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 * Static Probe Points:: Listing static probe points
3346 * Error in Breakpoints:: ``Cannot insert breakpoints''
3347 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3351 @subsection Setting Breakpoints
3353 @c FIXME LMB what does GDB do if no code on line of breakpt?
3354 @c consider in particular declaration with/without initialization.
3356 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3359 @kindex b @r{(@code{break})}
3360 @vindex $bpnum@r{, convenience variable}
3361 @cindex latest breakpoint
3362 Breakpoints are set with the @code{break} command (abbreviated
3363 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3364 number of the breakpoint you've set most recently; see @ref{Convenience
3365 Vars,, Convenience Variables}, for a discussion of what you can do with
3366 convenience variables.
3369 @item break @var{location}
3370 Set a breakpoint at the given @var{location}, which can specify a
3371 function name, a line number, or an address of an instruction.
3372 (@xref{Specify Location}, for a list of all the possible ways to
3373 specify a @var{location}.) The breakpoint will stop your program just
3374 before it executes any of the code in the specified @var{location}.
3376 When using source languages that permit overloading of symbols, such as
3377 C@t{++}, a function name may refer to more than one possible place to break.
3378 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3381 It is also possible to insert a breakpoint that will stop the program
3382 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3383 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3386 When called without any arguments, @code{break} sets a breakpoint at
3387 the next instruction to be executed in the selected stack frame
3388 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3389 innermost, this makes your program stop as soon as control
3390 returns to that frame. This is similar to the effect of a
3391 @code{finish} command in the frame inside the selected frame---except
3392 that @code{finish} does not leave an active breakpoint. If you use
3393 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3394 the next time it reaches the current location; this may be useful
3397 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3398 least one instruction has been executed. If it did not do this, you
3399 would be unable to proceed past a breakpoint without first disabling the
3400 breakpoint. This rule applies whether or not the breakpoint already
3401 existed when your program stopped.
3403 @item break @dots{} if @var{cond}
3404 Set a breakpoint with condition @var{cond}; evaluate the expression
3405 @var{cond} each time the breakpoint is reached, and stop only if the
3406 value is nonzero---that is, if @var{cond} evaluates as true.
3407 @samp{@dots{}} stands for one of the possible arguments described
3408 above (or no argument) specifying where to break. @xref{Conditions,
3409 ,Break Conditions}, for more information on breakpoint conditions.
3412 @item tbreak @var{args}
3413 Set a breakpoint enabled only for one stop. @var{args} are the
3414 same as for the @code{break} command, and the breakpoint is set in the same
3415 way, but the breakpoint is automatically deleted after the first time your
3416 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3419 @cindex hardware breakpoints
3420 @item hbreak @var{args}
3421 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3422 @code{break} command and the breakpoint is set in the same way, but the
3423 breakpoint requires hardware support and some target hardware may not
3424 have this support. The main purpose of this is EPROM/ROM code
3425 debugging, so you can set a breakpoint at an instruction without
3426 changing the instruction. This can be used with the new trap-generation
3427 provided by SPARClite DSU and most x86-based targets. These targets
3428 will generate traps when a program accesses some data or instruction
3429 address that is assigned to the debug registers. However the hardware
3430 breakpoint registers can take a limited number of breakpoints. For
3431 example, on the DSU, only two data breakpoints can be set at a time, and
3432 @value{GDBN} will reject this command if more than two are used. Delete
3433 or disable unused hardware breakpoints before setting new ones
3434 (@pxref{Disabling, ,Disabling Breakpoints}).
3435 @xref{Conditions, ,Break Conditions}.
3436 For remote targets, you can restrict the number of hardware
3437 breakpoints @value{GDBN} will use, see @ref{set remote
3438 hardware-breakpoint-limit}.
3441 @item thbreak @var{args}
3442 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3443 are the same as for the @code{hbreak} command and the breakpoint is set in
3444 the same way. However, like the @code{tbreak} command,
3445 the breakpoint is automatically deleted after the
3446 first time your program stops there. Also, like the @code{hbreak}
3447 command, the breakpoint requires hardware support and some target hardware
3448 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3449 See also @ref{Conditions, ,Break Conditions}.
3452 @cindex regular expression
3453 @cindex breakpoints at functions matching a regexp
3454 @cindex set breakpoints in many functions
3455 @item rbreak @var{regex}
3456 Set breakpoints on all functions matching the regular expression
3457 @var{regex}. This command sets an unconditional breakpoint on all
3458 matches, printing a list of all breakpoints it set. Once these
3459 breakpoints are set, they are treated just like the breakpoints set with
3460 the @code{break} command. You can delete them, disable them, or make
3461 them conditional the same way as any other breakpoint.
3463 The syntax of the regular expression is the standard one used with tools
3464 like @file{grep}. Note that this is different from the syntax used by
3465 shells, so for instance @code{foo*} matches all functions that include
3466 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3467 @code{.*} leading and trailing the regular expression you supply, so to
3468 match only functions that begin with @code{foo}, use @code{^foo}.
3470 @cindex non-member C@t{++} functions, set breakpoint in
3471 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3472 breakpoints on overloaded functions that are not members of any special
3475 @cindex set breakpoints on all functions
3476 The @code{rbreak} command can be used to set breakpoints in
3477 @strong{all} the functions in a program, like this:
3480 (@value{GