which is
24557 determined by the frame's current program counter). @var{variable}
24558 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
24559 @code{gdb.Block} object.
24562 @defun Frame.select ()
24563 Set this frame to be the selected frame. @xref{Stack, ,Examining the
24568 @node Blocks In Python
24569 @subsubsection Accessing frame blocks from Python.
24571 @cindex blocks in python
24574 Within each frame, @value{GDBN} maintains information on each block
24575 stored in that frame. These blocks are organized hierarchically, and
24576 are represented individually in Python as a @code{gdb.Block}.
24577 Please see @ref{Frames In Python}, for a more in-depth discussion on
24578 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
24579 detailed technical information on @value{GDBN}'s book-keeping of the
24582 A @code{gdb.Block} is iterable. The iterator returns the symbols
24583 (@pxref{Symbols In Python}) local to the block.
24585 The following block-related functions are available in the @code{gdb}
24588 @findex gdb.block_for_pc
24589 @defun gdb.block_for_pc (pc)
24590 Return the @code{gdb.Block} containing the given @var{pc} value. If the
24591 block cannot be found for the @var{pc} value specified, the function
24592 will return @code{None}.
24595 A @code{gdb.Block} object has the following methods:
24598 @defun Block.is_valid ()
24599 Returns @code{True} if the @code{gdb.Block} object is valid,
24600 @code{False} if not. A block object can become invalid if the block it
24601 refers to doesn't exist anymore in the inferior. All other
24602 @code{gdb.Block} methods will throw an exception if it is invalid at
24603 the time the method is called. The block's validity is also checked
24604 during iteration over symbols of the block.
24608 A @code{gdb.Block} object has the following attributes:
24611 @defvar Block.start
24612 The start address of the block. This attribute is not writable.
24616 The end address of the block. This attribute is not writable.
24619 @defvar Block.function
24620 The name of the block represented as a @code{gdb.Symbol}. If the
24621 block is not named, then this attribute holds @code{None}. This
24622 attribute is not writable.
24625 @defvar Block.superblock
24626 The block containing this block. If this parent block does not exist,
24627 this attribute holds @code{None}. This attribute is not writable.
24630 @defvar Block.global_block
24631 The global block associated with this block. This attribute is not
24635 @defvar Block.static_block
24636 The static block associated with this block. This attribute is not
24640 @defvar Block.is_global
24641 @code{True} if the @code{gdb.Block} object is a global block,
24642 @code{False} if not. This attribute is not
24646 @defvar Block.is_static
24647 @code{True} if the @code{gdb.Block} object is a static block,
24648 @code{False} if not. This attribute is not writable.
24652 @node Symbols In Python
24653 @subsubsection Python representation of Symbols.
24655 @cindex symbols in python
24658 @value{GDBN} represents every variable, function and type as an
24659 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
24660 Similarly, Python represents these symbols in @value{GDBN} with the
24661 @code{gdb.Symbol} object.
24663 The following symbol-related functions are available in the @code{gdb}
24666 @findex gdb.lookup_symbol
24667 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
24668 This function searches for a symbol by name. The search scope can be
24669 restricted to the parameters defined in the optional domain and block
24672 @var{name} is the name of the symbol. It must be a string. The
24673 optional @var{block} argument restricts the search to symbols visible
24674 in that @var{block}. The @var{block} argument must be a
24675 @code{gdb.Block} object. If omitted, the block for the current frame
24676 is used. The optional @var{domain} argument restricts
24677 the search to the domain type. The @var{domain} argument must be a
24678 domain constant defined in the @code{gdb} module and described later
24681 The result is a tuple of two elements.
24682 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
24684 If the symbol is found, the second element is @code{True} if the symbol
24685 is a field of a method's object (e.g., @code{this} in C@t{++}),
24686 otherwise it is @code{False}.
24687 If the symbol is not found, the second element is @code{False}.
24690 @findex gdb.lookup_global_symbol
24691 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
24692 This function searches for a global symbol by name.
24693 The search scope can be restricted to by the domain argument.
24695 @var{name} is the name of the symbol. It must be a string.
24696 The optional @var{domain} argument restricts the search to the domain type.
24697 The @var{domain} argument must be a domain constant defined in the @code{gdb}
24698 module and described later in this chapter.
24700 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
24704 A @code{gdb.Symbol} object has the following attributes:
24707 @defvar Symbol.type
24708 The type of the symbol or @code{None} if no type is recorded.
24709 This attribute is represented as a @code{gdb.Type} object.
24710 @xref{Types In Python}. This attribute is not writable.
24713 @defvar Symbol.symtab
24714 The symbol table in which the symbol appears. This attribute is
24715 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
24716 Python}. This attribute is not writable.
24719 @defvar Symbol.line
24720 The line number in the source code at which the symbol was defined.
24721 This is an integer.
24724 @defvar Symbol.name
24725 The name of the symbol as a string. This attribute is not writable.
24728 @defvar Symbol.linkage_name
24729 The name of the symbol, as used by the linker (i.e., may be mangled).
24730 This attribute is not writable.
24733 @defvar Symbol.print_name
24734 The name of the symbol in a form suitable for output. This is either
24735 @code{name} or @code{linkage_name}, depending on whether the user
24736 asked @value{GDBN} to display demangled or mangled names.
24739 @defvar Symbol.addr_class
24740 The address class of the symbol. This classifies how to find the value
24741 of a symbol. Each address class is a constant defined in the
24742 @code{gdb} module and described later in this chapter.
24745 @defvar Symbol.needs_frame
24746 This is @code{True} if evaluating this symbol's value requires a frame
24747 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
24748 local variables will require a frame, but other symbols will not.
24751 @defvar Symbol.is_argument
24752 @code{True} if the symbol is an argument of a function.
24755 @defvar Symbol.is_constant
24756 @code{True} if the symbol is a constant.
24759 @defvar Symbol.is_function
24760 @code{True} if the symbol is a function or a method.
24763 @defvar Symbol.is_variable
24764 @code{True} if the symbol is a variable.
24768 A @code{gdb.Symbol} object has the following methods:
24771 @defun Symbol.is_valid ()
24772 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24773 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24774 the symbol it refers to does not exist in @value{GDBN} any longer.
24775 All other @code{gdb.Symbol} methods will throw an exception if it is
24776 invalid at the time the method is called.
24779 @defun Symbol.value (@r{[}frame@r{]})
24780 Compute the value of the symbol, as a @code{gdb.Value}. For
24781 functions, this computes the address of the function, cast to the
24782 appropriate type. If the symbol requires a frame in order to compute
24783 its value, then @var{frame} must be given. If @var{frame} is not
24784 given, or if @var{frame} is invalid, then this method will throw an
24789 The available domain categories in @code{gdb.Symbol} are represented
24790 as constants in the @code{gdb} module:
24793 @findex SYMBOL_UNDEF_DOMAIN
24794 @findex gdb.SYMBOL_UNDEF_DOMAIN
24795 @item gdb.SYMBOL_UNDEF_DOMAIN
24796 This is used when a domain has not been discovered or none of the
24797 following domains apply. This usually indicates an error either
24798 in the symbol information or in @value{GDBN}'s handling of symbols.
24799 @findex SYMBOL_VAR_DOMAIN
24800 @findex gdb.SYMBOL_VAR_DOMAIN
24801 @item gdb.SYMBOL_VAR_DOMAIN
24802 This domain contains variables, function names, typedef names and enum
24804 @findex SYMBOL_STRUCT_DOMAIN
24805 @findex gdb.SYMBOL_STRUCT_DOMAIN
24806 @item gdb.SYMBOL_STRUCT_DOMAIN
24807 This domain holds struct, union and enum type names.
24808 @findex SYMBOL_LABEL_DOMAIN
24809 @findex gdb.SYMBOL_LABEL_DOMAIN
24810 @item gdb.SYMBOL_LABEL_DOMAIN
24811 This domain contains names of labels (for gotos).
24812 @findex SYMBOL_VARIABLES_DOMAIN
24813 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24814 @item gdb.SYMBOL_VARIABLES_DOMAIN
24815 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24816 contains everything minus functions and types.
24817 @findex SYMBOL_FUNCTIONS_DOMAIN
24818 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24819 @item gdb.SYMBOL_FUNCTION_DOMAIN
24820 This domain contains all functions.
24821 @findex SYMBOL_TYPES_DOMAIN
24822 @findex gdb.SYMBOL_TYPES_DOMAIN
24823 @item gdb.SYMBOL_TYPES_DOMAIN
24824 This domain contains all types.
24827 The available address class categories in @code{gdb.Symbol} are represented
24828 as constants in the @code{gdb} module:
24831 @findex SYMBOL_LOC_UNDEF
24832 @findex gdb.SYMBOL_LOC_UNDEF
24833 @item gdb.SYMBOL_LOC_UNDEF
24834 If this is returned by address class, it indicates an error either in
24835 the symbol information or in @value{GDBN}'s handling of symbols.
24836 @findex SYMBOL_LOC_CONST
24837 @findex gdb.SYMBOL_LOC_CONST
24838 @item gdb.SYMBOL_LOC_CONST
24839 Value is constant int.
24840 @findex SYMBOL_LOC_STATIC
24841 @findex gdb.SYMBOL_LOC_STATIC
24842 @item gdb.SYMBOL_LOC_STATIC
24843 Value is at a fixed address.
24844 @findex SYMBOL_LOC_REGISTER
24845 @findex gdb.SYMBOL_LOC_REGISTER
24846 @item gdb.SYMBOL_LOC_REGISTER
24847 Value is in a register.
24848 @findex SYMBOL_LOC_ARG
24849 @findex gdb.SYMBOL_LOC_ARG
24850 @item gdb.SYMBOL_LOC_ARG
24851 Value is an argument. This value is at the offset stored within the
24852 symbol inside the frame's argument list.
24853 @findex SYMBOL_LOC_REF_ARG
24854 @findex gdb.SYMBOL_LOC_REF_ARG
24855 @item gdb.SYMBOL_LOC_REF_ARG
24856 Value address is stored in the frame's argument list. Just like
24857 @code{LOC_ARG} except that the value's address is stored at the
24858 offset, not the value itself.
24859 @findex SYMBOL_LOC_REGPARM_ADDR
24860 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24861 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24862 Value is a specified register. Just like @code{LOC_REGISTER} except
24863 the register holds the address of the argument instead of the argument
24865 @findex SYMBOL_LOC_LOCAL
24866 @findex gdb.SYMBOL_LOC_LOCAL
24867 @item gdb.SYMBOL_LOC_LOCAL
24868 Value is a local variable.
24869 @findex SYMBOL_LOC_TYPEDEF
24870 @findex gdb.SYMBOL_LOC_TYPEDEF
24871 @item gdb.SYMBOL_LOC_TYPEDEF
24872 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24874 @findex SYMBOL_LOC_BLOCK
24875 @findex gdb.SYMBOL_LOC_BLOCK
24876 @item gdb.SYMBOL_LOC_BLOCK
24878 @findex SYMBOL_LOC_CONST_BYTES
24879 @findex gdb.SYMBOL_LOC_CONST_BYTES
24880 @item gdb.SYMBOL_LOC_CONST_BYTES
24881 Value is a byte-sequence.
24882 @findex SYMBOL_LOC_UNRESOLVED
24883 @findex gdb.SYMBOL_LOC_UNRESOLVED
24884 @item gdb.SYMBOL_LOC_UNRESOLVED
24885 Value is at a fixed address, but the address of the variable has to be
24886 determined from the minimal symbol table whenever the variable is
24888 @findex SYMBOL_LOC_OPTIMIZED_OUT
24889 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24890 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24891 The value does not actually exist in the program.
24892 @findex SYMBOL_LOC_COMPUTED
24893 @findex gdb.SYMBOL_LOC_COMPUTED
24894 @item gdb.SYMBOL_LOC_COMPUTED
24895 The value's address is a computed location.
24898 @node Symbol Tables In Python
24899 @subsubsection Symbol table representation in Python.
24901 @cindex symbol tables in python
24903 @tindex gdb.Symtab_and_line
24905 Access to symbol table data maintained by @value{GDBN} on the inferior
24906 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24907 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24908 from the @code{find_sal} method in @code{gdb.Frame} object.
24909 @xref{Frames In Python}.
24911 For more information on @value{GDBN}'s symbol table management, see
24912 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24914 A @code{gdb.Symtab_and_line} object has the following attributes:
24917 @defvar Symtab_and_line.symtab
24918 The symbol table object (@code{gdb.Symtab}) for this frame.
24919 This attribute is not writable.
24922 @defvar Symtab_and_line.pc
24923 Indicates the current program counter address. This attribute is not
24927 @defvar Symtab_and_line.line
24928 Indicates the current line number for this object. This
24929 attribute is not writable.
24933 A @code{gdb.Symtab_and_line} object has the following methods:
24936 @defun Symtab_and_line.is_valid ()
24937 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24938 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24939 invalid if the Symbol table and line object it refers to does not
24940 exist in @value{GDBN} any longer. All other
24941 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24942 invalid at the time the method is called.
24946 A @code{gdb.Symtab} object has the following attributes:
24949 @defvar Symtab.filename
24950 The symbol table's source filename. This attribute is not writable.
24953 @defvar Symtab.objfile
24954 The symbol table's backing object file. @xref{Objfiles In Python}.
24955 This attribute is not writable.
24959 A @code{gdb.Symtab} object has the following methods:
24962 @defun Symtab.is_valid ()
24963 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24964 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24965 the symbol table it refers to does not exist in @value{GDBN} any
24966 longer. All other @code{gdb.Symtab} methods will throw an exception
24967 if it is invalid at the time the method is called.
24970 @defun Symtab.fullname ()
24971 Return the symbol table's source absolute file name.
24975 @node Breakpoints In Python
24976 @subsubsection Manipulating breakpoints using Python
24978 @cindex breakpoints in python
24979 @tindex gdb.Breakpoint
24981 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24984 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24985 Create a new breakpoint. @var{spec} is a string naming the
24986 location of the breakpoint, or an expression that defines a
24987 watchpoint. The contents can be any location recognized by the
24988 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24989 command. The optional @var{type} denotes the breakpoint to create
24990 from the types defined later in this chapter. This argument can be
24991 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24992 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24993 allows the breakpoint to become invisible to the user. The breakpoint
24994 will neither be reported when created, nor will it be listed in the
24995 output from @code{info breakpoints} (but will be listed with the
24996 @code{maint info breakpoints} command). The optional @var{wp_class}
24997 argument defines the class of watchpoint to create, if @var{type} is
24998 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24999 assumed to be a @code{gdb.WP_WRITE} class.
25002 @defun Breakpoint.stop (self)
25003 The @code{gdb.Breakpoint} class can be sub-classed and, in
25004 particular, you may choose to implement the @code{stop} method.
25005 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25006 it will be called when the inferior reaches any location of a
25007 breakpoint which instantiates that sub-class. If the method returns
25008 @code{True}, the inferior will be stopped at the location of the
25009 breakpoint, otherwise the inferior will continue.
25011 If there are multiple breakpoints at the same location with a
25012 @code{stop} method, each one will be called regardless of the
25013 return status of the previous. This ensures that all @code{stop}
25014 methods have a chance to execute at that location. In this scenario
25015 if one of the methods returns @code{True} but the others return
25016 @code{False}, the inferior will still be stopped.
25018 You should not alter the execution state of the inferior (i.e.@:, step,
25019 next, etc.), alter the current frame context (i.e.@:, change the current
25020 active frame), or alter, add or delete any breakpoint. As a general
25021 rule, you should not alter any data within @value{GDBN} or the inferior
25024 Example @code{stop} implementation:
25027 class MyBreakpoint (gdb.Breakpoint):
25029 inf_val = gdb.parse_and_eval("foo")
25036 The available watchpoint types represented by constants are defined in the
25041 @findex gdb.WP_READ
25043 Read only watchpoint.
25046 @findex gdb.WP_WRITE
25048 Write only watchpoint.
25051 @findex gdb.WP_ACCESS
25052 @item gdb.WP_ACCESS
25053 Read/Write watchpoint.
25056 @defun Breakpoint.is_valid ()
25057 Return @code{True} if this @code{Breakpoint} object is valid,
25058 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25059 if the user deletes the breakpoint. In this case, the object still
25060 exists, but the underlying breakpoint does not. In the cases of
25061 watchpoint scope, the watchpoint remains valid even if execution of the
25062 inferior leaves the scope of that watchpoint.
25065 @defun Breakpoint.delete
25066 Permanently deletes the @value{GDBN} breakpoint. This also
25067 invalidates the Python @code{Breakpoint} object. Any further access
25068 to this object's attributes or methods will raise an error.
25071 @defvar Breakpoint.enabled
25072 This attribute is @code{True} if the breakpoint is enabled, and
25073 @code{False} otherwise. This attribute is writable.
25076 @defvar Breakpoint.silent
25077 This attribute is @code{True} if the breakpoint is silent, and
25078 @code{False} otherwise. This attribute is writable.
25080 Note that a breakpoint can also be silent if it has commands and the
25081 first command is @code{silent}. This is not reported by the
25082 @code{silent} attribute.
25085 @defvar Breakpoint.thread
25086 If the breakpoint is thread-specific, this attribute holds the thread
25087 id. If the breakpoint is not thread-specific, this attribute is
25088 @code{None}. This attribute is writable.
25091 @defvar Breakpoint.task
25092 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25093 id. If the breakpoint is not task-specific (or the underlying
25094 language is not Ada), this attribute is @code{None}. This attribute
25098 @defvar Breakpoint.ignore_count
25099 This attribute holds the ignore count for the breakpoint, an integer.
25100 This attribute is writable.
25103 @defvar Breakpoint.number
25104 This attribute holds the breakpoint's number --- the identifier used by
25105 the user to manipulate the breakpoint. This attribute is not writable.
25108 @defvar Breakpoint.type
25109 This attribute holds the breakpoint's type --- the identifier used to
25110 determine the actual breakpoint type or use-case. This attribute is not
25114 @defvar Breakpoint.visible
25115 This attribute tells whether the breakpoint is visible to the user
25116 when set, or when the @samp{info breakpoints} command is run. This
25117 attribute is not writable.
25120 The available types are represented by constants defined in the @code{gdb}
25124 @findex BP_BREAKPOINT
25125 @findex gdb.BP_BREAKPOINT
25126 @item gdb.BP_BREAKPOINT
25127 Normal code breakpoint.
25129 @findex BP_WATCHPOINT
25130 @findex gdb.BP_WATCHPOINT
25131 @item gdb.BP_WATCHPOINT
25132 Watchpoint breakpoint.
25134 @findex BP_HARDWARE_WATCHPOINT
25135 @findex gdb.BP_HARDWARE_WATCHPOINT
25136 @item gdb.BP_HARDWARE_WATCHPOINT
25137 Hardware assisted watchpoint.
25139 @findex BP_READ_WATCHPOINT
25140 @findex gdb.BP_READ_WATCHPOINT
25141 @item gdb.BP_READ_WATCHPOINT
25142 Hardware assisted read watchpoint.
25144 @findex BP_ACCESS_WATCHPOINT
25145 @findex gdb.BP_ACCESS_WATCHPOINT
25146 @item gdb.BP_ACCESS_WATCHPOINT
25147 Hardware assisted access watchpoint.
25150 @defvar Breakpoint.hit_count
25151 This attribute holds the hit count for the breakpoint, an integer.
25152 This attribute is writable, but currently it can only be set to zero.
25155 @defvar Breakpoint.location
25156 This attribute holds the location of the breakpoint, as specified by
25157 the user. It is a string. If the breakpoint does not have a location
25158 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25159 attribute is not writable.
25162 @defvar Breakpoint.expression
25163 This attribute holds a breakpoint expression, as specified by
25164 the user. It is a string. If the breakpoint does not have an
25165 expression (the breakpoint is not a watchpoint) the attribute's value
25166 is @code{None}. This attribute is not writable.
25169 @defvar Breakpoint.condition
25170 This attribute holds the condition of the breakpoint, as specified by
25171 the user. It is a string. If there is no condition, this attribute's
25172 value is @code{None}. This attribute is writable.
25175 @defvar Breakpoint.commands
25176 This attribute holds the commands attached to the breakpoint. If
25177 there are commands, this attribute's value is a string holding all the
25178 commands, separated by newlines. If there are no commands, this
25179 attribute is @code{None}. This attribute is not writable.
25182 @node Finish Breakpoints in Python
25183 @subsubsection Finish Breakpoints
25185 @cindex python finish breakpoints
25186 @tindex gdb.FinishBreakpoint
25188 A finish breakpoint is a temporary breakpoint set at the return address of
25189 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
25190 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
25191 and deleted when the execution will run out of the breakpoint scope (i.e.@:
25192 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
25193 Finish breakpoints are thread specific and must be create with the right
25196 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
25197 Create a finish breakpoint at the return address of the @code{gdb.Frame}
25198 object @var{frame}. If @var{frame} is not provided, this defaults to the
25199 newest frame. The optional @var{internal} argument allows the breakpoint to
25200 become invisible to the user. @xref{Breakpoints In Python}, for further
25201 details about this argument.
25204 @defun FinishBreakpoint.out_of_scope (self)
25205 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
25206 @code{return} command, @dots{}), a function may not properly terminate, and
25207 thus never hit the finish breakpoint. When @value{GDBN} notices such a
25208 situation, the @code{out_of_scope} callback will be triggered.
25210 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
25214 class MyFinishBreakpoint (gdb.FinishBreakpoint)
25216 print "normal finish"
25219 def out_of_scope ():
25220 print "abnormal finish"
25224 @defvar FinishBreakpoint.return_value
25225 When @value{GDBN} is stopped at a finish breakpoint and the frame
25226 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
25227 attribute will contain a @code{gdb.Value} object corresponding to the return
25228 value of the function. The value will be @code{None} if the function return
25229 type is @code{void} or if the return value was not computable. This attribute
25233 @node Lazy Strings In Python
25234 @subsubsection Python representation of lazy strings.
25236 @cindex lazy strings in python
25237 @tindex gdb.LazyString
25239 A @dfn{lazy string} is a string whose contents is not retrieved or
25240 encoded until it is needed.
25242 A @code{gdb.LazyString} is represented in @value{GDBN} as an
25243 @code{address} that points to a region of memory, an @code{encoding}
25244 that will be used to encode that region of memory, and a @code{length}
25245 to delimit the region of memory that represents the string. The
25246 difference between a @code{gdb.LazyString} and a string wrapped within
25247 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
25248 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
25249 retrieved and encoded during printing, while a @code{gdb.Value}
25250 wrapping a string is immediately retrieved and encoded on creation.
25252 A @code{gdb.LazyString} object has the following functions:
25254 @defun LazyString.value ()
25255 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
25256 will point to the string in memory, but will lose all the delayed
25257 retrieval, encoding and handling that @value{GDBN} applies to a
25258 @code{gdb.LazyString}.
25261 @defvar LazyString.address
25262 This attribute holds the address of the string. This attribute is not
25266 @defvar LazyString.length
25267 This attribute holds the length of the string in characters. If the
25268 length is -1, then the string will be fetched and encoded up to the
25269 first null of appropriate width. This attribute is not writable.
25272 @defvar LazyString.encoding
25273 This attribute holds the encoding that will be applied to the string
25274 when the string is printed by @value{GDBN}. If the encoding is not
25275 set, or contains an empty string, then @value{GDBN} will select the
25276 most appropriate encoding when the string is printed. This attribute
25280 @defvar LazyString.type
25281 This attribute holds the type that is represented by the lazy string's
25282 type. For a lazy string this will always be a pointer type. To
25283 resolve this to the lazy string's character type, use the type's
25284 @code{target} method. @xref{Types In Python}. This attribute is not
25288 @node Python Auto-loading
25289 @subsection Python Auto-loading
25290 @cindex Python auto-loading
25292 When a new object file is read (for example, due to the @code{file}
25293 command, or because the inferior has loaded a shared library),
25294 @value{GDBN} will look for Python support scripts in several ways:
25295 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
25296 and @code{.debug_gdb_scripts} section
25297 (@pxref{dotdebug_gdb_scripts section}).
25299 The auto-loading feature is useful for supplying application-specific
25300 debugging commands and scripts.
25302 Auto-loading can be enabled or disabled,
25303 and the list of auto-loaded scripts can be printed.
25306 @anchor{set auto-load python-scripts}
25307 @kindex set auto-load python-scripts
25308 @item set auto-load python-scripts [on|off]
25309 Enable or disable the auto-loading of Python scripts.
25311 @anchor{show auto-load python-scripts}
25312 @kindex show auto-load python-scripts
25313 @item show auto-load python-scripts
25314 Show whether auto-loading of Python scripts is enabled or disabled.
25316 @anchor{info auto-load python-scripts}
25317 @kindex info auto-load python-scripts
25318 @cindex print list of auto-loaded Python scripts
25319 @item info auto-load python-scripts [@var{regexp}]
25320 Print the list of all Python scripts that @value{GDBN} auto-loaded.
25322 Also printed is the list of Python scripts that were mentioned in
25323 the @code{.debug_gdb_scripts} section and were not found
25324 (@pxref{dotdebug_gdb_scripts section}).
25325 This is useful because their names are not printed when @value{GDBN}
25326 tries to load them and fails. There may be many of them, and printing
25327 an error message for each one is problematic.
25329 If @var{regexp} is supplied only Python scripts with matching names are printed.
25334 (gdb) info auto-load python-scripts
25336 Yes py-section-script.py
25337 full name: /tmp/py-section-script.py
25338 No my-foo-pretty-printers.py
25342 When reading an auto-loaded file, @value{GDBN} sets the
25343 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
25344 function (@pxref{Objfiles In Python}). This can be useful for
25345 registering objfile-specific pretty-printers.
25348 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
25349 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
25350 * Which flavor to choose?::
25353 @node objfile-gdb.py file
25354 @subsubsection The @file{@var{objfile}-gdb.py} file
25355 @cindex @file{@var{objfile}-gdb.py}
25357 When a new object file is read, @value{GDBN} looks for
25358 a file named @file{@var{objfile}-gdb.py},
25359 where @var{objfile} is the object file's real name, formed by ensuring
25360 that the file name is absolute, following all symlinks, and resolving
25361 @code{.} and @code{..} components. If this file exists and is
25362 readable, @value{GDBN} will evaluate it as a Python script.
25364 If this file does not exist, and if the parameter
25365 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
25366 then @value{GDBN} will look for @var{real-name} in all of the
25367 directories mentioned in the value of @code{debug-file-directory}.
25369 Finally, if this file does not exist, then @value{GDBN} will look for
25370 a file named @file{@var{data-directory}/auto-load/@var{real-name}}, where
25371 @var{data-directory} is @value{GDBN}'s data directory (available via
25372 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
25373 is the object file's real name, as described above.
25375 @value{GDBN} does not track which files it has already auto-loaded this way.
25376 @value{GDBN} will load the associated script every time the corresponding
25377 @var{objfile} is opened.
25378 So your @file{-gdb.py} file should be careful to avoid errors if it
25379 is evaluated more than once.
25381 @node dotdebug_gdb_scripts section
25382 @subsubsection The @code{.debug_gdb_scripts} section
25383 @cindex @code{.debug_gdb_scripts} section
25385 For systems using file formats like ELF and COFF,
25386 when @value{GDBN} loads a new object file
25387 it will look for a special section named @samp{.debug_gdb_scripts}.
25388 If this section exists, its contents is a list of names of scripts to load.
25390 @value{GDBN} will look for each specified script file first in the
25391 current directory and then along the source search path
25392 (@pxref{Source Path, ,Specifying Source Directories}),
25393 except that @file{$cdir} is not searched, since the compilation
25394 directory is not relevant to scripts.
25396 Entries can be placed in section @code{.debug_gdb_scripts} with,
25397 for example, this GCC macro:
25400 /* Note: The "MS" section flags are to remove duplicates. */
25401 #define DEFINE_GDB_SCRIPT(script_name) \
25403 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25405 .asciz \"" script_name "\"\n\
25411 Then one can reference the macro in a header or source file like this:
25414 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
25417 The script name may include directories if desired.
25419 If the macro is put in a header, any application or library
25420 using this header will get a reference to the specified script.
25422 @node Which flavor to choose?
25423 @subsubsection Which flavor to choose?
25425 Given the multiple ways of auto-loading Python scripts, it might not always
25426 be clear which one to choose. This section provides some guidance.
25428 Benefits of the @file{-gdb.py} way:
25432 Can be used with file formats that don't support multiple sections.
25435 Ease of finding scripts for public libraries.
25437 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25438 in the source search path.
25439 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25440 isn't a source directory in which to find the script.
25443 Doesn't require source code additions.
25446 Benefits of the @code{.debug_gdb_scripts} way:
25450 Works with static linking.
25452 Scripts for libraries done the @file{-gdb.py} way require an objfile to
25453 trigger their loading. When an application is statically linked the only
25454 objfile available is the executable, and it is cumbersome to attach all the
25455 scripts from all the input libraries to the executable's @file{-gdb.py} script.
25458 Works with classes that are entirely inlined.
25460 Some classes can be entirely inlined, and thus there may not be an associated
25461 shared library to attach a @file{-gdb.py} script to.
25464 Scripts needn't be copied out of the source tree.
25466 In some circumstances, apps can be built out of large collections of internal
25467 libraries, and the build infrastructure necessary to install the
25468 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
25469 cumbersome. It may be easier to specify the scripts in the
25470 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25471 top of the source tree to the source search path.
25474 @node Python modules
25475 @subsection Python modules
25476 @cindex python modules
25478 @value{GDBN} comes with several modules to assist writing Python code.
25481 * gdb.printing:: Building and registering pretty-printers.
25482 * gdb.types:: Utilities for working with types.
25483 * gdb.prompt:: Utilities for prompt value substitution.
25487 @subsubsection gdb.printing
25488 @cindex gdb.printing
25490 This module provides a collection of utilities for working with
25494 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
25495 This class specifies the API that makes @samp{info pretty-printer},
25496 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
25497 Pretty-printers should generally inherit from this class.
25499 @item SubPrettyPrinter (@var{name})
25500 For printers that handle multiple types, this class specifies the
25501 corresponding API for the subprinters.
25503 @item RegexpCollectionPrettyPrinter (@var{name})
25504 Utility class for handling multiple printers, all recognized via
25505 regular expressions.
25506 @xref{Writing a Pretty-Printer}, for an example.
25508 @item FlagEnumerationPrinter (@var{name})
25509 A pretty-printer which handles printing of @code{enum} values. Unlike
25510 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
25511 work properly when there is some overlap between the enumeration
25512 constants. @var{name} is the name of the printer and also the name of
25513 the @code{enum} type to look up.
25515 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
25516 Register @var{printer} with the pretty-printer list of @var{obj}.
25517 If @var{replace} is @code{True} then any existing copy of the printer
25518 is replaced. Otherwise a @code{RuntimeError} exception is raised
25519 if a printer with the same name already exists.
25523 @subsubsection gdb.types
25526 This module provides a collection of utilities for working with
25527 @code{gdb.Types} objects.
25530 @item get_basic_type (@var{type})
25531 Return @var{type} with const and volatile qualifiers stripped,
25532 and with typedefs and C@t{++} references converted to the underlying type.
25537 typedef const int const_int;
25539 const_int& foo_ref (foo);
25540 int main () @{ return 0; @}
25547 (gdb) python import gdb.types
25548 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
25549 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
25553 @item has_field (@var{type}, @var{field})
25554 Return @code{True} if @var{type}, assumed to be a type with fields
25555 (e.g., a structure or union), has field @var{field}.
25557 @item make_enum_dict (@var{enum_type})
25558 Return a Python @code{dictionary} type produced from @var{enum_type}.
25560 @item deep_items (@var{type})
25561 Returns a Python iterator similar to the standard
25562 @code{gdb.Type.iteritems} method, except that the iterator returned
25563 by @code{deep_items} will recursively traverse anonymous struct or
25564 union fields. For example:
25578 Then in @value{GDBN}:
25580 (@value{GDBP}) python import gdb.types
25581 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
25582 (@value{GDBP}) python print struct_a.keys ()
25584 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
25585 @{['a', 'b0', 'b1']@}
25591 @subsubsection gdb.prompt
25594 This module provides a method for prompt value-substitution.
25597 @item substitute_prompt (@var{string})
25598 Return @var{string} with escape sequences substituted by values. Some
25599 escape sequences take arguments. You can specify arguments inside
25600 ``@{@}'' immediately following the escape sequence.
25602 The escape sequences you can pass to this function are:
25606 Substitute a backslash.
25608 Substitute an ESC character.
25610 Substitute the selected frame; an argument names a frame parameter.
25612 Substitute a newline.
25614 Substitute a parameter's value; the argument names the parameter.
25616 Substitute a carriage return.
25618 Substitute the selected thread; an argument names a thread parameter.
25620 Substitute the version of GDB.
25622 Substitute the current working directory.
25624 Begin a sequence of non-printing characters. These sequences are
25625 typically used with the ESC character, and are not counted in the string
25626 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
25627 blue-colored ``(gdb)'' prompt where the length is five.
25629 End a sequence of non-printing characters.
25635 substitute_prompt (``frame: \f,
25636 print arguments: \p@{print frame-arguments@}'')
25639 @exdent will return the string:
25642 "frame: main, print arguments: scalars"
25647 @section Creating new spellings of existing commands
25648 @cindex aliases for commands
25650 It is often useful to define alternate spellings of existing commands.
25651 For example, if a new @value{GDBN} command defined in Python has
25652 a long name to type, it is handy to have an abbreviated version of it
25653 that involves less typing.
25655 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25656 of the @samp{step} command even though it is otherwise an ambiguous
25657 abbreviation of other commands like @samp{set} and @samp{show}.
25659 Aliases are also used to provide shortened or more common versions
25660 of multi-word commands. For example, @value{GDBN} provides the
25661 @samp{tty} alias of the @samp{set inferior-tty} command.
25663 You can define a new alias with the @samp{alias} command.
25668 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25672 @var{ALIAS} specifies the name of the new alias.
25673 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25676 @var{COMMAND} specifies the name of an existing command
25677 that is being aliased.
25679 The @samp{-a} option specifies that the new alias is an abbreviation
25680 of the command. Abbreviations are not shown in command
25681 lists displayed by the @samp{help} command.
25683 The @samp{--} option specifies the end of options,
25684 and is useful when @var{ALIAS} begins with a dash.
25686 Here is a simple example showing how to make an abbreviation
25687 of a command so that there is less to type.
25688 Suppose you were tired of typing @samp{disas}, the current
25689 shortest unambiguous abbreviation of the @samp{disassemble} command
25690 and you wanted an even shorter version named @samp{di}.
25691 The following will accomplish this.
25694 (gdb) alias -a di = disas
25697 Note that aliases are different from user-defined commands.
25698 With a user-defined command, you also need to write documentation
25699 for it with the @samp{document} command.
25700 An alias automatically picks up the documentation of the existing command.
25702 Here is an example where we make @samp{elms} an abbreviation of
25703 @samp{elements} in the @samp{set print elements} command.
25704 This is to show that you can make an abbreviation of any part
25708 (gdb) alias -a set print elms = set print elements
25709 (gdb) alias -a show print elms = show print elements
25710 (gdb) set p elms 20
25712 Limit on string chars or array elements to print is 200.
25715 Note that if you are defining an alias of a @samp{set} command,
25716 and you want to have an alias for the corresponding @samp{show}
25717 command, then you need to define the latter separately.
25719 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25720 @var{ALIAS}, just as they are normally.
25723 (gdb) alias -a set pr elms = set p ele
25726 Finally, here is an example showing the creation of a one word
25727 alias for a more complex command.
25728 This creates alias @samp{spe} of the command @samp{set print elements}.
25731 (gdb) alias spe = set print elements
25736 @chapter Command Interpreters
25737 @cindex command interpreters
25739 @value{GDBN} supports multiple command interpreters, and some command
25740 infrastructure to allow users or user interface writers to switch
25741 between interpreters or run commands in other interpreters.
25743 @value{GDBN} currently supports two command interpreters, the console
25744 interpreter (sometimes called the command-line interpreter or @sc{cli})
25745 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25746 describes both of these interfaces in great detail.
25748 By default, @value{GDBN} will start with the console interpreter.
25749 However, the user may choose to start @value{GDBN} with another
25750 interpreter by specifying the @option{-i} or @option{--interpreter}
25751 startup options. Defined interpreters include:
25755 @cindex console interpreter
25756 The traditional console or command-line interpreter. This is the most often
25757 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25758 @value{GDBN} will use this interpreter.
25761 @cindex mi interpreter
25762 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25763 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25764 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25768 @cindex mi2 interpreter
25769 The current @sc{gdb/mi} interface.
25772 @cindex mi1 interpreter
25773 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25777 @cindex invoke another interpreter
25778 The interpreter being used by @value{GDBN} may not be dynamically
25779 switched at runtime. Although possible, this could lead to a very
25780 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
25781 enters the command "interpreter-set console" in a console view,
25782 @value{GDBN} would switch to using the console interpreter, rendering
25783 the IDE inoperable!
25785 @kindex interpreter-exec
25786 Although you may only choose a single interpreter at startup, you may execute
25787 commands in any interpreter from the current interpreter using the appropriate
25788 command. If you are running the console interpreter, simply use the
25789 @code{interpreter-exec} command:
25792 interpreter-exec mi "-data-list-register-names"
25795 @sc{gdb/mi} has a similar command, although it is only available in versions of
25796 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25799 @chapter @value{GDBN} Text User Interface
25801 @cindex Text User Interface
25804 * TUI Overview:: TUI overview
25805 * TUI Keys:: TUI key bindings
25806 * TUI Single Key Mode:: TUI single key mode
25807 * TUI Commands:: TUI-specific commands
25808 * TUI Configuration:: TUI configuration variables
25811 The @value{GDBN} Text User Interface (TUI) is a terminal
25812 interface which uses the @code{curses} library to show the source
25813 file, the assembly output, the program registers and @value{GDBN}
25814 commands in separate text windows. The TUI mode is supported only
25815 on platforms where a suitable version of the @code{curses} library
25818 The TUI mode is enabled by default when you invoke @value{GDBN} as
25819 @samp{@value{GDBP} -tui}.
25820 You can also switch in and out of TUI mode while @value{GDBN} runs by
25821 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25822 @xref{TUI Keys, ,TUI Key Bindings}.
25825 @section TUI Overview
25827 In TUI mode, @value{GDBN} can display several text windows:
25831 This window is the @value{GDBN} command window with the @value{GDBN}
25832 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25833 managed using readline.
25836 The source window shows the source file of the program. The current
25837 line and active breakpoints are displayed in this window.
25840 The assembly window shows the disassembly output of the program.
25843 This window shows the processor registers. Registers are highlighted
25844 when their values change.
25847 The source and assembly windows show the current program position
25848 by highlighting the current line and marking it with a @samp{>} marker.
25849 Breakpoints are indicated with two markers. The first marker
25850 indicates the breakpoint type:
25854 Breakpoint which was hit at least once.
25857 Breakpoint which was never hit.
25860 Hardware breakpoint which was hit at least once.
25863 Hardware breakpoint which was never hit.
25866 The second marker indicates whether the breakpoint is enabled or not:
25870 Breakpoint is enabled.
25873 Breakpoint is disabled.
25876 The source, assembly and register windows are updated when the current
25877 thread changes, when the frame changes, or when the program counter
25880 These windows are not all visible at the same time. The command
25881 window is always visible. The others can be arranged in several
25892 source and assembly,
25895 source and registers, or
25898 assembly and registers.
25901 A status line above the command window shows the following information:
25905 Indicates the current @value{GDBN} target.
25906 (@pxref{Targets, ,Specifying a Debugging Target}).
25909 Gives the current process or thread number.
25910 When no process is being debugged, this field is set to @code{No process}.
25913 Gives the current function name for the selected frame.
25914 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25915 When there is no symbol corresponding to the current program counter,
25916 the string @code{??} is displayed.
25919 Indicates the current line number for the selected frame.
25920 When the current line number is not known, the string @code{??} is displayed.
25923 Indicates the current program counter address.
25927 @section TUI Key Bindings
25928 @cindex TUI key bindings
25930 The TUI installs several key bindings in the readline keymaps
25931 @ifset SYSTEM_READLINE
25932 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25934 @ifclear SYSTEM_READLINE
25935 (@pxref{Command Line Editing}).
25937 The following key bindings are installed for both TUI mode and the
25938 @value{GDBN} standard mode.
25947 Enter or leave the TUI mode. When leaving the TUI mode,
25948 the curses window management stops and @value{GDBN} operates using
25949 its standard mode, writing on the terminal directly. When reentering
25950 the TUI mode, control is given back to the curses windows.
25951 The screen is then refreshed.
25955 Use a TUI layout with only one window. The layout will
25956 either be @samp{source} or @samp{assembly}. When the TUI mode
25957 is not active, it will switch to the TUI mode.
25959 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25963 Use a TUI layout with at least two windows. When the current
25964 layout already has two windows, the next layout with two windows is used.
25965 When a new layout is chosen, one window will always be common to the
25966 previous layout and the new one.
25968 Think of it as the Emacs @kbd{C-x 2} binding.
25972 Change the active window. The TUI associates several key bindings
25973 (like scrolling and arrow keys) with the active window. This command
25974 gives the focus to the next TUI window.
25976 Think of it as the Emacs @kbd{C-x o} binding.
25980 Switch in and out of the TUI SingleKey mode that binds single
25981 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25984 The following key bindings only work in the TUI mode:
25989 Scroll the active window one page up.
25993 Scroll the active window one page down.
25997 Scroll the active window one line up.
26001 Scroll the active window one line down.
26005 Scroll the active window one column left.
26009 Scroll the active window one column right.
26013 Refresh the screen.
26016 Because the arrow keys scroll the active window in the TUI mode, they
26017 are not available for their normal use by readline unless the command
26018 window has the focus. When another window is active, you must use
26019 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26020 and @kbd{C-f} to control the command window.
26022 @node TUI Single Key Mode
26023 @section TUI Single Key Mode
26024 @cindex TUI single key mode
26026 The TUI also provides a @dfn{SingleKey} mode, which binds several
26027 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26028 switch into this mode, where the following key bindings are used:
26031 @kindex c @r{(SingleKey TUI key)}
26035 @kindex d @r{(SingleKey TUI key)}
26039 @kindex f @r{(SingleKey TUI key)}
26043 @kindex n @r{(SingleKey TUI key)}
26047 @kindex q @r{(SingleKey TUI key)}
26049 exit the SingleKey mode.
26051 @kindex r @r{(SingleKey TUI key)}
26055 @kindex s @r{(SingleKey TUI key)}
26059 @kindex u @r{(SingleKey TUI key)}
26063 @kindex v @r{(SingleKey TUI key)}
26067 @kindex w @r{(SingleKey TUI key)}
26072 Other keys temporarily switch to the @value{GDBN} command prompt.
26073 The key that was pressed is inserted in the editing buffer so that
26074 it is possible to type most @value{GDBN} commands without interaction
26075 with the TUI SingleKey mode. Once the command is entered the TUI
26076 SingleKey mode is restored. The only way to permanently leave
26077 this mode is by typing @kbd{q} or @kbd{C-x s}.
26081 @section TUI-specific Commands
26082 @cindex TUI commands
26084 The TUI has specific commands to control the text windows.
26085 These commands are always available, even when @value{GDBN} is not in
26086 the TUI mode. When @value{GDBN} is in the standard mode, most
26087 of these commands will automatically switch to the TUI mode.
26089 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26090 terminal, or @value{GDBN} has been started with the machine interface
26091 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26092 these commands will fail with an error, because it would not be
26093 possible or desirable to enable curses window management.
26098 List and give the size of all displayed windows.
26102 Display the next layout.
26105 Display the previous layout.
26108 Display the source window only.
26111 Display the assembly window only.
26114 Display the source and assembly window.
26117 Display the register window together with the source or assembly window.
26121 Make the next window active for scrolling.
26124 Make the previous window active for scrolling.
26127 Make the source window active for scrolling.
26130 Make the assembly window active for scrolling.
26133 Make the register window active for scrolling.
26136 Make the command window active for scrolling.
26140 Refresh the screen. This is similar to typing @kbd{C-L}.
26142 @item tui reg float
26144 Show the floating point registers in the register window.
26146 @item tui reg general
26147 Show the general registers in the register window.
26150 Show the next register group. The list of register groups as well as
26151 their order is target specific. The predefined register groups are the
26152 following: @code{general}, @code{float}, @code{system}, @code{vector},
26153 @code{all}, @code{save}, @code{restore}.
26155 @item tui reg system
26156 Show the system registers in the register window.
26160 Update the source window and the current execution point.
26162 @item winheight @var{name} +@var{count}
26163 @itemx winheight @var{name} -@var{count}
26165 Change the height of the window @var{name} by @var{count}
26166 lines. Positive counts increase the height, while negative counts
26169 @item tabset @var{nchars}
26171 Set the width of tab stops to be @var{nchars} characters.
26174 @node TUI Configuration
26175 @section TUI Configuration Variables
26176 @cindex TUI configuration variables
26178 Several configuration variables control the appearance of TUI windows.
26181 @item set tui border-kind @var{kind}
26182 @kindex set tui border-kind
26183 Select the border appearance for the source, assembly and register windows.
26184 The possible values are the following:
26187 Use a space character to draw the border.
26190 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26193 Use the Alternate Character Set to draw the border. The border is
26194 drawn using character line graphics if the terminal supports them.
26197 @item set tui border-mode @var{mode}
26198 @kindex set tui border-mode
26199 @itemx set tui active-border-mode @var{mode}
26200 @kindex set tui active-border-mode
26201 Select the display attributes for the borders of the inactive windows
26202 or the active window. The @var{mode} can be one of the following:
26205 Use normal attributes to display the border.
26211 Use reverse video mode.
26214 Use half bright mode.
26216 @item half-standout
26217 Use half bright and standout mode.
26220 Use extra bright or bold mode.
26222 @item bold-standout
26223 Use extra bright or bold and standout mode.
26228 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26231 @cindex @sc{gnu} Emacs
26232 A special interface allows you to use @sc{gnu} Emacs to view (and
26233 edit) the source files for the program you are debugging with
26236 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26237 executable file you want to debug as an argument. This command starts
26238 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26239 created Emacs buffer.
26240 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26242 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26247 All ``terminal'' input and output goes through an Emacs buffer, called
26250 This applies both to @value{GDBN} commands and their output, and to the input
26251 and output done by the program you are debugging.
26253 This is useful because it means that you can copy the text of previous
26254 commands and input them again; you can even use parts of the output
26257 All the facilities of Emacs' Shell mode are available for interacting
26258 with your program. In particular, you can send signals the usual
26259 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26263 @value{GDBN} displays source code through Emacs.
26265 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26266 source file for that frame and puts an arrow (@samp{=>}) at the
26267 left margin of the current line. Emacs uses a separate buffer for
26268 source display, and splits the screen to show both your @value{GDBN} session
26271 Explicit @value{GDBN} @code{list} or search commands still produce output as
26272 usual, but you probably have no reason to use them from Emacs.
26275 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26276 a graphical mode, enabled by default, which provides further buffers
26277 that can control the execution and describe the state of your program.
26278 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26280 If you specify an absolute file name when prompted for the @kbd{M-x
26281 gdb} argument, then Emacs sets your current working directory to where
26282 your program resides. If you only specify the file name, then Emacs
26283 sets your current working directory to the directory associated
26284 with the previous buffer. In this case, @value{GDBN} may find your
26285 program by searching your environment's @code{PATH} variable, but on
26286 some operating systems it might not find the source. So, although the
26287 @value{GDBN} input and output session proceeds normally, the auxiliary
26288 buffer does not display the current source and line of execution.
26290 The initial working directory of @value{GDBN} is printed on the top
26291 line of the GUD buffer and this serves as a default for the commands
26292 that specify files for @value{GDBN} to operate on. @xref{Files,
26293 ,Commands to Specify Files}.
26295 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26296 need to call @value{GDBN} by a different name (for example, if you
26297 keep several configurations around, with different names) you can
26298 customize the Emacs variable @code{gud-gdb-command-name} to run the
26301 In the GUD buffer, you can use these special Emacs commands in
26302 addition to the standard Shell mode commands:
26306 Describe the features of Emacs' GUD Mode.
26309 Execute to another source line, like the @value{GDBN} @code{step} command; also
26310 update the display window to show the current file and location.
26313 Execute to next source line in this function, skipping all function
26314 calls, like the @value{GDBN} @code{next} command. Then update the display window
26315 to show the current file and location.
26318 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26319 display window accordingly.
26322 Execute until exit from the selected stack frame, like the @value{GDBN}
26323 @code{finish} command.
26326 Continue execution of your program, like the @value{GDBN} @code{continue}
26330 Go up the number of frames indicated by the numeric argument
26331 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26332 like the @value{GDBN} @code{up} command.
26335 Go down the number of frames indicated by the numeric argument, like the
26336 @value{GDBN} @code{down} command.
26339 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26340 tells @value{GDBN} to set a breakpoint on the source line point is on.
26342 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26343 separate frame which shows a backtrace when the GUD buffer is current.
26344 Move point to any frame in the stack and type @key{RET} to make it
26345 become the current frame and display the associated source in the
26346 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26347 selected frame become the current one. In graphical mode, the
26348 speedbar displays watch expressions.
26350 If you accidentally delete the source-display buffer, an easy way to get
26351 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26352 request a frame display; when you run under Emacs, this recreates
26353 the source buffer if necessary to show you the context of the current
26356 The source files displayed in Emacs are in ordinary Emacs buffers
26357 which are visiting the source files in the usual way. You can edit
26358 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26359 communicates with Emacs in terms of line numbers. If you add or
26360 delete lines from the text, the line numbers that @value{GDBN} knows cease
26361 to correspond properly with the code.
26363 A more detailed description of Emacs' interaction with @value{GDBN} is
26364 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26367 @c The following dropped because Epoch is nonstandard. Reactivate
26368 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
26370 @kindex Emacs Epoch environment
26374 Version 18 of @sc{gnu} Emacs has a built-in window system
26375 called the @code{epoch}
26376 environment. Users of this environment can use a new command,
26377 @code{inspect} which performs identically to @code{print} except that
26378 each value is printed in its own window.
26383 @chapter The @sc{gdb/mi} Interface
26385 @unnumberedsec Function and Purpose
26387 @cindex @sc{gdb/mi}, its purpose
26388 @sc{gdb/mi} is a line based machine oriented text interface to
26389 @value{GDBN} and is activated by specifying using the
26390 @option{--interpreter} command line option (@pxref{Mode Options}). It
26391 is specifically intended to support the development of systems which
26392 use the debugger as just one small component of a larger system.
26394 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26395 in the form of a reference manual.
26397 Note that @sc{gdb/mi} is still under construction, so some of the
26398 features described below are incomplete and subject to change
26399 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26401 @unnumberedsec Notation and Terminology
26403 @cindex notational conventions, for @sc{gdb/mi}
26404 This chapter uses the following notation:
26408 @code{|} separates two alternatives.
26411 @code{[ @var{something} ]} indicates that @var{something} is optional:
26412 it may or may not be given.
26415 @code{( @var{group} )*} means that @var{group} inside the parentheses
26416 may repeat zero or more times.
26419 @code{( @var{group} )+} means that @var{group} inside the parentheses
26420 may repeat one or more times.
26423 @code{"@var{string}"} means a literal @var{string}.
26427 @heading Dependencies
26431 * GDB/MI General Design::
26432 * GDB/MI Command Syntax::
26433 * GDB/MI Compatibility with CLI::
26434 * GDB/MI Development and Front Ends::
26435 * GDB/MI Output Records::
26436 * GDB/MI Simple Examples::
26437 * GDB/MI Command Description Format::
26438 * GDB/MI Breakpoint Commands::
26439 * GDB/MI Program Context::
26440 * GDB/MI Thread Commands::
26441 * GDB/MI Ada Tasking Commands::
26442 * GDB/MI Program Execution::
26443 * GDB/MI Stack Manipulation::
26444 * GDB/MI Variable Objects::
26445 * GDB/MI Data Manipulation::
26446 * GDB/MI Tracepoint Commands::
26447 * GDB/MI Symbol Query::
26448 * GDB/MI File Commands::
26450 * GDB/MI Kod Commands::
26451 * GDB/MI Memory Overlay Commands::
26452 * GDB/MI Signal Handling Commands::
26454 * GDB/MI Target Manipulation::
26455 * GDB/MI File Transfer Commands::
26456 * GDB/MI Miscellaneous Commands::
26459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26460 @node GDB/MI General Design
26461 @section @sc{gdb/mi} General Design
26462 @cindex GDB/MI General Design
26464 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26465 parts---commands sent to @value{GDBN}, responses to those commands
26466 and notifications. Each command results in exactly one response,
26467 indicating either successful completion of the command, or an error.
26468 For the commands that do not resume the target, the response contains the
26469 requested information. For the commands that resume the target, the
26470 response only indicates whether the target was successfully resumed.
26471 Notifications is the mechanism for reporting changes in the state of the
26472 target, or in @value{GDBN} state, that cannot conveniently be associated with
26473 a command and reported as part of that command response.
26475 The important examples of notifications are:
26479 Exec notifications. These are used to report changes in
26480 target state---when a target is resumed, or stopped. It would not
26481 be feasible to include this information in response of resuming
26482 commands, because one resume commands can result in multiple events in
26483 different threads. Also, quite some time may pass before any event
26484 happens in the target, while a frontend needs to know whether the resuming
26485 command itself was successfully executed.
26488 Console output, and status notifications. Console output
26489 notifications are used to report output of CLI commands, as well as
26490 diagnostics for other commands. Status notifications are used to
26491 report the progress of a long-running operation. Naturally, including
26492 this information in command response would mean no output is produced
26493 until the command is finished, which is undesirable.
26496 General notifications. Commands may have various side effects on
26497 the @value{GDBN} or target state beyond their official purpose. For example,
26498 a command may change the selected thread. Although such changes can
26499 be included in command response, using notification allows for more
26500 orthogonal frontend design.
26504 There's no guarantee that whenever an MI command reports an error,
26505 @value{GDBN} or the target are in any specific state, and especially,
26506 the state is not reverted to the state before the MI command was
26507 processed. Therefore, whenever an MI command results in an error,
26508 we recommend that the frontend refreshes all the information shown in
26509 the user interface.
26513 * Context management::
26514 * Asynchronous and non-stop modes::
26518 @node Context management
26519 @subsection Context management
26521 In most cases when @value{GDBN} accesses the target, this access is
26522 done in context of a specific thread and frame (@pxref{Frames}).
26523 Often, even when accessing global data, the target requires that a thread
26524 be specified. The CLI interface maintains the selected thread and frame,
26525 and supplies them to target on each command. This is convenient,
26526 because a command line user would not want to specify that information
26527 explicitly on each command, and because user interacts with
26528 @value{GDBN} via a single terminal, so no confusion is possible as
26529 to what thread and frame are the current ones.
26531 In the case of MI, the concept of selected thread and frame is less
26532 useful. First, a frontend can easily remember this information
26533 itself. Second, a graphical frontend can have more than one window,
26534 each one used for debugging a different thread, and the frontend might
26535 want to access additional threads for internal purposes. This
26536 increases the risk that by relying on implicitly selected thread, the
26537 frontend may be operating on a wrong one. Therefore, each MI command
26538 should explicitly specify which thread and frame to operate on. To
26539 make it possible, each MI command accepts the @samp{--thread} and
26540 @samp{--frame} options, the value to each is @value{GDBN} identifier
26541 for thread and frame to operate on.
26543 Usually, each top-level window in a frontend allows the user to select
26544 a thread and a frame, and remembers the user selection for further
26545 operations. However, in some cases @value{GDBN} may suggest that the
26546 current thread be changed. For example, when stopping on a breakpoint
26547 it is reasonable to switch to the thread where breakpoint is hit. For
26548 another example, if the user issues the CLI @samp{thread} command via
26549 the frontend, it is desirable to change the frontend's selected thread to the
26550 one specified by user. @value{GDBN} communicates the suggestion to
26551 change current thread using the @samp{=thread-selected} notification.
26552 No such notification is available for the selected frame at the moment.
26554 Note that historically, MI shares the selected thread with CLI, so
26555 frontends used the @code{-thread-select} to execute commands in the
26556 right context. However, getting this to work right is cumbersome. The
26557 simplest way is for frontend to emit @code{-thread-select} command
26558 before every command. This doubles the number of commands that need
26559 to be sent. The alternative approach is to suppress @code{-thread-select}
26560 if the selected thread in @value{GDBN} is supposed to be identical to the
26561 thread the frontend wants to operate on. However, getting this
26562 optimization right can be tricky. In particular, if the frontend
26563 sends several commands to @value{GDBN}, and one of the commands changes the
26564 selected thread, then the behaviour of subsequent commands will
26565 change. So, a frontend should either wait for response from such
26566 problematic commands, or explicitly add @code{-thread-select} for
26567 all subsequent commands. No frontend is known to do this exactly
26568 right, so it is suggested to just always pass the @samp{--thread} and
26569 @samp{--frame} options.
26571 @node Asynchronous and non-stop modes
26572 @subsection Asynchronous command execution and non-stop mode
26574 On some targets, @value{GDBN} is capable of processing MI commands
26575 even while the target is running. This is called @dfn{asynchronous
26576 command execution} (@pxref{Background Execution}). The frontend may
26577 specify a preferrence for asynchronous execution using the
26578 @code{-gdb-set target-async 1} command, which should be emitted before
26579 either running the executable or attaching to the target. After the
26580 frontend has started the executable or attached to the target, it can
26581 find if asynchronous execution is enabled using the
26582 @code{-list-target-features} command.
26584 Even if @value{GDBN} can accept a command while target is running,
26585 many commands that access the target do not work when the target is
26586 running. Therefore, asynchronous command execution is most useful
26587 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26588 it is possible to examine the state of one thread, while other threads
26591 When a given thread is running, MI commands that try to access the
26592 target in the context of that thread may not work, or may work only on
26593 some targets. In particular, commands that try to operate on thread's
26594 stack will not work, on any target. Commands that read memory, or
26595 modify breakpoints, may work or not work, depending on the target. Note
26596 that even commands that operate on global state, such as @code{print},
26597 @code{set}, and breakpoint commands, still access the target in the
26598 context of a specific thread, so frontend should try to find a
26599 stopped thread and perform the operation on that thread (using the
26600 @samp{--thread} option).
26602 Which commands will work in the context of a running thread is
26603 highly target dependent. However, the two commands
26604 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26605 to find the state of a thread, will always work.
26607 @node Thread groups
26608 @subsection Thread groups
26609 @value{GDBN} may be used to debug several processes at the same time.
26610 On some platfroms, @value{GDBN} may support debugging of several
26611 hardware systems, each one having several cores with several different
26612 processes running on each core. This section describes the MI
26613 mechanism to support such debugging scenarios.
26615 The key observation is that regardless of the structure of the
26616 target, MI can have a global list of threads, because most commands that
26617 accept the @samp{--thread} option do not need to know what process that
26618 thread belongs to. Therefore, it is not necessary to introduce
26619 neither additional @samp{--process} option, nor an notion of the
26620 current process in the MI interface. The only strictly new feature
26621 that is required is the ability to find how the threads are grouped
26624 To allow the user to discover such grouping, and to support arbitrary
26625 hierarchy of machines/cores/processes, MI introduces the concept of a
26626 @dfn{thread group}. Thread group is a collection of threads and other
26627 thread groups. A thread group always has a string identifier, a type,
26628 and may have additional attributes specific to the type. A new
26629 command, @code{-list-thread-groups}, returns the list of top-level
26630 thread groups, which correspond to processes that @value{GDBN} is
26631 debugging at the moment. By passing an identifier of a thread group
26632 to the @code{-list-thread-groups} command, it is possible to obtain
26633 the members of specific thread group.
26635 To allow the user to easily discover processes, and other objects, he
26636 wishes to debug, a concept of @dfn{available thread group} is
26637 introduced. Available thread group is an thread group that
26638 @value{GDBN} is not debugging, but that can be attached to, using the
26639 @code{-target-attach} command. The list of available top-level thread
26640 groups can be obtained using @samp{-list-thread-groups --available}.
26641 In general, the content of a thread group may be only retrieved only
26642 after attaching to that thread group.
26644 Thread groups are related to inferiors (@pxref{Inferiors and
26645 Programs}). Each inferior corresponds to a thread group of a special
26646 type @samp{process}, and some additional operations are permitted on
26647 such thread groups.
26649 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26650 @node GDB/MI Command Syntax
26651 @section @sc{gdb/mi} Command Syntax
26654 * GDB/MI Input Syntax::
26655 * GDB/MI Output Syntax::
26658 @node GDB/MI Input Syntax
26659 @subsection @sc{gdb/mi} Input Syntax
26661 @cindex input syntax for @sc{gdb/mi}
26662 @cindex @sc{gdb/mi}, input syntax
26664 @item @var{command} @expansion{}
26665 @code{@var{cli-command} | @var{mi-command}}
26667 @item @var{cli-command} @expansion{}
26668 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26669 @var{cli-command} is any existing @value{GDBN} CLI command.
26671 @item @var{mi-command} @expansion{}
26672 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26673 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26675 @item @var{token} @expansion{}
26676 "any sequence of digits"
26678 @item @var{option} @expansion{}
26679 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26681 @item @var{parameter} @expansion{}
26682 @code{@var{non-blank-sequence} | @var{c-string}}
26684 @item @var{operation} @expansion{}
26685 @emph{any of the operations described in this chapter}
26687 @item @var{non-blank-sequence} @expansion{}
26688 @emph{anything, provided it doesn't contain special characters such as
26689 "-", @var{nl}, """ and of course " "}
26691 @item @var{c-string} @expansion{}
26692 @code{""" @var{seven-bit-iso-c-string-content} """}
26694 @item @var{nl} @expansion{}
26703 The CLI commands are still handled by the @sc{mi} interpreter; their
26704 output is described below.
26707 The @code{@var{token}}, when present, is passed back when the command
26711 Some @sc{mi} commands accept optional arguments as part of the parameter
26712 list. Each option is identified by a leading @samp{-} (dash) and may be
26713 followed by an optional argument parameter. Options occur first in the
26714 parameter list and can be delimited from normal parameters using
26715 @samp{--} (this is useful when some parameters begin with a dash).
26722 We want easy access to the existing CLI syntax (for debugging).
26725 We want it to be easy to spot a @sc{mi} operation.
26728 @node GDB/MI Output Syntax
26729 @subsection @sc{gdb/mi} Output Syntax
26731 @cindex output syntax of @sc{gdb/mi}
26732 @cindex @sc{gdb/mi}, output syntax
26733 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26734 followed, optionally, by a single result record. This result record
26735 is for the most recent command. The sequence of output records is
26736 terminated by @samp{(gdb)}.
26738 If an input command was prefixed with a @code{@var{token}} then the
26739 corresponding output for that command will also be prefixed by that same
26743 @item @var{output} @expansion{}
26744 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26746 @item @var{result-record} @expansion{}
26747 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26749 @item @var{out-of-band-record} @expansion{}
26750 @code{@var{async-record} | @var{stream-record}}
26752 @item @var{async-record} @expansion{}
26753 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26755 @item @var{exec-async-output} @expansion{}
26756 @code{[ @var{token} ] "*" @var{async-output}}
26758 @item @var{status-async-output} @expansion{}
26759 @code{[ @var{token} ] "+" @var{async-output}}
26761 @item @var{notify-async-output} @expansion{}
26762 @code{[ @var{token} ] "=" @var{async-output}}
26764 @item @var{async-output} @expansion{}
26765 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
26767 @item @var{result-class} @expansion{}
26768 @code{"done" | "running" | "connected" | "error" | "exit"}
26770 @item @var{async-class} @expansion{}
26771 @code{"stopped" | @var{others}} (where @var{others} will be added
26772 depending on the needs---this is still in development).
26774 @item @var{result} @expansion{}
26775 @code{ @var{variable} "=" @var{value}}
26777 @item @var{variable} @expansion{}
26778 @code{ @var{string} }
26780 @item @var{value} @expansion{}
26781 @code{ @var{const} | @var{tuple} | @var{list} }
26783 @item @var{const} @expansion{}
26784 @code{@var{c-string}}
26786 @item @var{tuple} @expansion{}
26787 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26789 @item @var{list} @expansion{}
26790 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26791 @var{result} ( "," @var{result} )* "]" }
26793 @item @var{stream-record} @expansion{}
26794 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26796 @item @var{console-stream-output} @expansion{}
26797 @code{"~" @var{c-string}}
26799 @item @var{target-stream-output} @expansion{}
26800 @code{"@@" @var{c-string}}
26802 @item @var{log-stream-output} @expansion{}
26803 @code{"&" @var{c-string}}
26805 @item @var{nl} @expansion{}
26808 @item @var{token} @expansion{}
26809 @emph{any sequence of digits}.
26817 All output sequences end in a single line containing a period.
26820 The @code{@var{token}} is from the corresponding request. Note that
26821 for all async output, while the token is allowed by the grammar and
26822 may be output by future versions of @value{GDBN} for select async
26823 output messages, it is generally omitted. Frontends should treat
26824 all async output as reporting general changes in the state of the
26825 target and there should be no need to associate async output to any
26829 @cindex status output in @sc{gdb/mi}
26830 @var{status-async-output} contains on-going status information about the
26831 progress of a slow operation. It can be discarded. All status output is
26832 prefixed by @samp{+}.
26835 @cindex async output in @sc{gdb/mi}
26836 @var{exec-async-output} contains asynchronous state change on the target
26837 (stopped, started, disappeared). All async output is prefixed by
26841 @cindex notify output in @sc{gdb/mi}
26842 @var{notify-async-output} contains supplementary information that the
26843 client should handle (e.g., a new breakpoint information). All notify
26844 output is prefixed by @samp{=}.
26847 @cindex console output in @sc{gdb/mi}
26848 @var{console-stream-output} is output that should be displayed as is in the
26849 console. It is the textual response to a CLI command. All the console
26850 output is prefixed by @samp{~}.
26853 @cindex target output in @sc{gdb/mi}
26854 @var{target-stream-output} is the output produced by the target program.
26855 All the target output is prefixed by @samp{@@}.
26858 @cindex log output in @sc{gdb/mi}
26859 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26860 instance messages that should be displayed as part of an error log. All
26861 the log output is prefixed by @samp{&}.
26864 @cindex list output in @sc{gdb/mi}
26865 New @sc{gdb/mi} commands should only output @var{lists} containing
26871 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26872 details about the various output records.
26874 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26875 @node GDB/MI Compatibility with CLI
26876 @section @sc{gdb/mi} Compatibility with CLI
26878 @cindex compatibility, @sc{gdb/mi} and CLI
26879 @cindex @sc{gdb/mi}, compatibility with CLI
26881 For the developers convenience CLI commands can be entered directly,
26882 but there may be some unexpected behaviour. For example, commands
26883 that query the user will behave as if the user replied yes, breakpoint
26884 command lists are not executed and some CLI commands, such as
26885 @code{if}, @code{when} and @code{define}, prompt for further input with
26886 @samp{>}, which is not valid MI output.
26888 This feature may be removed at some stage in the future and it is
26889 recommended that front ends use the @code{-interpreter-exec} command
26890 (@pxref{-interpreter-exec}).
26892 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26893 @node GDB/MI Development and Front Ends
26894 @section @sc{gdb/mi} Development and Front Ends
26895 @cindex @sc{gdb/mi} development
26897 The application which takes the MI output and presents the state of the
26898 program being debugged to the user is called a @dfn{front end}.
26900 Although @sc{gdb/mi} is still incomplete, it is currently being used
26901 by a variety of front ends to @value{GDBN}. This makes it difficult
26902 to introduce new functionality without breaking existing usage. This
26903 section tries to minimize the problems by describing how the protocol
26906 Some changes in MI need not break a carefully designed front end, and
26907 for these the MI version will remain unchanged. The following is a
26908 list of changes that may occur within one level, so front ends should
26909 parse MI output in a way that can handle them:
26913 New MI commands may be added.
26916 New fields may be added to the output of any MI command.
26919 The range of values for fields with specified values, e.g.,
26920 @code{in_scope} (@pxref{-var-update}) may be extended.
26922 @c The format of field's content e.g type prefix, may change so parse it
26923 @c at your own risk. Yes, in general?
26925 @c The order of fields may change? Shouldn't really matter but it might
26926 @c resolve inconsistencies.
26929 If the changes are likely to break front ends, the MI version level
26930 will be increased by one. This will allow the front end to parse the
26931 output according to the MI version. Apart from mi0, new versions of
26932 @value{GDBN} will not support old versions of MI and it will be the
26933 responsibility of the front end to work with the new one.
26935 @c Starting with mi3, add a new command -mi-version that prints the MI
26938 The best way to avoid unexpected changes in MI that might break your front
26939 end is to make your project known to @value{GDBN} developers and
26940 follow development on @email{gdb@@sourceware.org} and
26941 @email{gdb-patches@@sourceware.org}.
26942 @cindex mailing lists
26944 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26945 @node GDB/MI Output Records
26946 @section @sc{gdb/mi} Output Records
26949 * GDB/MI Result Records::
26950 * GDB/MI Stream Records::
26951 * GDB/MI Async Records::
26952 * GDB/MI Frame Information::
26953 * GDB/MI Thread Information::
26954 * GDB/MI Ada Exception Information::
26957 @node GDB/MI Result Records
26958 @subsection @sc{gdb/mi} Result Records
26960 @cindex result records in @sc{gdb/mi}
26961 @cindex @sc{gdb/mi}, result records
26962 In addition to a number of out-of-band notifications, the response to a
26963 @sc{gdb/mi} command includes one of the following result indications:
26967 @item "^done" [ "," @var{results} ]
26968 The synchronous operation was successful, @code{@var{results}} are the return
26973 This result record is equivalent to @samp{^done}. Historically, it
26974 was output instead of @samp{^done} if the command has resumed the
26975 target. This behaviour is maintained for backward compatibility, but
26976 all frontends should treat @samp{^done} and @samp{^running}
26977 identically and rely on the @samp{*running} output record to determine
26978 which threads are resumed.
26982 @value{GDBN} has connected to a remote target.
26984 @item "^error" "," @var{c-string}
26986 The operation failed. The @code{@var{c-string}} contains the corresponding
26991 @value{GDBN} has terminated.
26995 @node GDB/MI Stream Records
26996 @subsection @sc{gdb/mi} Stream Records
26998 @cindex @sc{gdb/mi}, stream records
26999 @cindex stream records in @sc{gdb/mi}
27000 @value{GDBN} internally maintains a number of output streams: the console, the
27001 target, and the log. The output intended for each of these streams is
27002 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27004 Each stream record begins with a unique @dfn{prefix character} which
27005 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27006 Syntax}). In addition to the prefix, each stream record contains a
27007 @code{@var{string-output}}. This is either raw text (with an implicit new
27008 line) or a quoted C string (which does not contain an implicit newline).
27011 @item "~" @var{string-output}
27012 The console output stream contains text that should be displayed in the
27013 CLI console window. It contains the textual responses to CLI commands.
27015 @item "@@" @var{string-output}
27016 The target output stream contains any textual output from the running
27017 target. This is only present when GDB's event loop is truly
27018 asynchronous, which is currently only the case for remote targets.
27020 @item "&" @var{string-output}
27021 The log stream contains debugging messages being produced by @value{GDBN}'s
27025 @node GDB/MI Async Records
27026 @subsection @sc{gdb/mi} Async Records
27028 @cindex async records in @sc{gdb/mi}
27029 @cindex @sc{gdb/mi}, async records
27030 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27031 additional changes that have occurred. Those changes can either be a
27032 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27033 target activity (e.g., target stopped).
27035 The following is the list of possible async records:
27039 @item *running,thread-id="@var{thread}"
27040 The target is now running. The @var{thread} field tells which
27041 specific thread is now running, and can be @samp{all} if all threads
27042 are running. The frontend should assume that no interaction with a
27043 running thread is possible after this notification is produced.
27044 The frontend should not assume that this notification is output
27045 only once for any command. @value{GDBN} may emit this notification
27046 several times, either for different threads, because it cannot resume
27047 all threads together, or even for a single thread, if the thread must
27048 be stepped though some code before letting it run freely.
27050 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27051 The target has stopped. The @var{reason} field can have one of the
27055 @item breakpoint-hit
27056 A breakpoint was reached.
27057 @item watchpoint-trigger
27058 A watchpoint was triggered.
27059 @item read-watchpoint-trigger
27060 A read watchpoint was triggered.
27061 @item access-watchpoint-trigger
27062 An access watchpoint was triggered.
27063 @item function-finished
27064 An -exec-finish or similar CLI command was accomplished.
27065 @item location-reached
27066 An -exec-until or similar CLI command was accomplished.
27067 @item watchpoint-scope
27068 A watchpoint has gone out of scope.
27069 @item end-stepping-range
27070 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27071 similar CLI command was accomplished.
27072 @item exited-signalled
27073 The inferior exited because of a signal.
27075 The inferior exited.
27076 @item exited-normally
27077 The inferior exited normally.
27078 @item signal-received
27079 A signal was received by the inferior.
27081 The inferior has stopped due to a library being loaded or unloaded.
27082 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27083 set or when a @code{catch load} or @code{catch unload} catchpoint is
27084 in use (@pxref{Set Catchpoints}).
27086 The inferior has forked. This is reported when @code{catch fork}
27087 (@pxref{Set Catchpoints}) has been used.
27089 The inferior has vforked. This is reported in when @code{catch vfork}
27090 (@pxref{Set Catchpoints}) has been used.
27091 @item syscall-entry
27092 The inferior entered a system call. This is reported when @code{catch
27093 syscall} (@pxref{Set Catchpoints}) has been used.
27094 @item syscall-entry
27095 The inferior returned from a system call. This is reported when
27096 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27098 The inferior called @code{exec}. This is reported when @code{catch exec}
27099 (@pxref{Set Catchpoints}) has been used.
27102 The @var{id} field identifies the thread that directly caused the stop
27103 -- for example by hitting a breakpoint. Depending on whether all-stop
27104 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27105 stop all threads, or only the thread that directly triggered the stop.
27106 If all threads are stopped, the @var{stopped} field will have the
27107 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27108 field will be a list of thread identifiers. Presently, this list will
27109 always include a single thread, but frontend should be prepared to see
27110 several threads in the list. The @var{core} field reports the
27111 processor core on which the stop event has happened. This field may be absent
27112 if such information is not available.
27114 @item =thread-group-added,id="@var{id}"
27115 @itemx =thread-group-removed,id="@var{id}"
27116 A thread group was either added or removed. The @var{id} field
27117 contains the @value{GDBN} identifier of the thread group. When a thread
27118 group is added, it generally might not be associated with a running
27119 process. When a thread group is removed, its id becomes invalid and
27120 cannot be used in any way.
27122 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27123 A thread group became associated with a running program,
27124 either because the program was just started or the thread group
27125 was attached to a program. The @var{id} field contains the
27126 @value{GDBN} identifier of the thread group. The @var{pid} field
27127 contains process identifier, specific to the operating system.
27129 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27130 A thread group is no longer associated with a running program,
27131 either because the program has exited, or because it was detached
27132 from. The @var{id} field contains the @value{GDBN} identifier of the
27133 thread group. @var{code} is the exit code of the inferior; it exists
27134 only when the inferior exited with some code.
27136 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27137 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27138 A thread either was created, or has exited. The @var{id} field
27139 contains the @value{GDBN} identifier of the thread. The @var{gid}
27140 field identifies the thread group this thread belongs to.
27142 @item =thread-selected,id="@var{id}"
27143 Informs that the selected thread was changed as result of the last
27144 command. This notification is not emitted as result of @code{-thread-select}
27145 command but is emitted whenever an MI command that is not documented
27146 to change the selected thread actually changes it. In particular,
27147 invoking, directly or indirectly (via user-defined command), the CLI
27148 @code{thread} command, will generate this notification.
27150 We suggest that in response to this notification, front ends
27151 highlight the selected thread and cause subsequent commands to apply to
27154 @item =library-loaded,...
27155 Reports that a new library file was loaded by the program. This
27156 notification has 4 fields---@var{id}, @var{target-name},
27157 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
27158 opaque identifier of the library. For remote debugging case,
27159 @var{target-name} and @var{host-name} fields give the name of the
27160 library file on the target, and on the host respectively. For native
27161 debugging, both those fields have the same value. The
27162 @var{symbols-loaded} field is emitted only for backward compatibility
27163 and should not be relied on to convey any useful information. The
27164 @var{thread-group} field, if present, specifies the id of the thread
27165 group in whose context the library was loaded. If the field is
27166 absent, it means the library was loaded in the context of all present
27169 @item =library-unloaded,...
27170 Reports that a library was unloaded by the program. This notification
27171 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27172 the same meaning as for the @code{=library-loaded} notification.
27173 The @var{thread-group} field, if present, specifies the id of the
27174 thread group in whose context the library was unloaded. If the field is
27175 absent, it means the library was unloaded in the context of all present
27178 @item =breakpoint-created,bkpt=@{...@}
27179 @itemx =breakpoint-modified,bkpt=@{...@}
27180 @itemx =breakpoint-deleted,bkpt=@{...@}
27181 Reports that a breakpoint was created, modified, or deleted,
27182 respectively. Only user-visible breakpoints are reported to the MI
27185 The @var{bkpt} argument is of the same form as returned by the various
27186 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
27188 Note that if a breakpoint is emitted in the result record of a
27189 command, then it will not also be emitted in an async record.
27193 @node GDB/MI Frame Information
27194 @subsection @sc{gdb/mi} Frame Information
27196 Response from many MI commands includes an information about stack
27197 frame. This information is a tuple that may have the following
27202 The level of the stack frame. The innermost frame has the level of
27203 zero. This field is always present.
27206 The name of the function corresponding to the frame. This field may
27207 be absent if @value{GDBN} is unable to determine the function name.
27210 The code address for the frame. This field is always present.
27213 The name of the source files that correspond to the frame's code
27214 address. This field may be absent.
27217 The source line corresponding to the frames' code address. This field
27221 The name of the binary file (either executable or shared library) the
27222 corresponds to the frame's code address. This field may be absent.
27226 @node GDB/MI Thread Information
27227 @subsection @sc{gdb/mi} Thread Information
27229 Whenever @value{GDBN} has to report an information about a thread, it
27230 uses a tuple with the following fields:
27234 The numeric id assigned to the thread by @value{GDBN}. This field is
27238 Target-specific string identifying the thread. This field is always present.
27241 Additional information about the thread provided by the target.
27242 It is supposed to be human-readable and not interpreted by the
27243 frontend. This field is optional.
27246 Either @samp{stopped} or @samp{running}, depending on whether the
27247 thread is presently running. This field is always present.
27250 The value of this field is an integer number of the processor core the
27251 thread was last seen on. This field is optional.
27254 @node GDB/MI Ada Exception Information
27255 @subsection @sc{gdb/mi} Ada Exception Information
27257 Whenever a @code{*stopped} record is emitted because the program
27258 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27259 @value{GDBN} provides the name of the exception that was raised via
27260 the @code{exception-name} field.
27262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27263 @node GDB/MI Simple Examples
27264 @section Simple Examples of @sc{gdb/mi} Interaction
27265 @cindex @sc{gdb/mi}, simple examples
27267 This subsection presents several simple examples of interaction using
27268 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27269 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27270 the output received from @sc{gdb/mi}.
27272 Note the line breaks shown in the examples are here only for
27273 readability, they don't appear in the real output.
27275 @subheading Setting a Breakpoint
27277 Setting a breakpoint generates synchronous output which contains detailed
27278 information of the breakpoint.
27281 -> -break-insert main
27282 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27283 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27284 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
27288 @subheading Program Execution
27290 Program execution generates asynchronous records and MI gives the
27291 reason that execution stopped.
27297 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27298 frame=@{addr="0x08048564",func="main",
27299 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27300 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27305 <- *stopped,reason="exited-normally"
27309 @subheading Quitting @value{GDBN}
27311 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27319 Please note that @samp{^exit} is printed immediately, but it might
27320 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27321 performs necessary cleanups, including killing programs being debugged
27322 or disconnecting from debug hardware, so the frontend should wait till
27323 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27324 fails to exit in reasonable time.
27326 @subheading A Bad Command
27328 Here's what happens if you pass a non-existent command:
27332 <- ^error,msg="Undefined MI command: rubbish"
27337 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27338 @node GDB/MI Command Description Format
27339 @section @sc{gdb/mi} Command Description Format
27341 The remaining sections describe blocks of commands. Each block of
27342 commands is laid out in a fashion similar to this section.
27344 @subheading Motivation
27346 The motivation for this collection of commands.
27348 @subheading Introduction
27350 A brief introduction to this collection of commands as a whole.
27352 @subheading Commands
27354 For each command in the block, the following is described:
27356 @subsubheading Synopsis
27359 -command @var{args}@dots{}
27362 @subsubheading Result
27364 @subsubheading @value{GDBN} Command
27366 The corresponding @value{GDBN} CLI command(s), if any.
27368 @subsubheading Example
27370 Example(s) formatted for readability. Some of the described commands have
27371 not been implemented yet and these are labeled N.A.@: (not available).
27374 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27375 @node GDB/MI Breakpoint Commands
27376 @section @sc{gdb/mi} Breakpoint Commands
27378 @cindex breakpoint commands for @sc{gdb/mi}
27379 @cindex @sc{gdb/mi}, breakpoint commands
27380 This section documents @sc{gdb/mi} commands for manipulating
27383 @subheading The @code{-break-after} Command
27384 @findex -break-after
27386 @subsubheading Synopsis
27389 -break-after @var{number} @var{count}
27392 The breakpoint number @var{number} is not in effect until it has been
27393 hit @var{count} times. To see how this is reflected in the output of
27394 the @samp{-break-list} command, see the description of the
27395 @samp{-break-list} command below.
27397 @subsubheading @value{GDBN} Command
27399 The corresponding @value{GDBN} command is @samp{ignore}.
27401 @subsubheading Example
27406 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27407 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27408 fullname="/home/foo/hello.c",line="5",times="0"@}
27415 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27416 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27417 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27418 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27419 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27420 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27421 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27422 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27423 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27424 line="5",times="0",ignore="3"@}]@}
27429 @subheading The @code{-break-catch} Command
27430 @findex -break-catch
27433 @subheading The @code{-break-commands} Command
27434 @findex -break-commands
27436 @subsubheading Synopsis
27439 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27442 Specifies the CLI commands that should be executed when breakpoint
27443 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27444 are the commands. If no command is specified, any previously-set
27445 commands are cleared. @xref{Break Commands}. Typical use of this
27446 functionality is tracing a program, that is, printing of values of
27447 some variables whenever breakpoint is hit and then continuing.
27449 @subsubheading @value{GDBN} Command
27451 The corresponding @value{GDBN} command is @samp{commands}.
27453 @subsubheading Example
27458 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27459 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27460 fullname="/home/foo/hello.c",line="5",times="0"@}
27462 -break-commands 1 "print v" "continue"
27467 @subheading The @code{-break-condition} Command
27468 @findex -break-condition
27470 @subsubheading Synopsis
27473 -break-condition @var{number} @var{expr}
27476 Breakpoint @var{number} will stop the program only if the condition in
27477 @var{expr} is true. The condition becomes part of the
27478 @samp{-break-list} output (see the description of the @samp{-break-list}
27481 @subsubheading @value{GDBN} Command
27483 The corresponding @value{GDBN} command is @samp{condition}.
27485 @subsubheading Example
27489 -break-condition 1 1
27493 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27494 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27495 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27496 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27497 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27498 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27499 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27500 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27501 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27502 line="5",cond="1",times="0",ignore="3"@}]@}
27506 @subheading The @code{-break-delete} Command
27507 @findex -break-delete
27509 @subsubheading Synopsis
27512 -break-delete ( @var{breakpoint} )+
27515 Delete the breakpoint(s) whose number(s) are specified in the argument
27516 list. This is obviously reflected in the breakpoint list.
27518 @subsubheading @value{GDBN} Command
27520 The corresponding @value{GDBN} command is @samp{delete}.
27522 @subsubheading Example
27530 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27531 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27532 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27533 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27534 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27535 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27536 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27541 @subheading The @code{-break-disable} Command
27542 @findex -break-disable
27544 @subsubheading Synopsis
27547 -break-disable ( @var{breakpoint} )+
27550 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27551 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27553 @subsubheading @value{GDBN} Command
27555 The corresponding @value{GDBN} command is @samp{disable}.
27557 @subsubheading Example
27565 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27566 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27567 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27568 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27569 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27570 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27571 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27572 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27573 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27574 line="5",times="0"@}]@}
27578 @subheading The @code{-break-enable} Command
27579 @findex -break-enable
27581 @subsubheading Synopsis
27584 -break-enable ( @var{breakpoint} )+
27587 Enable (previously disabled) @var{breakpoint}(s).
27589 @subsubheading @value{GDBN} Command
27591 The corresponding @value{GDBN} command is @samp{enable}.
27593 @subsubheading Example
27601 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27602 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27603 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27604 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27605 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27606 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27607 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27608 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27609 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27610 line="5",times="0"@}]@}
27614 @subheading The @code{-break-info} Command
27615 @findex -break-info
27617 @subsubheading Synopsis
27620 -break-info @var{breakpoint}
27624 Get information about a single breakpoint.
27626 @subsubheading @value{GDBN} Command
27628 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27630 @subsubheading Example
27633 @subheading The @code{-break-insert} Command
27634 @findex -break-insert
27636 @subsubheading Synopsis
27639 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27640 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27641 [ -p @var{thread} ] [ @var{location} ]
27645 If specified, @var{location}, can be one of:
27652 @item filename:linenum
27653 @item filename:function
27657 The possible optional parameters of this command are:
27661 Insert a temporary breakpoint.
27663 Insert a hardware breakpoint.
27664 @item -c @var{condition}
27665 Make the breakpoint conditional on @var{condition}.
27666 @item -i @var{ignore-count}
27667 Initialize the @var{ignore-count}.
27669 If @var{location} cannot be parsed (for example if it
27670 refers to unknown files or functions), create a pending
27671 breakpoint. Without this flag, @value{GDBN} will report
27672 an error, and won't create a breakpoint, if @var{location}
27675 Create a disabled breakpoint.
27677 Create a tracepoint. @xref{Tracepoints}. When this parameter
27678 is used together with @samp{-h}, a fast tracepoint is created.
27681 @subsubheading Result
27683 The result is in the form:
27686 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
27687 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
27688 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
27689 times="@var{times}"@}
27693 where @var{number} is the @value{GDBN} number for this breakpoint,
27694 @var{funcname} is the name of the function where the breakpoint was
27695 inserted, @var{filename} is the name of the source file which contains
27696 this function, @var{lineno} is the source line number within that file
27697 and @var{times} the number of times that the breakpoint has been hit
27698 (always 0 for -break-insert but may be greater for -break-info or -break-list
27699 which use the same output).
27701 Note: this format is open to change.
27702 @c An out-of-band breakpoint instead of part of the result?
27704 @subsubheading @value{GDBN} Command
27706 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27707 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
27709 @subsubheading Example
27714 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27715 fullname="/home/foo/recursive2.c,line="4",times="0"@}
27717 -break-insert -t foo
27718 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27719 fullname="/home/foo/recursive2.c,line="11",times="0"@}
27722 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27723 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27724 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27725 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27726 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27727 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27728 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27729 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27730 addr="0x0001072c", func="main",file="recursive2.c",
27731 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
27732 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27733 addr="0x00010774",func="foo",file="recursive2.c",
27734 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
27736 -break-insert -r foo.*
27737 ~int foo(int, int);
27738 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27739 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
27743 @subheading The @code{-break-list} Command
27744 @findex -break-list
27746 @subsubheading Synopsis
27752 Displays the list of inserted breakpoints, showing the following fields:
27756 number of the breakpoint
27758 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27760 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27763 is the breakpoint enabled or no: @samp{y} or @samp{n}
27765 memory location at which the breakpoint is set
27767 logical location of the breakpoint, expressed by function name, file
27770 number of times the breakpoint has been hit
27773 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27774 @code{body} field is an empty list.
27776 @subsubheading @value{GDBN} Command
27778 The corresponding @value{GDBN} command is @samp{info break}.
27780 @subsubheading Example
27785 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27786 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27787 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27788 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27789 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27790 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27791 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27792 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27793 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27794 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27795 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27796 line="13",times="0"@}]@}
27800 Here's an example of the result when there are no breakpoints:
27805 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27806 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27807 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27808 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27809 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27810 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27811 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27816 @subheading The @code{-break-passcount} Command
27817 @findex -break-passcount
27819 @subsubheading Synopsis
27822 -break-passcount @var{tracepoint-number} @var{passcount}
27825 Set the passcount for tracepoint @var{tracepoint-number} to
27826 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27827 is not a tracepoint, error is emitted. This corresponds to CLI
27828 command @samp{passcount}.
27830 @subheading The @code{-break-watch} Command
27831 @findex -break-watch
27833 @subsubheading Synopsis
27836 -break-watch [ -a | -r ]
27839 Create a watchpoint. With the @samp{-a} option it will create an
27840 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27841 read from or on a write to the memory location. With the @samp{-r}
27842 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27843 trigger only when the memory location is accessed for reading. Without
27844 either of the options, the watchpoint created is a regular watchpoint,
27845 i.e., it will trigger when the memory location is accessed for writing.
27846 @xref{Set Watchpoints, , Setting Watchpoints}.
27848 Note that @samp{-break-list} will report a single list of watchpoints and
27849 breakpoints inserted.
27851 @subsubheading @value{GDBN} Command
27853 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27856 @subsubheading Example
27858 Setting a watchpoint on a variable in the @code{main} function:
27863 ^done,wpt=@{number="2",exp="x"@}
27868 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27869 value=@{old="-268439212",new="55"@},
27870 frame=@{func="main",args=[],file="recursive2.c",
27871 fullname="/home/foo/bar/recursive2.c",line="5"@}
27875 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27876 the program execution twice: first for the variable changing value, then
27877 for the watchpoint going out of scope.
27882 ^done,wpt=@{number="5",exp="C"@}
27887 *stopped,reason="watchpoint-trigger",
27888 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27889 frame=@{func="callee4",args=[],
27890 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27891 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27896 *stopped,reason="watchpoint-scope",wpnum="5",
27897 frame=@{func="callee3",args=[@{name="strarg",
27898 value="0x11940 \"A string argument.\""@}],
27899 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27900 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27904 Listing breakpoints and watchpoints, at different points in the program
27905 execution. Note that once the watchpoint goes out of scope, it is
27911 ^done,wpt=@{number="2",exp="C"@}
27914 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27915 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27916 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27917 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27918 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27919 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27920 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27921 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27922 addr="0x00010734",func="callee4",
27923 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27924 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27925 bkpt=@{number="2",type="watchpoint",disp="keep",
27926 enabled="y",addr="",what="C",times="0"@}]@}
27931 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27932 value=@{old="-276895068",new="3"@},
27933 frame=@{func="callee4",args=[],
27934 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27935 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27938 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27939 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27940 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27941 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27942 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27943 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27944 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27945 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27946 addr="0x00010734",func="callee4",
27947 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27948 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27949 bkpt=@{number="2",type="watchpoint",disp="keep",
27950 enabled="y",addr="",what="C",times="-5"@}]@}
27954 ^done,reason="watchpoint-scope",wpnum="2",
27955 frame=@{func="callee3",args=[@{name="strarg",
27956 value="0x11940 \"A string argument.\""@}],
27957 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27958 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27961 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27962 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27963 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27964 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27965 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27966 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27967 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27968 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27969 addr="0x00010734",func="callee4",
27970 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27971 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27976 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27977 @node GDB/MI Program Context
27978 @section @sc{gdb/mi} Program Context
27980 @subheading The @code{-exec-arguments} Command
27981 @findex -exec-arguments
27984 @subsubheading Synopsis
27987 -exec-arguments @var{args}
27990 Set the inferior program arguments, to be used in the next
27993 @subsubheading @value{GDBN} Command
27995 The corresponding @value{GDBN} command is @samp{set args}.
27997 @subsubheading Example
28001 -exec-arguments -v word
28008 @subheading The @code{-exec-show-arguments} Command
28009 @findex -exec-show-arguments
28011 @subsubheading Synopsis
28014 -exec-show-arguments
28017 Print the arguments of the program.
28019 @subsubheading @value{GDBN} Command
28021 The corresponding @value{GDBN} command is @samp{show args}.
28023 @subsubheading Example
28028 @subheading The @code{-environment-cd} Command
28029 @findex -environment-cd
28031 @subsubheading Synopsis
28034 -environment-cd @var{pathdir}
28037 Set @value{GDBN}'s working directory.
28039 @subsubheading @value{GDBN} Command
28041 The corresponding @value{GDBN} command is @samp{cd}.
28043 @subsubheading Example
28047 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28053 @subheading The @code{-environment-directory} Command
28054 @findex -environment-directory
28056 @subsubheading Synopsis
28059 -environment-directory [ -r ] [ @var{pathdir} ]+
28062 Add directories @var{pathdir} to beginning of search path for source files.
28063 If the @samp{-r} option is used, the search path is reset to the default
28064 search path. If directories @var{pathdir} are supplied in addition to the
28065 @samp{-r} option, the search path is first reset and then addition
28067 Multiple directories may be specified, separated by blanks. Specifying
28068 multiple directories in a single command
28069 results in the directories added to the beginning of the
28070 search path in the same order they were presented in the command.
28071 If blanks are needed as
28072 part of a directory name, double-quotes should be used around
28073 the name. In the command output, the path will show up separated
28074 by the system directory-separator character. The directory-separator
28075 character must not be used
28076 in any directory name.
28077 If no directories are specified, the current search path is displayed.
28079 @subsubheading @value{GDBN} Command
28081 The corresponding @value{GDBN} command is @samp{dir}.
28083 @subsubheading Example
28087 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28088 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28090 -environment-directory ""
28091 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28093 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28094 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28096 -environment-directory -r
28097 ^done,source-path="$cdir:$cwd"
28102 @subheading The @code{-environment-path} Command
28103 @findex -environment-path
28105 @subsubheading Synopsis
28108 -environment-path [ -r ] [ @var{pathdir} ]+
28111 Add directories @var{pathdir} to beginning of search path for object files.
28112 If the @samp{-r} option is used, the search path is reset to the original
28113 search path that existed at gdb start-up. If directories @var{pathdir} are
28114 supplied in addition to the
28115 @samp{-r} option, the search path is first reset and then addition
28117 Multiple directories may be specified, separated by blanks. Specifying
28118 multiple directories in a single command
28119 results in the directories added to the beginning of the
28120 search path in the same order they were presented in the command.
28121 If blanks are needed as
28122 part of a directory name, double-quotes should be used around
28123 the name. In the command output, the path will show up separated
28124 by the system directory-separator character. The directory-separator
28125 character must not be used
28126 in any directory name.
28127 If no directories are specified, the current path is displayed.
28130 @subsubheading @value{GDBN} Command
28132 The corresponding @value{GDBN} command is @samp{path}.
28134 @subsubheading Example
28139 ^done,path="/usr/bin"
28141 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28142 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28144 -environment-path -r /usr/local/bin
28145 ^done,path="/usr/local/bin:/usr/bin"
28150 @subheading The @code{-environment-pwd} Command
28151 @findex -environment-pwd
28153 @subsubheading Synopsis
28159 Show the current working directory.
28161 @subsubheading @value{GDBN} Command
28163 The corresponding @value{GDBN} command is @samp{pwd}.
28165 @subsubheading Example
28170 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28174 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28175 @node GDB/MI Thread Commands
28176 @section @sc{gdb/mi} Thread Commands
28179 @subheading The @code{-thread-info} Command
28180 @findex -thread-info
28182 @subsubheading Synopsis
28185 -thread-info [ @var{thread-id} ]
28188 Reports information about either a specific thread, if
28189 the @var{thread-id} parameter is present, or about all
28190 threads. When printing information about all threads,
28191 also reports the current thread.
28193 @subsubheading @value{GDBN} Command
28195 The @samp{info thread} command prints the same information
28198 @subsubheading Result
28200 The result is a list of threads. The following attributes are
28201 defined for a given thread:
28205 This field exists only for the current thread. It has the value @samp{*}.
28208 The identifier that @value{GDBN} uses to refer to the thread.
28211 The identifier that the target uses to refer to the thread.
28214 Extra information about the thread, in a target-specific format. This
28218 The name of the thread. If the user specified a name using the
28219 @code{thread name} command, then this name is given. Otherwise, if
28220 @value{GDBN} can extract the thread name from the target, then that
28221 name is given. If @value{GDBN} cannot find the thread name, then this
28225 The stack frame currently executing in the thread.
28228 The thread's state. The @samp{state} field may have the following
28233 The thread is stopped. Frame information is available for stopped
28237 The thread is running. There's no frame information for running
28243 If @value{GDBN} can find the CPU core on which this thread is running,
28244 then this field is the core identifier. This field is optional.
28248 @subsubheading Example
28253 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28254 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28255 args=[]@},state="running"@},
28256 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28257 frame=@{level="0",addr="0x0804891f",func="foo",
28258 args=[@{name="i",value="10"@}],
28259 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28260 state="running"@}],
28261 current-thread-id="1"
28265 @subheading The @code{-thread-list-ids} Command
28266 @findex -thread-list-ids
28268 @subsubheading Synopsis
28274 Produces a list of the currently known @value{GDBN} thread ids. At the
28275 end of the list it also prints the total number of such threads.
28277 This command is retained for historical reasons, the
28278 @code{-thread-info} command should be used instead.
28280 @subsubheading @value{GDBN} Command
28282 Part of @samp{info threads} supplies the same information.
28284 @subsubheading Example
28289 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28290 current-thread-id="1",number-of-threads="3"
28295 @subheading The @code{-thread-select} Command
28296 @findex -thread-select
28298 @subsubheading Synopsis
28301 -thread-select @var{threadnum}
28304 Make @var{threadnum} the current thread. It prints the number of the new
28305 current thread, and the topmost frame for that thread.
28307 This command is deprecated in favor of explicitly using the
28308 @samp{--thread} option to each command.
28310 @subsubheading @value{GDBN} Command
28312 The corresponding @value{GDBN} command is @samp{thread}.
28314 @subsubheading Example
28321 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28322 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28326 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28327 number-of-threads="3"
28330 ^done,new-thread-id="3",
28331 frame=@{level="0",func="vprintf",
28332 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28333 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28337 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28338 @node GDB/MI Ada Tasking Commands
28339 @section @sc{gdb/mi} Ada Tasking Commands
28341 @subheading The @code{-ada-task-info} Command
28342 @findex -ada-task-info
28344 @subsubheading Synopsis
28347 -ada-task-info [ @var{task-id} ]
28350 Reports information about either a specific Ada task, if the
28351 @var{task-id} parameter is present, or about all Ada tasks.
28353 @subsubheading @value{GDBN} Command
28355 The @samp{info tasks} command prints the same information
28356 about all Ada tasks (@pxref{Ada Tasks}).
28358 @subsubheading Result
28360 The result is a table of Ada tasks. The following columns are
28361 defined for each Ada task:
28365 This field exists only for the current thread. It has the value @samp{*}.
28368 The identifier that @value{GDBN} uses to refer to the Ada task.
28371 The identifier that the target uses to refer to the Ada task.
28374 The identifier of the thread corresponding to the Ada task.
28376 This field should always exist, as Ada tasks are always implemented
28377 on top of a thread. But if @value{GDBN} cannot find this corresponding
28378 thread for any reason, the field is omitted.
28381 This field exists only when the task was created by another task.
28382 In this case, it provides the ID of the parent task.
28385 The base priority of the task.
28388 The current state of the task. For a detailed description of the
28389 possible states, see @ref{Ada Tasks}.
28392 The name of the task.
28396 @subsubheading Example
28400 ^done,tasks=@{nr_rows="3",nr_cols="8",
28401 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28402 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28403 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28404 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28405 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28406 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28407 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28408 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28409 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28410 state="Child Termination Wait",name="main_task"@}]@}
28414 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28415 @node GDB/MI Program Execution
28416 @section @sc{gdb/mi} Program Execution
28418 These are the asynchronous commands which generate the out-of-band
28419 record @samp{*stopped}. Currently @value{GDBN} only really executes
28420 asynchronously with remote targets and this interaction is mimicked in
28423 @subheading The @code{-exec-continue} Command
28424 @findex -exec-continue
28426 @subsubheading Synopsis
28429 -exec-continue [--reverse] [--all|--thread-group N]
28432 Resumes the execution of the inferior program, which will continue
28433 to execute until it reaches a debugger stop event. If the
28434 @samp{--reverse} option is specified, execution resumes in reverse until
28435 it reaches a stop event. Stop events may include
28438 breakpoints or watchpoints
28440 signals or exceptions
28442 the end of the process (or its beginning under @samp{--reverse})
28444 the end or beginning of a replay log if one is being used.
28446 In all-stop mode (@pxref{All-Stop
28447 Mode}), may resume only one thread, or all threads, depending on the
28448 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28449 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28450 ignored in all-stop mode. If the @samp{--thread-group} options is
28451 specified, then all threads in that thread group are resumed.
28453 @subsubheading @value{GDBN} Command
28455 The corresponding @value{GDBN} corresponding is @samp{continue}.
28457 @subsubheading Example
28464 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28465 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28471 @subheading The @code{-exec-finish} Command
28472 @findex -exec-finish
28474 @subsubheading Synopsis
28477 -exec-finish [--reverse]
28480 Resumes the execution of the inferior program until the current
28481 function is exited. Displays the results returned by the function.
28482 If the @samp{--reverse} option is specified, resumes the reverse
28483 execution of the inferior program until the point where current
28484 function was called.
28486 @subsubheading @value{GDBN} Command
28488 The corresponding @value{GDBN} command is @samp{finish}.
28490 @subsubheading Example
28492 Function returning @code{void}.
28499 *stopped,reason="function-finished",frame=@{func="main",args=[],
28500 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28504 Function returning other than @code{void}. The name of the internal
28505 @value{GDBN} variable storing the result is printed, together with the
28512 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28513 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28514 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28515 gdb-result-var="$1",return-value="0"
28520 @subheading The @code{-exec-interrupt} Command
28521 @findex -exec-interrupt
28523 @subsubheading Synopsis
28526 -exec-interrupt [--all|--thread-group N]
28529 Interrupts the background execution of the target. Note how the token
28530 associated with the stop message is the one for the execution command
28531 that has been interrupted. The token for the interrupt itself only
28532 appears in the @samp{^done} output. If the user is trying to
28533 interrupt a non-running program, an error message will be printed.
28535 Note that when asynchronous execution is enabled, this command is
28536 asynchronous just like other execution commands. That is, first the
28537 @samp{^done} response will be printed, and the target stop will be
28538 reported after that using the @samp{*stopped} notification.
28540 In non-stop mode, only the context thread is interrupted by default.
28541 All threads (in all inferiors) will be interrupted if the
28542 @samp{--all} option is specified. If the @samp{--thread-group}
28543 option is specified, all threads in that group will be interrupted.
28545 @subsubheading @value{GDBN} Command
28547 The corresponding @value{GDBN} command is @samp{interrupt}.
28549 @subsubheading Example
28560 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28561 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28562 fullname="/home/foo/bar/try.c",line="13"@}
28567 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28571 @subheading The @code{-exec-jump} Command
28574 @subsubheading Synopsis
28577 -exec-jump @var{location}
28580 Resumes execution of the inferior program at the location specified by
28581 parameter. @xref{Specify Location}, for a description of the
28582 different forms of @var{location}.
28584 @subsubheading @value{GDBN} Command
28586 The corresponding @value{GDBN} command is @samp{jump}.
28588 @subsubheading Example
28591 -exec-jump foo.c:10
28592 *running,thread-id="all"
28597 @subheading The @code{-exec-next} Command
28600 @subsubheading Synopsis
28603 -exec-next [--reverse]
28606 Resumes execution of the inferior program, stopping when the beginning
28607 of the next source line is reached.
28609 If the @samp{--reverse} option is specified, resumes reverse execution
28610 of the inferior program, stopping at the beginning of the previous
28611 source line. If you issue this command on the first line of a
28612 function, it will take you back to the caller of that function, to the
28613 source line where the function was called.
28616 @subsubheading @value{GDBN} Command
28618 The corresponding @value{GDBN} command is @samp{next}.
28620 @subsubheading Example
28626 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28631 @subheading The @code{-exec-next-instruction} Command
28632 @findex -exec-next-instruction
28634 @subsubheading Synopsis
28637 -exec-next-instruction [--reverse]
28640 Executes one machine instruction. If the instruction is a function
28641 call, continues until the function returns. If the program stops at an
28642 instruction in the middle of a source line, the address will be
28645 If the @samp{--reverse} option is specified, resumes reverse execution
28646 of the inferior program, stopping at the previous instruction. If the
28647 previously executed instruction was a return from another function,
28648 it will continue to execute in reverse until the call to that function
28649 (from the current stack frame) is reached.
28651 @subsubheading @value{GDBN} Command
28653 The corresponding @value{GDBN} command is @samp{nexti}.
28655 @subsubheading Example
28659 -exec-next-instruction
28663 *stopped,reason="end-stepping-range",
28664 addr="0x000100d4",line="5",file="hello.c"
28669 @subheading The @code{-exec-return} Command
28670 @findex -exec-return
28672 @subsubheading Synopsis
28678 Makes current function return immediately. Doesn't execute the inferior.
28679 Displays the new current frame.
28681 @subsubheading @value{GDBN} Command
28683 The corresponding @value{GDBN} command is @samp{return}.
28685 @subsubheading Example
28689 200-break-insert callee4
28690 200^done,bkpt=@{number="1",addr="0x00010734",
28691 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28696 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28697 frame=@{func="callee4",args=[],
28698 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28699 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28705 111^done,frame=@{level="0",func="callee3",
28706 args=[@{name="strarg",
28707 value="0x11940 \"A string argument.\""@}],
28708 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28709 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28714 @subheading The @code{-exec-run} Command
28717 @subsubheading Synopsis
28720 -exec-run [--all | --thread-group N]
28723 Starts execution of the inferior from the beginning. The inferior
28724 executes until either a breakpoint is encountered or the program
28725 exits. In the latter case the output will include an exit code, if
28726 the program has exited exceptionally.
28728 When no option is specified, the current inferior is started. If the
28729 @samp{--thread-group} option is specified, it should refer to a thread
28730 group of type @samp{process}, and that thread group will be started.
28731 If the @samp{--all} option is specified, then all inferiors will be started.
28733 @subsubheading @value{GDBN} Command
28735 The corresponding @value{GDBN} command is @samp{run}.
28737 @subsubheading Examples
28742 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28747 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28748 frame=@{func="main",args=[],file="recursive2.c",
28749 fullname="/home/foo/bar/recursive2.c",line="4"@}
28754 Program exited normally:
28762 *stopped,reason="exited-normally"
28767 Program exited exceptionally:
28775 *stopped,reason="exited",exit-code="01"
28779 Another way the program can terminate is if it receives a signal such as
28780 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28784 *stopped,reason="exited-signalled",signal-name="SIGINT",
28785 signal-meaning="Interrupt"
28789 @c @subheading -exec-signal
28792 @subheading The @code{-exec-step} Command
28795 @subsubheading Synopsis
28798 -exec-step [--reverse]
28801 Resumes execution of the inferior program, stopping when the beginning
28802 of the next source line is reached, if the next source line is not a
28803 function call. If it is, stop at the first instruction of the called
28804 function. If the @samp{--reverse} option is specified, resumes reverse
28805 execution of the inferior program, stopping at the beginning of the
28806 previously executed source line.
28808 @subsubheading @value{GDBN} Command
28810 The corresponding @value{GDBN} command is @samp{step}.
28812 @subsubheading Example
28814 Stepping into a function:
28820 *stopped,reason="end-stepping-range",
28821 frame=@{func="foo",args=[@{name="a",value="10"@},
28822 @{name="b",value="0"@}],file="recursive2.c",
28823 fullname="/home/foo/bar/recursive2.c",line="11"@}
28833 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28838 @subheading The @code{-exec-step-instruction} Command
28839 @findex -exec-step-instruction
28841 @subsubheading Synopsis
28844 -exec-step-instruction [--reverse]
28847 Resumes the inferior which executes one machine instruction. If the
28848 @samp{--reverse} option is specified, resumes reverse execution of the
28849 inferior program, stopping at the previously executed instruction.
28850 The output, once @value{GDBN} has stopped, will vary depending on
28851 whether we have stopped in the middle of a source line or not. In the
28852 former case, the address at which the program stopped will be printed
28855 @subsubheading @value{GDBN} Command
28857 The corresponding @value{GDBN} command is @samp{stepi}.
28859 @subsubheading Example
28863 -exec-step-instruction
28867 *stopped,reason="end-stepping-range",
28868 frame=@{func="foo",args=[],file="try.c",
28869 fullname="/home/foo/bar/try.c",line="10"@}
28871 -exec-step-instruction
28875 *stopped,reason="end-stepping-range",
28876 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28877 fullname="/home/foo/bar/try.c",line="10"@}
28882 @subheading The @code{-exec-until} Command
28883 @findex -exec-until
28885 @subsubheading Synopsis
28888 -exec-until [ @var{location} ]
28891 Executes the inferior until the @var{location} specified in the
28892 argument is reached. If there is no argument, the inferior executes
28893 until a source line greater than the current one is reached. The
28894 reason for stopping in this case will be @samp{location-reached}.
28896 @subsubheading @value{GDBN} Command
28898 The corresponding @value{GDBN} command is @samp{until}.
28900 @subsubheading Example
28904 -exec-until recursive2.c:6
28908 *stopped,reason="location-reached",frame=@{func="main",args=[],
28909 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28914 @subheading -file-clear
28915 Is this going away????
28918 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28919 @node GDB/MI Stack Manipulation
28920 @section @sc{gdb/mi} Stack Manipulation Commands
28923 @subheading The @code{-stack-info-frame} Command
28924 @findex -stack-info-frame
28926 @subsubheading Synopsis
28932 Get info on the selected frame.
28934 @subsubheading @value{GDBN} Command
28936 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28937 (without arguments).
28939 @subsubheading Example
28944 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28945 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28946 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28950 @subheading The @code{-stack-info-depth} Command
28951 @findex -stack-info-depth
28953 @subsubheading Synopsis
28956 -stack-info-depth [ @var{max-depth} ]
28959 Return the depth of the stack. If the integer argument @var{max-depth}
28960 is specified, do not count beyond @var{max-depth} frames.
28962 @subsubheading @value{GDBN} Command
28964 There's no equivalent @value{GDBN} command.
28966 @subsubheading Example
28968 For a stack with frame levels 0 through 11:
28975 -stack-info-depth 4
28978 -stack-info-depth 12
28981 -stack-info-depth 11
28984 -stack-info-depth 13
28989 @subheading The @code{-stack-list-arguments} Command
28990 @findex -stack-list-arguments
28992 @subsubheading Synopsis
28995 -stack-list-arguments @var{print-values}
28996 [ @var{low-frame} @var{high-frame} ]
28999 Display a list of the arguments for the frames between @var{low-frame}
29000 and @var{high-frame} (inclusive). If @var{low-frame} and
29001 @var{high-frame} are not provided, list the arguments for the whole
29002 call stack. If the two arguments are equal, show the single frame
29003 at the corresponding level. It is an error if @var{low-frame} is
29004 larger than the actual number of frames. On the other hand,
29005 @var{high-frame} may be larger than the actual number of frames, in
29006 which case only existing frames will be returned.
29008 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29009 the variables; if it is 1 or @code{--all-values}, print also their
29010 values; and if it is 2 or @code{--simple-values}, print the name,
29011 type and value for simple data types, and the name and type for arrays,
29012 structures and unions.
29014 Use of this command to obtain arguments in a single frame is
29015 deprecated in favor of the @samp{-stack-list-variables} command.
29017 @subsubheading @value{GDBN} Command
29019 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29020 @samp{gdb_get_args} command which partially overlaps with the
29021 functionality of @samp{-stack-list-arguments}.
29023 @subsubheading Example
29030 frame=@{level="0",addr="0x00010734",func="callee4",
29031 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29032 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29033 frame=@{level="1",addr="0x0001076c",func="callee3",
29034 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29035 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29036 frame=@{level="2",addr="0x0001078c",func="callee2",
29037 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29038 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29039 frame=@{level="3",addr="0x000107b4",func="callee1",
29040 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29041 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29042 frame=@{level="4",addr="0x000107e0",func="main",
29043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29044 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29046 -stack-list-arguments 0
29049 frame=@{level="0",args=[]@},
29050 frame=@{level="1",args=[name="strarg"]@},
29051 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29052 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29053 frame=@{level="4",args=[]@}]
29055 -stack-list-arguments 1
29058 frame=@{level="0",args=[]@},
29060 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29061 frame=@{level="2",args=[
29062 @{name="intarg",value="2"@},
29063 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29064 @{frame=@{level="3",args=[
29065 @{name="intarg",value="2"@},
29066 @{name="strarg",value="0x11940 \"A string argument.\""@},
29067 @{name="fltarg",value="3.5"@}]@},
29068 frame=@{level="4",args=[]@}]
29070 -stack-list-arguments 0 2 2
29071 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29073 -stack-list-arguments 1 2 2
29074 ^done,stack-args=[frame=@{level="2",
29075 args=[@{name="intarg",value="2"@},
29076 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29080 @c @subheading -stack-list-exception-handlers
29083 @subheading The @code{-stack-list-frames} Command
29084 @findex -stack-list-frames
29086 @subsubheading Synopsis
29089 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
29092 List the frames currently on the stack. For each frame it displays the
29097 The frame number, 0 being the topmost frame, i.e., the innermost function.
29099 The @code{$pc} value for that frame.
29103 File name of the source file where the function lives.
29104 @item @var{fullname}
29105 The full file name of the source file where the function lives.
29107 Line number corresponding to the @code{$pc}.
29109 The shared library where this function is defined. This is only given
29110 if the frame's function is not known.
29113 If invoked without arguments, this command prints a backtrace for the
29114 whole stack. If given two integer arguments, it shows the frames whose
29115 levels are between the two arguments (inclusive). If the two arguments
29116 are equal, it shows the single frame at the corresponding level. It is
29117 an error if @var{low-frame} is larger than the actual number of
29118 frames. On the other hand, @var{high-frame} may be larger than the
29119 actual number of frames, in which case only existing frames will be returned.
29121 @subsubheading @value{GDBN} Command
29123 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29125 @subsubheading Example
29127 Full stack backtrace:
29133 [frame=@{level="0",addr="0x0001076c",func="foo",
29134 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29135 frame=@{level="1",addr="0x000107a4",func="foo",
29136 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29137 frame=@{level="2",addr="0x000107a4",func="foo",
29138 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29139 frame=@{level="3",addr="0x000107a4",func="foo",
29140 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29141 frame=@{level="4",addr="0x000107a4",func="foo",
29142 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29143 frame=@{level="5",addr="0x000107a4",func="foo",
29144 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29145 frame=@{level="6",addr="0x000107a4",func="foo",
29146 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29147 frame=@{level="7",addr="0x000107a4",func="foo",
29148 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29149 frame=@{level="8",addr="0x000107a4",func="foo",
29150 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29151 frame=@{level="9",addr="0x000107a4",func="foo",
29152 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29153 frame=@{level="10",addr="0x000107a4",func="foo",
29154 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29155 frame=@{level="11",addr="0x00010738",func="main",
29156 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29160 Show frames between @var{low_frame} and @var{high_frame}:
29164 -stack-list-frames 3 5
29166 [frame=@{level="3",addr="0x000107a4",func="foo",
29167 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29168 frame=@{level="4",addr="0x000107a4",func="foo",
29169 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29170 frame=@{level="5",addr="0x000107a4",func="foo",
29171 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29175 Show a single frame:
29179 -stack-list-frames 3 3
29181 [frame=@{level="3",addr="0x000107a4",func="foo",
29182 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29187 @subheading The @code{-stack-list-locals} Command
29188 @findex -stack-list-locals
29190 @subsubheading Synopsis
29193 -stack-list-locals @var{print-values}
29196 Display the local variable names for the selected frame. If
29197 @var{print-values} is 0 or @code{--no-values}, print only the names of
29198 the variables; if it is 1 or @code{--all-values}, print also their
29199 values; and if it is 2 or @code{--simple-values}, print the name,
29200 type and value for simple data types, and the name and type for arrays,
29201 structures and unions. In this last case, a frontend can immediately
29202 display the value of simple data types and create variable objects for
29203 other data types when the user wishes to explore their values in
29206 This command is deprecated in favor of the
29207 @samp{-stack-list-variables} command.
29209 @subsubheading @value{GDBN} Command
29211 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29213 @subsubheading Example
29217 -stack-list-locals 0
29218 ^done,locals=[name="A",name="B",name="C"]
29220 -stack-list-locals --all-values
29221 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29222 @{name="C",value="@{1, 2, 3@}"@}]
29223 -stack-list-locals --simple-values
29224 ^done,locals=[@{name="A",type="int",value="1"@},
29225 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29229 @subheading The @code{-stack-list-variables} Command
29230 @findex -stack-list-variables
29232 @subsubheading Synopsis
29235 -stack-list-variables @var{print-values}
29238 Display the names of local variables and function arguments for the selected frame. If
29239 @var{print-values} is 0 or @code{--no-values}, print only the names of
29240 the variables; if it is 1 or @code{--all-values}, print also their
29241 values; and if it is 2 or @code{--simple-values}, print the name,
29242 type and value for simple data types, and the name and type for arrays,
29243 structures and unions.
29245 @subsubheading Example
29249 -stack-list-variables --thread 1 --frame 0 --all-values
29250 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29255 @subheading The @code{-stack-select-frame} Command
29256 @findex -stack-select-frame
29258 @subsubheading Synopsis
29261 -stack-select-frame @var{framenum}
29264 Change the selected frame. Select a different frame @var{framenum} on
29267 This command in deprecated in favor of passing the @samp{--frame}
29268 option to every command.
29270 @subsubheading @value{GDBN} Command
29272 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29273 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29275 @subsubheading Example
29279 -stack-select-frame 2
29284 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29285 @node GDB/MI Variable Objects
29286 @section @sc{gdb/mi} Variable Objects
29290 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29292 For the implementation of a variable debugger window (locals, watched
29293 expressions, etc.), we are proposing the adaptation of the existing code
29294 used by @code{Insight}.
29296 The two main reasons for that are:
29300 It has been proven in practice (it is already on its second generation).
29303 It will shorten development time (needless to say how important it is
29307 The original interface was designed to be used by Tcl code, so it was
29308 slightly changed so it could be used through @sc{gdb/mi}. This section
29309 describes the @sc{gdb/mi} operations that will be available and gives some
29310 hints about their use.
29312 @emph{Note}: In addition to the set of operations described here, we
29313 expect the @sc{gui} implementation of a variable window to require, at
29314 least, the following operations:
29317 @item @code{-gdb-show} @code{output-radix}
29318 @item @code{-stack-list-arguments}
29319 @item @code{-stack-list-locals}
29320 @item @code{-stack-select-frame}
29325 @subheading Introduction to Variable Objects
29327 @cindex variable objects in @sc{gdb/mi}
29329 Variable objects are "object-oriented" MI interface for examining and
29330 changing values of expressions. Unlike some other MI interfaces that
29331 work with expressions, variable objects are specifically designed for
29332 simple and efficient presentation in the frontend. A variable object
29333 is identified by string name. When a variable object is created, the
29334 frontend specifies the expression for that variable object. The
29335 expression can be a simple variable, or it can be an arbitrary complex
29336 expression, and can even involve CPU registers. After creating a
29337 variable object, the frontend can invoke other variable object
29338 operations---for example to obtain or change the value of a variable
29339 object, or to change display format.
29341 Variable objects have hierarchical tree structure. Any variable object
29342 that corresponds to a composite type, such as structure in C, has
29343 a number of child variable objects, for example corresponding to each
29344 element of a structure. A child variable object can itself have
29345 children, recursively. Recursion ends when we reach
29346 leaf variable objects, which always have built-in types. Child variable
29347 objects are created only by explicit request, so if a frontend
29348 is not interested in the children of a particular variable object, no
29349 child will be created.
29351 For a leaf variable object it is possible to obtain its value as a
29352 string, or set the value from a string. String value can be also
29353 obtained for a non-leaf variable object, but it's generally a string
29354 that only indicates the type of the object, and does not list its
29355 contents. Assignment to a non-leaf variable object is not allowed.
29357 A frontend does not need to read the values of all variable objects each time
29358 the program stops. Instead, MI provides an update command that lists all
29359 variable objects whose values has changed since the last update
29360 operation. This considerably reduces the amount of data that must
29361 be transferred to the frontend. As noted above, children variable
29362 objects are created on demand, and only leaf variable objects have a
29363 real value. As result, gdb will read target memory only for leaf
29364 variables that frontend has created.
29366 The automatic update is not always desirable. For example, a frontend
29367 might want to keep a value of some expression for future reference,
29368 and never update it. For another example, fetching memory is
29369 relatively slow for embedded targets, so a frontend might want
29370 to disable automatic update for the variables that are either not
29371 visible on the screen, or ``closed''. This is possible using so
29372 called ``frozen variable objects''. Such variable objects are never
29373 implicitly updated.
29375 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29376 fixed variable object, the expression is parsed when the variable
29377 object is created, including associating identifiers to specific
29378 variables. The meaning of expression never changes. For a floating
29379 variable object the values of variables whose names appear in the
29380 expressions are re-evaluated every time in the context of the current
29381 frame. Consider this example:
29386 struct work_state state;
29393 If a fixed variable object for the @code{state} variable is created in
29394 this function, and we enter the recursive call, the variable
29395 object will report the value of @code{state} in the top-level
29396 @code{do_work} invocation. On the other hand, a floating variable
29397 object will report the value of @code{state} in the current frame.
29399 If an expression specified when creating a fixed variable object
29400 refers to a local variable, the variable object becomes bound to the
29401 thread and frame in which the variable object is created. When such
29402 variable object is updated, @value{GDBN} makes sure that the
29403 thread/frame combination the variable object is bound to still exists,
29404 and re-evaluates the variable object in context of that thread/frame.
29406 The following is the complete set of @sc{gdb/mi} operations defined to
29407 access this functionality:
29409 @multitable @columnfractions .4 .6
29410 @item @strong{Operation}
29411 @tab @strong{Description}
29413 @item @code{-enable-pretty-printing}
29414 @tab enable Python-based pretty-printing
29415 @item @code{-var-create}
29416 @tab create a variable object
29417 @item @code{-var-delete}
29418 @tab delete the variable object and/or its children
29419 @item @code{-var-set-format}
29420 @tab set the display format of this variable
29421 @item @code{-var-show-format}
29422 @tab show the display format of this variable
29423 @item @code{-var-info-num-children}
29424 @tab tells how many children this object has
29425 @item @code{-var-list-children}
29426 @tab return a list of the object's children
29427 @item @code{-var-info-type}
29428 @tab show the type of this variable object
29429 @item @code{-var-info-expression}
29430 @tab print parent-relative expression that this variable object represents
29431 @item @code{-var-info-path-expression}
29432 @tab print full expression that this variable object represents
29433 @item @code{-var-show-attributes}
29434 @tab is this variable editable? does it exist here?
29435 @item @code{-var-evaluate-expression}
29436 @tab get the value of this variable
29437 @item @code{-var-assign}
29438 @tab set the value of this variable
29439 @item @code{-var-update}
29440 @tab update the variable and its children
29441 @item @code{-var-set-frozen}
29442 @tab set frozeness attribute
29443 @item @code{-var-set-update-range}
29444 @tab set range of children to display on update
29447 In the next subsection we describe each operation in detail and suggest
29448 how it can be used.
29450 @subheading Description And Use of Operations on Variable Objects
29452 @subheading The @code{-enable-pretty-printing} Command
29453 @findex -enable-pretty-printing
29456 -enable-pretty-printing
29459 @value{GDBN} allows Python-based visualizers to affect the output of the
29460 MI variable object commands. However, because there was no way to
29461 implement this in a fully backward-compatible way, a front end must
29462 request that this functionality be enabled.
29464 Once enabled, this feature cannot be disabled.
29466 Note that if Python support has not been compiled into @value{GDBN},
29467 this command will still succeed (and do nothing).
29469 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29470 may work differently in future versions of @value{GDBN}.
29472 @subheading The @code{-var-create} Command
29473 @findex -var-create
29475 @subsubheading Synopsis
29478 -var-create @{@var{name} | "-"@}
29479 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29482 This operation creates a variable object, which allows the monitoring of
29483 a variable, the result of an expression, a memory cell or a CPU
29486 The @var{name} parameter is the string by which the object can be
29487 referenced. It must be unique. If @samp{-} is specified, the varobj
29488 system will generate a string ``varNNNNNN'' automatically. It will be
29489 unique provided that one does not specify @var{name} of that format.
29490 The command fails if a duplicate name is found.
29492 The frame under which the expression should be evaluated can be
29493 specified by @var{frame-addr}. A @samp{*} indicates that the current
29494 frame should be used. A @samp{@@} indicates that a floating variable
29495 object must be created.
29497 @var{expression} is any expression valid on the current language set (must not
29498 begin with a @samp{*}), or one of the following:
29502 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29505 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29508 @samp{$@var{regname}} --- a CPU register name
29511 @cindex dynamic varobj
29512 A varobj's contents may be provided by a Python-based pretty-printer. In this
29513 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29514 have slightly different semantics in some cases. If the
29515 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29516 will never create a dynamic varobj. This ensures backward
29517 compatibility for existing clients.
29519 @subsubheading Result
29521 This operation returns attributes of the newly-created varobj. These
29526 The name of the varobj.
29529 The number of children of the varobj. This number is not necessarily
29530 reliable for a dynamic varobj. Instead, you must examine the
29531 @samp{has_more} attribute.
29534 The varobj's scalar value. For a varobj whose type is some sort of
29535 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29536 will not be interesting.
29539 The varobj's type. This is a string representation of the type, as
29540 would be printed by the @value{GDBN} CLI. If @samp{print object}
29541 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29542 @emph{actual} (derived) type of the object is shown rather than the
29543 @emph{declared} one.
29546 If a variable object is bound to a specific thread, then this is the
29547 thread's identifier.
29550 For a dynamic varobj, this indicates whether there appear to be any
29551 children available. For a non-dynamic varobj, this will be 0.
29554 This attribute will be present and have the value @samp{1} if the
29555 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29556 then this attribute will not be present.
29559 A dynamic varobj can supply a display hint to the front end. The
29560 value comes directly from the Python pretty-printer object's
29561 @code{display_hint} method. @xref{Pretty Printing API}.
29564 Typical output will look like this:
29567 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29568 has_more="@var{has_more}"
29572 @subheading The @code{-var-delete} Command
29573 @findex -var-delete
29575 @subsubheading Synopsis
29578 -var-delete [ -c ] @var{name}
29581 Deletes a previously created variable object and all of its children.
29582 With the @samp{-c} option, just deletes the children.
29584 Returns an error if the object @var{name} is not found.
29587 @subheading The @code{-var-set-format} Command
29588 @findex -var-set-format
29590 @subsubheading Synopsis
29593 -var-set-format @var{name} @var{format-spec}
29596 Sets the output format for the value of the object @var{name} to be
29599 @anchor{-var-set-format}
29600 The syntax for the @var{format-spec} is as follows:
29603 @var{format-spec} @expansion{}
29604 @{binary | decimal | hexadecimal | octal | natural@}
29607 The natural format is the default format choosen automatically
29608 based on the variable type (like decimal for an @code{int}, hex
29609 for pointers, etc.).
29611 For a variable with children, the format is set only on the
29612 variable itself, and the children are not affected.
29614 @subheading The @code{-var-show-format} Command
29615 @findex -var-show-format
29617 @subsubheading Synopsis
29620 -var-show-format @var{name}
29623 Returns the format used to display the value of the object @var{name}.
29626 @var{format} @expansion{}
29631 @subheading The @code{-var-info-num-children} Command
29632 @findex -var-info-num-children
29634 @subsubheading Synopsis
29637 -var-info-num-children @var{name}
29640 Returns the number of children of a variable object @var{name}:
29646 Note that this number is not completely reliable for a dynamic varobj.
29647 It will return the current number of children, but more children may
29651 @subheading The @code{-var-list-children} Command
29652 @findex -var-list-children
29654 @subsubheading Synopsis
29657 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29659 @anchor{-var-list-children}
29661 Return a list of the children of the specified variable object and
29662 create variable objects for them, if they do not already exist. With
29663 a single argument or if @var{print-values} has a value of 0 or
29664 @code{--no-values}, print only the names of the variables; if
29665 @var{print-values} is 1 or @code{--all-values}, also print their
29666 values; and if it is 2 or @code{--simple-values} print the name and
29667 value for simple data types and just the name for arrays, structures
29670 @var{from} and @var{to}, if specified, indicate the range of children
29671 to report. If @var{from} or @var{to} is less than zero, the range is
29672 reset and all children will be reported. Otherwise, children starting
29673 at @var{from} (zero-based) and up to and excluding @var{to} will be
29676 If a child range is requested, it will only affect the current call to
29677 @code{-var-list-children}, but not future calls to @code{-var-update}.
29678 For this, you must instead use @code{-var-set-update-range}. The
29679 intent of this approach is to enable a front end to implement any
29680 update approach it likes; for example, scrolling a view may cause the
29681 front end to request more children with @code{-var-list-children}, and
29682 then the front end could call @code{-var-set-update-range} with a
29683 different range to ensure that future updates are restricted to just
29686 For each child the following results are returned:
29691 Name of the variable object created for this child.
29694 The expression to be shown to the user by the front end to designate this child.
29695 For example this may be the name of a structure member.
29697 For a dynamic varobj, this value cannot be used to form an
29698 expression. There is no way to do this at all with a dynamic varobj.
29700 For C/C@t{++} structures there are several pseudo children returned to
29701 designate access qualifiers. For these pseudo children @var{exp} is
29702 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29703 type and value are not present.
29705 A dynamic varobj will not report the access qualifying
29706 pseudo-children, regardless of the language. This information is not
29707 available at all with a dynamic varobj.
29710 Number of children this child has. For a dynamic varobj, this will be
29714 The type of the child. If @samp{print object}
29715 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29716 @emph{actual} (derived) type of the object is shown rather than the
29717 @emph{declared} one.
29720 If values were requested, this is the value.
29723 If this variable object is associated with a thread, this is the thread id.
29724 Otherwise this result is not present.
29727 If the variable object is frozen, this variable will be present with a value of 1.
29730 The result may have its own attributes:
29734 A dynamic varobj can supply a display hint to the front end. The
29735 value comes directly from the Python pretty-printer object's
29736 @code{display_hint} method. @xref{Pretty Printing API}.
29739 This is an integer attribute which is nonzero if there are children
29740 remaining after the end of the selected range.
29743 @subsubheading Example
29747 -var-list-children n
29748 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29749 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29751 -var-list-children --all-values n
29752 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29753 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29757 @subheading The @code{-var-info-type} Command
29758 @findex -var-info-type
29760 @subsubheading Synopsis
29763 -var-info-type @var{name}
29766 Returns the type of the specified variable @var{name}. The type is
29767 returned as a string in the same format as it is output by the
29771 type=@var{typename}
29775 @subheading The @code{-var-info-expression} Command
29776 @findex -var-info-expression
29778 @subsubheading Synopsis
29781 -var-info-expression @var{name}
29784 Returns a string that is suitable for presenting this
29785 variable object in user interface. The string is generally
29786 not valid expression in the current language, and cannot be evaluated.
29788 For example, if @code{a} is an array, and variable object
29789 @code{A} was created for @code{a}, then we'll get this output:
29792 (gdb) -var-info-expression A.1
29793 ^done,lang="C",exp="1"
29797 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29799 Note that the output of the @code{-var-list-children} command also
29800 includes those expressions, so the @code{-var-info-expression} command
29803 @subheading The @code{-var-info-path-expression} Command
29804 @findex -var-info-path-expression
29806 @subsubheading Synopsis
29809 -var-info-path-expression @var{name}
29812 Returns an expression that can be evaluated in the current
29813 context and will yield the same value that a variable object has.
29814 Compare this with the @code{-var-info-expression} command, which
29815 result can be used only for UI presentation. Typical use of
29816 the @code{-var-info-path-expression} command is creating a
29817 watchpoint from a variable object.
29819 This command is currently not valid for children of a dynamic varobj,
29820 and will give an error when invoked on one.
29822 For example, suppose @code{C} is a C@t{++} class, derived from class
29823 @code{Base}, and that the @code{Base} class has a member called
29824 @code{m_size}. Assume a variable @code{c} is has the type of
29825 @code{C} and a variable object @code{C} was created for variable
29826 @code{c}. Then, we'll get this output:
29828 (gdb) -var-info-path-expression C.Base.public.m_size
29829 ^done,path_expr=((Base)c).m_size)
29832 @subheading The @code{-var-show-attributes} Command
29833 @findex -var-show-attributes
29835 @subsubheading Synopsis
29838 -var-show-attributes @var{name}
29841 List attributes of the specified variable object @var{name}:
29844 status=@var{attr} [ ( ,@var{attr} )* ]
29848 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29850 @subheading The @code{-var-evaluate-expression} Command
29851 @findex -var-evaluate-expression
29853 @subsubheading Synopsis
29856 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29859 Evaluates the expression that is represented by the specified variable
29860 object and returns its value as a string. The format of the string
29861 can be specified with the @samp{-f} option. The possible values of
29862 this option are the same as for @code{-var-set-format}
29863 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29864 the current display format will be used. The current display format
29865 can be changed using the @code{-var-set-format} command.
29871 Note that one must invoke @code{-var-list-children} for a variable
29872 before the value of a child variable can be evaluated.
29874 @subheading The @code{-var-assign} Command
29875 @findex -var-assign
29877 @subsubheading Synopsis
29880 -var-assign @var{name} @var{expression}
29883 Assigns the value of @var{expression} to the variable object specified
29884 by @var{name}. The object must be @samp{editable}. If the variable's
29885 value is altered by the assign, the variable will show up in any
29886 subsequent @code{-var-update} list.
29888 @subsubheading Example
29896 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29900 @subheading The @code{-var-update} Command
29901 @findex -var-update
29903 @subsubheading Synopsis
29906 -var-update [@var{print-values}] @{@var{name} | "*"@}
29909 Reevaluate the expressions corresponding to the variable object
29910 @var{name} and all its direct and indirect children, and return the
29911 list of variable objects whose values have changed; @var{name} must
29912 be a root variable object. Here, ``changed'' means that the result of
29913 @code{-var-evaluate-expression} before and after the
29914 @code{-var-update} is different. If @samp{*} is used as the variable
29915 object names, all existing variable objects are updated, except
29916 for frozen ones (@pxref{-var-set-frozen}). The option
29917 @var{print-values} determines whether both names and values, or just
29918 names are printed. The possible values of this option are the same
29919 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29920 recommended to use the @samp{--all-values} option, to reduce the
29921 number of MI commands needed on each program stop.
29923 With the @samp{*} parameter, if a variable object is bound to a
29924 currently running thread, it will not be updated, without any
29927 If @code{-var-set-update-range} was previously used on a varobj, then
29928 only the selected range of children will be reported.
29930 @code{-var-update} reports all the changed varobjs in a tuple named
29933 Each item in the change list is itself a tuple holding:
29937 The name of the varobj.
29940 If values were requested for this update, then this field will be
29941 present and will hold the value of the varobj.
29944 @anchor{-var-update}
29945 This field is a string which may take one of three values:
29949 The variable object's current value is valid.
29952 The variable object does not currently hold a valid value but it may
29953 hold one in the future if its associated expression comes back into
29957 The variable object no longer holds a valid value.
29958 This can occur when the executable file being debugged has changed,
29959 either through recompilation or by using the @value{GDBN} @code{file}
29960 command. The front end should normally choose to delete these variable
29964 In the future new values may be added to this list so the front should
29965 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29968 This is only present if the varobj is still valid. If the type
29969 changed, then this will be the string @samp{true}; otherwise it will
29972 When a varobj's type changes, its children are also likely to have
29973 become incorrect. Therefore, the varobj's children are automatically
29974 deleted when this attribute is @samp{true}. Also, the varobj's update
29975 range, when set using the @code{-var-set-update-range} command, is
29979 If the varobj's type changed, then this field will be present and will
29982 @item new_num_children
29983 For a dynamic varobj, if the number of children changed, or if the
29984 type changed, this will be the new number of children.
29986 The @samp{numchild} field in other varobj responses is generally not
29987 valid for a dynamic varobj -- it will show the number of children that
29988 @value{GDBN} knows about, but because dynamic varobjs lazily
29989 instantiate their children, this will not reflect the number of
29990 children which may be available.
29992 The @samp{new_num_children} attribute only reports changes to the
29993 number of children known by @value{GDBN}. This is the only way to
29994 detect whether an update has removed children (which necessarily can
29995 only happen at the end of the update range).
29998 The display hint, if any.
30001 This is an integer value, which will be 1 if there are more children
30002 available outside the varobj's update range.
30005 This attribute will be present and have the value @samp{1} if the
30006 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30007 then this attribute will not be present.
30010 If new children were added to a dynamic varobj within the selected
30011 update range (as set by @code{-var-set-update-range}), then they will
30012 be listed in this attribute.
30015 @subsubheading Example
30022 -var-update --all-values var1
30023 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30024 type_changed="false"@}]
30028 @subheading The @code{-var-set-frozen} Command
30029 @findex -var-set-frozen
30030 @anchor{-var-set-frozen}
30032 @subsubheading Synopsis
30035 -var-set-frozen @var{name} @var{flag}
30038 Set the frozenness flag on the variable object @var{name}. The
30039 @var{flag} parameter should be either @samp{1} to make the variable
30040 frozen or @samp{0} to make it unfrozen. If a variable object is
30041 frozen, then neither itself, nor any of its children, are
30042 implicitly updated by @code{-var-update} of
30043 a parent variable or by @code{-var-update *}. Only
30044 @code{-var-update} of the variable itself will update its value and
30045 values of its children. After a variable object is unfrozen, it is
30046 implicitly updated by all subsequent @code{-var-update} operations.
30047 Unfreezing a variable does not update it, only subsequent
30048 @code{-var-update} does.
30050 @subsubheading Example
30054 -var-set-frozen V 1
30059 @subheading The @code{-var-set-update-range} command
30060 @findex -var-set-update-range
30061 @anchor{-var-set-update-range}
30063 @subsubheading Synopsis
30066 -var-set-update-range @var{name} @var{from} @var{to}
30069 Set the range of children to be returned by future invocations of
30070 @code{-var-update}.
30072 @var{from} and @var{to} indicate the range of children to report. If
30073 @var{from} or @var{to} is less than zero, the range is reset and all
30074 children will be reported. Otherwise, children starting at @var{from}
30075 (zero-based) and up to and excluding @var{to} will be reported.
30077 @subsubheading Example
30081 -var-set-update-range V 1 2
30085 @subheading The @code{-var-set-visualizer} command
30086 @findex -var-set-visualizer
30087 @anchor{-var-set-visualizer}
30089 @subsubheading Synopsis
30092 -var-set-visualizer @var{name} @var{visualizer}
30095 Set a visualizer for the variable object @var{name}.
30097 @var{visualizer} is the visualizer to use. The special value
30098 @samp{None} means to disable any visualizer in use.
30100 If not @samp{None}, @var{visualizer} must be a Python expression.
30101 This expression must evaluate to a callable object which accepts a
30102 single argument. @value{GDBN} will call this object with the value of
30103 the varobj @var{name} as an argument (this is done so that the same
30104 Python pretty-printing code can be used for both the CLI and MI).
30105 When called, this object must return an object which conforms to the
30106 pretty-printing interface (@pxref{Pretty Printing API}).
30108 The pre-defined function @code{gdb.default_visualizer} may be used to
30109 select a visualizer by following the built-in process
30110 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30111 a varobj is created, and so ordinarily is not needed.
30113 This feature is only available if Python support is enabled. The MI
30114 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
30115 can be used to check this.
30117 @subsubheading Example
30119 Resetting the visualizer:
30123 -var-set-visualizer V None
30127 Reselecting the default (type-based) visualizer:
30131 -var-set-visualizer V gdb.default_visualizer
30135 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30136 can be used to instantiate this class for a varobj:
30140 -var-set-visualizer V "lambda val: SomeClass()"
30144 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30145 @node GDB/MI Data Manipulation
30146 @section @sc{gdb/mi} Data Manipulation
30148 @cindex data manipulation, in @sc{gdb/mi}
30149 @cindex @sc{gdb/mi}, data manipulation
30150 This section describes the @sc{gdb/mi} commands that manipulate data:
30151 examine memory and registers, evaluate expressions, etc.
30153 @c REMOVED FROM THE INTERFACE.
30154 @c @subheading -data-assign
30155 @c Change the value of a program variable. Plenty of side effects.
30156 @c @subsubheading GDB Command
30158 @c @subsubheading Example
30161 @subheading The @code{-data-disassemble} Command
30162 @findex -data-disassemble
30164 @subsubheading Synopsis
30168 [ -s @var{start-addr} -e @var{end-addr} ]
30169 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30177 @item @var{start-addr}
30178 is the beginning address (or @code{$pc})
30179 @item @var{end-addr}
30181 @item @var{filename}
30182 is the name of the file to disassemble
30183 @item @var{linenum}
30184 is the line number to disassemble around
30186 is the number of disassembly lines to be produced. If it is -1,
30187 the whole function will be disassembled, in case no @var{end-addr} is
30188 specified. If @var{end-addr} is specified as a non-zero value, and
30189 @var{lines} is lower than the number of disassembly lines between
30190 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30191 displayed; if @var{lines} is higher than the number of lines between
30192 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30195 is either 0 (meaning only disassembly), 1 (meaning mixed source and
30196 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
30197 mixed source and disassembly with raw opcodes).
30200 @subsubheading Result
30202 The output for each instruction is composed of four fields:
30211 Note that whatever included in the instruction field, is not manipulated
30212 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
30214 @subsubheading @value{GDBN} Command
30216 There's no direct mapping from this command to the CLI.
30218 @subsubheading Example
30220 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30224 -data-disassemble -s $pc -e "$pc + 20" -- 0
30227 @{address="0x000107c0",func-name="main",offset="4",
30228 inst="mov 2, %o0"@},
30229 @{address="0x000107c4",func-name="main",offset="8",
30230 inst="sethi %hi(0x11800), %o2"@},
30231 @{address="0x000107c8",func-name="main",offset="12",
30232 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30233 @{address="0x000107cc",func-name="main",offset="16",
30234 inst="sethi %hi(0x11800), %o2"@},
30235 @{address="0x000107d0",func-name="main",offset="20",
30236 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30240 Disassemble the whole @code{main} function. Line 32 is part of
30244 -data-disassemble -f basics.c -l 32 -- 0
30246 @{address="0x000107bc",func-name="main",offset="0",
30247 inst="save %sp, -112, %sp"@},
30248 @{address="0x000107c0",func-name="main",offset="4",
30249 inst="mov 2, %o0"@},
30250 @{address="0x000107c4",func-name="main",offset="8",
30251 inst="sethi %hi(0x11800), %o2"@},
30253 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30254 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30258 Disassemble 3 instructions from the start of @code{main}:
30262 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30264 @{address="0x000107bc",func-name="main",offset="0",
30265 inst="save %sp, -112, %sp"@},
30266 @{address="0x000107c0",func-name="main",offset="4",
30267 inst="mov 2, %o0"@},
30268 @{address="0x000107c4",func-name="main",offset="8",
30269 inst="sethi %hi(0x11800), %o2"@}]
30273 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30277 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30279 src_and_asm_line=@{line="31",
30280 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30281 testsuite/gdb.mi/basics.c",line_asm_insn=[
30282 @{address="0x000107bc",func-name="main",offset="0",
30283 inst="save %sp, -112, %sp"@}]@},
30284 src_and_asm_line=@{line="32",
30285 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30286 testsuite/gdb.mi/basics.c",line_asm_insn=[
30287 @{address="0x000107c0",func-name="main",offset="4",
30288 inst="mov 2, %o0"@},
30289 @{address="0x000107c4",func-name="main",offset="8",
30290 inst="sethi %hi(0x11800), %o2"@}]@}]
30295 @subheading The @code{-data-evaluate-expression} Command
30296 @findex -data-evaluate-expression
30298 @subsubheading Synopsis
30301 -data-evaluate-expression @var{expr}
30304 Evaluate @var{expr} as an expression. The expression could contain an
30305 inferior function call. The function call will execute synchronously.
30306 If the expression contains spaces, it must be enclosed in double quotes.
30308 @subsubheading @value{GDBN} Command
30310 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30311 @samp{call}. In @code{gdbtk} only, there's a corresponding
30312 @samp{gdb_eval} command.
30314 @subsubheading Example
30316 In the following example, the numbers that precede the commands are the
30317 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30318 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30322 211-data-evaluate-expression A
30325 311-data-evaluate-expression &A
30326 311^done,value="0xefffeb7c"
30328 411-data-evaluate-expression A+3
30331 511-data-evaluate-expression "A + 3"
30337 @subheading The @code{-data-list-changed-registers} Command
30338 @findex -data-list-changed-registers
30340 @subsubheading Synopsis
30343 -data-list-changed-registers
30346 Display a list of the registers that have changed.
30348 @subsubheading @value{GDBN} Command
30350 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30351 has the corresponding command @samp{gdb_changed_register_list}.
30353 @subsubheading Example
30355 On a PPC MBX board:
30363 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30364 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30367 -data-list-changed-registers
30368 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30369 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30370 "24","25","26","27","28","30","31","64","65","66","67","69"]
30375 @subheading The @code{-data-list-register-names} Command
30376 @findex -data-list-register-names
30378 @subsubheading Synopsis
30381 -data-list-register-names [ ( @var{regno} )+ ]
30384 Show a list of register names for the current target. If no arguments
30385 are given, it shows a list of the names of all the registers. If
30386 integer numbers are given as arguments, it will print a list of the
30387 names of the registers corresponding to the arguments. To ensure
30388 consistency between a register name and its number, the output list may
30389 include empty register names.
30391 @subsubheading @value{GDBN} Command
30393 @value{GDBN} does not have a command which corresponds to
30394 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30395 corresponding command @samp{gdb_regnames}.
30397 @subsubheading Example
30399 For the PPC MBX board:
30402 -data-list-register-names
30403 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30404 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30405 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30406 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30407 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30408 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30409 "", "pc","ps","cr","lr","ctr","xer"]
30411 -data-list-register-names 1 2 3
30412 ^done,register-names=["r1","r2","r3"]
30416 @subheading The @code{-data-list-register-values} Command
30417 @findex -data-list-register-values
30419 @subsubheading Synopsis
30422 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
30425 Display the registers' contents. @var{fmt} is the format according to
30426 which the registers' contents are to be returned, followed by an optional
30427 list of numbers specifying the registers to display. A missing list of
30428 numbers indicates that the contents of all the registers must be returned.
30430 Allowed formats for @var{fmt} are:
30447 @subsubheading @value{GDBN} Command
30449 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30450 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30452 @subsubheading Example
30454 For a PPC MBX board (note: line breaks are for readability only, they
30455 don't appear in the actual output):
30459 -data-list-register-values r 64 65
30460 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30461 @{number="65",value="0x00029002"@}]
30463 -data-list-register-values x
30464 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30465 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30466 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30467 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30468 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30469 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30470 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30471 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30472 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30473 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30474 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30475 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30476 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30477 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30478 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30479 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30480 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30481 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30482 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30483 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30484 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30485 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30486 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30487 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30488 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30489 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30490 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30491 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30492 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30493 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30494 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30495 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30496 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30497 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30498 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30499 @{number="69",value="0x20002b03"@}]
30504 @subheading The @code{-data-read-memory} Command
30505 @findex -data-read-memory
30507 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30509 @subsubheading Synopsis
30512 -data-read-memory [ -o @var{byte-offset} ]
30513 @var{address} @var{word-format} @var{word-size}
30514 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30521 @item @var{address}
30522 An expression specifying the address of the first memory word to be
30523 read. Complex expressions containing embedded white space should be
30524 quoted using the C convention.
30526 @item @var{word-format}
30527 The format to be used to print the memory words. The notation is the
30528 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30531 @item @var{word-size}
30532 The size of each memory word in bytes.
30534 @item @var{nr-rows}
30535 The number of rows in the output table.
30537 @item @var{nr-cols}
30538 The number of columns in the output table.
30541 If present, indicates that each row should include an @sc{ascii} dump. The
30542 value of @var{aschar} is used as a padding character when a byte is not a
30543 member of the printable @sc{ascii} character set (printable @sc{ascii}
30544 characters are those whose code is between 32 and 126, inclusively).
30546 @item @var{byte-offset}
30547 An offset to add to the @var{address} before fetching memory.
30550 This command displays memory contents as a table of @var{nr-rows} by
30551 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30552 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30553 (returned as @samp{total-bytes}). Should less than the requested number
30554 of bytes be returned by the target, the missing words are identified
30555 using @samp{N/A}. The number of bytes read from the target is returned
30556 in @samp{nr-bytes} and the starting address used to read memory in
30559 The address of the next/previous row or page is available in
30560 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30563 @subsubheading @value{GDBN} Command
30565 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30566 @samp{gdb_get_mem} memory read command.
30568 @subsubheading Example
30570 Read six bytes of memory starting at @code{bytes+6} but then offset by
30571 @code{-6} bytes. Format as three rows of two columns. One byte per
30572 word. Display each word in hex.
30576 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30577 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30578 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30579 prev-page="0x0000138a",memory=[
30580 @{addr="0x00001390",data=["0x00","0x01"]@},
30581 @{addr="0x00001392",data=["0x02","0x03"]@},
30582 @{addr="0x00001394",data=["0x04","0x05"]@}]
30586 Read two bytes of memory starting at address @code{shorts + 64} and
30587 display as a single word formatted in decimal.
30591 5-data-read-memory shorts+64 d 2 1 1
30592 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30593 next-row="0x00001512",prev-row="0x0000150e",
30594 next-page="0x00001512",prev-page="0x0000150e",memory=[
30595 @{addr="0x00001510",data=["128"]@}]
30599 Read thirty two bytes of memory starting at @code{bytes+16} and format
30600 as eight rows of four columns. Include a string encoding with @samp{x}
30601 used as the non-printable character.
30605 4-data-read-memory bytes+16 x 1 8 4 x
30606 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30607 next-row="0x000013c0",prev-row="0x0000139c",
30608 next-page="0x000013c0",prev-page="0x00001380",memory=[
30609 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30610 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30611 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30612 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30613 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30614 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30615 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30616 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30620 @subheading The @code{-data-read-memory-bytes} Command
30621 @findex -data-read-memory-bytes
30623 @subsubheading Synopsis
30626 -data-read-memory-bytes [ -o @var{byte-offset} ]
30627 @var{address} @var{count}
30634 @item @var{address}
30635 An expression specifying the address of the first memory word to be
30636 read. Complex expressions containing embedded white space should be
30637 quoted using the C convention.
30640 The number of bytes to read. This should be an integer literal.
30642 @item @var{byte-offset}
30643 The offsets in bytes relative to @var{address} at which to start
30644 reading. This should be an integer literal. This option is provided
30645 so that a frontend is not required to first evaluate address and then
30646 perform address arithmetics itself.
30650 This command attempts to read all accessible memory regions in the
30651 specified range. First, all regions marked as unreadable in the memory
30652 map (if one is defined) will be skipped. @xref{Memory Region
30653 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30654 regions. For each one, if reading full region results in an errors,
30655 @value{GDBN} will try to read a subset of the region.
30657 In general, every single byte in the region may be readable or not,
30658 and the only way to read every readable byte is to try a read at
30659 every address, which is not practical. Therefore, @value{GDBN} will
30660 attempt to read all accessible bytes at either beginning or the end
30661 of the region, using a binary division scheme. This heuristic works
30662 well for reading accross a memory map boundary. Note that if a region
30663 has a readable range that is neither at the beginning or the end,
30664 @value{GDBN} will not read it.
30666 The result record (@pxref{GDB/MI Result Records}) that is output of
30667 the command includes a field named @samp{memory} whose content is a
30668 list of tuples. Each tuple represent a successfully read memory block
30669 and has the following fields:
30673 The start address of the memory block, as hexadecimal literal.
30676 The end address of the memory block, as hexadecimal literal.
30679 The offset of the memory block, as hexadecimal literal, relative to
30680 the start address passed to @code{-data-read-memory-bytes}.
30683 The contents of the memory block, in hex.
30689 @subsubheading @value{GDBN} Command
30691 The corresponding @value{GDBN} command is @samp{x}.
30693 @subsubheading Example
30697 -data-read-memory-bytes &a 10
30698 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30700 contents="01000000020000000300"@}]
30705 @subheading The @code{-data-write-memory-bytes} Command
30706 @findex -data-write-memory-bytes
30708 @subsubheading Synopsis
30711 -data-write-memory-bytes @var{address} @var{contents}
30718 @item @var{address}
30719 An expression specifying the address of the first memory word to be
30720 read. Complex expressions containing embedded white space should be
30721 quoted using the C convention.
30723 @item @var{contents}
30724 The hex-encoded bytes to write.
30728 @subsubheading @value{GDBN} Command
30730 There's no corresponding @value{GDBN} command.
30732 @subsubheading Example
30736 -data-write-memory-bytes &a "aabbccdd"
30742 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30743 @node GDB/MI Tracepoint Commands
30744 @section @sc{gdb/mi} Tracepoint Commands
30746 The commands defined in this section implement MI support for
30747 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30749 @subheading The @code{-trace-find} Command
30750 @findex -trace-find
30752 @subsubheading Synopsis
30755 -trace-find @var{mode} [@var{parameters}@dots{}]
30758 Find a trace frame using criteria defined by @var{mode} and
30759 @var{parameters}. The following table lists permissible
30760 modes and their parameters. For details of operation, see @ref{tfind}.
30765 No parameters are required. Stops examining trace frames.
30768 An integer is required as parameter. Selects tracepoint frame with
30771 @item tracepoint-number
30772 An integer is required as parameter. Finds next
30773 trace frame that corresponds to tracepoint with the specified number.
30776 An address is required as parameter. Finds
30777 next trace frame that corresponds to any tracepoint at the specified
30780 @item pc-inside-range
30781 Two addresses are required as parameters. Finds next trace
30782 frame that corresponds to a tracepoint at an address inside the
30783 specified range. Both bounds are considered to be inside the range.
30785 @item pc-outside-range
30786 Two addresses are required as parameters. Finds
30787 next trace frame that corresponds to a tracepoint at an address outside
30788 the specified range. Both bounds are considered to be inside the range.
30791 Line specification is required as parameter. @xref{Specify Location}.
30792 Finds next trace frame that corresponds to a tracepoint at
30793 the specified location.
30797 If @samp{none} was passed as @var{mode}, the response does not
30798 have fields. Otherwise, the response may have the following fields:
30802 This field has either @samp{0} or @samp{1} as the value, depending
30803 on whether a matching tracepoint was found.
30806 The index of the found traceframe. This field is present iff
30807 the @samp{found} field has value of @samp{1}.
30810 The index of the found tracepoint. This field is present iff
30811 the @samp{found} field has value of @samp{1}.
30814 The information about the frame corresponding to the found trace
30815 frame. This field is present only if a trace frame was found.
30816 @xref{GDB/MI Frame Information}, for description of this field.
30820 @subsubheading @value{GDBN} Command
30822 The corresponding @value{GDBN} command is @samp{tfind}.
30824 @subheading -trace-define-variable
30825 @findex -trace-define-variable
30827 @subsubheading Synopsis
30830 -trace-define-variable @var{name} [ @var{value} ]
30833 Create trace variable @var{name} if it does not exist. If
30834 @var{value} is specified, sets the initial value of the specified
30835 trace variable to that value. Note that the @var{name} should start
30836 with the @samp{$} character.
30838 @subsubheading @value{GDBN} Command
30840 The corresponding @value{GDBN} command is @samp{tvariable}.
30842 @subheading -trace-list-variables
30843 @findex -trace-list-variables
30845 @subsubheading Synopsis
30848 -trace-list-variables
30851 Return a table of all defined trace variables. Each element of the
30852 table has the following fields:
30856 The name of the trace variable. This field is always present.
30859 The initial value. This is a 64-bit signed integer. This
30860 field is always present.
30863 The value the trace variable has at the moment. This is a 64-bit
30864 signed integer. This field is absent iff current value is
30865 not defined, for example if the trace was never run, or is
30870 @subsubheading @value{GDBN} Command
30872 The corresponding @value{GDBN} command is @samp{tvariables}.
30874 @subsubheading Example
30878 -trace-list-variables
30879 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30880 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30881 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30882 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30883 body=[variable=@{name="$trace_timestamp",initial="0"@}
30884 variable=@{name="$foo",initial="10",current="15"@}]@}
30888 @subheading -trace-save
30889 @findex -trace-save
30891 @subsubheading Synopsis
30894 -trace-save [-r ] @var{filename}
30897 Saves the collected trace data to @var{filename}. Without the
30898 @samp{-r} option, the data is downloaded from the target and saved
30899 in a local file. With the @samp{-r} option the target is asked
30900 to perform the save.
30902 @subsubheading @value{GDBN} Command
30904 The corresponding @value{GDBN} command is @samp{tsave}.
30907 @subheading -trace-start
30908 @findex -trace-start
30910 @subsubheading Synopsis
30916 Starts a tracing experiments. The result of this command does not
30919 @subsubheading @value{GDBN} Command
30921 The corresponding @value{GDBN} command is @samp{tstart}.
30923 @subheading -trace-status
30924 @findex -trace-status
30926 @subsubheading Synopsis
30932 Obtains the status of a tracing experiment. The result may include
30933 the following fields:
30938 May have a value of either @samp{0}, when no tracing operations are
30939 supported, @samp{1}, when all tracing operations are supported, or
30940 @samp{file} when examining trace file. In the latter case, examining
30941 of trace frame is possible but new tracing experiement cannot be
30942 started. This field is always present.
30945 May have a value of either @samp{0} or @samp{1} depending on whether
30946 tracing experiement is in progress on target. This field is present
30947 if @samp{supported} field is not @samp{0}.
30950 Report the reason why the tracing was stopped last time. This field
30951 may be absent iff tracing was never stopped on target yet. The
30952 value of @samp{request} means the tracing was stopped as result of
30953 the @code{-trace-stop} command. The value of @samp{overflow} means
30954 the tracing buffer is full. The value of @samp{disconnection} means
30955 tracing was automatically stopped when @value{GDBN} has disconnected.
30956 The value of @samp{passcount} means tracing was stopped when a
30957 tracepoint was passed a maximal number of times for that tracepoint.
30958 This field is present if @samp{supported} field is not @samp{0}.
30960 @item stopping-tracepoint
30961 The number of tracepoint whose passcount as exceeded. This field is
30962 present iff the @samp{stop-reason} field has the value of
30966 @itemx frames-created
30967 The @samp{frames} field is a count of the total number of trace frames
30968 in the trace buffer, while @samp{frames-created} is the total created
30969 during the run, including ones that were discarded, such as when a
30970 circular trace buffer filled up. Both fields are optional.
30974 These fields tell the current size of the tracing buffer and the
30975 remaining space. These fields are optional.
30978 The value of the circular trace buffer flag. @code{1} means that the
30979 trace buffer is circular and old trace frames will be discarded if
30980 necessary to make room, @code{0} means that the trace buffer is linear
30984 The value of the disconnected tracing flag. @code{1} means that
30985 tracing will continue after @value{GDBN} disconnects, @code{0} means
30986 that the trace run will stop.
30990 @subsubheading @value{GDBN} Command
30992 The corresponding @value{GDBN} command is @samp{tstatus}.
30994 @subheading -trace-stop
30995 @findex -trace-stop
30997 @subsubheading Synopsis
31003 Stops a tracing experiment. The result of this command has the same
31004 fields as @code{-trace-status}, except that the @samp{supported} and
31005 @samp{running} fields are not output.
31007 @subsubheading @value{GDBN} Command
31009 The corresponding @value{GDBN} command is @samp{tstop}.
31012 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31013 @node GDB/MI Symbol Query
31014 @section @sc{gdb/mi} Symbol Query Commands
31018 @subheading The @code{-symbol-info-address} Command
31019 @findex -symbol-info-address
31021 @subsubheading Synopsis
31024 -symbol-info-address @var{symbol}
31027 Describe where @var{symbol} is stored.
31029 @subsubheading @value{GDBN} Command
31031 The corresponding @value{GDBN} command is @samp{info address}.
31033 @subsubheading Example
31037 @subheading The @code{-symbol-info-file} Command
31038 @findex -symbol-info-file
31040 @subsubheading Synopsis
31046 Show the file for the symbol.
31048 @subsubheading @value{GDBN} Command
31050 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31051 @samp{gdb_find_file}.
31053 @subsubheading Example
31057 @subheading The @code{-symbol-info-function} Command
31058 @findex -symbol-info-function
31060 @subsubheading Synopsis
31063 -symbol-info-function
31066 Show which function the symbol lives in.
31068 @subsubheading @value{GDBN} Command
31070 @samp{gdb_get_function} in @code{gdbtk}.
31072 @subsubheading Example
31076 @subheading The @code{-symbol-info-line} Command
31077 @findex -symbol-info-line
31079 @subsubheading Synopsis
31085 Show the core addresses of the code for a source line.
31087 @subsubheading @value{GDBN} Command
31089 The corresponding @value{GDBN} command is @samp{info line}.
31090 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31092 @subsubheading Example
31096 @subheading The @code{-symbol-info-symbol} Command
31097 @findex -symbol-info-symbol
31099 @subsubheading Synopsis
31102 -symbol-info-symbol @var{addr}
31105 Describe what symbol is at location @var{addr}.
31107 @subsubheading @value{GDBN} Command
31109 The corresponding @value{GDBN} command is @samp{info symbol}.
31111 @subsubheading Example
31115 @subheading The @code{-symbol-list-functions} Command
31116 @findex -symbol-list-functions
31118 @subsubheading Synopsis
31121 -symbol-list-functions
31124 List the functions in the executable.
31126 @subsubheading @value{GDBN} Command
31128 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31129 @samp{gdb_search} in @code{gdbtk}.
31131 @subsubheading Example
31136 @subheading The @code{-symbol-list-lines} Command
31137 @findex -symbol-list-lines
31139 @subsubheading Synopsis
31142 -symbol-list-lines @var{filename}
31145 Print the list of lines that contain code and their associated program
31146 addresses for the given source filename. The entries are sorted in
31147 ascending PC order.
31149 @subsubheading @value{GDBN} Command
31151 There is no corresponding @value{GDBN} command.
31153 @subsubheading Example
31156 -symbol-list-lines basics.c
31157 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31163 @subheading The @code{-symbol-list-types} Command
31164 @findex -symbol-list-types
31166 @subsubheading Synopsis
31172 List all the type names.
31174 @subsubheading @value{GDBN} Command
31176 The corresponding commands are @samp{info types} in @value{GDBN},
31177 @samp{gdb_search} in @code{gdbtk}.
31179 @subsubheading Example
31183 @subheading The @code{-symbol-list-variables} Command
31184 @findex -symbol-list-variables
31186 @subsubheading Synopsis
31189 -symbol-list-variables
31192 List all the global and static variable names.
31194 @subsubheading @value{GDBN} Command
31196 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31198 @subsubheading Example
31202 @subheading The @code{-symbol-locate} Command
31203 @findex -symbol-locate
31205 @subsubheading Synopsis
31211 @subsubheading @value{GDBN} Command
31213 @samp{gdb_loc} in @code{gdbtk}.
31215 @subsubheading Example
31219 @subheading The @code{-symbol-type} Command
31220 @findex -symbol-type
31222 @subsubheading Synopsis
31225 -symbol-type @var{variable}
31228 Show type of @var{variable}.
31230 @subsubheading @value{GDBN} Command
31232 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31233 @samp{gdb_obj_variable}.
31235 @subsubheading Example
31240 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31241 @node GDB/MI File Commands
31242 @section @sc{gdb/mi} File Commands
31244 This section describes the GDB/MI commands to specify executable file names
31245 and to read in and obtain symbol table information.
31247 @subheading The @code{-file-exec-and-symbols} Command
31248 @findex -file-exec-and-symbols
31250 @subsubheading Synopsis
31253 -file-exec-and-symbols @var{file}
31256 Specify the executable file to be debugged. This file is the one from
31257 which the symbol table is also read. If no file is specified, the
31258 command clears the executable and symbol information. If breakpoints
31259 are set when using this command with no arguments, @value{GDBN} will produce
31260 error messages. Otherwise, no output is produced, except a completion
31263 @subsubheading @value{GDBN} Command
31265 The corresponding @value{GDBN} command is @samp{file}.
31267 @subsubheading Example
31271 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31277 @subheading The @code{-file-exec-file} Command
31278 @findex -file-exec-file
31280 @subsubheading Synopsis
31283 -file-exec-file @var{file}
31286 Specify the executable file to be debugged. Unlike
31287 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31288 from this file. If used without argument, @value{GDBN} clears the information
31289 about the executable file. No output is produced, except a completion
31292 @subsubheading @value{GDBN} Command
31294 The corresponding @value{GDBN} command is @samp{exec-file}.
31296 @subsubheading Example
31300 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31307 @subheading The @code{-file-list-exec-sections} Command
31308 @findex -file-list-exec-sections
31310 @subsubheading Synopsis
31313 -file-list-exec-sections
31316 List the sections of the current executable file.
31318 @subsubheading @value{GDBN} Command
31320 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31321 information as this command. @code{gdbtk} has a corresponding command
31322 @samp{gdb_load_info}.
31324 @subsubheading Example
31329 @subheading The @code{-file-list-exec-source-file} Command
31330 @findex -file-list-exec-source-file
31332 @subsubheading Synopsis
31335 -file-list-exec-source-file
31338 List the line number, the current source file, and the absolute path
31339 to the current source file for the current executable. The macro
31340 information field has a value of @samp{1} or @samp{0} depending on
31341 whether or not the file includes preprocessor macro information.
31343 @subsubheading @value{GDBN} Command
31345 The @value{GDBN} equivalent is @samp{info source}
31347 @subsubheading Example
31351 123-file-list-exec-source-file
31352 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31357 @subheading The @code{-file-list-exec-source-files} Command
31358 @findex -file-list-exec-source-files
31360 @subsubheading Synopsis
31363 -file-list-exec-source-files
31366 List the source files for the current executable.
31368 It will always output the filename, but only when @value{GDBN} can find
31369 the absolute file name of a source file, will it output the fullname.
31371 @subsubheading @value{GDBN} Command
31373 The @value{GDBN} equivalent is @samp{info sources}.
31374 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31376 @subsubheading Example
31379 -file-list-exec-source-files
31381 @{file=foo.c,fullname=/home/foo.c@},
31382 @{file=/home/bar.c,fullname=/home/bar.c@},
31383 @{file=gdb_could_not_find_fullpath.c@}]
31388 @subheading The @code{-file-list-shared-libraries} Command
31389 @findex -file-list-shared-libraries
31391 @subsubheading Synopsis
31394 -file-list-shared-libraries
31397 List the shared libraries in the program.
31399 @subsubheading @value{GDBN} Command
31401 The corresponding @value{GDBN} command is @samp{info shared}.
31403 @subsubheading Example
31407 @subheading The @code{-file-list-symbol-files} Command
31408 @findex -file-list-symbol-files
31410 @subsubheading Synopsis
31413 -file-list-symbol-files
31418 @subsubheading @value{GDBN} Command
31420 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31422 @subsubheading Example
31427 @subheading The @code{-file-symbol-file} Command
31428 @findex -file-symbol-file
31430 @subsubheading Synopsis
31433 -file-symbol-file @var{file}
31436 Read symbol table info from the specified @var{file} argument. When
31437 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31438 produced, except for a completion notification.
31440 @subsubheading @value{GDBN} Command
31442 The corresponding @value{GDBN} command is @samp{symbol-file}.
31444 @subsubheading Example
31448 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31454 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31455 @node GDB/MI Memory Overlay Commands
31456 @section @sc{gdb/mi} Memory Overlay Commands
31458 The memory overlay commands are not implemented.
31460 @c @subheading -overlay-auto
31462 @c @subheading -overlay-list-mapping-state
31464 @c @subheading -overlay-list-overlays
31466 @c @subheading -overlay-map
31468 @c @subheading -overlay-off
31470 @c @subheading -overlay-on
31472 @c @subheading -overlay-unmap
31474 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31475 @node GDB/MI Signal Handling Commands
31476 @section @sc{gdb/mi} Signal Handling Commands
31478 Signal handling commands are not implemented.
31480 @c @subheading -signal-handle
31482 @c @subheading -signal-list-handle-actions
31484 @c @subheading -signal-list-signal-types
31488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31489 @node GDB/MI Target Manipulation
31490 @section @sc{gdb/mi} Target Manipulation Commands
31493 @subheading The @code{-target-attach} Command
31494 @findex -target-attach
31496 @subsubheading Synopsis
31499 -target-attach @var{pid} | @var{gid} | @var{file}
31502 Attach to a process @var{pid} or a file @var{file} outside of
31503 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31504 group, the id previously returned by
31505 @samp{-list-thread-groups --available} must be used.
31507 @subsubheading @value{GDBN} Command
31509 The corresponding @value{GDBN} command is @samp{attach}.
31511 @subsubheading Example
31515 =thread-created,id="1"
31516 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31522 @subheading The @code{-target-compare-sections} Command
31523 @findex -target-compare-sections
31525 @subsubheading Synopsis
31528 -target-compare-sections [ @var{section} ]
31531 Compare data of section @var{section} on target to the exec file.
31532 Without the argument, all sections are compared.
31534 @subsubheading @value{GDBN} Command
31536 The @value{GDBN} equivalent is @samp{compare-sections}.
31538 @subsubheading Example
31543 @subheading The @code{-target-detach} Command
31544 @findex -target-detach
31546 @subsubheading Synopsis
31549 -target-detach [ @var{pid} | @var{gid} ]
31552 Detach from the remote target which normally resumes its execution.
31553 If either @var{pid} or @var{gid} is specified, detaches from either
31554 the specified process, or specified thread group. There's no output.
31556 @subsubheading @value{GDBN} Command
31558 The corresponding @value{GDBN} command is @samp{detach}.
31560 @subsubheading Example
31570 @subheading The @code{-target-disconnect} Command
31571 @findex -target-disconnect
31573 @subsubheading Synopsis
31579 Disconnect from the remote target. There's no output and the target is
31580 generally not resumed.
31582 @subsubheading @value{GDBN} Command
31584 The corresponding @value{GDBN} command is @samp{disconnect}.
31586 @subsubheading Example
31596 @subheading The @code{-target-download} Command
31597 @findex -target-download
31599 @subsubheading Synopsis
31605 Loads the executable onto the remote target.
31606 It prints out an update message every half second, which includes the fields:
31610 The name of the section.
31612 The size of what has been sent so far for that section.
31614 The size of the section.
31616 The total size of what was sent so far (the current and the previous sections).
31618 The size of the overall executable to download.
31622 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31623 @sc{gdb/mi} Output Syntax}).
31625 In addition, it prints the name and size of the sections, as they are
31626 downloaded. These messages include the following fields:
31630 The name of the section.
31632 The size of the section.
31634 The size of the overall executable to download.
31638 At the end, a summary is printed.
31640 @subsubheading @value{GDBN} Command
31642 The corresponding @value{GDBN} command is @samp{load}.
31644 @subsubheading Example
31646 Note: each status message appears on a single line. Here the messages
31647 have been broken down so that they can fit onto a page.
31652 +download,@{section=".text",section-size="6668",total-size="9880"@}
31653 +download,@{section=".text",section-sent="512",section-size="6668",
31654 total-sent="512",total-size="9880"@}
31655 +download,@{section=".text",section-sent="1024",section-size="6668",
31656 total-sent="1024",total-size="9880"@}
31657 +download,@{section=".text",section-sent="1536",section-size="6668",
31658 total-sent="1536",total-size="9880"@}
31659 +download,@{section=".text",section-sent="2048",section-size="6668",
31660 total-sent="2048",total-size="9880"@}
31661 +download,@{section=".text",section-sent="2560",section-size="6668",
31662 total-sent="2560",total-size="9880"@}
31663 +download,@{section=".text",section-sent="3072",section-size="6668",
31664 total-sent="3072",total-size="9880"@}
31665 +download,@{section=".text",section-sent="3584",section-size="6668",
31666 total-sent="3584",total-size="9880"@}
31667 +download,@{section=".text",section-sent="4096",section-size="6668",
31668 total-sent="4096",total-size="9880"@}
31669 +download,@{section=".text",section-sent="4608",section-size="6668",
31670 total-sent="4608",total-size="9880"@}
31671 +download,@{section=".text",section-sent="5120",section-size="6668",
31672 total-sent="5120",total-size="9880"@}
31673 +download,@{section=".text",section-sent="5632",section-size="6668",
31674 total-sent="5632",total-size="9880"@}
31675 +download,@{section=".text",section-sent="6144",section-size="6668",
31676 total-sent="6144",total-size="9880"@}
31677 +download,@{section=".text",section-sent="6656",section-size="6668",
31678 total-sent="6656",total-size="9880"@}
31679 +download,@{section=".init",section-size="28",total-size="9880"@}
31680 +download,@{section=".fini",section-size="28",total-size="9880"@}
31681 +download,@{section=".data",section-size="3156",total-size="9880"@}
31682 +download,@{section=".data",section-sent="512",section-size="3156",
31683 total-sent="7236",total-size="9880"@}
31684 +download,@{section=".data",section-sent="1024",section-size="3156",
31685 total-sent="7748",total-size="9880"@}
31686 +download,@{section=".data",section-sent="1536",section-size="3156",
31687 total-sent="8260",total-size="9880"@}
31688 +download,@{section=".data",section-sent="2048",section-size="3156",
31689 total-sent="8772",total-size="9880"@}
31690 +download,@{section=".data",section-sent="2560",section-size="3156",
31691 total-sent="9284",total-size="9880"@}
31692 +download,@{section=".data",section-sent="3072",section-size="3156",
31693 total-sent="9796",total-size="9880"@}
31694 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31701 @subheading The @code{-target-exec-status} Command
31702 @findex -target-exec-status
31704 @subsubheading Synopsis
31707 -target-exec-status
31710 Provide information on the state of the target (whether it is running or
31711 not, for instance).
31713 @subsubheading @value{GDBN} Command
31715 There's no equivalent @value{GDBN} command.
31717 @subsubheading Example
31721 @subheading The @code{-target-list-available-targets} Command
31722 @findex -target-list-available-targets
31724 @subsubheading Synopsis
31727 -target-list-available-targets
31730 List the possible targets to connect to.
31732 @subsubheading @value{GDBN} Command
31734 The corresponding @value{GDBN} command is @samp{help target}.
31736 @subsubheading Example
31740 @subheading The @code{-target-list-current-targets} Command
31741 @findex -target-list-current-targets
31743 @subsubheading Synopsis
31746 -target-list-current-targets
31749 Describe the current target.
31751 @subsubheading @value{GDBN} Command
31753 The corresponding information is printed by @samp{info file} (among
31756 @subsubheading Example
31760 @subheading The @code{-target-list-parameters} Command
31761 @findex -target-list-parameters
31763 @subsubheading Synopsis
31766 -target-list-parameters
31772 @subsubheading @value{GDBN} Command
31776 @subsubheading Example
31780 @subheading The @code{-target-select} Command
31781 @findex -target-select
31783 @subsubheading Synopsis
31786 -target-select @var{type} @var{parameters @dots{}}
31789 Connect @value{GDBN} to the remote target. This command takes two args:
31793 The type of target, for instance @samp{remote}, etc.
31794 @item @var{parameters}
31795 Device names, host names and the like. @xref{Target Commands, ,
31796 Commands for Managing Targets}, for more details.
31799 The output is a connection notification, followed by the address at
31800 which the target program is, in the following form:
31803 ^connected,addr="@var{address}",func="@var{function name}",
31804 args=[@var{arg list}]
31807 @subsubheading @value{GDBN} Command
31809 The corresponding @value{GDBN} command is @samp{target}.
31811 @subsubheading Example
31815 -target-select remote /dev/ttya
31816 ^connected,addr="0xfe00a300",func="??",args=[]
31820 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31821 @node GDB/MI File Transfer Commands
31822 @section @sc{gdb/mi} File Transfer Commands
31825 @subheading The @code{-target-file-put} Command
31826 @findex -target-file-put
31828 @subsubheading Synopsis
31831 -target-file-put @var{hostfile} @var{targetfile}
31834 Copy file @var{hostfile} from the host system (the machine running
31835 @value{GDBN}) to @var{targetfile} on the target system.
31837 @subsubheading @value{GDBN} Command
31839 The corresponding @value{GDBN} command is @samp{remote put}.
31841 @subsubheading Example
31845 -target-file-put localfile remotefile
31851 @subheading The @code{-target-file-get} Command
31852 @findex -target-file-get
31854 @subsubheading Synopsis
31857 -target-file-get @var{targetfile} @var{hostfile}
31860 Copy file @var{targetfile} from the target system to @var{hostfile}
31861 on the host system.
31863 @subsubheading @value{GDBN} Command
31865 The corresponding @value{GDBN} command is @samp{remote get}.
31867 @subsubheading Example
31871 -target-file-get remotefile localfile
31877 @subheading The @code{-target-file-delete} Command
31878 @findex -target-file-delete
31880 @subsubheading Synopsis
31883 -target-file-delete @var{targetfile}
31886 Delete @var{targetfile} from the target system.
31888 @subsubheading @value{GDBN} Command
31890 The corresponding @value{GDBN} command is @samp{remote delete}.
31892 @subsubheading Example
31896 -target-file-delete remotefile
31902 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31903 @node GDB/MI Miscellaneous Commands
31904 @section Miscellaneous @sc{gdb/mi} Commands
31906 @c @subheading -gdb-complete
31908 @subheading The @code{-gdb-exit} Command
31911 @subsubheading Synopsis
31917 Exit @value{GDBN} immediately.
31919 @subsubheading @value{GDBN} Command
31921 Approximately corresponds to @samp{quit}.
31923 @subsubheading Example
31933 @subheading The @code{-exec-abort} Command
31934 @findex -exec-abort
31936 @subsubheading Synopsis
31942 Kill the inferior running program.
31944 @subsubheading @value{GDBN} Command
31946 The corresponding @value{GDBN} command is @samp{kill}.
31948 @subsubheading Example
31953 @subheading The @code{-gdb-set} Command
31956 @subsubheading Synopsis
31962 Set an internal @value{GDBN} variable.
31963 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31965 @subsubheading @value{GDBN} Command
31967 The corresponding @value{GDBN} command is @samp{set}.
31969 @subsubheading Example
31979 @subheading The @code{-gdb-show} Command
31982 @subsubheading Synopsis
31988 Show the current value of a @value{GDBN} variable.
31990 @subsubheading @value{GDBN} Command
31992 The corresponding @value{GDBN} command is @samp{show}.
31994 @subsubheading Example
32003 @c @subheading -gdb-source
32006 @subheading The @code{-gdb-version} Command
32007 @findex -gdb-version
32009 @subsubheading Synopsis
32015 Show version information for @value{GDBN}. Used mostly in testing.
32017 @subsubheading @value{GDBN} Command
32019 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32020 default shows this information when you start an interactive session.
32022 @subsubheading Example
32024 @c This example modifies the actual output from GDB to avoid overfull
32030 ~Copyright 2000 Free Software Foundation, Inc.
32031 ~GDB is free software, covered by the GNU General Public License, and
32032 ~you are welcome to change it and/or distribute copies of it under
32033 ~ certain conditions.
32034 ~Type "show copying" to see the conditions.
32035 ~There is absolutely no warranty for GDB. Type "show warranty" for
32037 ~This GDB was configured as
32038 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32043 @subheading The @code{-list-features} Command
32044 @findex -list-features
32046 Returns a list of particular features of the MI protocol that
32047 this version of gdb implements. A feature can be a command,
32048 or a new field in an output of some command, or even an
32049 important bugfix. While a frontend can sometimes detect presence
32050 of a feature at runtime, it is easier to perform detection at debugger
32053 The command returns a list of strings, with each string naming an
32054 available feature. Each returned string is just a name, it does not
32055 have any internal structure. The list of possible feature names
32061 (gdb) -list-features
32062 ^done,result=["feature1","feature2"]
32065 The current list of features is:
32068 @item frozen-varobjs
32069 Indicates support for the @code{-var-set-frozen} command, as well
32070 as possible presense of the @code{frozen} field in the output
32071 of @code{-varobj-create}.
32072 @item pending-breakpoints
32073 Indicates support for the @option{-f} option to the @code{-break-insert}
32076 Indicates Python scripting support, Python-based
32077 pretty-printing commands, and possible presence of the
32078 @samp{display_hint} field in the output of @code{-var-list-children}
32080 Indicates support for the @code{-thread-info} command.
32081 @item data-read-memory-bytes
32082 Indicates support for the @code{-data-read-memory-bytes} and the
32083 @code{-data-write-memory-bytes} commands.
32084 @item breakpoint-notifications
32085 Indicates that changes to breakpoints and breakpoints created via the
32086 CLI will be announced via async records.
32087 @item ada-task-info
32088 Indicates support for the @code{-ada-task-info} command.
32091 @subheading The @code{-list-target-features} Command
32092 @findex -list-target-features
32094 Returns a list of particular features that are supported by the
32095 target. Those features affect the permitted MI commands, but
32096 unlike the features reported by the @code{-list-features} command, the
32097 features depend on which target GDB is using at the moment. Whenever
32098 a target can change, due to commands such as @code{-target-select},
32099 @code{-target-attach} or @code{-exec-run}, the list of target features
32100 may change, and the frontend should obtain it again.
32104 (gdb) -list-features
32105 ^done,result=["async"]
32108 The current list of features is:
32112 Indicates that the target is capable of asynchronous command
32113 execution, which means that @value{GDBN} will accept further commands
32114 while the target is running.
32117 Indicates that the target is capable of reverse execution.
32118 @xref{Reverse Execution}, for more information.
32122 @subheading The @code{-list-thread-groups} Command
32123 @findex -list-thread-groups
32125 @subheading Synopsis
32128 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32131 Lists thread groups (@pxref{Thread groups}). When a single thread
32132 group is passed as the argument, lists the children of that group.
32133 When several thread group are passed, lists information about those
32134 thread groups. Without any parameters, lists information about all
32135 top-level thread groups.
32137 Normally, thread groups that are being debugged are reported.
32138 With the @samp{--available} option, @value{GDBN} reports thread groups
32139 available on the target.
32141 The output of this command may have either a @samp{threads} result or
32142 a @samp{groups} result. The @samp{thread} result has a list of tuples
32143 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32144 Information}). The @samp{groups} result has a list of tuples as value,
32145 each tuple describing a thread group. If top-level groups are
32146 requested (that is, no parameter is passed), or when several groups
32147 are passed, the output always has a @samp{groups} result. The format
32148 of the @samp{group} result is described below.
32150 To reduce the number of roundtrips it's possible to list thread groups
32151 together with their children, by passing the @samp{--recurse} option
32152 and the recursion depth. Presently, only recursion depth of 1 is
32153 permitted. If this option is present, then every reported thread group
32154 will also include its children, either as @samp{group} or
32155 @samp{threads} field.
32157 In general, any combination of option and parameters is permitted, with
32158 the following caveats:
32162 When a single thread group is passed, the output will typically
32163 be the @samp{threads} result. Because threads may not contain
32164 anything, the @samp{recurse} option will be ignored.
32167 When the @samp{--available} option is passed, limited information may
32168 be available. In particular, the list of threads of a process might
32169 be inaccessible. Further, specifying specific thread groups might
32170 not give any performance advantage over listing all thread groups.
32171 The frontend should assume that @samp{-list-thread-groups --available}
32172 is always an expensive operation and cache the results.
32176 The @samp{groups} result is a list of tuples, where each tuple may
32177 have the following fields:
32181 Identifier of the thread group. This field is always present.
32182 The identifier is an opaque string; frontends should not try to
32183 convert it to an integer, even though it might look like one.
32186 The type of the thread group. At present, only @samp{process} is a
32190 The target-specific process identifier. This field is only present
32191 for thread groups of type @samp{process} and only if the process exists.
32194 The number of children this thread group has. This field may be
32195 absent for an available thread group.
32198 This field has a list of tuples as value, each tuple describing a
32199 thread. It may be present if the @samp{--recurse} option is
32200 specified, and it's actually possible to obtain the threads.
32203 This field is a list of integers, each identifying a core that one
32204 thread of the group is running on. This field may be absent if
32205 such information is not available.
32208 The name of the executable file that corresponds to this thread group.
32209 The field is only present for thread groups of type @samp{process},
32210 and only if there is a corresponding executable file.
32214 @subheading Example
32218 -list-thread-groups
32219 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32220 -list-thread-groups 17
32221 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32222 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32223 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32224 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32225 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32226 -list-thread-groups --available
32227 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32228 -list-thread-groups --available --recurse 1
32229 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32230 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32231 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32232 -list-thread-groups --available --recurse 1 17 18
32233 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32234 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32235 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32239 @subheading The @code{-add-inferior} Command
32240 @findex -add-inferior
32242 @subheading Synopsis
32248 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32249 inferior is not associated with any executable. Such association may
32250 be established with the @samp{-file-exec-and-symbols} command
32251 (@pxref{GDB/MI File Commands}). The command response has a single
32252 field, @samp{thread-group}, whose value is the identifier of the
32253 thread group corresponding to the new inferior.
32255 @subheading Example
32260 ^done,thread-group="i3"
32263 @subheading The @code{-interpreter-exec} Command
32264 @findex -interpreter-exec
32266 @subheading Synopsis
32269 -interpreter-exec @var{interpreter} @var{command}
32271 @anchor{-interpreter-exec}
32273 Execute the specified @var{command} in the given @var{interpreter}.
32275 @subheading @value{GDBN} Command
32277 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32279 @subheading Example
32283 -interpreter-exec console "break main"
32284 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32285 &"During symbol reading, bad structure-type format.\n"
32286 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32291 @subheading The @code{-inferior-tty-set} Command
32292 @findex -inferior-tty-set
32294 @subheading Synopsis
32297 -inferior-tty-set /dev/pts/1
32300 Set terminal for future runs of the program being debugged.
32302 @subheading @value{GDBN} Command
32304 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32306 @subheading Example
32310 -inferior-tty-set /dev/pts/1
32315 @subheading The @code{-inferior-tty-show} Command
32316 @findex -inferior-tty-show
32318 @subheading Synopsis
32324 Show terminal for future runs of program being debugged.
32326 @subheading @value{GDBN} Command
32328 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32330 @subheading Example
32334 -inferior-tty-set /dev/pts/1
32338 ^done,inferior_tty_terminal="/dev/pts/1"
32342 @subheading The @code{-enable-timings} Command
32343 @findex -enable-timings
32345 @subheading Synopsis
32348 -enable-timings [yes | no]
32351 Toggle the printing of the wallclock, user and system times for an MI
32352 command as a field in its output. This command is to help frontend
32353 developers optimize the performance of their code. No argument is
32354 equivalent to @samp{yes}.
32356 @subheading @value{GDBN} Command
32360 @subheading Example
32368 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32369 addr="0x080484ed",func="main",file="myprog.c",
32370 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
32371 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32379 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32380 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32381 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32382 fullname="/home/nickrob/myprog.c",line="73"@}
32387 @chapter @value{GDBN} Annotations
32389 This chapter describes annotations in @value{GDBN}. Annotations were
32390 designed to interface @value{GDBN} to graphical user interfaces or other
32391 similar programs which want to interact with @value{GDBN} at a
32392 relatively high level.
32394 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32398 This is Edition @value{EDITION}, @value{DATE}.
32402 * Annotations Overview:: What annotations are; the general syntax.
32403 * Server Prefix:: Issuing a command without affecting user state.
32404 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32405 * Errors:: Annotations for error messages.
32406 * Invalidation:: Some annotations describe things now invalid.
32407 * Annotations for Running::
32408 Whether the program is running, how it stopped, etc.
32409 * Source Annotations:: Annotations describing source code.
32412 @node Annotations Overview
32413 @section What is an Annotation?
32414 @cindex annotations
32416 Annotations start with a newline character, two @samp{control-z}
32417 characters, and the name of the annotation. If there is no additional
32418 information associated with this annotation, the name of the annotation
32419 is followed immediately by a newline. If there is additional
32420 information, the name of the annotation is followed by a space, the
32421 additional information, and a newline. The additional information
32422 cannot contain newline characters.
32424 Any output not beginning with a newline and two @samp{control-z}
32425 characters denotes literal output from @value{GDBN}. Currently there is
32426 no need for @value{GDBN} to output a newline followed by two
32427 @samp{control-z} characters, but if there was such a need, the
32428 annotations could be extended with an @samp{escape} annotation which
32429 means those three characters as output.
32431 The annotation @var{level}, which is specified using the
32432 @option{--annotate} command line option (@pxref{Mode Options}), controls
32433 how much information @value{GDBN} prints together with its prompt,
32434 values of expressions, source lines, and other types of output. Level 0
32435 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32436 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32437 for programs that control @value{GDBN}, and level 2 annotations have
32438 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32439 Interface, annotate, GDB's Obsolete Annotations}).
32442 @kindex set annotate
32443 @item set annotate @var{level}
32444 The @value{GDBN} command @code{set annotate} sets the level of
32445 annotations to the specified @var{level}.
32447 @item show annotate
32448 @kindex show annotate
32449 Show the current annotation level.
32452 This chapter describes level 3 annotations.
32454 A simple example of starting up @value{GDBN} with annotations is:
32457 $ @kbd{gdb --annotate=3}
32459 Copyright 2003 Free Software Foundation, Inc.
32460 GDB is free software, covered by the GNU General Public License,
32461 and you are welcome to change it and/or distribute copies of it
32462 under certain conditions.
32463 Type "show copying" to see the conditions.
32464 There is absolutely no warranty for GDB. Type "show warranty"
32466 This GDB was configured as "i386-pc-linux-gnu"
32477 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32478 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32479 denotes a @samp{control-z} character) are annotations; the rest is
32480 output from @value{GDBN}.
32482 @node Server Prefix
32483 @section The Server Prefix
32484 @cindex server prefix
32486 If you prefix a command with @samp{server } then it will not affect
32487 the command history, nor will it affect @value{GDBN}'s notion of which
32488 command to repeat if @key{RET} is pressed on a line by itself. This
32489 means that commands can be run behind a user's back by a front-end in
32490 a transparent manner.
32492 The @code{server } prefix does not affect the recording of values into
32493 the value history; to print a value without recording it into the
32494 value history, use the @code{output} command instead of the
32495 @code{print} command.
32497 Using this prefix also disables confirmation requests
32498 (@pxref{confirmation requests}).
32501 @section Annotation for @value{GDBN} Input
32503 @cindex annotations for prompts
32504 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32505 to know when to send output, when the output from a given command is
32508 Different kinds of input each have a different @dfn{input type}. Each
32509 input type has three annotations: a @code{pre-} annotation, which
32510 denotes the beginning of any prompt which is being output, a plain
32511 annotation, which denotes the end of the prompt, and then a @code{post-}
32512 annotation which denotes the end of any echo which may (or may not) be
32513 associated with the input. For example, the @code{prompt} input type
32514 features the following annotations:
32522 The input types are
32525 @findex pre-prompt annotation
32526 @findex prompt annotation
32527 @findex post-prompt annotation
32529 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32531 @findex pre-commands annotation
32532 @findex commands annotation
32533 @findex post-commands annotation
32535 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32536 command. The annotations are repeated for each command which is input.
32538 @findex pre-overload-choice annotation
32539 @findex overload-choice annotation
32540 @findex post-overload-choice annotation
32541 @item overload-choice
32542 When @value{GDBN} wants the user to select between various overloaded functions.
32544 @findex pre-query annotation
32545 @findex query annotation
32546 @findex post-query annotation
32548 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32550 @findex pre-prompt-for-continue annotation
32551 @findex prompt-for-continue annotation
32552 @findex post-prompt-for-continue annotation
32553 @item prompt-for-continue
32554 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32555 expect this to work well; instead use @code{set height 0} to disable
32556 prompting. This is because the counting of lines is buggy in the
32557 presence of annotations.
32562 @cindex annotations for errors, warnings and interrupts
32564 @findex quit annotation
32569 This annotation occurs right before @value{GDBN} responds to an interrupt.
32571 @findex error annotation
32576 This annotation occurs right before @value{GDBN} responds to an error.
32578 Quit and error annotations indicate that any annotations which @value{GDBN} was
32579 in the middle of may end abruptly. For example, if a
32580 @code{value-history-begin} annotation is followed by a @code{error}, one
32581 cannot expect to receive the matching @code{value-history-end}. One
32582 cannot expect not to receive it either, however; an error annotation
32583 does not necessarily mean that @value{GDBN} is immediately returning all the way
32586 @findex error-begin annotation
32587 A quit or error annotation may be preceded by
32593 Any output between that and the quit or error annotation is the error
32596 Warning messages are not yet annotated.
32597 @c If we want to change that, need to fix warning(), type_error(),
32598 @c range_error(), and possibly other places.
32601 @section Invalidation Notices
32603 @cindex annotations for invalidation messages
32604 The following annotations say that certain pieces of state may have
32608 @findex frames-invalid annotation
32609 @item ^Z^Zframes-invalid
32611 The frames (for example, output from the @code{backtrace} command) may
32614 @findex breakpoints-invalid annotation
32615 @item ^Z^Zbreakpoints-invalid
32617 The breakpoints may have changed. For example, the user just added or
32618 deleted a breakpoint.
32621 @node Annotations for Running
32622 @section Running the Program
32623 @cindex annotations for running programs
32625 @findex starting annotation
32626 @findex stopping annotation
32627 When the program starts executing due to a @value{GDBN} command such as
32628 @code{step} or @code{continue},
32634 is output. When the program stops,
32640 is output. Before the @code{stopped} annotation, a variety of
32641 annotations describe how the program stopped.
32644 @findex exited annotation
32645 @item ^Z^Zexited @var{exit-status}
32646 The program exited, and @var{exit-status} is the exit status (zero for
32647 successful exit, otherwise nonzero).
32649 @findex signalled annotation
32650 @findex signal-name annotation
32651 @findex signal-name-end annotation
32652 @findex signal-string annotation
32653 @findex signal-string-end annotation
32654 @item ^Z^Zsignalled
32655 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32656 annotation continues:
32662 ^Z^Zsignal-name-end
32666 ^Z^Zsignal-string-end
32671 where @var{name} is the name of the signal, such as @code{SIGILL} or
32672 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32673 as @code{Illegal Instruction} or @code{Segmentation fault}.
32674 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32675 user's benefit and have no particular format.
32677 @findex signal annotation
32679 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32680 just saying that the program received the signal, not that it was
32681 terminated with it.
32683 @findex breakpoint annotation
32684 @item ^Z^Zbreakpoint @var{number}
32685 The program hit breakpoint number @var{number}.
32687 @findex watchpoint annotation
32688 @item ^Z^Zwatchpoint @var{number}
32689 The program hit watchpoint number @var{number}.
32692 @node Source Annotations
32693 @section Displaying Source
32694 @cindex annotations for source display
32696 @findex source annotation
32697 The following annotation is used instead of displaying source code:
32700 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32703 where @var{filename} is an absolute file name indicating which source
32704 file, @var{line} is the line number within that file (where 1 is the
32705 first line in the file), @var{character} is the character position
32706 within the file (where 0 is the first character in the file) (for most
32707 debug formats this will necessarily point to the beginning of a line),
32708 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32709 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32710 @var{addr} is the address in the target program associated with the
32711 source which is being displayed. @var{addr} is in the form @samp{0x}
32712 followed by one or more lowercase hex digits (note that this does not
32713 depend on the language).
32715 @node JIT Interface
32716 @chapter JIT Compilation Interface
32717 @cindex just-in-time compilation
32718 @cindex JIT compilation interface
32720 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32721 interface. A JIT compiler is a program or library that generates native
32722 executable code at runtime and executes it, usually in order to achieve good
32723 performance while maintaining platform independence.
32725 Programs that use JIT compilation are normally difficult to debug because
32726 portions of their code are generated at runtime, instead of being loaded from
32727 object files, which is where @value{GDBN} normally finds the program's symbols
32728 and debug information. In order to debug programs that use JIT compilation,
32729 @value{GDBN} has an interface that allows the program to register in-memory
32730 symbol files with @value{GDBN} at runtime.
32732 If you are using @value{GDBN} to debug a program that uses this interface, then
32733 it should work transparently so long as you have not stripped the binary. If
32734 you are developing a JIT compiler, then the interface is documented in the rest
32735 of this chapter. At this time, the only known client of this interface is the
32738 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32739 JIT compiler communicates with @value{GDBN} by writing data into a global
32740 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32741 attaches, it reads a linked list of symbol files from the global variable to
32742 find existing code, and puts a breakpoint in the function so that it can find
32743 out about additional code.
32746 * Declarations:: Relevant C struct declarations
32747 * Registering Code:: Steps to register code
32748 * Unregistering Code:: Steps to unregister code
32749 * Custom Debug Info:: Emit debug information in a custom format
32753 @section JIT Declarations
32755 These are the relevant struct declarations that a C program should include to
32756 implement the interface:
32766 struct jit_code_entry
32768 struct jit_code_entry *next_entry;
32769 struct jit_code_entry *prev_entry;
32770 const char *symfile_addr;
32771 uint64_t symfile_size;
32774 struct jit_descriptor
32777 /* This type should be jit_actions_t, but we use uint32_t
32778 to be explicit about the bitwidth. */
32779 uint32_t action_flag;
32780 struct jit_code_entry *relevant_entry;
32781 struct jit_code_entry *first_entry;
32784 /* GDB puts a breakpoint in this function. */
32785 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32787 /* Make sure to specify the version statically, because the
32788 debugger may check the version before we can set it. */
32789 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32792 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32793 modifications to this global data properly, which can easily be done by putting
32794 a global mutex around modifications to these structures.
32796 @node Registering Code
32797 @section Registering Code
32799 To register code with @value{GDBN}, the JIT should follow this protocol:
32803 Generate an object file in memory with symbols and other desired debug
32804 information. The file must include the virtual addresses of the sections.
32807 Create a code entry for the file, which gives the start and size of the symbol
32811 Add it to the linked list in the JIT descriptor.
32814 Point the relevant_entry field of the descriptor at the entry.
32817 Set @code{action_flag} to @code{JIT_REGISTER} and call
32818 @code{__jit_debug_register_code}.
32821 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32822 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32823 new code. However, the linked list must still be maintained in order to allow
32824 @value{GDBN} to attach to a running process and still find the symbol files.
32826 @node Unregistering Code
32827 @section Unregistering Code
32829 If code is freed, then the JIT should use the following protocol:
32833 Remove the code entry corresponding to the code from the linked list.
32836 Point the @code{relevant_entry} field of the descriptor at the code entry.
32839 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32840 @code{__jit_debug_register_code}.
32843 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32844 and the JIT will leak the memory used for the associated symbol files.
32846 @node Custom Debug Info
32847 @section Custom Debug Info
32848 @cindex custom JIT debug info
32849 @cindex JIT debug info reader
32851 Generating debug information in platform-native file formats (like ELF
32852 or COFF) may be an overkill for JIT compilers; especially if all the
32853 debug info is used for is displaying a meaningful backtrace. The
32854 issue can be resolved by having the JIT writers decide on a debug info
32855 format and also provide a reader that parses the debug info generated
32856 by the JIT compiler. This section gives a brief overview on writing
32857 such a parser. More specific details can be found in the source file
32858 @file{gdb/jit-reader.in}, which is also installed as a header at
32859 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32861 The reader is implemented as a shared object (so this functionality is
32862 not available on platforms which don't allow loading shared objects at
32863 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32864 @code{jit-reader-unload} are provided, to be used to load and unload
32865 the readers from a preconfigured directory. Once loaded, the shared
32866 object is used the parse the debug information emitted by the JIT
32870 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32871 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32874 @node Using JIT Debug Info Readers
32875 @subsection Using JIT Debug Info Readers
32876 @kindex jit-reader-load
32877 @kindex jit-reader-unload
32879 Readers can be loaded and unloaded using the @code{jit-reader-load}
32880 and @code{jit-reader-unload} commands.
32883 @item jit-reader-load @var{reader-name}
32884 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32885 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32886 @var{libdir} is the system library directory, usually
32887 @file{/usr/local/lib}. Only one reader can be active at a time;
32888 trying to load a second reader when one is already loaded will result
32889 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32890 first unloading the current one using @code{jit-reader-load} and then
32891 invoking @code{jit-reader-load}.
32893 @item jit-reader-unload
32894 Unload the currently loaded JIT reader.
32898 @node Writing JIT Debug Info Readers
32899 @subsection Writing JIT Debug Info Readers
32900 @cindex writing JIT debug info readers
32902 As mentioned, a reader is essentially a shared object conforming to a
32903 certain ABI. This ABI is described in @file{jit-reader.h}.
32905 @file{jit-reader.h} defines the structures, macros and functions
32906 required to write a reader. It is installed (along with
32907 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32908 the system include directory.
32910 Readers need to be released under a GPL compatible license. A reader
32911 can be declared as released under such a license by placing the macro
32912 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32914 The entry point for readers is the symbol @code{gdb_init_reader},
32915 which is expected to be a function with the prototype
32917 @findex gdb_init_reader
32919 extern struct gdb_reader_funcs *gdb_init_reader (void);
32922 @cindex @code{struct gdb_reader_funcs}
32924 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32925 functions. These functions are executed to read the debug info
32926 generated by the JIT compiler (@code{read}), to unwind stack frames
32927 (@code{unwind}) and to create canonical frame IDs
32928 (@code{get_Frame_id}). It also has a callback that is called when the
32929 reader is being unloaded (@code{destroy}). The struct looks like this
32932 struct gdb_reader_funcs
32934 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32935 int reader_version;
32937 /* For use by the reader. */
32940 gdb_read_debug_info *read;
32941 gdb_unwind_frame *unwind;
32942 gdb_get_frame_id *get_frame_id;
32943 gdb_destroy_reader *destroy;
32947 @cindex @code{struct gdb_symbol_callbacks}
32948 @cindex @code{struct gdb_unwind_callbacks}
32950 The callbacks are provided with another set of callbacks by
32951 @value{GDBN} to do their job. For @code{read}, these callbacks are
32952 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32953 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32954 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32955 files and new symbol tables inside those object files. @code{struct
32956 gdb_unwind_callbacks} has callbacks to read registers off the current
32957 frame and to write out the values of the registers in the previous
32958 frame. Both have a callback (@code{target_read}) to read bytes off the
32959 target's address space.
32961 @node In-Process Agent
32962 @chapter In-Process Agent
32963 @cindex debugging agent
32964 The traditional debugging model is conceptually low-speed, but works fine,
32965 because most bugs can be reproduced in debugging-mode execution. However,
32966 as multi-core or many-core processors are becoming mainstream, and
32967 multi-threaded programs become more and more popular, there should be more
32968 and more bugs that only manifest themselves at normal-mode execution, for
32969 example, thread races, because debugger's interference with the program's
32970 timing may conceal the bugs. On the other hand, in some applications,
32971 it is not feasible for the debugger to interrupt the program's execution
32972 long enough for the developer to learn anything helpful about its behavior.
32973 If the program's correctness depends on its real-time behavior, delays
32974 introduced by a debugger might cause the program to fail, even when the
32975 code itself is correct. It is useful to be able to observe the program's
32976 behavior without interrupting it.
32978 Therefore, traditional debugging model is too intrusive to reproduce
32979 some bugs. In order to reduce the interference with the program, we can
32980 reduce the number of operations performed by debugger. The
32981 @dfn{In-Process Agent}, a shared library, is running within the same
32982 process with inferior, and is able to perform some debugging operations
32983 itself. As a result, debugger is only involved when necessary, and
32984 performance of debugging can be improved accordingly. Note that
32985 interference with program can be reduced but can't be removed completely,
32986 because the in-process agent will still stop or slow down the program.
32988 The in-process agent can interpret and execute Agent Expressions
32989 (@pxref{Agent Expressions}) during performing debugging operations. The
32990 agent expressions can be used for different purposes, such as collecting
32991 data in tracepoints, and condition evaluation in breakpoints.
32993 @anchor{Control Agent}
32994 You can control whether the in-process agent is used as an aid for
32995 debugging with the following commands:
32998 @kindex set agent on
33000 Causes the in-process agent to perform some operations on behalf of the
33001 debugger. Just which operations requested by the user will be done
33002 by the in-process agent depends on the its capabilities. For example,
33003 if you request to evaluate breakpoint conditions in the in-process agent,
33004 and the in-process agent has such capability as well, then breakpoint
33005 conditions will be evaluated in the in-process agent.
33007 @kindex set agent off
33008 @item set agent off
33009 Disables execution of debugging operations by the in-process agent. All
33010 of the operations will be performed by @value{GDBN}.
33014 Display the current setting of execution of debugging operations by
33015 the in-process agent.
33019 @chapter Reporting Bugs in @value{GDBN}
33020 @cindex bugs in @value{GDBN}
33021 @cindex reporting bugs in @value{GDBN}
33023 Your bug reports play an essential role in making @value{GDBN} reliable.
33025 Reporting a bug may help you by bringing a solution to your problem, or it
33026 may not. But in any case the principal function of a bug report is to help
33027 the entire community by making the next version of @value{GDBN} work better. Bug
33028 reports are your contribution to the maintenance of @value{GDBN}.
33030 In order for a bug report to serve its purpose, you must include the
33031 information that enables us to fix the bug.
33034 * Bug Criteria:: Have you found a bug?
33035 * Bug Reporting:: How to report bugs
33039 @section Have You Found a Bug?
33040 @cindex bug criteria
33042 If you are not sure whether you have found a bug, here are some guidelines:
33045 @cindex fatal signal
33046 @cindex debugger crash
33047 @cindex crash of debugger
33049 If the debugger gets a fatal signal, for any input whatever, that is a
33050 @value{GDBN} bug. Reliable debuggers never crash.
33052 @cindex error on valid input
33054 If @value{GDBN} produces an error message for valid input, that is a
33055 bug. (Note that if you're cross debugging, the problem may also be
33056 somewhere in the connection to the target.)
33058 @cindex invalid input
33060 If @value{GDBN} does not produce an error message for invalid input,
33061 that is a bug. However, you should note that your idea of
33062 ``invalid input'' might be our idea of ``an extension'' or ``support
33063 for traditional practice''.
33066 If you are an experienced user of debugging tools, your suggestions
33067 for improvement of @value{GDBN} are welcome in any case.
33070 @node Bug Reporting
33071 @section How to Report Bugs
33072 @cindex bug reports
33073 @cindex @value{GDBN} bugs, reporting
33075 A number of companies and individuals offer support for @sc{gnu} products.
33076 If you obtained @value{GDBN} from a support organization, we recommend you
33077 contact that organization first.
33079 You can find contact information for many support companies and
33080 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33082 @c should add a web page ref...
33085 @ifset BUGURL_DEFAULT
33086 In any event, we also recommend that you submit bug reports for
33087 @value{GDBN}. The preferred method is to submit them directly using
33088 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33089 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33092 @strong{Do not send bug reports to @samp{info-gdb}, or to
33093 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33094 not want to receive bug reports. Those that do have arranged to receive
33097 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33098 serves as a repeater. The mailing list and the newsgroup carry exactly
33099 the same messages. Often people think of posting bug reports to the
33100 newsgroup instead of mailing them. This appears to work, but it has one
33101 problem which can be crucial: a newsgroup posting often lacks a mail
33102 path back to the sender. Thus, if we need to ask for more information,
33103 we may be unable to reach you. For this reason, it is better to send
33104 bug reports to the mailing list.
33106 @ifclear BUGURL_DEFAULT
33107 In any event, we also recommend that you submit bug reports for
33108 @value{GDBN} to @value{BUGURL}.
33112 The fundamental principle of reporting bugs usefully is this:
33113 @strong{report all the facts}. If you are not sure whether to state a
33114 fact or leave it out, state it!
33116 Often people omit facts because they think they know what causes the
33117 problem and assume that some details do not matter. Thus, you might
33118 assume that the name of the variable you use in an example does not matter.
33119 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33120 stray memory reference which happens to fetch from the location where that
33121 name is stored in memory; perhaps, if the name were different, the contents
33122 of that location would fool the debugger into doing the right thing despite
33123 the bug. Play it safe and give a specific, complete example. That is the
33124 easiest thing for you to do, and the most helpful.
33126 Keep in mind that the purpose of a bug report is to enable us to fix the
33127 bug. It may be that the bug has been reported previously, but neither
33128 you nor we can know that unless your bug report is complete and
33131 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33132 bell?'' Those bug reports are useless, and we urge everyone to
33133 @emph{refuse to respond to them} except to chide the sender to report
33136 To enable us to fix the bug, you should include all these things:
33140 The version of @value{GDBN}. @value{GDBN} announces it if you start
33141 with no arguments; you can also print it at any time using @code{show
33144 Without this, we will not know whether there is any point in looking for
33145 the bug in the current version of @value{GDBN}.
33148 The type of machine you are using, and the operating system name and
33152 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33153 ``@value{GCC}--2.8.1''.
33156 What compiler (and its version) was used to compile the program you are
33157 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33158 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33159 to get this information; for other compilers, see the documentation for
33163 The command arguments you gave the compiler to compile your example and
33164 observe the bug. For example, did you use @samp{-O}? To guarantee
33165 you will not omit something important, list them all. A copy of the
33166 Makefile (or the output from make) is sufficient.
33168 If we were to try to guess the arguments, we would probably guess wrong
33169 and then we might not encounter the bug.
33172 A complete input script, and all necessary source files, that will
33176 A description of what behavior you observe that you believe is
33177 incorrect. For example, ``It gets a fatal signal.''
33179 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33180 will certainly notice it. But if the bug is incorrect output, we might
33181 not notice unless it is glaringly wrong. You might as well not give us
33182 a chance to make a mistake.
33184 Even if the problem you experience is a fatal signal, you should still
33185 say so explicitly. Suppose something strange is going on, such as, your
33186 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33187 the C library on your system. (This has happened!) Your copy might
33188 crash and ours would not. If you told us to expect a crash, then when
33189 ours fails to crash, we would know that the bug was not happening for
33190 us. If you had not told us to expect a crash, then we would not be able
33191 to draw any conclusion from our observations.
33194 @cindex recording a session script
33195 To collect all this information, you can use a session recording program
33196 such as @command{script}, which is available on many Unix systems.
33197 Just run your @value{GDBN} session inside @command{script} and then
33198 include the @file{typescript} file with your bug report.
33200 Another way to record a @value{GDBN} session is to run @value{GDBN}
33201 inside Emacs and then save the entire buffer to a file.
33204 If you wish to suggest changes to the @value{GDBN} source, send us context
33205 diffs. If you even discuss something in the @value{GDBN} source, refer to
33206 it by context, not by line number.
33208 The line numbers in our development sources will not match those in your
33209 sources. Your line numbers would convey no useful information to us.
33213 Here are some things that are not necessary:
33217 A description of the envelope of the bug.
33219 Often people who encounter a bug spend a lot of time investigating
33220 which changes to the input file will make the bug go away and which
33221 changes will not affect it.
33223 This is often time consuming and not very useful, because the way we
33224 will find the bug is by running a single example under the debugger
33225 with breakpoints, not by pure deduction from a series of examples.
33226 We recommend that you save your time for something else.
33228 Of course, if you can find a simpler example to report @emph{instead}
33229 of the original one, that is a convenience for us. Errors in the
33230 output will be easier to spot, running under the debugger will take
33231 less time, and so on.
33233 However, simplification is not vital; if you do not want to do this,
33234 report the bug anyway and send us the entire test case you used.
33237 A patch for the bug.
33239 A patch for the bug does help us if it is a good one. But do not omit
33240 the necessary information, such as the test case, on the assumption that
33241 a patch is all we need. We might see problems with your patch and decide
33242 to fix the problem another way, or we might not understand it at all.
33244 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33245 construct an example that will make the program follow a certain path
33246 through the code. If you do not send us the example, we will not be able
33247 to construct one, so we will not be able to verify that the bug is fixed.
33249 And if we cannot understand what bug you are trying to fix, or why your
33250 patch should be an improvement, we will not install it. A test case will
33251 help us to understand.
33254 A guess about what the bug is or what it depends on.
33256 Such guesses are usually wrong. Even we cannot guess right about such
33257 things without first using the debugger to find the facts.
33260 @c The readline documentation is distributed with the readline code
33261 @c and consists of the two following files:
33264 @c Use -I with makeinfo to point to the appropriate directory,
33265 @c environment var TEXINPUTS with TeX.
33266 @ifclear SYSTEM_READLINE
33267 @include rluser.texi
33268 @include hsuser.texi
33272 @appendix In Memoriam
33274 The @value{GDBN} project mourns the loss of the following long-time
33279 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33280 to Free Software in general. Outside of @value{GDBN}, he was known in
33281 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33283 @item Michael Snyder
33284 Michael was one of the Global Maintainers of the @value{GDBN} project,
33285 with contributions recorded as early as 1996, until 2011. In addition
33286 to his day to day participation, he was a large driving force behind
33287 adding Reverse Debugging to @value{GDBN}.
33290 Beyond their technical contributions to the project, they were also
33291 enjoyable members of the Free Software Community. We will miss them.
33293 @node Formatting Documentation
33294 @appendix Formatting Documentation
33296 @cindex @value{GDBN} reference card
33297 @cindex reference card
33298 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33299 for printing with PostScript or Ghostscript, in the @file{gdb}
33300 subdirectory of the main source directory@footnote{In
33301 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33302 release.}. If you can use PostScript or Ghostscript with your printer,
33303 you can print the reference card immediately with @file{refcard.ps}.
33305 The release also includes the source for the reference card. You
33306 can format it, using @TeX{}, by typing:
33312 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33313 mode on US ``letter'' size paper;
33314 that is, on a sheet 11 inches wide by 8.5 inches
33315 high. You will need to specify this form of printing as an option to
33316 your @sc{dvi} output program.
33318 @cindex documentation
33320 All the documentation for @value{GDBN} comes as part of the machine-readable
33321 distribution. The documentation is written in Texinfo format, which is
33322 a documentation system that uses a single source file to produce both
33323 on-line information and a printed manual. You can use one of the Info
33324 formatting commands to create the on-line version of the documentation
33325 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33327 @value{GDBN} includes an already formatted copy of the on-line Info
33328 version of this manual in the @file{gdb} subdirectory. The main Info
33329 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33330 subordinate files matching @samp{gdb.info*} in the same directory. If
33331 necessary, you can print out these files, or read them with any editor;
33332 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33333 Emacs or the standalone @code{info} program, available as part of the
33334 @sc{gnu} Texinfo distribution.
33336 If you want to format these Info files yourself, you need one of the
33337 Info formatting programs, such as @code{texinfo-format-buffer} or
33340 If you have @code{makeinfo} installed, and are in the top level
33341 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33342 version @value{GDBVN}), you can make the Info file by typing:
33349 If you want to typeset and print copies of this manual, you need @TeX{},
33350 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33351 Texinfo definitions file.
33353 @TeX{} is a typesetting program; it does not print files directly, but
33354 produces output files called @sc{dvi} files. To print a typeset
33355 document, you need a program to print @sc{dvi} files. If your system
33356 has @TeX{} installed, chances are it has such a program. The precise
33357 command to use depends on your system; @kbd{lpr -d} is common; another
33358 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33359 require a file name without any extension or a @samp{.dvi} extension.
33361 @TeX{} also requires a macro definitions file called
33362 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33363 written in Texinfo format. On its own, @TeX{} cannot either read or
33364 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33365 and is located in the @file{gdb-@var{version-number}/texinfo}
33368 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33369 typeset and print this manual. First switch to the @file{gdb}
33370 subdirectory of the main source directory (for example, to
33371 @file{gdb-@value{GDBVN}/gdb}) and type:
33377 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33379 @node Installing GDB
33380 @appendix Installing @value{GDBN}
33381 @cindex installation
33384 * Requirements:: Requirements for building @value{GDBN}
33385 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33386 * Separate Objdir:: Compiling @value{GDBN} in another directory
33387 * Config Names:: Specifying names for hosts and targets
33388 * Configure Options:: Summary of options for configure
33389 * System-wide configuration:: Having a system-wide init file
33393 @section Requirements for Building @value{GDBN}
33394 @cindex building @value{GDBN}, requirements for
33396 Building @value{GDBN} requires various tools and packages to be available.
33397 Other packages will be used only if they are found.
33399 @heading Tools/Packages Necessary for Building @value{GDBN}
33401 @item ISO C90 compiler
33402 @value{GDBN} is written in ISO C90. It should be buildable with any
33403 working C90 compiler, e.g.@: GCC.
33407 @heading Tools/Packages Optional for Building @value{GDBN}
33411 @value{GDBN} can use the Expat XML parsing library. This library may be
33412 included with your operating system distribution; if it is not, you
33413 can get the latest version from @url{http://expat.sourceforge.net}.
33414 The @file{configure} script will search for this library in several
33415 standard locations; if it is installed in an unusual path, you can
33416 use the @option{--with-libexpat-prefix} option to specify its location.
33422 Remote protocol memory maps (@pxref{Memory Map Format})
33424 Target descriptions (@pxref{Target Descriptions})
33426 Remote shared library lists (@xref{Library List Format},
33427 or alternatively @pxref{Library List Format for SVR4 Targets})
33429 MS-Windows shared libraries (@pxref{Shared Libraries})
33431 Traceframe info (@pxref{Traceframe Info Format})
33435 @cindex compressed debug sections
33436 @value{GDBN} will use the @samp{zlib} library, if available, to read
33437 compressed debug sections. Some linkers, such as GNU gold, are capable
33438 of producing binaries with compressed debug sections. If @value{GDBN}
33439 is compiled with @samp{zlib}, it will be able to read the debug
33440 information in such binaries.
33442 The @samp{zlib} library is likely included with your operating system
33443 distribution; if it is not, you can get the latest version from
33444 @url{http://zlib.net}.
33447 @value{GDBN}'s features related to character sets (@pxref{Character
33448 Sets}) require a functioning @code{iconv} implementation. If you are
33449 on a GNU system, then this is provided by the GNU C Library. Some
33450 other systems also provide a working @code{iconv}.
33452 If @value{GDBN} is using the @code{iconv} program which is installed
33453 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33454 This is done with @option{--with-iconv-bin} which specifies the
33455 directory that contains the @code{iconv} program.
33457 On systems without @code{iconv}, you can install GNU Libiconv. If you
33458 have previously installed Libiconv, you can use the
33459 @option{--with-libiconv-prefix} option to configure.
33461 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33462 arrange to build Libiconv if a directory named @file{libiconv} appears
33463 in the top-most source directory. If Libiconv is built this way, and
33464 if the operating system does not provide a suitable @code{iconv}
33465 implementation, then the just-built library will automatically be used
33466 by @value{GDBN}. One easy way to set this up is to download GNU
33467 Libiconv, unpack it, and then rename the directory holding the
33468 Libiconv source code to @samp{libiconv}.
33471 @node Running Configure
33472 @section Invoking the @value{GDBN} @file{configure} Script
33473 @cindex configuring @value{GDBN}
33474 @value{GDBN} comes with a @file{configure} script that automates the process
33475 of preparing @value{GDBN} for installation; you can then use @code{make} to
33476 build the @code{gdb} program.
33478 @c irrelevant in info file; it's as current as the code it lives with.
33479 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33480 look at the @file{README} file in the sources; we may have improved the
33481 installation procedures since publishing this manual.}
33484 The @value{GDBN} distribution includes all the source code you need for
33485 @value{GDBN} in a single directory, whose name is usually composed by
33486 appending the version number to @samp{gdb}.
33488 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33489 @file{gdb-@value{GDBVN}} directory. That directory contains:
33492 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33493 script for configuring @value{GDBN} and all its supporting libraries
33495 @item gdb-@value{GDBVN}/gdb
33496 the source specific to @value{GDBN} itself
33498 @item gdb-@value{GDBVN}/bfd
33499 source for the Binary File Descriptor library
33501 @item gdb-@value{GDBVN}/include
33502 @sc{gnu} include files
33504 @item gdb-@value{GDBVN}/libiberty
33505 source for the @samp{-liberty} free software library
33507 @item gdb-@value{GDBVN}/opcodes
33508 source for the library of opcode tables and disassemblers
33510 @item gdb-@value{GDBVN}/readline
33511 source for the @sc{gnu} command-line interface
33513 @item gdb-@value{GDBVN}/glob
33514 source for the @sc{gnu} filename pattern-matching subroutine
33516 @item gdb-@value{GDBVN}/mmalloc
33517 source for the @sc{gnu} memory-mapped malloc package
33520 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33521 from the @file{gdb-@var{version-number}} source directory, which in
33522 this example is the @file{gdb-@value{GDBVN}} directory.
33524 First switch to the @file{gdb-@var{version-number}} source directory
33525 if you are not already in it; then run @file{configure}. Pass the
33526 identifier for the platform on which @value{GDBN} will run as an
33532 cd gdb-@value{GDBVN}
33533 ./configure @var{host}
33538 where @var{host} is an identifier such as @samp{sun4} or
33539 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33540 (You can often leave off @var{host}; @file{configure} tries to guess the
33541 correct value by examining your system.)
33543 Running @samp{configure @var{host}} and then running @code{make} builds the
33544 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33545 libraries, then @code{gdb} itself. The configured source files, and the
33546 binaries, are left in the corresponding source directories.
33549 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33550 system does not recognize this automatically when you run a different
33551 shell, you may need to run @code{sh} on it explicitly:
33554 sh configure @var{host}
33557 If you run @file{configure} from a directory that contains source
33558 directories for multiple libraries or programs, such as the
33559 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33561 creates configuration files for every directory level underneath (unless
33562 you tell it not to, with the @samp{--norecursion} option).
33564 You should run the @file{configure} script from the top directory in the
33565 source tree, the @file{gdb-@var{version-number}} directory. If you run
33566 @file{configure} from one of the subdirectories, you will configure only
33567 that subdirectory. That is usually not what you want. In particular,
33568 if you run the first @file{configure} from the @file{gdb} subdirectory
33569 of the @file{gdb-@var{version-number}} directory, you will omit the
33570 configuration of @file{bfd}, @file{readline}, and other sibling
33571 directories of the @file{gdb} subdirectory. This leads to build errors
33572 about missing include files such as @file{bfd/bfd.h}.
33574 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33575 However, you should make sure that the shell on your path (named by
33576 the @samp{SHELL} environment variable) is publicly readable. Remember
33577 that @value{GDBN} uses the shell to start your program---some systems refuse to
33578 let @value{GDBN} debug child processes whose programs are not readable.
33580 @node Separate Objdir
33581 @section Compiling @value{GDBN} in Another Directory
33583 If you want to run @value{GDBN} versions for several host or target machines,
33584 you need a different @code{gdb} compiled for each combination of
33585 host and target. @file{configure} is designed to make this easy by
33586 allowing you to generate each configuration in a separate subdirectory,
33587 rather than in the source directory. If your @code{make} program
33588 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33589 @code{make} in each of these directories builds the @code{gdb}
33590 program specified there.
33592 To build @code{gdb} in a separate directory, run @file{configure}
33593 with the @samp{--srcdir} option to specify where to find the source.
33594 (You also need to specify a path to find @file{configure}
33595 itself from your working directory. If the path to @file{configure}
33596 would be the same as the argument to @samp{--srcdir}, you can leave out
33597 the @samp{--srcdir} option; it is assumed.)
33599 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33600 separate directory for a Sun 4 like this:
33604 cd gdb-@value{GDBVN}
33607 ../gdb-@value{GDBVN}/configure sun4
33612 When @file{configure} builds a configuration using a remote source
33613 directory, it creates a tree for the binaries with the same structure
33614 (and using the same names) as the tree under the source directory. In
33615 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33616 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33617 @file{gdb-sun4/gdb}.
33619 Make sure that your path to the @file{configure} script has just one
33620 instance of @file{gdb} in it. If your path to @file{configure} looks
33621 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33622 one subdirectory of @value{GDBN}, not the whole package. This leads to
33623 build errors about missing include files such as @file{bfd/bfd.h}.
33625 One popular reason to build several @value{GDBN} configurations in separate
33626 directories is to configure @value{GDBN} for cross-compiling (where
33627 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33628 programs that run on another machine---the @dfn{target}).
33629 You specify a cross-debugging target by
33630 giving the @samp{--target=@var{target}} option to @file{configure}.
33632 When you run @code{make} to build a program or library, you must run
33633 it in a configured directory---whatever directory you were in when you
33634 called @file{configure} (or one of its subdirectories).
33636 The @code{Makefile} that @file{configure} generates in each source
33637 directory also runs recursively. If you type @code{make} in a source
33638 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33639 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33640 will build all the required libraries, and then build GDB.
33642 When you have multiple hosts or targets configured in separate
33643 directories, you can run @code{make} on them in parallel (for example,
33644 if they are NFS-mounted on each of the hosts); they will not interfere
33648 @section Specifying Names for Hosts and Targets
33650 The specifications used for hosts and targets in the @file{configure}
33651 script are based on a three-part naming scheme, but some short predefined
33652 aliases are also supported. The full naming scheme encodes three pieces
33653 of information in the following pattern:
33656 @var{architecture}-@var{vendor}-@var{os}
33659 For example, you can use the alias @code{sun4} as a @var{host} argument,
33660 or as the value for @var{target} in a @code{--target=@var{target}}
33661 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33663 The @file{configure} script accompanying @value{GDBN} does not provide
33664 any query facility to list all supported host and target names or
33665 aliases. @file{configure} calls the Bourne shell script
33666 @code{config.sub} to map abbreviations to full names; you can read the
33667 script, if you wish, or you can use it to test your guesses on
33668 abbreviations---for example:
33671 % sh config.sub i386-linux
33673 % sh config.sub alpha-linux
33674 alpha-unknown-linux-gnu
33675 % sh config.sub hp9k700
33677 % sh config.sub sun4
33678 sparc-sun-sunos4.1.1
33679 % sh config.sub sun3
33680 m68k-sun-sunos4.1.1
33681 % sh config.sub i986v
33682 Invalid configuration `i986v': machine `i986v' not recognized
33686 @code{config.sub} is also distributed in the @value{GDBN} source
33687 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33689 @node Configure Options
33690 @section @file{configure} Options
33692 Here is a summary of the @file{configure} options and arguments that
33693 are most often useful for building @value{GDBN}. @file{configure} also has
33694 several other options not listed here. @inforef{What Configure
33695 Does,,configure.info}, for a full explanation of @file{configure}.
33698 configure @r{[}--help@r{]}
33699 @r{[}--prefix=@var{dir}@r{]}
33700 @r{[}--exec-prefix=@var{dir}@r{]}
33701 @r{[}--srcdir=@var{dirname}@r{]}
33702 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33703 @r{[}--target=@var{target}@r{]}
33708 You may introduce options with a single @samp{-} rather than
33709 @samp{--} if you prefer; but you may abbreviate option names if you use
33714 Display a quick summary of how to invoke @file{configure}.
33716 @item --prefix=@var{dir}
33717 Configure the source to install programs and files under directory
33720 @item --exec-prefix=@var{dir}
33721 Configure the source to install programs under directory
33724 @c avoid splitting the warning from the explanation:
33726 @item --srcdir=@var{dirname}
33727 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33728 @code{make} that implements the @code{VPATH} feature.}@*
33729 Use this option to make configurations in directories separate from the
33730 @value{GDBN} source directories. Among other things, you can use this to
33731 build (or maintain) several configurations simultaneously, in separate
33732 directories. @file{configure} writes configuration-specific files in
33733 the current directory, but arranges for them to use the source in the
33734 directory @var{dirname}. @file{configure} creates directories under
33735 the working directory in parallel to the source directories below
33738 @item --norecursion
33739 Configure only the directory level where @file{configure} is executed; do not
33740 propagate configuration to subdirectories.
33742 @item --target=@var{target}
33743 Configure @value{GDBN} for cross-debugging programs running on the specified
33744 @var{target}. Without this option, @value{GDBN} is configured to debug
33745 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33747 There is no convenient way to generate a list of all available targets.
33749 @item @var{host} @dots{}
33750 Configure @value{GDBN} to run on the specified @var{host}.
33752 There is no convenient way to generate a list of all available hosts.
33755 There are many other options available as well, but they are generally
33756 needed for special purposes only.
33758 @node System-wide configuration
33759 @section System-wide configuration and settings
33760 @cindex system-wide init file
33762 @value{GDBN} can be configured to have a system-wide init file;
33763 this file will be read and executed at startup (@pxref{Startup, , What
33764 @value{GDBN} does during startup}).
33766 Here is the corresponding configure option:
33769 @item --with-system-gdbinit=@var{file}
33770 Specify that the default location of the system-wide init file is
33774 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33775 it may be subject to relocation. Two possible cases:
33779 If the default location of this init file contains @file{$prefix},
33780 it will be subject to relocation. Suppose that the configure options
33781 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33782 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33783 init file is looked for as @file{$install/etc/gdbinit} instead of
33784 @file{$prefix/etc/gdbinit}.
33787 By contrast, if the default location does not contain the prefix,
33788 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33789 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33790 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33791 wherever @value{GDBN} is installed.
33794 @node Maintenance Commands
33795 @appendix Maintenance Commands
33796 @cindex maintenance commands
33797 @cindex internal commands
33799 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33800 includes a number of commands intended for @value{GDBN} developers,
33801 that are not documented elsewhere in this manual. These commands are
33802 provided here for reference. (For commands that turn on debugging
33803 messages, see @ref{Debugging Output}.)
33806 @kindex maint agent
33807 @kindex maint agent-eval
33808 @item maint agent @var{expression}
33809 @itemx maint agent-eval @var{expression}
33810 Translate the given @var{expression} into remote agent bytecodes.
33811 This command is useful for debugging the Agent Expression mechanism
33812 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33813 expression useful for data collection, such as by tracepoints, while
33814 @samp{maint agent-eval} produces an expression that evaluates directly
33815 to a result. For instance, a collection expression for @code{globa +
33816 globb} will include bytecodes to record four bytes of memory at each
33817 of the addresses of @code{globa} and @code{globb}, while discarding
33818 the result of the addition, while an evaluation expression will do the
33819 addition and return the sum.
33821 @kindex maint info breakpoints
33822 @item @anchor{maint info breakpoints}maint info breakpoints
33823 Using the same format as @samp{info breakpoints}, display both the
33824 breakpoints you've set explicitly, and those @value{GDBN} is using for
33825 internal purposes. Internal breakpoints are shown with negative
33826 breakpoint numbers. The type column identifies what kind of breakpoint
33831 Normal, explicitly set breakpoint.
33834 Normal, explicitly set watchpoint.
33837 Internal breakpoint, used to handle correctly stepping through
33838 @code{longjmp} calls.
33840 @item longjmp resume
33841 Internal breakpoint at the target of a @code{longjmp}.
33844 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33847 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33850 Shared library events.
33854 @kindex set displaced-stepping
33855 @kindex show displaced-stepping
33856 @cindex displaced stepping support
33857 @cindex out-of-line single-stepping
33858 @item set displaced-stepping
33859 @itemx show displaced-stepping
33860 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33861 if the target supports it. Displaced stepping is a way to single-step
33862 over breakpoints without removing them from the inferior, by executing
33863 an out-of-line copy of the instruction that was originally at the
33864 breakpoint location. It is also known as out-of-line single-stepping.
33867 @item set displaced-stepping on
33868 If the target architecture supports it, @value{GDBN} will use
33869 displaced stepping to step over breakpoints.
33871 @item set displaced-stepping off
33872 @value{GDBN} will not use displaced stepping to step over breakpoints,
33873 even if such is supported by the target architecture.
33875 @cindex non-stop mode, and @samp{set displaced-stepping}
33876 @item set displaced-stepping auto
33877 This is the default mode. @value{GDBN} will use displaced stepping
33878 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33879 architecture supports displaced stepping.
33882 @kindex maint check-symtabs
33883 @item maint check-symtabs
33884 Check the consistency of psymtabs and symtabs.
33886 @kindex maint cplus first_component
33887 @item maint cplus first_component @var{name}
33888 Print the first C@t{++} class/namespace component of @var{name}.
33890 @kindex maint cplus namespace
33891 @item maint cplus namespace
33892 Print the list of possible C@t{++} namespaces.
33894 @kindex maint demangle
33895 @item maint demangle @var{name}
33896 Demangle a C@t{++} or Objective-C mangled @var{name}.
33898 @kindex maint deprecate
33899 @kindex maint undeprecate
33900 @cindex deprecated commands
33901 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33902 @itemx maint undeprecate @var{command}
33903 Deprecate or undeprecate the named @var{command}. Deprecated commands
33904 cause @value{GDBN} to issue a warning when you use them. The optional
33905 argument @var{replacement} says which newer command should be used in
33906 favor of the deprecated one; if it is given, @value{GDBN} will mention
33907 the replacement as part of the warning.
33909 @kindex maint dump-me
33910 @item maint dump-me
33911 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33912 Cause a fatal signal in the debugger and force it to dump its core.
33913 This is supported only on systems which support aborting a program
33914 with the @code{SIGQUIT} signal.
33916 @kindex maint internal-error
33917 @kindex maint internal-warning
33918 @item maint internal-error @r{[}@var{message-text}@r{]}
33919 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33920 Cause @value{GDBN} to call the internal function @code{internal_error}
33921 or @code{internal_warning} and hence behave as though an internal error
33922 or internal warning has been detected. In addition to reporting the
33923 internal problem, these functions give the user the opportunity to
33924 either quit @value{GDBN} or create a core file of the current
33925 @value{GDBN} session.
33927 These commands take an optional parameter @var{message-text} that is
33928 used as the text of the error or warning message.
33930 Here's an example of using @code{internal-error}:
33933 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33934 @dots{}/maint.c:121: internal-error: testing, 1, 2
33935 A problem internal to GDB has been detected. Further
33936 debugging may prove unreliable.
33937 Quit this debugging session? (y or n) @kbd{n}
33938 Create a core file? (y or n) @kbd{n}
33942 @cindex @value{GDBN} internal error
33943 @cindex internal errors, control of @value{GDBN} behavior
33945 @kindex maint set internal-error
33946 @kindex maint show internal-error
33947 @kindex maint set internal-warning
33948 @kindex maint show internal-warning
33949 @item maint set internal-error @var{action} [ask|yes|no]
33950 @itemx maint show internal-error @var{action}
33951 @itemx maint set internal-warning @var{action} [ask|yes|no]
33952 @itemx maint show internal-warning @var{action}
33953 When @value{GDBN} reports an internal problem (error or warning) it
33954 gives the user the opportunity to both quit @value{GDBN} and create a
33955 core file of the current @value{GDBN} session. These commands let you
33956 override the default behaviour for each particular @var{action},
33957 described in the table below.
33961 You can specify that @value{GDBN} should always (yes) or never (no)
33962 quit. The default is to ask the user what to do.
33965 You can specify that @value{GDBN} should always (yes) or never (no)
33966 create a core file. The default is to ask the user what to do.
33969 @kindex maint packet
33970 @item maint packet @var{text}
33971 If @value{GDBN} is talking to an inferior via the serial protocol,
33972 then this command sends the string @var{text} to the inferior, and
33973 displays the response packet. @value{GDBN} supplies the initial
33974 @samp{$} character, the terminating @samp{#} character, and the
33977 @kindex maint print architecture
33978 @item maint print architecture @r{[}@var{file}@r{]}
33979 Print the entire architecture configuration. The optional argument
33980 @var{file} names the file where the output goes.
33982 @kindex maint print c-tdesc
33983 @item maint print c-tdesc
33984 Print the current target description (@pxref{Target Descriptions}) as
33985 a C source file. The created source file can be used in @value{GDBN}
33986 when an XML parser is not available to parse the description.
33988 @kindex maint print dummy-frames
33989 @item maint print dummy-frames
33990 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33993 (@value{GDBP}) @kbd{b add}
33995 (@value{GDBP}) @kbd{print add(2,3)}
33996 Breakpoint 2, add (a=2, b=3) at @dots{}
33998 The program being debugged stopped while in a function called from GDB.
34000 (@value{GDBP}) @kbd{maint print dummy-frames}
34001 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
34002 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
34003 call_lo=0x01014000 call_hi=0x01014001
34007 Takes an optional file parameter.
34009 @kindex maint print registers
34010 @kindex maint print raw-registers
34011 @kindex maint print cooked-registers
34012 @kindex maint print register-groups
34013 @kindex maint print remote-registers
34014 @item maint print registers @r{[}@var{file}@r{]}
34015 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34016 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34017 @itemx maint print register-groups @r{[}@var{file}@r{]}
34018 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34019 Print @value{GDBN}'s internal register data structures.
34021 The command @code{maint print raw-registers} includes the contents of
34022 the raw register cache; the command @code{maint print
34023 cooked-registers} includes the (cooked) value of all registers,
34024 including registers which aren't available on the target nor visible
34025 to user; the command @code{maint print register-groups} includes the
34026 groups that each register is a member of; and the command @code{maint
34027 print remote-registers} includes the remote target's register numbers
34028 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
34029 @value{GDBN} Internals}.
34031 These commands take an optional parameter, a file name to which to
34032 write the information.
34034 @kindex maint print reggroups
34035 @item maint print reggroups @r{[}@var{file}@r{]}
34036 Print @value{GDBN}'s internal register group data structures. The
34037 optional argument @var{file} tells to what file to write the
34040 The register groups info looks like this:
34043 (@value{GDBP}) @kbd{maint print reggroups}
34056 This command forces @value{GDBN} to flush its internal register cache.
34058 @kindex maint print objfiles
34059 @cindex info for known object files
34060 @item maint print objfiles
34061 Print a dump of all known object files. For each object file, this
34062 command prints its name, address in memory, and all of its psymtabs
34065 @kindex maint print section-scripts
34066 @cindex info for known .debug_gdb_scripts-loaded scripts
34067 @item maint print section-scripts [@var{regexp}]
34068 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34069 If @var{regexp} is specified, only print scripts loaded by object files
34070 matching @var{regexp}.
34071 For each script, this command prints its name as specified in the objfile,
34072 and the full path if known.
34073 @xref{dotdebug_gdb_scripts section}.
34075 @kindex maint print statistics
34076 @cindex bcache statistics
34077 @item maint print statistics
34078 This command prints, for each object file in the program, various data
34079 about that object file followed by the byte cache (@dfn{bcache})
34080 statistics for the object file. The objfile data includes the number
34081 of minimal, partial, full, and stabs symbols, the number of types
34082 defined by the objfile, the number of as yet unexpanded psym tables,
34083 the number of line tables and string tables, and the amount of memory
34084 used by the various tables. The bcache statistics include the counts,
34085 sizes, and counts of duplicates of all and unique objects, max,
34086 average, and median entry size, total memory used and its overhead and
34087 savings, and various measures of the hash table size and chain
34090 @kindex maint print target-stack
34091 @cindex target stack description
34092 @item maint print target-stack
34093 A @dfn{target} is an interface between the debugger and a particular
34094 kind of file or process. Targets can be stacked in @dfn{strata},
34095 so that more than one target can potentially respond to a request.
34096 In particular, memory accesses will walk down the stack of targets
34097 until they find a target that is interested in handling that particular
34100 This command prints a short description of each layer that was pushed on
34101 the @dfn{target stack}, starting from the top layer down to the bottom one.
34103 @kindex maint print type
34104 @cindex type chain of a data type
34105 @item maint print type @var{expr}
34106 Print the type chain for a type specified by @var{expr}. The argument
34107 can be either a type name or a symbol. If it is a symbol, the type of
34108 that symbol is described. The type chain produced by this command is
34109 a recursive definition of the data type as stored in @value{GDBN}'s
34110 data structures, including its flags and contained types.
34112 @kindex maint set dwarf2 always-disassemble
34113 @kindex maint show dwarf2 always-disassemble
34114 @item maint set dwarf2 always-disassemble
34115 @item maint show dwarf2 always-disassemble
34116 Control the behavior of @code{info address} when using DWARF debugging
34119 The default is @code{off}, which means that @value{GDBN} should try to
34120 describe a variable's location in an easily readable format. When
34121 @code{on}, @value{GDBN} will instead display the DWARF location
34122 expression in an assembly-like format. Note that some locations are
34123 too complex for @value{GDBN} to describe simply; in this case you will
34124 always see the disassembly form.
34126 Here is an example of the resulting disassembly:
34129 (gdb) info addr argc
34130 Symbol "argc" is a complex DWARF expression:
34134 For more information on these expressions, see
34135 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34137 @kindex maint set dwarf2 max-cache-age
34138 @kindex maint show dwarf2 max-cache-age
34139 @item maint set dwarf2 max-cache-age
34140 @itemx maint show dwarf2 max-cache-age
34141 Control the DWARF 2 compilation unit cache.
34143 @cindex DWARF 2 compilation units cache
34144 In object files with inter-compilation-unit references, such as those
34145 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34146 reader needs to frequently refer to previously read compilation units.
34147 This setting controls how long a compilation unit will remain in the
34148 cache if it is not referenced. A higher limit means that cached
34149 compilation units will be stored in memory longer, and more total
34150 memory will be used. Setting it to zero disables caching, which will
34151 slow down @value{GDBN} startup, but reduce memory consumption.
34153 @kindex maint set profile
34154 @kindex maint show profile
34155 @cindex profiling GDB
34156 @item maint set profile
34157 @itemx maint show profile
34158 Control profiling of @value{GDBN}.
34160 Profiling will be disabled until you use the @samp{maint set profile}
34161 command to enable it. When you enable profiling, the system will begin
34162 collecting timing and execution count data; when you disable profiling or
34163 exit @value{GDBN}, the results will be written to a log file. Remember that
34164 if you use profiling, @value{GDBN} will overwrite the profiling log file
34165 (often called @file{gmon.out}). If you have a record of important profiling
34166 data in a @file{gmon.out} file, be sure to move it to a safe location.
34168 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34169 compiled with the @samp{-pg} compiler option.
34171 @kindex maint set show-debug-regs
34172 @kindex maint show show-debug-regs
34173 @cindex hardware debug registers
34174 @item maint set show-debug-regs
34175 @itemx maint show show-debug-regs
34176 Control whether to show variables that mirror the hardware debug
34177 registers. Use @code{ON} to enable, @code{OFF} to disable. If
34178 enabled, the debug registers values are shown when @value{GDBN} inserts or
34179 removes a hardware breakpoint or watchpoint, and when the inferior
34180 triggers a hardware-assisted breakpoint or watchpoint.
34182 @kindex maint set show-all-tib
34183 @kindex maint show show-all-tib
34184 @item maint set show-all-tib
34185 @itemx maint show show-all-tib
34186 Control whether to show all non zero areas within a 1k block starting
34187 at thread local base, when using the @samp{info w32 thread-information-block}
34190 @kindex maint space
34191 @cindex memory used by commands
34193 Control whether to display memory usage for each command. If set to a
34194 nonzero value, @value{GDBN} will display how much memory each command
34195 took, following the command's own output. This can also be requested
34196 by invoking @value{GDBN} with the @option{--statistics} command-line
34197 switch (@pxref{Mode Options}).
34200 @cindex time of command execution
34202 Control whether to display the execution time of @value{GDBN} for each command.
34203 If set to a nonzero value, @value{GDBN} will display how much time it
34204 took to execute each command, following the command's own output.
34205 Both CPU time and wallclock time are printed.
34206 Printing both is useful when trying to determine whether the cost is
34207 CPU or, e.g., disk/network, latency.
34208 Note that the CPU time printed is for @value{GDBN} only, it does not include
34209 the execution time of the inferior because there's no mechanism currently
34210 to compute how much time was spent by @value{GDBN} and how much time was
34211 spent by the program been debugged.
34212 This can also be requested by invoking @value{GDBN} with the
34213 @option{--statistics} command-line switch (@pxref{Mode Options}).
34215 @kindex maint translate-address
34216 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34217 Find the symbol stored at the location specified by the address
34218 @var{addr} and an optional section name @var{section}. If found,
34219 @value{GDBN} prints the name of the closest symbol and an offset from
34220 the symbol's location to the specified address. This is similar to
34221 the @code{info address} command (@pxref{Symbols}), except that this
34222 command also allows to find symbols in other sections.
34224 If section was not specified, the section in which the symbol was found
34225 is also printed. For dynamically linked executables, the name of
34226 executable or shared library containing the symbol is printed as well.
34230 The following command is useful for non-interactive invocations of
34231 @value{GDBN}, such as in the test suite.
34234 @item set watchdog @var{nsec}
34235 @kindex set watchdog
34236 @cindex watchdog timer
34237 @cindex timeout for commands
34238 Set the maximum number of seconds @value{GDBN} will wait for the
34239 target operation to finish. If this time expires, @value{GDBN}
34240 reports and error and the command is aborted.
34242 @item show watchdog
34243 Show the current setting of the target wait timeout.
34246 @node Remote Protocol
34247 @appendix @value{GDBN} Remote Serial Protocol
34252 * Stop Reply Packets::
34253 * General Query Packets::
34254 * Architecture-Specific Protocol Details::
34255 * Tracepoint Packets::
34256 * Host I/O Packets::
34258 * Notification Packets::
34259 * Remote Non-Stop::
34260 * Packet Acknowledgment::
34262 * File-I/O Remote Protocol Extension::
34263 * Library List Format::
34264 * Library List Format for SVR4 Targets::
34265 * Memory Map Format::
34266 * Thread List Format::
34267 * Traceframe Info Format::
34273 There may be occasions when you need to know something about the
34274 protocol---for example, if there is only one serial port to your target
34275 machine, you might want your program to do something special if it
34276 recognizes a packet meant for @value{GDBN}.
34278 In the examples below, @samp{->} and @samp{<-} are used to indicate
34279 transmitted and received data, respectively.
34281 @cindex protocol, @value{GDBN} remote serial
34282 @cindex serial protocol, @value{GDBN} remote
34283 @cindex remote serial protocol
34284 All @value{GDBN} commands and responses (other than acknowledgments
34285 and notifications, see @ref{Notification Packets}) are sent as a
34286 @var{packet}. A @var{packet} is introduced with the character
34287 @samp{$}, the actual @var{packet-data}, and the terminating character
34288 @samp{#} followed by a two-digit @var{checksum}:
34291 @code{$}@var{packet-data}@code{#}@var{checksum}
34295 @cindex checksum, for @value{GDBN} remote
34297 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34298 characters between the leading @samp{$} and the trailing @samp{#} (an
34299 eight bit unsigned checksum).
34301 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34302 specification also included an optional two-digit @var{sequence-id}:
34305 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34308 @cindex sequence-id, for @value{GDBN} remote
34310 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34311 has never output @var{sequence-id}s. Stubs that handle packets added
34312 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34314 When either the host or the target machine receives a packet, the first
34315 response expected is an acknowledgment: either @samp{+} (to indicate
34316 the package was received correctly) or @samp{-} (to request
34320 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34325 The @samp{+}/@samp{-} acknowledgments can be disabled
34326 once a connection is established.
34327 @xref{Packet Acknowledgment}, for details.
34329 The host (@value{GDBN}) sends @var{command}s, and the target (the
34330 debugging stub incorporated in your program) sends a @var{response}. In
34331 the case of step and continue @var{command}s, the response is only sent
34332 when the operation has completed, and the target has again stopped all
34333 threads in all attached processes. This is the default all-stop mode
34334 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34335 execution mode; see @ref{Remote Non-Stop}, for details.
34337 @var{packet-data} consists of a sequence of characters with the
34338 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34341 @cindex remote protocol, field separator
34342 Fields within the packet should be separated using @samp{,} @samp{;} or
34343 @samp{:}. Except where otherwise noted all numbers are represented in
34344 @sc{hex} with leading zeros suppressed.
34346 Implementors should note that prior to @value{GDBN} 5.0, the character
34347 @samp{:} could not appear as the third character in a packet (as it
34348 would potentially conflict with the @var{sequence-id}).
34350 @cindex remote protocol, binary data
34351 @anchor{Binary Data}
34352 Binary data in most packets is encoded either as two hexadecimal
34353 digits per byte of binary data. This allowed the traditional remote
34354 protocol to work over connections which were only seven-bit clean.
34355 Some packets designed more recently assume an eight-bit clean
34356 connection, and use a more efficient encoding to send and receive
34359 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34360 as an escape character. Any escaped byte is transmitted as the escape
34361 character followed by the original character XORed with @code{0x20}.
34362 For example, the byte @code{0x7d} would be transmitted as the two
34363 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34364 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34365 @samp{@}}) must always be escaped. Responses sent by the stub
34366 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34367 is not interpreted as the start of a run-length encoded sequence
34370 Response @var{data} can be run-length encoded to save space.
34371 Run-length encoding replaces runs of identical characters with one
34372 instance of the repeated character, followed by a @samp{*} and a
34373 repeat count. The repeat count is itself sent encoded, to avoid
34374 binary characters in @var{data}: a value of @var{n} is sent as
34375 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34376 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34377 code 32) for a repeat count of 3. (This is because run-length
34378 encoding starts to win for counts 3 or more.) Thus, for example,
34379 @samp{0* } is a run-length encoding of ``0000'': the space character
34380 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34383 The printable characters @samp{#} and @samp{$} or with a numeric value
34384 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34385 seven repeats (@samp{$}) can be expanded using a repeat count of only
34386 five (@samp{"}). For example, @samp{00000000} can be encoded as
34389 The error response returned for some packets includes a two character
34390 error number. That number is not well defined.
34392 @cindex empty response, for unsupported packets
34393 For any @var{command} not supported by the stub, an empty response
34394 (@samp{$#00}) should be returned. That way it is possible to extend the
34395 protocol. A newer @value{GDBN} can tell if a packet is supported based
34398 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34399 commands for register access, and the @samp{m} and @samp{M} commands
34400 for memory access. Stubs that only control single-threaded targets
34401 can implement run control with the @samp{c} (continue), and @samp{s}
34402 (step) commands. Stubs that support multi-threading targets should
34403 support the @samp{vCont} command. All other commands are optional.
34408 The following table provides a complete list of all currently defined
34409 @var{command}s and their corresponding response @var{data}.
34410 @xref{File-I/O Remote Protocol Extension}, for details about the File
34411 I/O extension of the remote protocol.
34413 Each packet's description has a template showing the packet's overall
34414 syntax, followed by an explanation of the packet's meaning. We
34415 include spaces in some of the templates for clarity; these are not
34416 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34417 separate its components. For example, a template like @samp{foo
34418 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34419 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34420 @var{baz}. @value{GDBN} does not transmit a space character between the
34421 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34424 @cindex @var{thread-id}, in remote protocol
34425 @anchor{thread-id syntax}
34426 Several packets and replies include a @var{thread-id} field to identify
34427 a thread. Normally these are positive numbers with a target-specific
34428 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34429 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34432 In addition, the remote protocol supports a multiprocess feature in
34433 which the @var{thread-id} syntax is extended to optionally include both
34434 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34435 The @var{pid} (process) and @var{tid} (thread) components each have the
34436 format described above: a positive number with target-specific
34437 interpretation formatted as a big-endian hex string, literal @samp{-1}
34438 to indicate all processes or threads (respectively), or @samp{0} to
34439 indicate an arbitrary process or thread. Specifying just a process, as
34440 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34441 error to specify all processes but a specific thread, such as
34442 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34443 for those packets and replies explicitly documented to include a process
34444 ID, rather than a @var{thread-id}.
34446 The multiprocess @var{thread-id} syntax extensions are only used if both
34447 @value{GDBN} and the stub report support for the @samp{multiprocess}
34448 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34451 Note that all packet forms beginning with an upper- or lower-case
34452 letter, other than those described here, are reserved for future use.
34454 Here are the packet descriptions.
34459 @cindex @samp{!} packet
34460 @anchor{extended mode}
34461 Enable extended mode. In extended mode, the remote server is made
34462 persistent. The @samp{R} packet is used to restart the program being
34468 The remote target both supports and has enabled extended mode.
34472 @cindex @samp{?} packet
34473 Indicate the reason the target halted. The reply is the same as for
34474 step and continue. This packet has a special interpretation when the
34475 target is in non-stop mode; see @ref{Remote Non-Stop}.
34478 @xref{Stop Reply Packets}, for the reply specifications.
34480 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34481 @cindex @samp{A} packet
34482 Initialized @code{argv[]} array passed into program. @var{arglen}
34483 specifies the number of bytes in the hex encoded byte stream
34484 @var{arg}. See @code{gdbserver} for more details.
34489 The arguments were set.
34495 @cindex @samp{b} packet
34496 (Don't use this packet; its behavior is not well-defined.)
34497 Change the serial line speed to @var{baud}.
34499 JTC: @emph{When does the transport layer state change? When it's
34500 received, or after the ACK is transmitted. In either case, there are
34501 problems if the command or the acknowledgment packet is dropped.}
34503 Stan: @emph{If people really wanted to add something like this, and get
34504 it working for the first time, they ought to modify ser-unix.c to send
34505 some kind of out-of-band message to a specially-setup stub and have the
34506 switch happen "in between" packets, so that from remote protocol's point
34507 of view, nothing actually happened.}
34509 @item B @var{addr},@var{mode}
34510 @cindex @samp{B} packet
34511 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34512 breakpoint at @var{addr}.
34514 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34515 (@pxref{insert breakpoint or watchpoint packet}).
34517 @cindex @samp{bc} packet
34520 Backward continue. Execute the target system in reverse. No parameter.
34521 @xref{Reverse Execution}, for more information.
34524 @xref{Stop Reply Packets}, for the reply specifications.
34526 @cindex @samp{bs} packet
34529 Backward single step. Execute one instruction in reverse. No parameter.
34530 @xref{Reverse Execution}, for more information.
34533 @xref{Stop Reply Packets}, for the reply specifications.
34535 @item c @r{[}@var{addr}@r{]}
34536 @cindex @samp{c} packet
34537 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
34538 resume at current address.
34540 This packet is deprecated for multi-threading support. @xref{vCont
34544 @xref{Stop Reply Packets}, for the reply specifications.
34546 @item C @var{sig}@r{[};@var{addr}@r{]}
34547 @cindex @samp{C} packet
34548 Continue with signal @var{sig} (hex signal number). If
34549 @samp{;@var{addr}} is omitted, resume at same address.
34551 This packet is deprecated for multi-threading support. @xref{vCont
34555 @xref{Stop Reply Packets}, for the reply specifications.
34558 @cindex @samp{d} packet
34561 Don't use this packet; instead, define a general set packet
34562 (@pxref{General Query Packets}).
34566 @cindex @samp{D} packet
34567 The first form of the packet is used to detach @value{GDBN} from the
34568 remote system. It is sent to the remote target
34569 before @value{GDBN} disconnects via the @code{detach} command.
34571 The second form, including a process ID, is used when multiprocess
34572 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34573 detach only a specific process. The @var{pid} is specified as a
34574 big-endian hex string.
34584 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34585 @cindex @samp{F} packet
34586 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34587 This is part of the File-I/O protocol extension. @xref{File-I/O
34588 Remote Protocol Extension}, for the specification.
34591 @anchor{read registers packet}
34592 @cindex @samp{g} packet
34593 Read general registers.
34597 @item @var{XX@dots{}}
34598 Each byte of register data is described by two hex digits. The bytes
34599 with the register are transmitted in target byte order. The size of
34600 each register and their position within the @samp{g} packet are
34601 determined by the @value{GDBN} internal gdbarch functions
34602 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34603 specification of several standard @samp{g} packets is specified below.
34605 When reading registers from a trace frame (@pxref{Analyze Collected
34606 Data,,Using the Collected Data}), the stub may also return a string of
34607 literal @samp{x}'s in place of the register data digits, to indicate
34608 that the corresponding register has not been collected, thus its value
34609 is unavailable. For example, for an architecture with 4 registers of
34610 4 bytes each, the following reply indicates to @value{GDBN} that
34611 registers 0 and 2 have not been collected, while registers 1 and 3
34612 have been collected, and both have zero value:
34616 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34623 @item G @var{XX@dots{}}
34624 @cindex @samp{G} packet
34625 Write general registers. @xref{read registers packet}, for a
34626 description of the @var{XX@dots{}} data.
34636 @item H @var{op} @var{thread-id}
34637 @cindex @samp{H} packet
34638 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34639 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
34640 it should be @samp{c} for step and continue operations (note that this
34641 is deprecated, supporting the @samp{vCont} command is a better
34642 option), @samp{g} for other operations. The thread designator
34643 @var{thread-id} has the format and interpretation described in
34644 @ref{thread-id syntax}.
34655 @c 'H': How restrictive (or permissive) is the thread model. If a
34656 @c thread is selected and stopped, are other threads allowed
34657 @c to continue to execute? As I mentioned above, I think the
34658 @c semantics of each command when a thread is selected must be
34659 @c described. For example:
34661 @c 'g': If the stub supports threads and a specific thread is
34662 @c selected, returns the register block from that thread;
34663 @c otherwise returns current registers.
34665 @c 'G' If the stub supports threads and a specific thread is
34666 @c selected, sets the registers of the register block of
34667 @c that thread; otherwise sets current registers.
34669 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34670 @anchor{cycle step packet}
34671 @cindex @samp{i} packet
34672 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34673 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34674 step starting at that address.
34677 @cindex @samp{I} packet
34678 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34682 @cindex @samp{k} packet
34685 FIXME: @emph{There is no description of how to operate when a specific
34686 thread context has been selected (i.e.@: does 'k' kill only that
34689 @item m @var{addr},@var{length}
34690 @cindex @samp{m} packet
34691 Read @var{length} bytes of memory starting at address @var{addr}.
34692 Note that @var{addr} may not be aligned to any particular boundary.
34694 The stub need not use any particular size or alignment when gathering
34695 data from memory for the response; even if @var{addr} is word-aligned
34696 and @var{length} is a multiple of the word size, the stub is free to
34697 use byte accesses, or not. For this reason, this packet may not be
34698 suitable for accessing memory-mapped I/O devices.
34699 @cindex alignment of remote memory accesses
34700 @cindex size of remote memory accesses
34701 @cindex memory, alignment and size of remote accesses
34705 @item @var{XX@dots{}}
34706 Memory contents; each byte is transmitted as a two-digit hexadecimal
34707 number. The reply may contain fewer bytes than requested if the
34708 server was able to read only part of the region of memory.
34713 @item M @var{addr},@var{length}:@var{XX@dots{}}
34714 @cindex @samp{M} packet
34715 Write @var{length} bytes of memory starting at address @var{addr}.
34716 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
34717 hexadecimal number.
34724 for an error (this includes the case where only part of the data was
34729 @cindex @samp{p} packet
34730 Read the value of register @var{n}; @var{n} is in hex.
34731 @xref{read registers packet}, for a description of how the returned
34732 register value is encoded.
34736 @item @var{XX@dots{}}
34737 the register's value
34741 Indicating an unrecognized @var{query}.
34744 @item P @var{n@dots{}}=@var{r@dots{}}
34745 @anchor{write register packet}
34746 @cindex @samp{P} packet
34747 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34748 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34749 digits for each byte in the register (target byte order).
34759 @item q @var{name} @var{params}@dots{}
34760 @itemx Q @var{name} @var{params}@dots{}
34761 @cindex @samp{q} packet
34762 @cindex @samp{Q} packet
34763 General query (@samp{q}) and set (@samp{Q}). These packets are
34764 described fully in @ref{General Query Packets}.
34767 @cindex @samp{r} packet
34768 Reset the entire system.
34770 Don't use this packet; use the @samp{R} packet instead.
34773 @cindex @samp{R} packet
34774 Restart the program being debugged. @var{XX}, while needed, is ignored.
34775 This packet is only available in extended mode (@pxref{extended mode}).
34777 The @samp{R} packet has no reply.
34779 @item s @r{[}@var{addr}@r{]}
34780 @cindex @samp{s} packet
34781 Single step. @var{addr} is the address at which to resume. If
34782 @var{addr} is omitted, resume at same address.
34784 This packet is deprecated for multi-threading support. @xref{vCont
34788 @xref{Stop Reply Packets}, for the reply specifications.
34790 @item S @var{sig}@r{[};@var{addr}@r{]}
34791 @anchor{step with signal packet}
34792 @cindex @samp{S} packet
34793 Step with signal. This is analogous to the @samp{C} packet, but
34794 requests a single-step, rather than a normal resumption of execution.
34796 This packet is deprecated for multi-threading support. @xref{vCont
34800 @xref{Stop Reply Packets}, for the reply specifications.
34802 @item t @var{addr}:@var{PP},@var{MM}
34803 @cindex @samp{t} packet
34804 Search backwards starting at address @var{addr} for a match with pattern
34805 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
34806 @var{addr} must be at least 3 digits.
34808 @item T @var{thread-id}
34809 @cindex @samp{T} packet
34810 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34815 thread is still alive
34821 Packets starting with @samp{v} are identified by a multi-letter name,
34822 up to the first @samp{;} or @samp{?} (or the end of the packet).
34824 @item vAttach;@var{pid}
34825 @cindex @samp{vAttach} packet
34826 Attach to a new process with the specified process ID @var{pid}.
34827 The process ID is a
34828 hexadecimal integer identifying the process. In all-stop mode, all
34829 threads in the attached process are stopped; in non-stop mode, it may be
34830 attached without being stopped if that is supported by the target.
34832 @c In non-stop mode, on a successful vAttach, the stub should set the
34833 @c current thread to a thread of the newly-attached process. After
34834 @c attaching, GDB queries for the attached process's thread ID with qC.
34835 @c Also note that, from a user perspective, whether or not the
34836 @c target is stopped on attach in non-stop mode depends on whether you
34837 @c use the foreground or background version of the attach command, not
34838 @c on what vAttach does; GDB does the right thing with respect to either
34839 @c stopping or restarting threads.
34841 This packet is only available in extended mode (@pxref{extended mode}).
34847 @item @r{Any stop packet}
34848 for success in all-stop mode (@pxref{Stop Reply Packets})
34850 for success in non-stop mode (@pxref{Remote Non-Stop})
34853 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34854 @cindex @samp{vCont} packet
34855 @anchor{vCont packet}
34856 Resume the inferior, specifying different actions for each thread.
34857 If an action is specified with no @var{thread-id}, then it is applied to any
34858 threads that don't have a specific action specified; if no default action is
34859 specified then other threads should remain stopped in all-stop mode and
34860 in their current state in non-stop mode.
34861 Specifying multiple
34862 default actions is an error; specifying no actions is also an error.
34863 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34865 Currently supported actions are:
34871 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34875 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34880 The optional argument @var{addr} normally associated with the
34881 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34882 not supported in @samp{vCont}.
34884 The @samp{t} action is only relevant in non-stop mode
34885 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34886 A stop reply should be generated for any affected thread not already stopped.
34887 When a thread is stopped by means of a @samp{t} action,
34888 the corresponding stop reply should indicate that the thread has stopped with
34889 signal @samp{0}, regardless of whether the target uses some other signal
34890 as an implementation detail.
34892 The stub must support @samp{vCont} if it reports support for
34893 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34894 this case @samp{vCont} actions can be specified to apply to all threads
34895 in a process by using the @samp{p@var{pid}.-1} form of the
34899 @xref{Stop Reply Packets}, for the reply specifications.
34902 @cindex @samp{vCont?} packet
34903 Request a list of actions supported by the @samp{vCont} packet.
34907 @item vCont@r{[};@var{action}@dots{}@r{]}
34908 The @samp{vCont} packet is supported. Each @var{action} is a supported
34909 command in the @samp{vCont} packet.
34911 The @samp{vCont} packet is not supported.
34914 @item vFile:@var{operation}:@var{parameter}@dots{}
34915 @cindex @samp{vFile} packet
34916 Perform a file operation on the target system. For details,
34917 see @ref{Host I/O Packets}.
34919 @item vFlashErase:@var{addr},@var{length}
34920 @cindex @samp{vFlashErase} packet
34921 Direct the stub to erase @var{length} bytes of flash starting at
34922 @var{addr}. The region may enclose any number of flash blocks, but
34923 its start and end must fall on block boundaries, as indicated by the
34924 flash block size appearing in the memory map (@pxref{Memory Map
34925 Format}). @value{GDBN} groups flash memory programming operations
34926 together, and sends a @samp{vFlashDone} request after each group; the
34927 stub is allowed to delay erase operation until the @samp{vFlashDone}
34928 packet is received.
34938 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34939 @cindex @samp{vFlashWrite} packet
34940 Direct the stub to write data to flash address @var{addr}. The data
34941 is passed in binary form using the same encoding as for the @samp{X}
34942 packet (@pxref{Binary Data}). The memory ranges specified by
34943 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34944 not overlap, and must appear in order of increasing addresses
34945 (although @samp{vFlashErase} packets for higher addresses may already
34946 have been received; the ordering is guaranteed only between
34947 @samp{vFlashWrite} packets). If a packet writes to an address that was
34948 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34949 target-specific method, the results are unpredictable.
34957 for vFlashWrite addressing non-flash memory
34963 @cindex @samp{vFlashDone} packet
34964 Indicate to the stub that flash programming operation is finished.
34965 The stub is permitted to delay or batch the effects of a group of
34966 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34967 @samp{vFlashDone} packet is received. The contents of the affected
34968 regions of flash memory are unpredictable until the @samp{vFlashDone}
34969 request is completed.
34971 @item vKill;@var{pid}
34972 @cindex @samp{vKill} packet
34973 Kill the process with the specified process ID. @var{pid} is a
34974 hexadecimal integer identifying the process. This packet is used in
34975 preference to @samp{k} when multiprocess protocol extensions are
34976 supported; see @ref{multiprocess extensions}.
34986 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34987 @cindex @samp{vRun} packet
34988 Run the program @var{filename}, passing it each @var{argument} on its
34989 command line. The file and arguments are hex-encoded strings. If
34990 @var{filename} is an empty string, the stub may use a default program
34991 (e.g.@: the last program run). The program is created in the stopped
34994 @c FIXME: What about non-stop mode?
34996 This packet is only available in extended mode (@pxref{extended mode}).
35002 @item @r{Any stop packet}
35003 for success (@pxref{Stop Reply Packets})
35007 @anchor{vStopped packet}
35008 @cindex @samp{vStopped} packet
35010 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
35011 reply and prompt for the stub to report another one.
35015 @item @r{Any stop packet}
35016 if there is another unreported stop event (@pxref{Stop Reply Packets})
35018 if there are no unreported stop events
35021 @item X @var{addr},@var{length}:@var{XX@dots{}}
35023 @cindex @samp{X} packet
35024 Write data to memory, where the data is transmitted in binary.
35025 @var{addr} is address, @var{length} is number of bytes,
35026 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35036 @item z @var{type},@var{addr},@var{kind}
35037 @itemx Z @var{type},@var{addr},@var{kind}
35038 @anchor{insert breakpoint or watchpoint packet}
35039 @cindex @samp{z} packet
35040 @cindex @samp{Z} packets
35041 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35042 watchpoint starting at address @var{address} of kind @var{kind}.
35044 Each breakpoint and watchpoint packet @var{type} is documented
35047 @emph{Implementation notes: A remote target shall return an empty string
35048 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35049 remote target shall support either both or neither of a given
35050 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35051 avoid potential problems with duplicate packets, the operations should
35052 be implemented in an idempotent way.}
35054 @item z0,@var{addr},@var{kind}
35055 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35056 @cindex @samp{z0} packet
35057 @cindex @samp{Z0} packet
35058 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35059 @var{addr} of type @var{kind}.
35061 A memory breakpoint is implemented by replacing the instruction at
35062 @var{addr} with a software breakpoint or trap instruction. The
35063 @var{kind} is target-specific and typically indicates the size of
35064 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35065 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35066 architectures have additional meanings for @var{kind};
35067 @var{cond_list} is an optional list of conditional expressions in bytecode
35068 form that should be evaluated on the target's side. These are the
35069 conditions that should be taken into consideration when deciding if
35070 the breakpoint trigger should be reported back to @var{GDBN}.
35072 The @var{cond_list} parameter is comprised of a series of expressions,
35073 concatenated without separators. Each expression has the following form:
35077 @item X @var{len},@var{expr}
35078 @var{len} is the length of the bytecode expression and @var{expr} is the
35079 actual conditional expression in bytecode form.
35083 see @ref{Architecture-Specific Protocol Details}.
35085 @emph{Implementation note: It is possible for a target to copy or move
35086 code that contains memory breakpoints (e.g., when implementing
35087 overlays). The behavior of this packet, in the presence of such a
35088 target, is not defined.}
35100 @item z1,@var{addr},@var{kind}
35101 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35102 @cindex @samp{z1} packet
35103 @cindex @samp{Z1} packet
35104 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35105 address @var{addr}.
35107 A hardware breakpoint is implemented using a mechanism that is not
35108 dependant on being able to modify the target's memory. @var{kind}
35109 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35111 @emph{Implementation note: A hardware breakpoint is not affected by code
35124 @item z2,@var{addr},@var{kind}
35125 @itemx Z2,@var{addr},@var{kind}
35126 @cindex @samp{z2} packet
35127 @cindex @samp{Z2} packet
35128 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35129 @var{kind} is interpreted as the number of bytes to watch.
35141 @item z3,@var{addr},@var{kind}
35142 @itemx Z3,@var{addr},@var{kind}
35143 @cindex @samp{z3} packet
35144 @cindex @samp{Z3} packet
35145 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35146 @var{kind} is interpreted as the number of bytes to watch.
35158 @item z4,@var{addr},@var{kind}
35159 @itemx Z4,@var{addr},@var{kind}
35160 @cindex @samp{z4} packet
35161 @cindex @samp{Z4} packet
35162 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35163 @var{kind} is interpreted as the number of bytes to watch.
35177 @node Stop Reply Packets
35178 @section Stop Reply Packets
35179 @cindex stop reply packets
35181 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35182 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35183 receive any of the below as a reply. Except for @samp{?}
35184 and @samp{vStopped}, that reply is only returned
35185 when the target halts. In the below the exact meaning of @dfn{signal
35186 number} is defined by the header @file{include/gdb/signals.h} in the
35187 @value{GDBN} source code.
35189 As in the description of request packets, we include spaces in the
35190 reply templates for clarity; these are not part of the reply packet's
35191 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35197 The program received signal number @var{AA} (a two-digit hexadecimal
35198 number). This is equivalent to a @samp{T} response with no
35199 @var{n}:@var{r} pairs.
35201 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35202 @cindex @samp{T} packet reply
35203 The program received signal number @var{AA} (a two-digit hexadecimal
35204 number). This is equivalent to an @samp{S} response, except that the
35205 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35206 and other information directly in the stop reply packet, reducing
35207 round-trip latency. Single-step and breakpoint traps are reported
35208 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35212 If @var{n} is a hexadecimal number, it is a register number, and the
35213 corresponding @var{r} gives that register's value. @var{r} is a
35214 series of bytes in target byte order, with each byte given by a
35215 two-digit hex number.
35218 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35219 the stopped thread, as specified in @ref{thread-id syntax}.
35222 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35223 the core on which the stop event was detected.
35226 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35227 specific event that stopped the target. The currently defined stop
35228 reasons are listed below. @var{aa} should be @samp{05}, the trap
35229 signal. At most one stop reason should be present.
35232 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35233 and go on to the next; this allows us to extend the protocol in the
35237 The currently defined stop reasons are:
35243 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35246 @cindex shared library events, remote reply
35248 The packet indicates that the loaded libraries have changed.
35249 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35250 list of loaded libraries. @var{r} is ignored.
35252 @cindex replay log events, remote reply
35254 The packet indicates that the target cannot continue replaying
35255 logged execution events, because it has reached the end (or the
35256 beginning when executing backward) of the log. The value of @var{r}
35257 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35258 for more information.
35262 @itemx W @var{AA} ; process:@var{pid}
35263 The process exited, and @var{AA} is the exit status. This is only
35264 applicable to certain targets.
35266 The second form of the response, including the process ID of the exited
35267 process, can be used only when @value{GDBN} has reported support for
35268 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35269 The @var{pid} is formatted as a big-endian hex string.
35272 @itemx X @var{AA} ; process:@var{pid}
35273 The process terminated with signal @var{AA}.
35275 The second form of the response, including the process ID of the
35276 terminated process, can be used only when @value{GDBN} has reported
35277 support for multiprocess protocol extensions; see @ref{multiprocess
35278 extensions}. The @var{pid} is formatted as a big-endian hex string.
35280 @item O @var{XX}@dots{}
35281 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35282 written as the program's console output. This can happen at any time
35283 while the program is running and the debugger should continue to wait
35284 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35286 @item F @var{call-id},@var{parameter}@dots{}
35287 @var{call-id} is the identifier which says which host system call should
35288 be called. This is just the name of the function. Translation into the
35289 correct system call is only applicable as it's defined in @value{GDBN}.
35290 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35293 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35294 this very system call.
35296 The target replies with this packet when it expects @value{GDBN} to
35297 call a host system call on behalf of the target. @value{GDBN} replies
35298 with an appropriate @samp{F} packet and keeps up waiting for the next
35299 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35300 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35301 Protocol Extension}, for more details.
35305 @node General Query Packets
35306 @section General Query Packets
35307 @cindex remote query requests
35309 Packets starting with @samp{q} are @dfn{general query packets};
35310 packets starting with @samp{Q} are @dfn{general set packets}. General
35311 query and set packets are a semi-unified form for retrieving and
35312 sending information to and from the stub.
35314 The initial letter of a query or set packet is followed by a name
35315 indicating what sort of thing the packet applies to. For example,
35316 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35317 definitions with the stub. These packet names follow some
35322 The name must not contain commas, colons or semicolons.
35324 Most @value{GDBN} query and set packets have a leading upper case
35327 The names of custom vendor packets should use a company prefix, in
35328 lower case, followed by a period. For example, packets designed at
35329 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35330 foos) or @samp{Qacme.bar} (for setting bars).
35333 The name of a query or set packet should be separated from any
35334 parameters by a @samp{:}; the parameters themselves should be
35335 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35336 full packet name, and check for a separator or the end of the packet,
35337 in case two packet names share a common prefix. New packets should not begin
35338 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35339 packets predate these conventions, and have arguments without any terminator
35340 for the packet name; we suspect they are in widespread use in places that
35341 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35342 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35345 Like the descriptions of the other packets, each description here
35346 has a template showing the packet's overall syntax, followed by an
35347 explanation of the packet's meaning. We include spaces in some of the
35348 templates for clarity; these are not part of the packet's syntax. No
35349 @value{GDBN} packet uses spaces to separate its components.
35351 Here are the currently defined query and set packets:
35357 Turn on or off the agent as a helper to perform some debugging operations
35358 delegated from @value{GDBN} (@pxref{Control Agent}).
35360 @item QAllow:@var{op}:@var{val}@dots{}
35361 @cindex @samp{QAllow} packet
35362 Specify which operations @value{GDBN} expects to request of the
35363 target, as a semicolon-separated list of operation name and value
35364 pairs. Possible values for @var{op} include @samp{WriteReg},
35365 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35366 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35367 indicating that @value{GDBN} will not request the operation, or 1,
35368 indicating that it may. (The target can then use this to set up its
35369 own internals optimally, for instance if the debugger never expects to
35370 insert breakpoints, it may not need to install its own trap handler.)
35373 @cindex current thread, remote request
35374 @cindex @samp{qC} packet
35375 Return the current thread ID.
35379 @item QC @var{thread-id}
35380 Where @var{thread-id} is a thread ID as documented in
35381 @ref{thread-id syntax}.
35382 @item @r{(anything else)}
35383 Any other reply implies the old thread ID.
35386 @item qCRC:@var{addr},@var{length}
35387 @cindex CRC of memory block, remote request
35388 @cindex @samp{qCRC} packet
35389 Compute the CRC checksum of a block of memory using CRC-32 defined in
35390 IEEE 802.3. The CRC is computed byte at a time, taking the most
35391 significant bit of each byte first. The initial pattern code
35392 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35394 @emph{Note:} This is the same CRC used in validating separate debug
35395 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35396 Files}). However the algorithm is slightly different. When validating
35397 separate debug files, the CRC is computed taking the @emph{least}
35398 significant bit of each byte first, and the final result is inverted to
35399 detect trailing zeros.
35404 An error (such as memory fault)
35405 @item C @var{crc32}
35406 The specified memory region's checksum is @var{crc32}.
35409 @item QDisableRandomization:@var{value}
35410 @cindex disable address space randomization, remote request
35411 @cindex @samp{QDisableRandomization} packet
35412 Some target operating systems will randomize the virtual address space
35413 of the inferior process as a security feature, but provide a feature
35414 to disable such randomization, e.g.@: to allow for a more deterministic
35415 debugging experience. On such systems, this packet with a @var{value}
35416 of 1 directs the target to disable address space randomization for
35417 processes subsequently started via @samp{vRun} packets, while a packet
35418 with a @var{value} of 0 tells the target to enable address space
35421 This packet is only available in extended mode (@pxref{extended mode}).
35426 The request succeeded.
35429 An error occurred. @var{nn} are hex digits.
35432 An empty reply indicates that @samp{QDisableRandomization} is not supported
35436 This packet is not probed by default; the remote stub must request it,
35437 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35438 This should only be done on targets that actually support disabling
35439 address space randomization.
35442 @itemx qsThreadInfo
35443 @cindex list active threads, remote request
35444 @cindex @samp{qfThreadInfo} packet
35445 @cindex @samp{qsThreadInfo} packet
35446 Obtain a list of all active thread IDs from the target (OS). Since there
35447 may be too many active threads to fit into one reply packet, this query
35448 works iteratively: it may require more than one query/reply sequence to
35449 obtain the entire list of threads. The first query of the sequence will
35450 be the @samp{qfThreadInfo} query; subsequent queries in the
35451 sequence will be the @samp{qsThreadInfo} query.
35453 NOTE: This packet replaces the @samp{qL} query (see below).
35457 @item m @var{thread-id}
35459 @item m @var{thread-id},@var{thread-id}@dots{}
35460 a comma-separated list of thread IDs
35462 (lower case letter @samp{L}) denotes end of list.
35465 In response to each query, the target will reply with a list of one or
35466 more thread IDs, separated by commas.
35467 @value{GDBN} will respond to each reply with a request for more thread
35468 ids (using the @samp{qs} form of the query), until the target responds
35469 with @samp{l} (lower-case ell, for @dfn{last}).
35470 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35473 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35474 @cindex get thread-local storage address, remote request
35475 @cindex @samp{qGetTLSAddr} packet
35476 Fetch the address associated with thread local storage specified
35477 by @var{thread-id}, @var{offset}, and @var{lm}.
35479 @var{thread-id} is the thread ID associated with the
35480 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35482 @var{offset} is the (big endian, hex encoded) offset associated with the
35483 thread local variable. (This offset is obtained from the debug
35484 information associated with the variable.)
35486 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35487 load module associated with the thread local storage. For example,
35488 a @sc{gnu}/Linux system will pass the link map address of the shared
35489 object associated with the thread local storage under consideration.
35490 Other operating environments may choose to represent the load module
35491 differently, so the precise meaning of this parameter will vary.
35495 @item @var{XX}@dots{}
35496 Hex encoded (big endian) bytes representing the address of the thread
35497 local storage requested.
35500 An error occurred. @var{nn} are hex digits.
35503 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35506 @item qGetTIBAddr:@var{thread-id}
35507 @cindex get thread information block address
35508 @cindex @samp{qGetTIBAddr} packet
35509 Fetch address of the Windows OS specific Thread Information Block.
35511 @var{thread-id} is the thread ID associated with the thread.
35515 @item @var{XX}@dots{}
35516 Hex encoded (big endian) bytes representing the linear address of the
35517 thread information block.
35520 An error occured. This means that either the thread was not found, or the
35521 address could not be retrieved.
35524 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35527 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35528 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35529 digit) is one to indicate the first query and zero to indicate a
35530 subsequent query; @var{threadcount} (two hex digits) is the maximum
35531 number of threads the response packet can contain; and @var{nextthread}
35532 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35533 returned in the response as @var{argthread}.
35535 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35539 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35540 Where: @var{count} (two hex digits) is the number of threads being
35541 returned; @var{done} (one hex digit) is zero to indicate more threads
35542 and one indicates no further threads; @var{argthreadid} (eight hex
35543 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35544 is a sequence of thread IDs from the target. @var{threadid} (eight hex
35545 digits). See @code{remote.c:parse_threadlist_response()}.
35549 @cindex section offsets, remote request
35550 @cindex @samp{qOffsets} packet
35551 Get section offsets that the target used when relocating the downloaded
35556 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35557 Relocate the @code{Text} section by @var{xxx} from its original address.
35558 Relocate the @code{Data} section by @var{yyy} from its original address.
35559 If the object file format provides segment information (e.g.@: @sc{elf}
35560 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35561 segments by the supplied offsets.
35563 @emph{Note: while a @code{Bss} offset may be included in the response,
35564 @value{GDBN} ignores this and instead applies the @code{Data} offset
35565 to the @code{Bss} section.}
35567 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35568 Relocate the first segment of the object file, which conventionally
35569 contains program code, to a starting address of @var{xxx}. If
35570 @samp{DataSeg} is specified, relocate the second segment, which
35571 conventionally contains modifiable data, to a starting address of
35572 @var{yyy}. @value{GDBN} will report an error if the object file
35573 does not contain segment information, or does not contain at least
35574 as many segments as mentioned in the reply. Extra segments are
35575 kept at fixed offsets relative to the last relocated segment.
35578 @item qP @var{mode} @var{thread-id}
35579 @cindex thread information, remote request
35580 @cindex @samp{qP} packet
35581 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35582 encoded 32 bit mode; @var{thread-id} is a thread ID
35583 (@pxref{thread-id syntax}).
35585 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35588 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35592 @cindex non-stop mode, remote request
35593 @cindex @samp{QNonStop} packet
35595 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35596 @xref{Remote Non-Stop}, for more information.
35601 The request succeeded.
35604 An error occurred. @var{nn} are hex digits.
35607 An empty reply indicates that @samp{QNonStop} is not supported by
35611 This packet is not probed by default; the remote stub must request it,
35612 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35613 Use of this packet is controlled by the @code{set non-stop} command;
35614 @pxref{Non-Stop Mode}.
35616 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35617 @cindex pass signals to inferior, remote request
35618 @cindex @samp{QPassSignals} packet
35619 @anchor{QPassSignals}
35620 Each listed @var{signal} should be passed directly to the inferior process.
35621 Signals are numbered identically to continue packets and stop replies
35622 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35623 strictly greater than the previous item. These signals do not need to stop
35624 the inferior, or be reported to @value{GDBN}. All other signals should be
35625 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35626 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35627 new list. This packet improves performance when using @samp{handle
35628 @var{signal} nostop noprint pass}.
35633 The request succeeded.
35636 An error occurred. @var{nn} are hex digits.
35639 An empty reply indicates that @samp{QPassSignals} is not supported by
35643 Use of this packet is controlled by the @code{set remote pass-signals}
35644 command (@pxref{Remote Configuration, set remote pass-signals}).
35645 This packet is not probed by default; the remote stub must request it,
35646 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35648 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35649 @cindex signals the inferior may see, remote request
35650 @cindex @samp{QProgramSignals} packet
35651 @anchor{QProgramSignals}
35652 Each listed @var{signal} may be delivered to the inferior process.
35653 Others should be silently discarded.
35655 In some cases, the remote stub may need to decide whether to deliver a
35656 signal to the program or not without @value{GDBN} involvement. One
35657 example of that is while detaching --- the program's threads may have
35658 stopped for signals that haven't yet had a chance of being reported to
35659 @value{GDBN}, and so the remote stub can use the signal list specified
35660 by this packet to know whether to deliver or ignore those pending
35663 This does not influence whether to deliver a signal as requested by a
35664 resumption packet (@pxref{vCont packet}).
35666 Signals are numbered identically to continue packets and stop replies
35667 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35668 strictly greater than the previous item. Multiple
35669 @samp{QProgramSignals} packets do not combine; any earlier
35670 @samp{QProgramSignals} list is completely replaced by the new list.
35675 The request succeeded.
35678 An error occurred. @var{nn} are hex digits.
35681 An empty reply indicates that @samp{QProgramSignals} is not supported
35685 Use of this packet is controlled by the @code{set remote program-signals}
35686 command (@pxref{Remote Configuration, set remote program-signals}).
35687 This packet is not probed by default; the remote stub must request it,
35688 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35690 @item qRcmd,@var{command}
35691 @cindex execute remote command, remote request
35692 @cindex @samp{qRcmd} packet
35693 @var{command} (hex encoded) is passed to the local interpreter for
35694 execution. Invalid commands should be reported using the output
35695 string. Before the final result packet, the target may also respond
35696 with a number of intermediate @samp{O@var{output}} console output
35697 packets. @emph{Implementors should note that providing access to a
35698 stubs's interpreter may have security implications}.
35703 A command response with no output.
35705 A command response with the hex encoded output string @var{OUTPUT}.
35707 Indicate a badly formed request.
35709 An empty reply indicates that @samp{qRcmd} is not recognized.
35712 (Note that the @code{qRcmd} packet's name is separated from the
35713 command by a @samp{,}, not a @samp{:}, contrary to the naming
35714 conventions above. Please don't use this packet as a model for new
35717 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35718 @cindex searching memory, in remote debugging
35719 @cindex @samp{qSearch:memory} packet
35720 @anchor{qSearch memory}
35721 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35722 @var{address} and @var{length} are encoded in hex.
35723 @var{search-pattern} is a sequence of bytes, hex encoded.
35728 The pattern was not found.
35730 The pattern was found at @var{address}.
35732 A badly formed request or an error was encountered while searching memory.
35734 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35737 @item QStartNoAckMode
35738 @cindex @samp{QStartNoAckMode} packet
35739 @anchor{QStartNoAckMode}
35740 Request that the remote stub disable the normal @samp{+}/@samp{-}
35741 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35746 The stub has switched to no-acknowledgment mode.
35747 @value{GDBN} acknowledges this reponse,
35748 but neither the stub nor @value{GDBN} shall send or expect further
35749 @samp{+}/@samp{-} acknowledgments in the current connection.
35751 An empty reply indicates that the stub does not support no-acknowledgment mode.
35754 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35755 @cindex supported packets, remote query
35756 @cindex features of the remote protocol
35757 @cindex @samp{qSupported} packet
35758 @anchor{qSupported}
35759 Tell the remote stub about features supported by @value{GDBN}, and
35760 query the stub for features it supports. This packet allows
35761 @value{GDBN} and the remote stub to take advantage of each others'
35762 features. @samp{qSupported} also consolidates multiple feature probes
35763 at startup, to improve @value{GDBN} performance---a single larger
35764 packet performs better than multiple smaller probe packets on
35765 high-latency links. Some features may enable behavior which must not
35766 be on by default, e.g.@: because it would confuse older clients or
35767 stubs. Other features may describe packets which could be
35768 automatically probed for, but are not. These features must be
35769 reported before @value{GDBN} will use them. This ``default
35770 unsupported'' behavior is not appropriate for all packets, but it
35771 helps to keep the initial connection time under control with new
35772 versions of @value{GDBN} which support increasing numbers of packets.
35776 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35777 The stub supports or does not support each returned @var{stubfeature},
35778 depending on the form of each @var{stubfeature} (see below for the
35781 An empty reply indicates that @samp{qSupported} is not recognized,
35782 or that no features needed to be reported to @value{GDBN}.
35785 The allowed forms for each feature (either a @var{gdbfeature} in the
35786 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35790 @item @var{name}=@var{value}
35791 The remote protocol feature @var{name} is supported, and associated
35792 with the specified @var{value}. The format of @var{value} depends
35793 on the feature, but it must not include a semicolon.
35795 The remote protocol feature @var{name} is supported, and does not
35796 need an associated value.
35798 The remote protocol feature @var{name} is not supported.
35800 The remote protocol feature @var{name} may be supported, and
35801 @value{GDBN} should auto-detect support in some other way when it is
35802 needed. This form will not be used for @var{gdbfeature} notifications,
35803 but may be used for @var{stubfeature} responses.
35806 Whenever the stub receives a @samp{qSupported} request, the
35807 supplied set of @value{GDBN} features should override any previous
35808 request. This allows @value{GDBN} to put the stub in a known
35809 state, even if the stub had previously been communicating with
35810 a different version of @value{GDBN}.
35812 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35817 This feature indicates whether @value{GDBN} supports multiprocess
35818 extensions to the remote protocol. @value{GDBN} does not use such
35819 extensions unless the stub also reports that it supports them by
35820 including @samp{multiprocess+} in its @samp{qSupported} reply.
35821 @xref{multiprocess extensions}, for details.
35824 This feature indicates that @value{GDBN} supports the XML target
35825 description. If the stub sees @samp{xmlRegisters=} with target
35826 specific strings separated by a comma, it will report register
35830 This feature indicates whether @value{GDBN} supports the
35831 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35832 instruction reply packet}).
35835 Stubs should ignore any unknown values for
35836 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35837 packet supports receiving packets of unlimited length (earlier
35838 versions of @value{GDBN} may reject overly long responses). Additional values
35839 for @var{gdbfeature} may be defined in the future to let the stub take
35840 advantage of new features in @value{GDBN}, e.g.@: incompatible
35841 improvements in the remote protocol---the @samp{multiprocess} feature is
35842 an example of such a feature. The stub's reply should be independent
35843 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35844 describes all the features it supports, and then the stub replies with
35845 all the features it supports.
35847 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35848 responses, as long as each response uses one of the standard forms.
35850 Some features are flags. A stub which supports a flag feature
35851 should respond with a @samp{+} form response. Other features
35852 require values, and the stub should respond with an @samp{=}
35855 Each feature has a default value, which @value{GDBN} will use if
35856 @samp{qSupported} is not available or if the feature is not mentioned
35857 in the @samp{qSupported} response. The default values are fixed; a
35858 stub is free to omit any feature responses that match the defaults.
35860 Not all features can be probed, but for those which can, the probing
35861 mechanism is useful: in some cases, a stub's internal
35862 architecture may not allow the protocol layer to know some information
35863 about the underlying target in advance. This is especially common in
35864 stubs which may be configured for multiple targets.
35866 These are the currently defined stub features and their properties:
35868 @multitable @columnfractions 0.35 0.2 0.12 0.2
35869 @c NOTE: The first row should be @headitem, but we do not yet require
35870 @c a new enough version of Texinfo (4.7) to use @headitem.
35872 @tab Value Required
35876 @item @samp{PacketSize}
35881 @item @samp{qXfer:auxv:read}
35886 @item @samp{qXfer:features:read}
35891 @item @samp{qXfer:libraries:read}
35896 @item @samp{qXfer:memory-map:read}
35901 @item @samp{qXfer:sdata:read}
35906 @item @samp{qXfer:spu:read}
35911 @item @samp{qXfer:spu:write}
35916 @item @samp{qXfer:siginfo:read}
35921 @item @samp{qXfer:siginfo:write}
35926 @item @samp{qXfer:threads:read}
35931 @item @samp{qXfer:traceframe-info:read}
35936 @item @samp{qXfer:uib:read}
35941 @item @samp{qXfer:fdpic:read}
35946 @item @samp{QNonStop}
35951 @item @samp{QPassSignals}
35956 @item @samp{QStartNoAckMode}
35961 @item @samp{multiprocess}
35966 @item @samp{ConditionalBreakpoints}
35971 @item @samp{ConditionalTracepoints}
35976 @item @samp{ReverseContinue}
35981 @item @samp{ReverseStep}
35986 @item @samp{TracepointSource}
35991 @item @samp{QAgent}
35996 @item @samp{QAllow}
36001 @item @samp{QDisableRandomization}
36006 @item @samp{EnableDisableTracepoints}
36011 @item @samp{tracenz}
36018 These are the currently defined stub features, in more detail:
36021 @cindex packet size, remote protocol
36022 @item PacketSize=@var{bytes}
36023 The remote stub can accept packets up to at least @var{bytes} in
36024 length. @value{GDBN} will send packets up to this size for bulk
36025 transfers, and will never send larger packets. This is a limit on the
36026 data characters in the packet, including the frame and checksum.
36027 There is no trailing NUL byte in a remote protocol packet; if the stub
36028 stores packets in a NUL-terminated format, it should allow an extra
36029 byte in its buffer for the NUL. If this stub feature is not supported,
36030 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36032 @item qXfer:auxv:read
36033 The remote stub understands the @samp{qXfer:auxv:read} packet
36034 (@pxref{qXfer auxiliary vector read}).
36036 @item qXfer:features:read
36037 The remote stub understands the @samp{qXfer:features:read} packet
36038 (@pxref{qXfer target description read}).
36040 @item qXfer:libraries:read
36041 The remote stub understands the @samp{qXfer:libraries:read} packet
36042 (@pxref{qXfer library list read}).
36044 @item qXfer:libraries-svr4:read
36045 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36046 (@pxref{qXfer svr4 library list read}).
36048 @item qXfer:memory-map:read
36049 The remote stub understands the @samp{qXfer:memory-map:read} packet
36050 (@pxref{qXfer memory map read}).
36052 @item qXfer:sdata:read
36053 The remote stub understands the @samp{qXfer:sdata:read} packet
36054 (@pxref{qXfer sdata read}).
36056 @item qXfer:spu:read
36057 The remote stub understands the @samp{qXfer:spu:read} packet
36058 (@pxref{qXfer spu read}).
36060 @item qXfer:spu:write
36061 The remote stub understands the @samp{qXfer:spu:write} packet
36062 (@pxref{qXfer spu write}).
36064 @item qXfer:siginfo:read
36065 The remote stub understands the @samp{qXfer:siginfo:read} packet
36066 (@pxref{qXfer siginfo read}).
36068 @item qXfer:siginfo:write
36069 The remote stub understands the @samp{qXfer:siginfo:write} packet
36070 (@pxref{qXfer siginfo write}).
36072 @item qXfer:threads:read
36073 The remote stub understands the @samp{qXfer:threads:read} packet
36074 (@pxref{qXfer threads read}).
36076 @item qXfer:traceframe-info:read
36077 The remote stub understands the @samp{qXfer:traceframe-info:read}
36078 packet (@pxref{qXfer traceframe info read}).
36080 @item qXfer:uib:read
36081 The remote stub understands the @samp{qXfer:uib:read}
36082 packet (@pxref{qXfer unwind info block}).
36084 @item qXfer:fdpic:read
36085 The remote stub understands the @samp{qXfer:fdpic:read}
36086 packet (@pxref{qXfer fdpic loadmap read}).
36089 The remote stub understands the @samp{QNonStop} packet
36090 (@pxref{QNonStop}).
36093 The remote stub understands the @samp{QPassSignals} packet
36094 (@pxref{QPassSignals}).
36096 @item QStartNoAckMode
36097 The remote stub understands the @samp{QStartNoAckMode} packet and
36098 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36101 @anchor{multiprocess extensions}
36102 @cindex multiprocess extensions, in remote protocol
36103 The remote stub understands the multiprocess extensions to the remote
36104 protocol syntax. The multiprocess extensions affect the syntax of
36105 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36106 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36107 replies. Note that reporting this feature indicates support for the
36108 syntactic extensions only, not that the stub necessarily supports
36109 debugging of more than one process at a time. The stub must not use
36110 multiprocess extensions in packet replies unless @value{GDBN} has also
36111 indicated it supports them in its @samp{qSupported} request.
36113 @item qXfer:osdata:read
36114 The remote stub understands the @samp{qXfer:osdata:read} packet
36115 ((@pxref{qXfer osdata read}).
36117 @item ConditionalBreakpoints
36118 The target accepts and implements evaluation of conditional expressions
36119 defined for breakpoints. The target will only report breakpoint triggers
36120 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36122 @item ConditionalTracepoints
36123 The remote stub accepts and implements conditional expressions defined
36124 for tracepoints (@pxref{Tracepoint Conditions}).
36126 @item ReverseContinue
36127 The remote stub accepts and implements the reverse continue packet
36131 The remote stub accepts and implements the reverse step packet
36134 @item TracepointSource
36135 The remote stub understands the @samp{QTDPsrc} packet that supplies
36136 the source form of tracepoint definitions.
36139 The remote stub understands the @samp{QAgent} packet.
36142 The remote stub understands the @samp{QAllow} packet.
36144 @item QDisableRandomization
36145 The remote stub understands the @samp{QDisableRandomization} packet.
36147 @item StaticTracepoint
36148 @cindex static tracepoints, in remote protocol
36149 The remote stub supports static tracepoints.
36151 @item InstallInTrace
36152 @anchor{install tracepoint in tracing}
36153 The remote stub supports installing tracepoint in tracing.
36155 @item EnableDisableTracepoints
36156 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36157 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36158 to be enabled and disabled while a trace experiment is running.
36161 @cindex string tracing, in remote protocol
36162 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36163 See @ref{Bytecode Descriptions} for details about the bytecode.
36168 @cindex symbol lookup, remote request
36169 @cindex @samp{qSymbol} packet
36170 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36171 requests. Accept requests from the target for the values of symbols.
36176 The target does not need to look up any (more) symbols.
36177 @item qSymbol:@var{sym_name}
36178 The target requests the value of symbol @var{sym_name} (hex encoded).
36179 @value{GDBN} may provide the value by using the
36180 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36184 @item qSymbol:@var{sym_value}:@var{sym_name}
36185 Set the value of @var{sym_name} to @var{sym_value}.
36187 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36188 target has previously requested.
36190 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36191 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36197 The target does not need to look up any (more) symbols.
36198 @item qSymbol:@var{sym_name}
36199 The target requests the value of a new symbol @var{sym_name} (hex
36200 encoded). @value{GDBN} will continue to supply the values of symbols
36201 (if available), until the target ceases to request them.
36206 @item QTDisconnected
36213 @itemx qTMinFTPILen
36215 @xref{Tracepoint Packets}.
36217 @item qThreadExtraInfo,@var{thread-id}
36218 @cindex thread attributes info, remote request
36219 @cindex @samp{qThreadExtraInfo} packet
36220 Obtain a printable string description of a thread's attributes from
36221 the target OS. @var{thread-id} is a thread ID;
36222 see @ref{thread-id syntax}. This
36223 string may contain anything that the target OS thinks is interesting
36224 for @value{GDBN} to tell the user about the thread. The string is
36225 displayed in @value{GDBN}'s @code{info threads} display. Some
36226 examples of possible thread extra info strings are @samp{Runnable}, or
36227 @samp{Blocked on Mutex}.
36231 @item @var{XX}@dots{}
36232 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36233 comprising the printable string containing the extra information about
36234 the thread's attributes.
36237 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36238 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36239 conventions above. Please don't use this packet as a model for new
36258 @xref{Tracepoint Packets}.
36260 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36261 @cindex read special object, remote request
36262 @cindex @samp{qXfer} packet
36263 @anchor{qXfer read}
36264 Read uninterpreted bytes from the target's special data area
36265 identified by the keyword @var{object}. Request @var{length} bytes
36266 starting at @var{offset} bytes into the data. The content and
36267 encoding of @var{annex} is specific to @var{object}; it can supply
36268 additional details about what data to access.
36270 Here are the specific requests of this form defined so far. All
36271 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36272 formats, listed below.
36275 @item qXfer:auxv:read::@var{offset},@var{length}
36276 @anchor{qXfer auxiliary vector read}
36277 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36278 auxiliary vector}. Note @var{annex} must be empty.
36280 This packet is not probed by default; the remote stub must request it,
36281 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36283 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36284 @anchor{qXfer target description read}
36285 Access the @dfn{target description}. @xref{Target Descriptions}. The
36286 annex specifies which XML document to access. The main description is
36287 always loaded from the @samp{target.xml} annex.
36289 This packet is not probed by default; the remote stub must request it,
36290 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36292 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36293 @anchor{qXfer library list read}
36294 Access the target's list of loaded libraries. @xref{Library List Format}.
36295 The annex part of the generic @samp{qXfer} packet must be empty
36296 (@pxref{qXfer read}).
36298 Targets which maintain a list of libraries in the program's memory do
36299 not need to implement this packet; it is designed for platforms where
36300 the operating system manages the list of loaded libraries.
36302 This packet is not probed by default; the remote stub must request it,
36303 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36305 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36306 @anchor{qXfer svr4 library list read}
36307 Access the target's list of loaded libraries when the target is an SVR4
36308 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36309 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36311 This packet is optional for better performance on SVR4 targets.
36312 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36314 This packet is not probed by default; the remote stub must request it,
36315 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36317 @item qXfer:memory-map:read::@var{offset},@var{length}
36318 @anchor{qXfer memory map read}
36319 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36320 annex part of the generic @samp{qXfer} packet must be empty
36321 (@pxref{qXfer read}).
36323 This packet is not probed by default; the remote stub must request it,
36324 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36326 @item qXfer:sdata:read::@var{offset},@var{length}
36327 @anchor{qXfer sdata read}
36329 Read contents of the extra collected static tracepoint marker
36330 information. The annex part of the generic @samp{qXfer} packet must
36331 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36334 This packet is not probed by default; the remote stub must request it,
36335 by supplying an appropriate @samp{qSupported} response
36336 (@pxref{qSupported}).
36338 @item qXfer:siginfo:read::@var{offset},@var{length}
36339 @anchor{qXfer siginfo read}
36340 Read contents of the extra signal information on the target
36341 system. The annex part of the generic @samp{qXfer} packet must be
36342 empty (@pxref{qXfer read}).
36344 This packet is not probed by default; the remote stub must request it,
36345 by supplying an appropriate @samp{qSupported} response
36346 (@pxref{qSupported}).
36348 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36349 @anchor{qXfer spu read}
36350 Read contents of an @code{spufs} file on the target system. The
36351 annex specifies which file to read; it must be of the form
36352 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36353 in the target process, and @var{name} identifes the @code{spufs} file
36354 in that context to be accessed.
36356 This packet is not probed by default; the remote stub must request it,
36357 by supplying an appropriate @samp{qSupported} response
36358 (@pxref{qSupported}).
36360 @item qXfer:threads:read::@var{offset},@var{length}
36361 @anchor{qXfer threads read}
36362 Access the list of threads on target. @xref{Thread List Format}. The
36363 annex part of the generic @samp{qXfer} packet must be empty
36364 (@pxref{qXfer read}).
36366 This packet is not probed by default; the remote stub must request it,
36367 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36369 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36370 @anchor{qXfer traceframe info read}
36372 Return a description of the current traceframe's contents.
36373 @xref{Traceframe Info Format}. The annex part of the generic
36374 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36376 This packet is not probed by default; the remote stub must request it,
36377 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36379 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36380 @anchor{qXfer unwind info block}
36382 Return the unwind information block for @var{pc}. This packet is used
36383 on OpenVMS/ia64 to ask the kernel unwind information.
36385 This packet is not probed by default.
36387 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36388 @anchor{qXfer fdpic loadmap read}
36389 Read contents of @code{loadmap}s on the target system. The
36390 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36391 executable @code{loadmap} or interpreter @code{loadmap} to read.
36393 This packet is not probed by default; the remote stub must request it,
36394 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36396 @item qXfer:osdata:read::@var{offset},@var{length}
36397 @anchor{qXfer osdata read}
36398 Access the target's @dfn{operating system information}.
36399 @xref{Operating System Information}.
36406 Data @var{data} (@pxref{Binary Data}) has been read from the
36407 target. There may be more data at a higher address (although
36408 it is permitted to return @samp{m} even for the last valid
36409 block of data, as long as at least one byte of data was read).
36410 @var{data} may have fewer bytes than the @var{length} in the
36414 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36415 There is no more data to be read. @var{data} may have fewer bytes
36416 than the @var{length} in the request.
36419 The @var{offset} in the request is at the end of the data.
36420 There is no more data to be read.
36423 The request was malformed, or @var{annex} was invalid.
36426 The offset was invalid, or there was an error encountered reading the data.
36427 @var{nn} is a hex-encoded @code{errno} value.
36430 An empty reply indicates the @var{object} string was not recognized by
36431 the stub, or that the object does not support reading.
36434 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36435 @cindex write data into object, remote request
36436 @anchor{qXfer write}
36437 Write uninterpreted bytes into the target's special data area
36438 identified by the keyword @var{object}, starting at @var{offset} bytes
36439 into the data. @var{data}@dots{} is the binary-encoded data
36440 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
36441 is specific to @var{object}; it can supply additional details about what data
36444 Here are the specific requests of this form defined so far. All
36445 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36446 formats, listed below.
36449 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36450 @anchor{qXfer siginfo write}
36451 Write @var{data} to the extra signal information on the target system.
36452 The annex part of the generic @samp{qXfer} packet must be
36453 empty (@pxref{qXfer write}).
36455 This packet is not probed by default; the remote stub must request it,
36456 by supplying an appropriate @samp{qSupported} response
36457 (@pxref{qSupported}).
36459 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36460 @anchor{qXfer spu write}
36461 Write @var{data} to an @code{spufs} file on the target system. The
36462 annex specifies which file to write; it must be of the form
36463 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36464 in the target process, and @var{name} identifes the @code{spufs} file
36465 in that context to be accessed.
36467 This packet is not probed by default; the remote stub must request it,
36468 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36474 @var{nn} (hex encoded) is the number of bytes written.
36475 This may be fewer bytes than supplied in the request.
36478 The request was malformed, or @var{annex} was invalid.
36481 The offset was invalid, or there was an error encountered writing the data.
36482 @var{nn} is a hex-encoded @code{errno} value.
36485 An empty reply indicates the @var{object} string was not
36486 recognized by the stub, or that the object does not support writing.
36489 @item qXfer:@var{object}:@var{operation}:@dots{}
36490 Requests of this form may be added in the future. When a stub does
36491 not recognize the @var{object} keyword, or its support for
36492 @var{object} does not recognize the @var{operation} keyword, the stub
36493 must respond with an empty packet.
36495 @item qAttached:@var{pid}
36496 @cindex query attached, remote request
36497 @cindex @samp{qAttached} packet
36498 Return an indication of whether the remote server attached to an
36499 existing process or created a new process. When the multiprocess
36500 protocol extensions are supported (@pxref{multiprocess extensions}),
36501 @var{pid} is an integer in hexadecimal format identifying the target
36502 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36503 the query packet will be simplified as @samp{qAttached}.
36505 This query is used, for example, to know whether the remote process
36506 should be detached or killed when a @value{GDBN} session is ended with
36507 the @code{quit} command.
36512 The remote server attached to an existing process.
36514 The remote server created a new process.
36516 A badly formed request or an error was encountered.
36521 @node Architecture-Specific Protocol Details
36522 @section Architecture-Specific Protocol Details
36524 This section describes how the remote protocol is applied to specific
36525 target architectures. Also see @ref{Standard Target Features}, for
36526 details of XML target descriptions for each architecture.
36530 @subsubsection Breakpoint Kinds
36532 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36537 16-bit Thumb mode breakpoint.
36540 32-bit Thumb mode (Thumb-2) breakpoint.
36543 32-bit ARM mode breakpoint.
36549 @subsubsection Register Packet Format
36551 The following @code{g}/@code{G} packets have previously been defined.
36552 In the below, some thirty-two bit registers are transferred as
36553 sixty-four bits. Those registers should be zero/sign extended (which?)
36554 to fill the space allocated. Register bytes are transferred in target
36555 byte order. The two nibbles within a register byte are transferred
36556 most-significant - least-significant.
36562 All registers are transferred as thirty-two bit quantities in the order:
36563 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36564 registers; fsr; fir; fp.
36568 All registers are transferred as sixty-four bit quantities (including
36569 thirty-two bit registers such as @code{sr}). The ordering is the same
36574 @node Tracepoint Packets
36575 @section Tracepoint Packets
36576 @cindex tracepoint packets
36577 @cindex packets, tracepoint
36579 Here we describe the packets @value{GDBN} uses to implement
36580 tracepoints (@pxref{Tracepoints}).
36584 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36585 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36586 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36587 the tracepoint is disabled. @var{step} is the tracepoint's step
36588 count, and @var{pass} is its pass count. If an @samp{F} is present,
36589 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36590 the number of bytes that the target should copy elsewhere to make room
36591 for the tracepoint. If an @samp{X} is present, it introduces a
36592 tracepoint condition, which consists of a hexadecimal length, followed
36593 by a comma and hex-encoded bytes, in a manner similar to action
36594 encodings as described below. If the trailing @samp{-} is present,
36595 further @samp{QTDP} packets will follow to specify this tracepoint's
36601 The packet was understood and carried out.
36603 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36605 The packet was not recognized.
36608 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36609 Define actions to be taken when a tracepoint is hit. @var{n} and
36610 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36611 this tracepoint. This packet may only be sent immediately after
36612 another @samp{QTDP} packet that ended with a @samp{-}. If the
36613 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36614 specifying more actions for this tracepoint.
36616 In the series of action packets for a given tracepoint, at most one
36617 can have an @samp{S} before its first @var{action}. If such a packet
36618 is sent, it and the following packets define ``while-stepping''
36619 actions. Any prior packets define ordinary actions --- that is, those
36620 taken when the tracepoint is first hit. If no action packet has an
36621 @samp{S}, then all the packets in the series specify ordinary
36622 tracepoint actions.
36624 The @samp{@var{action}@dots{}} portion of the packet is a series of
36625 actions, concatenated without separators. Each action has one of the
36631 Collect the registers whose bits are set in @var{mask}. @var{mask} is
36632 a hexadecimal number whose @var{i}'th bit is set if register number
36633 @var{i} should be collected. (The least significant bit is numbered
36634 zero.) Note that @var{mask} may be any number of digits long; it may
36635 not fit in a 32-bit word.
36637 @item M @var{basereg},@var{offset},@var{len}
36638 Collect @var{len} bytes of memory starting at the address in register
36639 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36640 @samp{-1}, then the range has a fixed address: @var{offset} is the
36641 address of the lowest byte to collect. The @var{basereg},
36642 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36643 values (the @samp{-1} value for @var{basereg} is a special case).
36645 @item X @var{len},@var{expr}
36646 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36647 it directs. @var{expr} is an agent expression, as described in
36648 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36649 two-digit hex number in the packet; @var{len} is the number of bytes
36650 in the expression (and thus one-half the number of hex digits in the
36655 Any number of actions may be packed together in a single @samp{QTDP}
36656 packet, as long as the packet does not exceed the maximum packet
36657 length (400 bytes, for many stubs). There may be only one @samp{R}
36658 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36659 actions. Any registers referred to by @samp{M} and @samp{X} actions
36660 must be collected by a preceding @samp{R} action. (The
36661 ``while-stepping'' actions are treated as if they were attached to a
36662 separate tracepoint, as far as these restrictions are concerned.)
36667 The packet was understood and carried out.
36669 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36671 The packet was not recognized.
36674 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36675 @cindex @samp{QTDPsrc} packet
36676 Specify a source string of tracepoint @var{n} at address @var{addr}.
36677 This is useful to get accurate reproduction of the tracepoints
36678 originally downloaded at the beginning of the trace run. @var{type}
36679 is the name of the tracepoint part, such as @samp{cond} for the
36680 tracepoint's conditional expression (see below for a list of types), while
36681 @var{bytes} is the string, encoded in hexadecimal.
36683 @var{start} is the offset of the @var{bytes} within the overall source
36684 string, while @var{slen} is the total length of the source string.
36685 This is intended for handling source strings that are longer than will
36686 fit in a single packet.
36687 @c Add detailed example when this info is moved into a dedicated
36688 @c tracepoint descriptions section.
36690 The available string types are @samp{at} for the location,
36691 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36692 @value{GDBN} sends a separate packet for each command in the action
36693 list, in the same order in which the commands are stored in the list.
36695 The target does not need to do anything with source strings except
36696 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36699 Although this packet is optional, and @value{GDBN} will only send it
36700 if the target replies with @samp{TracepointSource} @xref{General
36701 Query Packets}, it makes both disconnected tracing and trace files
36702 much easier to use. Otherwise the user must be careful that the
36703 tracepoints in effect while looking at trace frames are identical to
36704 the ones in effect during the trace run; even a small discrepancy
36705 could cause @samp{tdump} not to work, or a particular trace frame not
36708 @item QTDV:@var{n}:@var{value}
36709 @cindex define trace state variable, remote request
36710 @cindex @samp{QTDV} packet
36711 Create a new trace state variable, number @var{n}, with an initial
36712 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36713 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36714 the option of not using this packet for initial values of zero; the
36715 target should simply create the trace state variables as they are
36716 mentioned in expressions.
36718 @item QTFrame:@var{n}
36719 Select the @var{n}'th tracepoint frame from the buffer, and use the
36720 register and memory contents recorded there to answer subsequent
36721 request packets from @value{GDBN}.
36723 A successful reply from the stub indicates that the stub has found the
36724 requested frame. The response is a series of parts, concatenated
36725 without separators, describing the frame we selected. Each part has
36726 one of the following forms:
36730 The selected frame is number @var{n} in the trace frame buffer;
36731 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36732 was no frame matching the criteria in the request packet.
36735 The selected trace frame records a hit of tracepoint number @var{t};
36736 @var{t} is a hexadecimal number.
36740 @item QTFrame:pc:@var{addr}
36741 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36742 currently selected frame whose PC is @var{addr};
36743 @var{addr} is a hexadecimal number.
36745 @item QTFrame:tdp:@var{t}
36746 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36747 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36748 is a hexadecimal number.
36750 @item QTFrame:range:@var{start}:@var{end}
36751 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36752 currently selected frame whose PC is between @var{start} (inclusive)
36753 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36756 @item QTFrame:outside:@var{start}:@var{end}
36757 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36758 frame @emph{outside} the given range of addresses (exclusive).
36761 This packet requests the minimum length of instruction at which a fast
36762 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36763 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36764 it depends on the target system being able to create trampolines in
36765 the first 64K of memory, which might or might not be possible for that
36766 system. So the reply to this packet will be 4 if it is able to
36773 The minimum instruction length is currently unknown.
36775 The minimum instruction length is @var{length}, where @var{length} is greater
36776 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
36777 that a fast tracepoint may be placed on any instruction regardless of size.
36779 An error has occurred.
36781 An empty reply indicates that the request is not supported by the stub.
36785 Begin the tracepoint experiment. Begin collecting data from
36786 tracepoint hits in the trace frame buffer. This packet supports the
36787 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36788 instruction reply packet}).
36791 End the tracepoint experiment. Stop collecting trace frames.
36793 @item QTEnable:@var{n}:@var{addr}
36795 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36796 experiment. If the tracepoint was previously disabled, then collection
36797 of data from it will resume.
36799 @item QTDisable:@var{n}:@var{addr}
36801 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36802 experiment. No more data will be collected from the tracepoint unless
36803 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36806 Clear the table of tracepoints, and empty the trace frame buffer.
36808 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36809 Establish the given ranges of memory as ``transparent''. The stub
36810 will answer requests for these ranges from memory's current contents,
36811 if they were not collected as part of the tracepoint hit.
36813 @value{GDBN} uses this to mark read-only regions of memory, like those
36814 containing program code. Since these areas never change, they should
36815 still have the same contents they did when the tracepoint was hit, so
36816 there's no reason for the stub to refuse to provide their contents.
36818 @item QTDisconnected:@var{value}
36819 Set the choice to what to do with the tracing run when @value{GDBN}
36820 disconnects from the target. A @var{value} of 1 directs the target to
36821 continue the tracing run, while 0 tells the target to stop tracing if
36822 @value{GDBN} is no longer in the picture.
36825 Ask the stub if there is a trace experiment running right now.
36827 The reply has the form:
36831 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36832 @var{running} is a single digit @code{1} if the trace is presently
36833 running, or @code{0} if not. It is followed by semicolon-separated
36834 optional fields that an agent may use to report additional status.
36838 If the trace is not running, the agent may report any of several
36839 explanations as one of the optional fields:
36844 No trace has been run yet.
36846 @item tstop[:@var{text}]:0
36847 The trace was stopped by a user-originated stop command. The optional
36848 @var{text} field is a user-supplied string supplied as part of the
36849 stop command (for instance, an explanation of why the trace was
36850 stopped manually). It is hex-encoded.
36853 The trace stopped because the trace buffer filled up.
36855 @item tdisconnected:0
36856 The trace stopped because @value{GDBN} disconnected from the target.
36858 @item tpasscount:@var{tpnum}
36859 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36861 @item terror:@var{text}:@var{tpnum}
36862 The trace stopped because tracepoint @var{tpnum} had an error. The
36863 string @var{text} is available to describe the nature of the error
36864 (for instance, a divide by zero in the condition expression).
36865 @var{text} is hex encoded.
36868 The trace stopped for some other reason.
36872 Additional optional fields supply statistical and other information.
36873 Although not required, they are extremely useful for users monitoring
36874 the progress of a trace run. If a trace has stopped, and these
36875 numbers are reported, they must reflect the state of the just-stopped
36880 @item tframes:@var{n}
36881 The number of trace frames in the buffer.
36883 @item tcreated:@var{n}
36884 The total number of trace frames created during the run. This may
36885 be larger than the trace frame count, if the buffer is circular.
36887 @item tsize:@var{n}
36888 The total size of the trace buffer, in bytes.
36890 @item tfree:@var{n}
36891 The number of bytes still unused in the buffer.
36893 @item circular:@var{n}
36894 The value of the circular trace buffer flag. @code{1} means that the
36895 trace buffer is circular and old trace frames will be discarded if
36896 necessary to make room, @code{0} means that the trace buffer is linear
36899 @item disconn:@var{n}
36900 The value of the disconnected tracing flag. @code{1} means that
36901 tracing will continue after @value{GDBN} disconnects, @code{0} means
36902 that the trace run will stop.
36906 @item qTP:@var{tp}:@var{addr}
36907 @cindex tracepoint status, remote request
36908 @cindex @samp{qTP} packet
36909 Ask the stub for the current state of tracepoint number @var{tp} at
36910 address @var{addr}.
36914 @item V@var{hits}:@var{usage}
36915 The tracepoint has been hit @var{hits} times so far during the trace
36916 run, and accounts for @var{usage} in the trace buffer. Note that
36917 @code{while-stepping} steps are not counted as separate hits, but the
36918 steps' space consumption is added into the usage number.
36922 @item qTV:@var{var}
36923 @cindex trace state variable value, remote request
36924 @cindex @samp{qTV} packet
36925 Ask the stub for the value of the trace state variable number @var{var}.
36930 The value of the variable is @var{value}. This will be the current
36931 value of the variable if the user is examining a running target, or a
36932 saved value if the variable was collected in the trace frame that the
36933 user is looking at. Note that multiple requests may result in
36934 different reply values, such as when requesting values while the
36935 program is running.
36938 The value of the variable is unknown. This would occur, for example,
36939 if the user is examining a trace frame in which the requested variable
36945 These packets request data about tracepoints that are being used by
36946 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36947 of data, and multiple @code{qTsP} to get additional pieces. Replies
36948 to these packets generally take the form of the @code{QTDP} packets
36949 that define tracepoints. (FIXME add detailed syntax)
36953 These packets request data about trace state variables that are on the
36954 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36955 and multiple @code{qTsV} to get additional variables. Replies to
36956 these packets follow the syntax of the @code{QTDV} packets that define
36957 trace state variables.
36961 These packets request data about static tracepoint markers that exist
36962 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36963 first piece of data, and multiple @code{qTsSTM} to get additional
36964 pieces. Replies to these packets take the following form:
36968 @item m @var{address}:@var{id}:@var{extra}
36970 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36971 a comma-separated list of markers
36973 (lower case letter @samp{L}) denotes end of list.
36975 An error occurred. @var{nn} are hex digits.
36977 An empty reply indicates that the request is not supported by the
36981 @var{address} is encoded in hex.
36982 @var{id} and @var{extra} are strings encoded in hex.
36984 In response to each query, the target will reply with a list of one or
36985 more markers, separated by commas. @value{GDBN} will respond to each
36986 reply with a request for more markers (using the @samp{qs} form of the
36987 query), until the target responds with @samp{l} (lower-case ell, for
36990 @item qTSTMat:@var{address}
36991 This packets requests data about static tracepoint markers in the
36992 target program at @var{address}. Replies to this packet follow the
36993 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36994 tracepoint markers.
36996 @item QTSave:@var{filename}
36997 This packet directs the target to save trace data to the file name
36998 @var{filename} in the target's filesystem. @var{filename} is encoded
36999 as a hex string; the interpretation of the file name (relative vs
37000 absolute, wild cards, etc) is up to the target.
37002 @item qTBuffer:@var{offset},@var{len}
37003 Return up to @var{len} bytes of the current contents of trace buffer,
37004 starting at @var{offset}. The trace buffer is treated as if it were
37005 a contiguous collection of traceframes, as per the trace file format.
37006 The reply consists as many hex-encoded bytes as the target can deliver
37007 in a packet; it is not an error to return fewer than were asked for.
37008 A reply consisting of just @code{l} indicates that no bytes are
37011 @item QTBuffer:circular:@var{value}
37012 This packet directs the target to use a circular trace buffer if
37013 @var{value} is 1, or a linear buffer if the value is 0.
37015 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37016 This packet adds optional textual notes to the trace run. Allowable
37017 types include @code{user}, @code{notes}, and @code{tstop}, the
37018 @var{text} fields are arbitrary strings, hex-encoded.
37022 @subsection Relocate instruction reply packet
37023 When installing fast tracepoints in memory, the target may need to
37024 relocate the instruction currently at the tracepoint address to a
37025 different address in memory. For most instructions, a simple copy is
37026 enough, but, for example, call instructions that implicitly push the
37027 return address on the stack, and relative branches or other
37028 PC-relative instructions require offset adjustment, so that the effect
37029 of executing the instruction at a different address is the same as if
37030 it had executed in the original location.
37032 In response to several of the tracepoint packets, the target may also
37033 respond with a number of intermediate @samp{qRelocInsn} request
37034 packets before the final result packet, to have @value{GDBN} handle
37035 this relocation operation. If a packet supports this mechanism, its
37036 documentation will explicitly say so. See for example the above
37037 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37038 format of the request is:
37041 @item qRelocInsn:@var{from};@var{to}
37043 This requests @value{GDBN} to copy instruction at address @var{from}
37044 to address @var{to}, possibly adjusted so that executing the
37045 instruction at @var{to} has the same effect as executing it at
37046 @var{from}. @value{GDBN} writes the adjusted instruction to target
37047 memory starting at @var{to}.
37052 @item qRelocInsn:@var{adjusted_size}
37053 Informs the stub the relocation is complete. @var{adjusted_size} is
37054 the length in bytes of resulting relocated instruction sequence.
37056 A badly formed request was detected, or an error was encountered while
37057 relocating the instruction.
37060 @node Host I/O Packets
37061 @section Host I/O Packets
37062 @cindex Host I/O, remote protocol
37063 @cindex file transfer, remote protocol
37065 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37066 operations on the far side of a remote link. For example, Host I/O is
37067 used to upload and download files to a remote target with its own
37068 filesystem. Host I/O uses the same constant values and data structure
37069 layout as the target-initiated File-I/O protocol. However, the
37070 Host I/O packets are structured differently. The target-initiated
37071 protocol relies on target memory to store parameters and buffers.
37072 Host I/O requests are initiated by @value{GDBN}, and the
37073 target's memory is not involved. @xref{File-I/O Remote Protocol
37074 Extension}, for more details on the target-initiated protocol.
37076 The Host I/O request packets all encode a single operation along with
37077 its arguments. They have this format:
37081 @item vFile:@var{operation}: @var{parameter}@dots{}
37082 @var{operation} is the name of the particular request; the target
37083 should compare the entire packet name up to the second colon when checking
37084 for a supported operation. The format of @var{parameter} depends on
37085 the operation. Numbers are always passed in hexadecimal. Negative
37086 numbers have an explicit minus sign (i.e.@: two's complement is not
37087 used). Strings (e.g.@: filenames) are encoded as a series of
37088 hexadecimal bytes. The last argument to a system call may be a
37089 buffer of escaped binary data (@pxref{Binary Data}).
37093 The valid responses to Host I/O packets are:
37097 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37098 @var{result} is the integer value returned by this operation, usually
37099 non-negative for success and -1 for errors. If an error has occured,
37100 @var{errno} will be included in the result. @var{errno} will have a
37101 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37102 operations which return data, @var{attachment} supplies the data as a
37103 binary buffer. Binary buffers in response packets are escaped in the
37104 normal way (@pxref{Binary Data}). See the individual packet
37105 documentation for the interpretation of @var{result} and
37109 An empty response indicates that this operation is not recognized.
37113 These are the supported Host I/O operations:
37116 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
37117 Open a file at @var{pathname} and return a file descriptor for it, or
37118 return -1 if an error occurs. @var{pathname} is a string,
37119 @var{flags} is an integer indicating a mask of open flags
37120 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37121 of mode bits to use if the file is created (@pxref{mode_t Values}).
37122 @xref{open}, for details of the open flags and mode values.
37124 @item vFile:close: @var{fd}
37125 Close the open file corresponding to @var{fd} and return 0, or
37126 -1 if an error occurs.
37128 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37129 Read data from the open file corresponding to @var{fd}. Up to
37130 @var{count} bytes will be read from the file, starting at @var{offset}
37131 relative to the start of the file. The target may read fewer bytes;
37132 common reasons include packet size limits and an end-of-file
37133 condition. The number of bytes read is returned. Zero should only be
37134 returned for a successful read at the end of the file, or if
37135 @var{count} was zero.
37137 The data read should be returned as a binary attachment on success.
37138 If zero bytes were read, the response should include an empty binary
37139 attachment (i.e.@: a trailing semicolon). The return value is the
37140 number of target bytes read; the binary attachment may be longer if
37141 some characters were escaped.
37143 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37144 Write @var{data} (a binary buffer) to the open file corresponding
37145 to @var{fd}. Start the write at @var{offset} from the start of the
37146 file. Unlike many @code{write} system calls, there is no
37147 separate @var{count} argument; the length of @var{data} in the
37148 packet is used. @samp{vFile:write} returns the number of bytes written,
37149 which may be shorter than the length of @var{data}, or -1 if an
37152 @item vFile:unlink: @var{pathname}
37153 Delete the file at @var{pathname} on the target. Return 0,
37154 or -1 if an error occurs. @var{pathname} is a string.
37156 @item vFile:readlink: @var{filename}
37157 Read value of symbolic link @var{filename} on the target. Return
37158 the number of bytes read, or -1 if an error occurs.
37160 The data read should be returned as a binary attachment on success.
37161 If zero bytes were read, the response should include an empty binary
37162 attachment (i.e.@: a trailing semicolon). The return value is the
37163 number of target bytes read; the binary attachment may be longer if
37164 some characters were escaped.
37169 @section Interrupts
37170 @cindex interrupts (remote protocol)
37172 When a program on the remote target is running, @value{GDBN} may
37173 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37174 a @code{BREAK} followed by @code{g},
37175 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37177 The precise meaning of @code{BREAK} is defined by the transport
37178 mechanism and may, in fact, be undefined. @value{GDBN} does not
37179 currently define a @code{BREAK} mechanism for any of the network
37180 interfaces except for TCP, in which case @value{GDBN} sends the
37181 @code{telnet} BREAK sequence.
37183 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37184 transport mechanisms. It is represented by sending the single byte
37185 @code{0x03} without any of the usual packet overhead described in
37186 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37187 transmitted as part of a packet, it is considered to be packet data
37188 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37189 (@pxref{X packet}), used for binary downloads, may include an unescaped
37190 @code{0x03} as part of its packet.
37192 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37193 When Linux kernel receives this sequence from serial port,
37194 it stops execution and connects to gdb.
37196 Stubs are not required to recognize these interrupt mechanisms and the
37197 precise meaning associated with receipt of the interrupt is
37198 implementation defined. If the target supports debugging of multiple
37199 threads and/or processes, it should attempt to interrupt all
37200 currently-executing threads and processes.
37201 If the stub is successful at interrupting the
37202 running program, it should send one of the stop
37203 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37204 of successfully stopping the program in all-stop mode, and a stop reply
37205 for each stopped thread in non-stop mode.
37206 Interrupts received while the
37207 program is stopped are discarded.
37209 @node Notification Packets
37210 @section Notification Packets
37211 @cindex notification packets
37212 @cindex packets, notification
37214 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37215 packets that require no acknowledgment. Both the GDB and the stub
37216 may send notifications (although the only notifications defined at
37217 present are sent by the stub). Notifications carry information
37218 without incurring the round-trip latency of an acknowledgment, and so
37219 are useful for low-impact communications where occasional packet loss
37222 A notification packet has the form @samp{% @var{data} #
37223 @var{checksum}}, where @var{data} is the content of the notification,
37224 and @var{checksum} is a checksum of @var{data}, computed and formatted
37225 as for ordinary @value{GDBN} packets. A notification's @var{data}
37226 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37227 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37228 to acknowledge the notification's receipt or to report its corruption.
37230 Every notification's @var{data} begins with a name, which contains no
37231 colon characters, followed by a colon character.
37233 Recipients should silently ignore corrupted notifications and
37234 notifications they do not understand. Recipients should restart
37235 timeout periods on receipt of a well-formed notification, whether or
37236 not they understand it.
37238 Senders should only send the notifications described here when this
37239 protocol description specifies that they are permitted. In the
37240 future, we may extend the protocol to permit existing notifications in
37241 new contexts; this rule helps older senders avoid confusing newer
37244 (Older versions of @value{GDBN} ignore bytes received until they see
37245 the @samp{$} byte that begins an ordinary packet, so new stubs may
37246 transmit notifications without fear of confusing older clients. There
37247 are no notifications defined for @value{GDBN} to send at the moment, but we
37248 assume that most older stubs would ignore them, as well.)
37250 The following notification packets from the stub to @value{GDBN} are
37254 @item Stop: @var{reply}
37255 Report an asynchronous stop event in non-stop mode.
37256 The @var{reply} has the form of a stop reply, as
37257 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37258 for information on how these notifications are acknowledged by
37262 @node Remote Non-Stop
37263 @section Remote Protocol Support for Non-Stop Mode
37265 @value{GDBN}'s remote protocol supports non-stop debugging of
37266 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37267 supports non-stop mode, it should report that to @value{GDBN} by including
37268 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37270 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37271 establishing a new connection with the stub. Entering non-stop mode
37272 does not alter the state of any currently-running threads, but targets
37273 must stop all threads in any already-attached processes when entering
37274 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37275 probe the target state after a mode change.
37277 In non-stop mode, when an attached process encounters an event that
37278 would otherwise be reported with a stop reply, it uses the
37279 asynchronous notification mechanism (@pxref{Notification Packets}) to
37280 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37281 in all processes are stopped when a stop reply is sent, in non-stop
37282 mode only the thread reporting the stop event is stopped. That is,
37283 when reporting a @samp{S} or @samp{T} response to indicate completion
37284 of a step operation, hitting a breakpoint, or a fault, only the
37285 affected thread is stopped; any other still-running threads continue
37286 to run. When reporting a @samp{W} or @samp{X} response, all running
37287 threads belonging to other attached processes continue to run.
37289 Only one stop reply notification at a time may be pending; if
37290 additional stop events occur before @value{GDBN} has acknowledged the
37291 previous notification, they must be queued by the stub for later
37292 synchronous transmission in response to @samp{vStopped} packets from
37293 @value{GDBN}. Because the notification mechanism is unreliable,
37294 the stub is permitted to resend a stop reply notification
37295 if it believes @value{GDBN} may not have received it. @value{GDBN}
37296 ignores additional stop reply notifications received before it has
37297 finished processing a previous notification and the stub has completed
37298 sending any queued stop events.
37300 Otherwise, @value{GDBN} must be prepared to receive a stop reply
37301 notification at any time. Specifically, they may appear when
37302 @value{GDBN} is not otherwise reading input from the stub, or when
37303 @value{GDBN} is expecting to read a normal synchronous response or a
37304 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37305 Notification packets are distinct from any other communication from
37306 the stub so there is no ambiguity.
37308 After receiving a stop reply notification, @value{GDBN} shall
37309 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
37310 as a regular, synchronous request to the stub. Such acknowledgment
37311 is not required to happen immediately, as @value{GDBN} is permitted to
37312 send other, unrelated packets to the stub first, which the stub should
37315 Upon receiving a @samp{vStopped} packet, if the stub has other queued
37316 stop events to report to @value{GDBN}, it shall respond by sending a
37317 normal stop reply response. @value{GDBN} shall then send another
37318 @samp{vStopped} packet to solicit further responses; again, it is
37319 permitted to send other, unrelated packets as well which the stub
37320 should process normally.
37322 If the stub receives a @samp{vStopped} packet and there are no
37323 additional stop events to report, the stub shall return an @samp{OK}
37324 response. At this point, if further stop events occur, the stub shall
37325 send a new stop reply notification, @value{GDBN} shall accept the
37326 notification, and the process shall be repeated.
37328 In non-stop mode, the target shall respond to the @samp{?} packet as
37329 follows. First, any incomplete stop reply notification/@samp{vStopped}
37330 sequence in progress is abandoned. The target must begin a new
37331 sequence reporting stop events for all stopped threads, whether or not
37332 it has previously reported those events to @value{GDBN}. The first
37333 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37334 subsequent stop replies are sent as responses to @samp{vStopped} packets
37335 using the mechanism described above. The target must not send
37336 asynchronous stop reply notifications until the sequence is complete.
37337 If all threads are running when the target receives the @samp{?} packet,
37338 or if the target is not attached to any process, it shall respond
37341 @node Packet Acknowledgment
37342 @section Packet Acknowledgment
37344 @cindex acknowledgment, for @value{GDBN} remote
37345 @cindex packet acknowledgment, for @value{GDBN} remote
37346 By default, when either the host or the target machine receives a packet,
37347 the first response expected is an acknowledgment: either @samp{+} (to indicate
37348 the package was received correctly) or @samp{-} (to request retransmission).
37349 This mechanism allows the @value{GDBN} remote protocol to operate over
37350 unreliable transport mechanisms, such as a serial line.
37352 In cases where the transport mechanism is itself reliable (such as a pipe or
37353 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37354 It may be desirable to disable them in that case to reduce communication
37355 overhead, or for other reasons. This can be accomplished by means of the
37356 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37358 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37359 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37360 and response format still includes the normal checksum, as described in
37361 @ref{Overview}, but the checksum may be ignored by the receiver.
37363 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37364 no-acknowledgment mode, it should report that to @value{GDBN}
37365 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37366 @pxref{qSupported}.
37367 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37368 disabled via the @code{set remote noack-packet off} command
37369 (@pxref{Remote Configuration}),
37370 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37371 Only then may the stub actually turn off packet acknowledgments.
37372 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37373 response, which can be safely ignored by the stub.
37375 Note that @code{set remote noack-packet} command only affects negotiation
37376 between @value{GDBN} and the stub when subsequent connections are made;
37377 it does not affect the protocol acknowledgment state for any current
37379 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37380 new connection is established,
37381 there is also no protocol request to re-enable the acknowledgments
37382 for the current connection, once disabled.
37387 Example sequence of a target being re-started. Notice how the restart
37388 does not get any direct output:
37393 @emph{target restarts}
37396 <- @code{T001:1234123412341234}
37400 Example sequence of a target being stepped by a single instruction:
37403 -> @code{G1445@dots{}}
37408 <- @code{T001:1234123412341234}
37412 <- @code{1455@dots{}}
37416 @node File-I/O Remote Protocol Extension
37417 @section File-I/O Remote Protocol Extension
37418 @cindex File-I/O remote protocol extension
37421 * File-I/O Overview::
37422 * Protocol Basics::
37423 * The F Request Packet::
37424 * The F Reply Packet::
37425 * The Ctrl-C Message::
37427 * List of Supported Calls::
37428 * Protocol-specific Representation of Datatypes::
37430 * File-I/O Examples::
37433 @node File-I/O Overview
37434 @subsection File-I/O Overview
37435 @cindex file-i/o overview
37437 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37438 target to use the host's file system and console I/O to perform various
37439 system calls. System calls on the target system are translated into a
37440 remote protocol packet to the host system, which then performs the needed
37441 actions and returns a response packet to the target system.
37442 This simulates file system operations even on targets that lack file systems.
37444 The protocol is defined to be independent of both the host and target systems.
37445 It uses its own internal representation of datatypes and values. Both
37446 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37447 translating the system-dependent value representations into the internal
37448 protocol representations when data is transmitted.
37450 The communication is synchronous. A system call is possible only when
37451 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37452 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37453 the target is stopped to allow deterministic access to the target's
37454 memory. Therefore File-I/O is not interruptible by target signals. On
37455 the other hand, it is possible to interrupt File-I/O by a user interrupt
37456 (@samp{Ctrl-C}) within @value{GDBN}.
37458 The target's request to perform a host system call does not finish
37459 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37460 after finishing the system call, the target returns to continuing the
37461 previous activity (continue, step). No additional continue or step
37462 request from @value{GDBN} is required.
37465 (@value{GDBP}) continue
37466 <- target requests 'system call X'
37467 target is stopped, @value{GDBN} executes system call
37468 -> @value{GDBN} returns result
37469 ... target continues, @value{GDBN} returns to wait for the target
37470 <- target hits breakpoint and sends a Txx packet
37473 The protocol only supports I/O on the console and to regular files on
37474 the host file system. Character or block special devices, pipes,
37475 named pipes, sockets or any other communication method on the host
37476 system are not supported by this protocol.
37478 File I/O is not supported in non-stop mode.
37480 @node Protocol Basics
37481 @subsection Protocol Basics
37482 @cindex protocol basics, file-i/o
37484 The File-I/O protocol uses the @code{F} packet as the request as well
37485 as reply packet. Since a File-I/O system call can only occur when
37486 @value{GDBN} is waiting for a response from the continuing or stepping target,
37487 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37488 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37489 This @code{F} packet contains all information needed to allow @value{GDBN}
37490 to call the appropriate host system call:
37494 A unique identifier for the requested system call.
37497 All parameters to the system call. Pointers are given as addresses
37498 in the target memory address space. Pointers to strings are given as
37499 pointer/length pair. Numerical values are given as they are.
37500 Numerical control flags are given in a protocol-specific representation.
37504 At this point, @value{GDBN} has to perform the following actions.
37508 If the parameters include pointer values to data needed as input to a
37509 system call, @value{GDBN} requests this data from the target with a
37510 standard @code{m} packet request. This additional communication has to be
37511 expected by the target implementation and is handled as any other @code{m}
37515 @value{GDBN} translates all value from protocol representation to host
37516 representation as needed. Datatypes are coerced into the host types.
37519 @value{GDBN} calls the system call.
37522 It then coerces datatypes back to protocol representation.
37525 If the system call is expected to return data in buffer space specified
37526 by pointer parameters to the call, the data is transmitted to the
37527 target using a @code{M} or @code{X} packet. This packet has to be expected
37528 by the target implementation and is handled as any other @code{M} or @code{X}
37533 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37534 necessary information for the target to continue. This at least contains
37541 @code{errno}, if has been changed by the system call.
37548 After having done the needed type and value coercion, the target continues
37549 the latest continue or step action.
37551 @node The F Request Packet
37552 @subsection The @code{F} Request Packet
37553 @cindex file-i/o request packet
37554 @cindex @code{F} request packet
37556 The @code{F} request packet has the following format:
37559 @item F@var{call-id},@var{parameter@dots{}}
37561 @var{call-id} is the identifier to indicate the host system call to be called.
37562 This is just the name of the function.
37564 @var{parameter@dots{}} are the parameters to the system call.
37565 Parameters are hexadecimal integer values, either the actual values in case
37566 of scalar datatypes, pointers to target buffer space in case of compound
37567 datatypes and unspecified memory areas, or pointer/length pairs in case
37568 of string parameters. These are appended to the @var{call-id} as a
37569 comma-delimited list. All values are transmitted in ASCII
37570 string representation, pointer/length pairs separated by a slash.
37576 @node The F Reply Packet
37577 @subsection The @code{F} Reply Packet
37578 @cindex file-i/o reply packet
37579 @cindex @code{F} reply packet
37581 The @code{F} reply packet has the following format:
37585 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37587 @var{retcode} is the return code of the system call as hexadecimal value.
37589 @var{errno} is the @code{errno} set by the call, in protocol-specific
37591 This parameter can be omitted if the call was successful.
37593 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37594 case, @var{errno} must be sent as well, even if the call was successful.
37595 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37602 or, if the call was interrupted before the host call has been performed:
37609 assuming 4 is the protocol-specific representation of @code{EINTR}.
37614 @node The Ctrl-C Message
37615 @subsection The @samp{Ctrl-C} Message
37616 @cindex ctrl-c message, in file-i/o protocol
37618 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37619 reply packet (@pxref{The F Reply Packet}),
37620 the target should behave as if it had
37621 gotten a break message. The meaning for the target is ``system call
37622 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37623 (as with a break message) and return to @value{GDBN} with a @code{T02}
37626 It's important for the target to know in which
37627 state the system call was interrupted. There are two possible cases:
37631 The system call hasn't been performed on the host yet.
37634 The system call on the host has been finished.
37638 These two states can be distinguished by the target by the value of the
37639 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37640 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37641 on POSIX systems. In any other case, the target may presume that the
37642 system call has been finished --- successfully or not --- and should behave
37643 as if the break message arrived right after the system call.
37645 @value{GDBN} must behave reliably. If the system call has not been called
37646 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37647 @code{errno} in the packet. If the system call on the host has been finished
37648 before the user requests a break, the full action must be finished by
37649 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37650 The @code{F} packet may only be sent when either nothing has happened
37651 or the full action has been completed.
37654 @subsection Console I/O
37655 @cindex console i/o as part of file-i/o
37657 By default and if not explicitly closed by the target system, the file
37658 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37659 on the @value{GDBN} console is handled as any other file output operation
37660 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37661 by @value{GDBN} so that after the target read request from file descriptor
37662 0 all following typing is buffered until either one of the following
37667 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37669 system call is treated as finished.
37672 The user presses @key{RET}. This is treated as end of input with a trailing
37676 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37677 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37681 If the user has typed more characters than fit in the buffer given to
37682 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37683 either another @code{read(0, @dots{})} is requested by the target, or debugging
37684 is stopped at the user's request.
37687 @node List of Supported Calls
37688 @subsection List of Supported Calls
37689 @cindex list of supported file-i/o calls
37706 @unnumberedsubsubsec open
37707 @cindex open, file-i/o system call
37712 int open(const char *pathname, int flags);
37713 int open(const char *pathname, int flags, mode_t mode);
37717 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37720 @var{flags} is the bitwise @code{OR} of the following values:
37724 If the file does not exist it will be created. The host
37725 rules apply as far as file ownership and time stamps
37729 When used with @code{O_CREAT}, if the file already exists it is
37730 an error and open() fails.
37733 If the file already exists and the open mode allows
37734 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37735 truncated to zero length.
37738 The file is opened in append mode.
37741 The file is opened for reading only.
37744 The file is opened for writing only.
37747 The file is opened for reading and writing.
37751 Other bits are silently ignored.
37755 @var{mode} is the bitwise @code{OR} of the following values:
37759 User has read permission.
37762 User has write permission.
37765 Group has read permission.
37768 Group has write permission.
37771 Others have read permission.
37774 Others have write permission.
37778 Other bits are silently ignored.
37781 @item Return value:
37782 @code{open} returns the new file descriptor or -1 if an error
37789 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37792 @var{pathname} refers to a directory.
37795 The requested access is not allowed.
37798 @var{pathname} was too long.
37801 A directory component in @var{pathname} does not exist.
37804 @var{pathname} refers to a device, pipe, named pipe or socket.
37807 @var{pathname} refers to a file on a read-only filesystem and
37808 write access was requested.
37811 @var{pathname} is an invalid pointer value.
37814 No space on device to create the file.
37817 The process already has the maximum number of files open.
37820 The limit on the total number of files open on the system
37824 The call was interrupted by the user.
37830 @unnumberedsubsubsec close
37831 @cindex close, file-i/o system call
37840 @samp{Fclose,@var{fd}}
37842 @item Return value:
37843 @code{close} returns zero on success, or -1 if an error occurred.
37849 @var{fd} isn't a valid open file descriptor.
37852 The call was interrupted by the user.
37858 @unnumberedsubsubsec read
37859 @cindex read, file-i/o system call
37864 int read(int fd, void *buf, unsigned int count);
37868 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37870 @item Return value:
37871 On success, the number of bytes read is returned.
37872 Zero indicates end of file. If count is zero, read
37873 returns zero as well. On error, -1 is returned.
37879 @var{fd} is not a valid file descriptor or is not open for
37883 @var{bufptr} is an invalid pointer value.
37886 The call was interrupted by the user.
37892 @unnumberedsubsubsec write
37893 @cindex write, file-i/o system call
37898 int write(int fd, const void *buf, unsigned int count);
37902 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37904 @item Return value:
37905 On success, the number of bytes written are returned.
37906 Zero indicates nothing was written. On error, -1
37913 @var{fd} is not a valid file descriptor or is not open for
37917 @var{bufptr} is an invalid pointer value.
37920 An attempt was made to write a file that exceeds the
37921 host-specific maximum file size allowed.
37924 No space on device to write the data.
37927 The call was interrupted by the user.
37933 @unnumberedsubsubsec lseek
37934 @cindex lseek, file-i/o system call
37939 long lseek (int fd, long offset, int flag);
37943 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37945 @var{flag} is one of:
37949 The offset is set to @var{offset} bytes.
37952 The offset is set to its current location plus @var{offset}
37956 The offset is set to the size of the file plus @var{offset}
37960 @item Return value:
37961 On success, the resulting unsigned offset in bytes from
37962 the beginning of the file is returned. Otherwise, a
37963 value of -1 is returned.
37969 @var{fd} is not a valid open file descriptor.
37972 @var{fd} is associated with the @value{GDBN} console.
37975 @var{flag} is not a proper value.
37978 The call was interrupted by the user.
37984 @unnumberedsubsubsec rename
37985 @cindex rename, file-i/o system call
37990 int rename(const char *oldpath, const char *newpath);
37994 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37996 @item Return value:
37997 On success, zero is returned. On error, -1 is returned.
38003 @var{newpath} is an existing directory, but @var{oldpath} is not a
38007 @var{newpath} is a non-empty directory.
38010 @var{oldpath} or @var{newpath} is a directory that is in use by some
38014 An attempt was made to make a directory a subdirectory
38018 A component used as a directory in @var{oldpath} or new
38019 path is not a directory. Or @var{oldpath} is a directory
38020 and @var{newpath} exists but is not a directory.
38023 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38026 No access to the file or the path of the file.
38030 @var{oldpath} or @var{newpath} was too long.
38033 A directory component in @var{oldpath} or @var{newpath} does not exist.
38036 The file is on a read-only filesystem.
38039 The device containing the file has no room for the new
38043 The call was interrupted by the user.
38049 @unnumberedsubsubsec unlink
38050 @cindex unlink, file-i/o system call
38055 int unlink(const char *pathname);
38059 @samp{Funlink,@var{pathnameptr}/@var{len}}
38061 @item Return value:
38062 On success, zero is returned. On error, -1 is returned.
38068 No access to the file or the path of the file.
38071 The system does not allow unlinking of directories.
38074 The file @var{pathname} cannot be unlinked because it's
38075 being used by another process.
38078 @var{pathnameptr} is an invalid pointer value.
38081 @var{pathname} was too long.
38084 A directory component in @var{pathname} does not exist.
38087 A component of the path is not a directory.
38090 The file is on a read-only filesystem.
38093 The call was interrupted by the user.
38099 @unnumberedsubsubsec stat/fstat
38100 @cindex fstat, file-i/o system call
38101 @cindex stat, file-i/o system call
38106 int stat(const char *pathname, struct stat *buf);
38107 int fstat(int fd, struct stat *buf);
38111 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38112 @samp{Ffstat,@var{fd},@var{bufptr}}
38114 @item Return value:
38115 On success, zero is returned. On error, -1 is returned.
38121 @var{fd} is not a valid open file.
38124 A directory component in @var{pathname} does not exist or the
38125 path is an empty string.
38128 A component of the path is not a directory.
38131 @var{pathnameptr} is an invalid pointer value.
38134 No access to the file or the path of the file.
38137 @var{pathname} was too long.
38140 The call was interrupted by the user.
38146 @unnumberedsubsubsec gettimeofday
38147 @cindex gettimeofday, file-i/o system call
38152 int gettimeofday(struct timeval *tv, void *tz);
38156 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38158 @item Return value:
38159 On success, 0 is returned, -1 otherwise.
38165 @var{tz} is a non-NULL pointer.
38168 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38174 @unnumberedsubsubsec isatty
38175 @cindex isatty, file-i/o system call
38180 int isatty(int fd);
38184 @samp{Fisatty,@var{fd}}
38186 @item Return value:
38187 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38193 The call was interrupted by the user.
38198 Note that the @code{isatty} call is treated as a special case: it returns
38199 1 to the target if the file descriptor is attached
38200 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38201 would require implementing @code{ioctl} and would be more complex than
38206 @unnumberedsubsubsec system
38207 @cindex system, file-i/o system call
38212 int system(const char *command);
38216 @samp{Fsystem,@var{commandptr}/@var{len}}
38218 @item Return value:
38219 If @var{len} is zero, the return value indicates whether a shell is
38220 available. A zero return value indicates a shell is not available.
38221 For non-zero @var{len}, the value returned is -1 on error and the
38222 return status of the command otherwise. Only the exit status of the
38223 command is returned, which is extracted from the host's @code{system}
38224 return value by calling @code{WEXITSTATUS(retval)}. In case
38225 @file{/bin/sh} could not be executed, 127 is returned.
38231 The call was interrupted by the user.
38236 @value{GDBN} takes over the full task of calling the necessary host calls
38237 to perform the @code{system} call. The return value of @code{system} on
38238 the host is simplified before it's returned
38239 to the target. Any termination signal information from the child process
38240 is discarded, and the return value consists
38241 entirely of the exit status of the called command.
38243 Due to security concerns, the @code{system} call is by default refused
38244 by @value{GDBN}. The user has to allow this call explicitly with the
38245 @code{set remote system-call-allowed 1} command.
38248 @item set remote system-call-allowed
38249 @kindex set remote system-call-allowed
38250 Control whether to allow the @code{system} calls in the File I/O
38251 protocol for the remote target. The default is zero (disabled).
38253 @item show remote system-call-allowed
38254 @kindex show remote system-call-allowed
38255 Show whether the @code{system} calls are allowed in the File I/O
38259 @node Protocol-specific Representation of Datatypes
38260 @subsection Protocol-specific Representation of Datatypes
38261 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38264 * Integral Datatypes::
38266 * Memory Transfer::
38271 @node Integral Datatypes
38272 @unnumberedsubsubsec Integral Datatypes
38273 @cindex integral datatypes, in file-i/o protocol
38275 The integral datatypes used in the system calls are @code{int},
38276 @code{unsigned int}, @code{long}, @code{unsigned long},
38277 @code{mode_t}, and @code{time_t}.
38279 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38280 implemented as 32 bit values in this protocol.
38282 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38284 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38285 in @file{limits.h}) to allow range checking on host and target.
38287 @code{time_t} datatypes are defined as seconds since the Epoch.
38289 All integral datatypes transferred as part of a memory read or write of a
38290 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38293 @node Pointer Values
38294 @unnumberedsubsubsec Pointer Values
38295 @cindex pointer values, in file-i/o protocol
38297 Pointers to target data are transmitted as they are. An exception
38298 is made for pointers to buffers for which the length isn't
38299 transmitted as part of the function call, namely strings. Strings
38300 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38307 which is a pointer to data of length 18 bytes at position 0x1aaf.
38308 The length is defined as the full string length in bytes, including
38309 the trailing null byte. For example, the string @code{"hello world"}
38310 at address 0x123456 is transmitted as
38316 @node Memory Transfer
38317 @unnumberedsubsubsec Memory Transfer
38318 @cindex memory transfer, in file-i/o protocol
38320 Structured data which is transferred using a memory read or write (for
38321 example, a @code{struct stat}) is expected to be in a protocol-specific format
38322 with all scalar multibyte datatypes being big endian. Translation to
38323 this representation needs to be done both by the target before the @code{F}
38324 packet is sent, and by @value{GDBN} before
38325 it transfers memory to the target. Transferred pointers to structured
38326 data should point to the already-coerced data at any time.
38330 @unnumberedsubsubsec struct stat
38331 @cindex struct stat, in file-i/o protocol
38333 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38334 is defined as follows:
38338 unsigned int st_dev; /* device */
38339 unsigned int st_ino; /* inode */
38340 mode_t st_mode; /* protection */
38341 unsigned int st_nlink; /* number of hard links */
38342 unsigned int st_uid; /* user ID of owner */
38343 unsigned int st_gid; /* group ID of owner */
38344 unsigned int st_rdev; /* device type (if inode device) */
38345 unsigned long st_size; /* total size, in bytes */
38346 unsigned long st_blksize; /* blocksize for filesystem I/O */
38347 unsigned long st_blocks; /* number of blocks allocated */
38348 time_t st_atime; /* time of last access */
38349 time_t st_mtime; /* time of last modification */
38350 time_t st_ctime; /* time of last change */
38354 The integral datatypes conform to the definitions given in the
38355 appropriate section (see @ref{Integral Datatypes}, for details) so this
38356 structure is of size 64 bytes.
38358 The values of several fields have a restricted meaning and/or
38364 A value of 0 represents a file, 1 the console.
38367 No valid meaning for the target. Transmitted unchanged.
38370 Valid mode bits are described in @ref{Constants}. Any other
38371 bits have currently no meaning for the target.
38376 No valid meaning for the target. Transmitted unchanged.
38381 These values have a host and file system dependent
38382 accuracy. Especially on Windows hosts, the file system may not
38383 support exact timing values.
38386 The target gets a @code{struct stat} of the above representation and is
38387 responsible for coercing it to the target representation before
38390 Note that due to size differences between the host, target, and protocol
38391 representations of @code{struct stat} members, these members could eventually
38392 get truncated on the target.
38394 @node struct timeval
38395 @unnumberedsubsubsec struct timeval
38396 @cindex struct timeval, in file-i/o protocol
38398 The buffer of type @code{struct timeval} used by the File-I/O protocol
38399 is defined as follows:
38403 time_t tv_sec; /* second */
38404 long tv_usec; /* microsecond */
38408 The integral datatypes conform to the definitions given in the
38409 appropriate section (see @ref{Integral Datatypes}, for details) so this
38410 structure is of size 8 bytes.
38413 @subsection Constants
38414 @cindex constants, in file-i/o protocol
38416 The following values are used for the constants inside of the
38417 protocol. @value{GDBN} and target are responsible for translating these
38418 values before and after the call as needed.
38429 @unnumberedsubsubsec Open Flags
38430 @cindex open flags, in file-i/o protocol
38432 All values are given in hexadecimal representation.
38444 @node mode_t Values
38445 @unnumberedsubsubsec mode_t Values
38446 @cindex mode_t values, in file-i/o protocol
38448 All values are given in octal representation.
38465 @unnumberedsubsubsec Errno Values
38466 @cindex errno values, in file-i/o protocol
38468 All values are given in decimal representation.
38493 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38494 any error value not in the list of supported error numbers.
38497 @unnumberedsubsubsec Lseek Flags
38498 @cindex lseek flags, in file-i/o protocol
38507 @unnumberedsubsubsec Limits
38508 @cindex limits, in file-i/o protocol
38510 All values are given in decimal representation.
38513 INT_MIN -2147483648
38515 UINT_MAX 4294967295
38516 LONG_MIN -9223372036854775808
38517 LONG_MAX 9223372036854775807
38518 ULONG_MAX 18446744073709551615
38521 @node File-I/O Examples
38522 @subsection File-I/O Examples
38523 @cindex file-i/o examples
38525 Example sequence of a write call, file descriptor 3, buffer is at target
38526 address 0x1234, 6 bytes should be written:
38529 <- @code{Fwrite,3,1234,6}
38530 @emph{request memory read from target}
38533 @emph{return "6 bytes written"}
38537 Example sequence of a read call, file descriptor 3, buffer is at target
38538 address 0x1234, 6 bytes should be read:
38541 <- @code{Fread,3,1234,6}
38542 @emph{request memory write to target}
38543 -> @code{X1234,6:XXXXXX}
38544 @emph{return "6 bytes read"}
38548 Example sequence of a read call, call fails on the host due to invalid
38549 file descriptor (@code{EBADF}):
38552 <- @code{Fread,3,1234,6}
38556 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38560 <- @code{Fread,3,1234,6}
38565 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38569 <- @code{Fread,3,1234,6}
38570 -> @code{X1234,6:XXXXXX}
38574 @node Library List Format
38575 @section Library List Format
38576 @cindex library list format, remote protocol
38578 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38579 same process as your application to manage libraries. In this case,
38580 @value{GDBN} can use the loader's symbol table and normal memory
38581 operations to maintain a list of shared libraries. On other
38582 platforms, the operating system manages loaded libraries.
38583 @value{GDBN} can not retrieve the list of currently loaded libraries
38584 through memory operations, so it uses the @samp{qXfer:libraries:read}
38585 packet (@pxref{qXfer library list read}) instead. The remote stub
38586 queries the target's operating system and reports which libraries
38589 The @samp{qXfer:libraries:read} packet returns an XML document which
38590 lists loaded libraries and their offsets. Each library has an
38591 associated name and one or more segment or section base addresses,
38592 which report where the library was loaded in memory.
38594 For the common case of libraries that are fully linked binaries, the
38595 library should have a list of segments. If the target supports
38596 dynamic linking of a relocatable object file, its library XML element
38597 should instead include a list of allocated sections. The segment or
38598 section bases are start addresses, not relocation offsets; they do not
38599 depend on the library's link-time base addresses.
38601 @value{GDBN} must be linked with the Expat library to support XML
38602 library lists. @xref{Expat}.
38604 A simple memory map, with one loaded library relocated by a single
38605 offset, looks like this:
38609 <library name="/lib/libc.so.6">
38610 <segment address="0x10000000"/>
38615 Another simple memory map, with one loaded library with three
38616 allocated sections (.text, .data, .bss), looks like this:
38620 <library name="sharedlib.o">
38621 <section address="0x10000000"/>
38622 <section address="0x20000000"/>
38623 <section address="0x30000000"/>
38628 The format of a library list is described by this DTD:
38631 <!-- library-list: Root element with versioning -->
38632 <!ELEMENT library-list (library)*>
38633 <!ATTLIST library-list version CDATA #FIXED "1.0">
38634 <!ELEMENT library (segment*, section*)>
38635 <!ATTLIST library name CDATA #REQUIRED>
38636 <!ELEMENT segment EMPTY>
38637 <!ATTLIST segment address CDATA #REQUIRED>
38638 <!ELEMENT section EMPTY>
38639 <!ATTLIST section address CDATA #REQUIRED>
38642 In addition, segments and section descriptors cannot be mixed within a
38643 single library element, and you must supply at least one segment or
38644 section for each library.
38646 @node Library List Format for SVR4 Targets
38647 @section Library List Format for SVR4 Targets
38648 @cindex library list format, remote protocol
38650 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38651 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38652 shared libraries. Still a special library list provided by this packet is
38653 more efficient for the @value{GDBN} remote protocol.
38655 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38656 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38657 target, the following parameters are reported:
38661 @code{name}, the absolute file name from the @code{l_name} field of
38662 @code{struct link_map}.
38664 @code{lm} with address of @code{struct link_map} used for TLS
38665 (Thread Local Storage) access.
38667 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38668 @code{struct link_map}. For prelinked libraries this is not an absolute
38669 memory address. It is a displacement of absolute memory address against
38670 address the file was prelinked to during the library load.
38672 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38675 Additionally the single @code{main-lm} attribute specifies address of
38676 @code{struct link_map} used for the main executable. This parameter is used
38677 for TLS access and its presence is optional.
38679 @value{GDBN} must be linked with the Expat library to support XML
38680 SVR4 library lists. @xref{Expat}.
38682 A simple memory map, with two loaded libraries (which do not use prelink),
38686 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38687 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38689 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38691 </library-list-svr>
38694 The format of an SVR4 library list is described by this DTD:
38697 <!-- library-list-svr4: Root element with versioning -->
38698 <!ELEMENT library-list-svr4 (library)*>
38699 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38700 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38701 <!ELEMENT library EMPTY>
38702 <!ATTLIST library name CDATA #REQUIRED>
38703 <!ATTLIST library lm CDATA #REQUIRED>
38704 <!ATTLIST library l_addr CDATA #REQUIRED>
38705 <!ATTLIST library l_ld CDATA #REQUIRED>
38708 @node Memory Map Format
38709 @section Memory Map Format
38710 @cindex memory map format
38712 To be able to write into flash memory, @value{GDBN} needs to obtain a
38713 memory map from the target. This section describes the format of the
38716 The memory map is obtained using the @samp{qXfer:memory-map:read}
38717 (@pxref{qXfer memory map read}) packet and is an XML document that
38718 lists memory regions.
38720 @value{GDBN} must be linked with the Expat library to support XML
38721 memory maps. @xref{Expat}.
38723 The top-level structure of the document is shown below:
38726 <?xml version="1.0"?>
38727 <!DOCTYPE memory-map
38728 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38729 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38735 Each region can be either:
38740 A region of RAM starting at @var{addr} and extending for @var{length}
38744 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38749 A region of read-only memory:
38752 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38757 A region of flash memory, with erasure blocks @var{blocksize}
38761 <memory type="flash" start="@var{addr}" length="@var{length}">
38762 <property name="blocksize">@var{blocksize}</property>
38768 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38769 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38770 packets to write to addresses in such ranges.
38772 The formal DTD for memory map format is given below:
38775 <!-- ................................................... -->
38776 <!-- Memory Map XML DTD ................................ -->
38777 <!-- File: memory-map.dtd .............................. -->
38778 <!-- .................................... .............. -->
38779 <!-- memory-map.dtd -->
38780 <!-- memory-map: Root element with versioning -->
38781 <!ELEMENT memory-map (memory | property)>
38782 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38783 <!ELEMENT memory (property)>
38784 <!-- memory: Specifies a memory region,
38785 and its type, or device. -->
38786 <!ATTLIST memory type CDATA #REQUIRED
38787 start CDATA #REQUIRED
38788 length CDATA #REQUIRED
38789 device CDATA #IMPLIED>
38790 <!-- property: Generic attribute tag -->
38791 <!ELEMENT property (#PCDATA | property)*>
38792 <!ATTLIST property name CDATA #REQUIRED>
38795 @node Thread List Format
38796 @section Thread List Format
38797 @cindex thread list format
38799 To efficiently update the list of threads and their attributes,
38800 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38801 (@pxref{qXfer threads read}) and obtains the XML document with
38802 the following structure:
38805 <?xml version="1.0"?>
38807 <thread id="id" core="0">
38808 ... description ...
38813 Each @samp{thread} element must have the @samp{id} attribute that
38814 identifies the thread (@pxref{thread-id syntax}). The
38815 @samp{core} attribute, if present, specifies which processor core
38816 the thread was last executing on. The content of the of @samp{thread}
38817 element is interpreted as human-readable auxilliary information.
38819 @node Traceframe Info Format
38820 @section Traceframe Info Format
38821 @cindex traceframe info format
38823 To be able to know which objects in the inferior can be examined when
38824 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38825 memory ranges, registers and trace state variables that have been
38826 collected in a traceframe.
38828 This list is obtained using the @samp{qXfer:traceframe-info:read}
38829 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38831 @value{GDBN} must be linked with the Expat library to support XML
38832 traceframe info discovery. @xref{Expat}.
38834 The top-level structure of the document is shown below:
38837 <?xml version="1.0"?>
38838 <!DOCTYPE traceframe-info
38839 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38840 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38846 Each traceframe block can be either:
38851 A region of collected memory starting at @var{addr} and extending for
38852 @var{length} bytes from there:
38855 <memory start="@var{addr}" length="@var{length}"/>
38860 The formal DTD for the traceframe info format is given below:
38863 <!ELEMENT traceframe-info (memory)* >
38864 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38866 <!ELEMENT memory EMPTY>
38867 <!ATTLIST memory start CDATA #REQUIRED
38868 length CDATA #REQUIRED>
38871 @include agentexpr.texi
38873 @node Target Descriptions
38874 @appendix Target Descriptions
38875 @cindex target descriptions
38877 One of the challenges of using @value{GDBN} to debug embedded systems
38878 is that there are so many minor variants of each processor
38879 architecture in use. It is common practice for vendors to start with
38880 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
38881 and then make changes to adapt it to a particular market niche. Some
38882 architectures have hundreds of variants, available from dozens of
38883 vendors. This leads to a number of problems:
38887 With so many different customized processors, it is difficult for
38888 the @value{GDBN} maintainers to keep up with the changes.
38890 Since individual variants may have short lifetimes or limited
38891 audiences, it may not be worthwhile to carry information about every
38892 variant in the @value{GDBN} source tree.
38894 When @value{GDBN} does support the architecture of the embedded system
38895 at hand, the task of finding the correct architecture name to give the
38896 @command{set architecture} command can be error-prone.
38899 To address these problems, the @value{GDBN} remote protocol allows a
38900 target system to not only identify itself to @value{GDBN}, but to
38901 actually describe its own features. This lets @value{GDBN} support
38902 processor variants it has never seen before --- to the extent that the
38903 descriptions are accurate, and that @value{GDBN} understands them.
38905 @value{GDBN} must be linked with the Expat library to support XML
38906 target descriptions. @xref{Expat}.
38909 * Retrieving Descriptions:: How descriptions are fetched from a target.
38910 * Target Description Format:: The contents of a target description.
38911 * Predefined Target Types:: Standard types available for target
38913 * Standard Target Features:: Features @value{GDBN} knows about.
38916 @node Retrieving Descriptions
38917 @section Retrieving Descriptions
38919 Target descriptions can be read from the target automatically, or
38920 specified by the user manually. The default behavior is to read the
38921 description from the target. @value{GDBN} retrieves it via the remote
38922 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38923 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38924 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38925 XML document, of the form described in @ref{Target Description
38928 Alternatively, you can specify a file to read for the target description.
38929 If a file is set, the target will not be queried. The commands to
38930 specify a file are:
38933 @cindex set tdesc filename
38934 @item set tdesc filename @var{path}
38935 Read the target description from @var{path}.
38937 @cindex unset tdesc filename
38938 @item unset tdesc filename
38939 Do not read the XML target description from a file. @value{GDBN}
38940 will use the description supplied by the current target.
38942 @cindex show tdesc filename
38943 @item show tdesc filename
38944 Show the filename to read for a target description, if any.
38948 @node Target Description Format
38949 @section Target Description Format
38950 @cindex target descriptions, XML format
38952 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38953 document which complies with the Document Type Definition provided in
38954 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38955 means you can use generally available tools like @command{xmllint} to
38956 check that your feature descriptions are well-formed and valid.
38957 However, to help people unfamiliar with XML write descriptions for
38958 their targets, we also describe the grammar here.
38960 Target descriptions can identify the architecture of the remote target
38961 and (for some architectures) provide information about custom register
38962 sets. They can also identify the OS ABI of the remote target.
38963 @value{GDBN} can use this information to autoconfigure for your
38964 target, or to warn you if you connect to an unsupported target.
38966 Here is a simple target description:
38969 <target version="1.0">
38970 <architecture>i386:x86-64</architecture>
38975 This minimal description only says that the target uses
38976 the x86-64 architecture.
38978 A target description has the following overall form, with [ ] marking
38979 optional elements and @dots{} marking repeatable elements. The elements
38980 are explained further below.
38983 <?xml version="1.0"?>
38984 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38985 <target version="1.0">
38986 @r{[}@var{architecture}@r{]}
38987 @r{[}@var{osabi}@r{]}
38988 @r{[}@var{compatible}@r{]}
38989 @r{[}@var{feature}@dots{}@r{]}
38994 The description is generally insensitive to whitespace and line
38995 breaks, under the usual common-sense rules. The XML version
38996 declaration and document type declaration can generally be omitted
38997 (@value{GDBN} does not require them), but specifying them may be
38998 useful for XML validation tools. The @samp{version} attribute for
38999 @samp{<target>} may also be omitted, but we recommend
39000 including it; if future versions of @value{GDBN} use an incompatible
39001 revision of @file{gdb-target.dtd}, they will detect and report
39002 the version mismatch.
39004 @subsection Inclusion
39005 @cindex target descriptions, inclusion
39008 @cindex <xi:include>
39011 It can sometimes be valuable to split a target description up into
39012 several different annexes, either for organizational purposes, or to
39013 share files between different possible target descriptions. You can
39014 divide a description into multiple files by replacing any element of
39015 the target description with an inclusion directive of the form:
39018 <xi:include href="@var{document}"/>
39022 When @value{GDBN} encounters an element of this form, it will retrieve
39023 the named XML @var{document}, and replace the inclusion directive with
39024 the contents of that document. If the current description was read
39025 using @samp{qXfer}, then so will be the included document;
39026 @var{document} will be interpreted as the name of an annex. If the
39027 current description was read from a file, @value{GDBN} will look for
39028 @var{document} as a file in the same directory where it found the
39029 original description.
39031 @subsection Architecture
39032 @cindex <architecture>
39034 An @samp{<architecture>} element has this form:
39037 <architecture>@var{arch}</architecture>
39040 @var{arch} is one of the architectures from the set accepted by
39041 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39044 @cindex @code{<osabi>}
39046 This optional field was introduced in @value{GDBN} version 7.0.
39047 Previous versions of @value{GDBN} ignore it.
39049 An @samp{<osabi>} element has this form:
39052 <osabi>@var{abi-name}</osabi>
39055 @var{abi-name} is an OS ABI name from the same selection accepted by
39056 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39058 @subsection Compatible Architecture
39059 @cindex @code{<compatible>}
39061 This optional field was introduced in @value{GDBN} version 7.0.
39062 Previous versions of @value{GDBN} ignore it.
39064 A @samp{<compatible>} element has this form:
39067 <compatible>@var{arch}</compatible>
39070 @var{arch} is one of the architectures from the set accepted by
39071 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39073 A @samp{<compatible>} element is used to specify that the target
39074 is able to run binaries in some other than the main target architecture
39075 given by the @samp{<architecture>} element. For example, on the
39076 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39077 or @code{powerpc:common64}, but the system is able to run binaries
39078 in the @code{spu} architecture as well. The way to describe this
39079 capability with @samp{<compatible>} is as follows:
39082 <architecture>powerpc:common</architecture>
39083 <compatible>spu</compatible>
39086 @subsection Features
39089 Each @samp{<feature>} describes some logical portion of the target
39090 system. Features are currently used to describe available CPU
39091 registers and the types of their contents. A @samp{<feature>} element
39095 <feature name="@var{name}">
39096 @r{[}@var{type}@dots{}@r{]}
39102 Each feature's name should be unique within the description. The name
39103 of a feature does not matter unless @value{GDBN} has some special
39104 knowledge of the contents of that feature; if it does, the feature
39105 should have its standard name. @xref{Standard Target Features}.
39109 Any register's value is a collection of bits which @value{GDBN} must
39110 interpret. The default interpretation is a two's complement integer,
39111 but other types can be requested by name in the register description.
39112 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39113 Target Types}), and the description can define additional composite types.
39115 Each type element must have an @samp{id} attribute, which gives
39116 a unique (within the containing @samp{<feature>}) name to the type.
39117 Types must be defined before they are used.
39120 Some targets offer vector registers, which can be treated as arrays
39121 of scalar elements. These types are written as @samp{<vector>} elements,
39122 specifying the array element type, @var{type}, and the number of elements,
39126 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39130 If a register's value is usefully viewed in multiple ways, define it
39131 with a union type containing the useful representations. The
39132 @samp{<union>} element contains one or more @samp{<field>} elements,
39133 each of which has a @var{name} and a @var{type}:
39136 <union id="@var{id}">
39137 <field name="@var{name}" type="@var{type}"/>
39143 If a register's value is composed from several separate values, define
39144 it with a structure type. There are two forms of the @samp{<struct>}
39145 element; a @samp{<struct>} element must either contain only bitfields
39146 or contain no bitfields. If the structure contains only bitfields,
39147 its total size in bytes must be specified, each bitfield must have an
39148 explicit start and end, and bitfields are automatically assigned an
39149 integer type. The field's @var{start} should be less than or
39150 equal to its @var{end}, and zero represents the least significant bit.
39153 <struct id="@var{id}" size="@var{size}">
39154 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39159 If the structure contains no bitfields, then each field has an
39160 explicit type, and no implicit padding is added.
39163 <struct id="@var{id}">
39164 <field name="@var{name}" type="@var{type}"/>
39170 If a register's value is a series of single-bit flags, define it with
39171 a flags type. The @samp{<flags>} element has an explicit @var{size}
39172 and contains one or more @samp{<field>} elements. Each field has a
39173 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39177 <flags id="@var{id}" size="@var{size}">
39178 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39183 @subsection Registers
39186 Each register is represented as an element with this form:
39189 <reg name="@var{name}"
39190 bitsize="@var{size}"
39191 @r{[}regnum="@var{num}"@r{]}
39192 @r{[}save-restore="@var{save-restore}"@r{]}
39193 @r{[}type="@var{type}"@r{]}
39194 @r{[}group="@var{group}"@r{]}/>
39198 The components are as follows:
39203 The register's name; it must be unique within the target description.
39206 The register's size, in bits.
39209 The register's number. If omitted, a register's number is one greater
39210 than that of the previous register (either in the current feature or in
39211 a preceding feature); the first register in the target description
39212 defaults to zero. This register number is used to read or write
39213 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39214 packets, and registers appear in the @code{g} and @code{G} packets
39215 in order of increasing register number.
39218 Whether the register should be preserved across inferior function
39219 calls; this must be either @code{yes} or @code{no}. The default is
39220 @code{yes}, which is appropriate for most registers except for
39221 some system control registers; this is not related to the target's
39225 The type of the register. @var{type} may be a predefined type, a type
39226 defined in the current feature, or one of the special types @code{int}
39227 and @code{float}. @code{int} is an integer type of the correct size
39228 for @var{bitsize}, and @code{float} is a floating point type (in the
39229 architecture's normal floating point format) of the correct size for
39230 @var{bitsize}. The default is @code{int}.
39233 The register group to which this register belongs. @var{group} must
39234 be either @code{general}, @code{float}, or @code{vector}. If no
39235 @var{group} is specified, @value{GDBN} will not display the register
39236 in @code{info registers}.
39240 @node Predefined Target Types
39241 @section Predefined Target Types
39242 @cindex target descriptions, predefined types
39244 Type definitions in the self-description can build up composite types
39245 from basic building blocks, but can not define fundamental types. Instead,
39246 standard identifiers are provided by @value{GDBN} for the fundamental
39247 types. The currently supported types are:
39256 Signed integer types holding the specified number of bits.
39263 Unsigned integer types holding the specified number of bits.
39267 Pointers to unspecified code and data. The program counter and
39268 any dedicated return address register may be marked as code
39269 pointers; printing a code pointer converts it into a symbolic
39270 address. The stack pointer and any dedicated address registers
39271 may be marked as data pointers.
39274 Single precision IEEE floating point.
39277 Double precision IEEE floating point.
39280 The 12-byte extended precision format used by ARM FPA registers.
39283 The 10-byte extended precision format used by x87 registers.
39286 32bit @sc{eflags} register used by x86.
39289 32bit @sc{mxcsr} register used by x86.
39293 @node Standard Target Features
39294 @section Standard Target Features
39295 @cindex target descriptions, standard features
39297 A target description must contain either no registers or all the
39298 target's registers. If the description contains no registers, then
39299 @value{GDBN} will assume a default register layout, selected based on
39300 the architecture. If the description contains any registers, the
39301 default layout will not be used; the standard registers must be
39302 described in the target description, in such a way that @value{GDBN}
39303 can recognize them.
39305 This is accomplished by giving specific names to feature elements
39306 which contain standard registers. @value{GDBN} will look for features
39307 with those names and verify that they contain the expected registers;
39308 if any known feature is missing required registers, or if any required
39309 feature is missing, @value{GDBN} will reject the target
39310 description. You can add additional registers to any of the
39311 standard features --- @value{GDBN} will display them just as if
39312 they were added to an unrecognized feature.
39314 This section lists the known features and their expected contents.
39315 Sample XML documents for these features are included in the
39316 @value{GDBN} source tree, in the directory @file{gdb/features}.
39318 Names recognized by @value{GDBN} should include the name of the
39319 company or organization which selected the name, and the overall
39320 architecture to which the feature applies; so e.g.@: the feature
39321 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39323 The names of registers are not case sensitive for the purpose
39324 of recognizing standard features, but @value{GDBN} will only display
39325 registers using the capitalization used in the description.
39332 * PowerPC Features::
39338 @subsection ARM Features
39339 @cindex target descriptions, ARM features
39341 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39343 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39344 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39346 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39347 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39348 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39351 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39352 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39354 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39355 it should contain at least registers @samp{wR0} through @samp{wR15} and
39356 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39357 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39359 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39360 should contain at least registers @samp{d0} through @samp{d15}. If
39361 they are present, @samp{d16} through @samp{d31} should also be included.
39362 @value{GDBN} will synthesize the single-precision registers from
39363 halves of the double-precision registers.
39365 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39366 need to contain registers; it instructs @value{GDBN} to display the
39367 VFP double-precision registers as vectors and to synthesize the
39368 quad-precision registers from pairs of double-precision registers.
39369 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39370 be present and include 32 double-precision registers.
39372 @node i386 Features
39373 @subsection i386 Features
39374 @cindex target descriptions, i386 features
39376 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39377 targets. It should describe the following registers:
39381 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39383 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39385 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39386 @samp{fs}, @samp{gs}
39388 @samp{st0} through @samp{st7}
39390 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39391 @samp{foseg}, @samp{fooff} and @samp{fop}
39394 The register sets may be different, depending on the target.
39396 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39397 describe registers:
39401 @samp{xmm0} through @samp{xmm7} for i386
39403 @samp{xmm0} through @samp{xmm15} for amd64
39408 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39409 @samp{org.gnu.gdb.i386.sse} feature. It should
39410 describe the upper 128 bits of @sc{ymm} registers:
39414 @samp{ymm0h} through @samp{ymm7h} for i386
39416 @samp{ymm0h} through @samp{ymm15h} for amd64
39419 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39420 describe a single register, @samp{orig_eax}.
39422 @node MIPS Features
39423 @subsection MIPS Features
39424 @cindex target descriptions, MIPS features
39426 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
39427 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39428 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39431 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39432 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39433 registers. They may be 32-bit or 64-bit depending on the target.
39435 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39436 it may be optional in a future version of @value{GDBN}. It should
39437 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39438 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39440 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39441 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39442 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39443 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39445 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39446 contain a single register, @samp{restart}, which is used by the
39447 Linux kernel to control restartable syscalls.
39449 @node M68K Features
39450 @subsection M68K Features
39451 @cindex target descriptions, M68K features
39454 @item @samp{org.gnu.gdb.m68k.core}
39455 @itemx @samp{org.gnu.gdb.coldfire.core}
39456 @itemx @samp{org.gnu.gdb.fido.core}
39457 One of those features must be always present.
39458 The feature that is present determines which flavor of m68k is
39459 used. The feature that is present should contain registers
39460 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39461 @samp{sp}, @samp{ps} and @samp{pc}.
39463 @item @samp{org.gnu.gdb.coldfire.fp}
39464 This feature is optional. If present, it should contain registers
39465 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39469 @node PowerPC Features
39470 @subsection PowerPC Features
39471 @cindex target descriptions, PowerPC features
39473 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39474 targets. It should contain registers @samp{r0} through @samp{r31},
39475 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39476 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39478 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39479 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39481 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39482 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39485 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39486 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39487 will combine these registers with the floating point registers
39488 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39489 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39490 through @samp{vs63}, the set of vector registers for POWER7.
39492 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39493 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39494 @samp{spefscr}. SPE targets should provide 32-bit registers in
39495 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39496 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39497 these to present registers @samp{ev0} through @samp{ev31} to the
39500 @node TIC6x Features
39501 @subsection TMS320C6x Features
39502 @cindex target descriptions, TIC6x features
39503 @cindex target descriptions, TMS320C6x features
39504 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39505 targets. It should contain registers @samp{A0} through @samp{A15},
39506 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39508 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39509 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39510 through @samp{B31}.
39512 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39513 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39515 @node Operating System Information
39516 @appendix Operating System Information
39517 @cindex operating system information
39523 Users of @value{GDBN} often wish to obtain information about the state of
39524 the operating system running on the target---for example the list of
39525 processes, or the list of open files. This section describes the
39526 mechanism that makes it possible. This mechanism is similar to the
39527 target features mechanism (@pxref{Target Descriptions}), but focuses
39528 on a different aspect of target.
39530 Operating system information is retrived from the target via the
39531 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39532 read}). The object name in the request should be @samp{osdata}, and
39533 the @var{annex} identifies the data to be fetched.
39536 @appendixsection Process list
39537 @cindex operating system information, process list
39539 When requesting the process list, the @var{annex} field in the
39540 @samp{qXfer} request should be @samp{processes}. The returned data is
39541 an XML document. The formal syntax of this document is defined in
39542 @file{gdb/features/osdata.dtd}.
39544 An example document is:
39547 <?xml version="1.0"?>
39548 <!DOCTYPE target SYSTEM "osdata.dtd">
39549 <osdata type="processes">
39551 <column name="pid">1</column>
39552 <column name="user">root</column>
39553 <column name="command">/sbin/init</column>
39554 <column name="cores">1,2,3</column>
39559 Each item should include a column whose name is @samp{pid}. The value
39560 of that column should identify the process on the target. The
39561 @samp{user} and @samp{command} columns are optional, and will be
39562 displayed by @value{GDBN}. The @samp{cores} column, if present,
39563 should contain a comma-separated list of cores that this process
39564 is running on. Target may provide additional columns,
39565 which @value{GDBN} currently ignores.
39567 @node Trace File Format
39568 @appendix Trace File Format
39569 @cindex trace file format
39571 The trace file comes in three parts: a header, a textual description
39572 section, and a trace frame section with binary data.
39574 The header has the form @code{\x7fTRACE0\n}. The first byte is
39575 @code{0x7f} so as to indicate that the file contains binary data,
39576 while the @code{0} is a version number that may have different values
39579 The description section consists of multiple lines of @sc{ascii} text
39580 separated by newline characters (@code{0xa}). The lines may include a
39581 variety of optional descriptive or context-setting information, such
39582 as tracepoint definitions or register set size. @value{GDBN} will
39583 ignore any line that it does not recognize. An empty line marks the end
39586 @c FIXME add some specific types of data
39588 The trace frame section consists of a number of consecutive frames.
39589 Each frame begins with a two-byte tracepoint number, followed by a
39590 four-byte size giving the amount of data in the frame. The data in
39591 the frame consists of a number of blocks, each introduced by a
39592 character indicating its type (at least register, memory, and trace
39593 state variable). The data in this section is raw binary, not a
39594 hexadecimal or other encoding; its endianness matches the target's
39597 @c FIXME bi-arch may require endianness/arch info in description section
39600 @item R @var{bytes}
39601 Register block. The number and ordering of bytes matches that of a
39602 @code{g} packet in the remote protocol. Note that these are the
39603 actual bytes, in target order and @value{GDBN} register order, not a
39604 hexadecimal encoding.
39606 @item M @var{address} @var{length} @var{bytes}...
39607 Memory block. This is a contiguous block of memory, at the 8-byte
39608 address @var{address}, with a 2-byte length @var{length}, followed by
39609 @var{length} bytes.
39611 @item V @var{number} @var{value}
39612 Trace state variable block. This records the 8-byte signed value
39613 @var{value} of trace state variable numbered @var{number}.
39617 Future enhancements of the trace file format may include additional types
39620 @node Index Section Format
39621 @appendix @code{.gdb_index} section format
39622 @cindex .gdb_index section format
39623 @cindex index section format
39625 This section documents the index section that is created by @code{save
39626 gdb-index} (@pxref{Index Files}). The index section is
39627 DWARF-specific; some knowledge of DWARF is assumed in this
39630 The mapped index file format is designed to be directly
39631 @code{mmap}able on any architecture. In most cases, a datum is
39632 represented using a little-endian 32-bit integer value, called an
39633 @code{offset_type}. Big endian machines must byte-swap the values
39634 before using them. Exceptions to this rule are noted. The data is
39635 laid out such that alignment is always respected.
39637 A mapped index consists of several areas, laid out in order.
39641 The file header. This is a sequence of values, of @code{offset_type}
39642 unless otherwise noted:
39646 The version number, currently 6. Versions 1, 2 and 3 are obsolete.
39647 Version 4 uses a different hashing function from versions 5 and 6.
39648 Version 6 includes symbols for inlined functions, whereas versions
39649 4 and 5 do not. @value{GDBN} will only read version 4 and 5 indices
39650 if the @code{--use-deprecated-index-sections} option is used.
39653 The offset, from the start of the file, of the CU list.
39656 The offset, from the start of the file, of the types CU list. Note
39657 that this area can be empty, in which case this offset will be equal
39658 to the next offset.
39661 The offset, from the start of the file, of the address area.
39664 The offset, from the start of the file, of the symbol table.
39667 The offset, from the start of the file, of the constant pool.
39671 The CU list. This is a sequence of pairs of 64-bit little-endian
39672 values, sorted by the CU offset. The first element in each pair is
39673 the offset of a CU in the @code{.debug_info} section. The second
39674 element in each pair is the length of that CU. References to a CU
39675 elsewhere in the map are done using a CU index, which is just the
39676 0-based index into this table. Note that if there are type CUs, then
39677 conceptually CUs and type CUs form a single list for the purposes of
39681 The types CU list. This is a sequence of triplets of 64-bit
39682 little-endian values. In a triplet, the first value is the CU offset,
39683 the second value is the type offset in the CU, and the third value is
39684 the type signature. The types CU list is not sorted.
39687 The address area. The address area consists of a sequence of address
39688 entries. Each address entry has three elements:
39692 The low address. This is a 64-bit little-endian value.
39695 The high address. This is a 64-bit little-endian value. Like
39696 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39699 The CU index. This is an @code{offset_type} value.
39703 The symbol table. This is an open-addressed hash table. The size of
39704 the hash table is always a power of 2.
39706 Each slot in the hash table consists of a pair of @code{offset_type}
39707 values. The first value is the offset of the symbol's name in the
39708 constant pool. The second value is the offset of the CU vector in the
39711 If both values are 0, then this slot in the hash table is empty. This
39712 is ok because while 0 is a valid constant pool index, it cannot be a
39713 valid index for both a string and a CU vector.
39715 The hash value for a table entry is computed by applying an
39716 iterative hash function to the symbol's name. Starting with an
39717 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39718 the string is incorporated into the hash using the formula depending on the
39723 The formula is @code{r = r * 67 + c - 113}.
39725 @item Versions 5 and 6
39726 The formula is @code{r = r * 67 + tolower (c) - 113}.
39729 The terminating @samp{\0} is not incorporated into the hash.
39731 The step size used in the hash table is computed via
39732 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39733 value, and @samp{size} is the size of the hash table. The step size
39734 is used to find the next candidate slot when handling a hash
39737 The names of C@t{++} symbols in the hash table are canonicalized. We
39738 don't currently have a simple description of the canonicalization
39739 algorithm; if you intend to create new index sections, you must read
39743 The constant pool. This is simply a bunch of bytes. It is organized
39744 so that alignment is correct: CU vectors are stored first, followed by
39747 A CU vector in the constant pool is a sequence of @code{offset_type}
39748 values. The first value is the number of CU indices in the vector.
39749 Each subsequent value is the index of a CU in the CU list. This
39750 element in the hash table is used to indicate which CUs define the
39753 A string in the constant pool is zero-terminated.
39758 @node GNU Free Documentation License
39759 @appendix GNU Free Documentation License
39768 % I think something like @colophon should be in texinfo. In the
39770 \long\def\colophon{\hbox to0pt{}\vfill
39771 \centerline{The body of this manual is set in}
39772 \centerline{\fontname\tenrm,}
39773 \centerline{with headings in {\bf\fontname\tenbf}}
39774 \centerline{and examples in {\tt\fontname\tentt}.}
39775 \centerline{{\it\fontname\tenit\/},}
39776 \centerline{{\bf\fontname\tenbf}, and}
39777 \centerline{{\sl\fontname\tensl\/}}
39778 \centerline{are used for emphasis.}\vfill}
39780 % Blame: doc@cygnus.com, 1991.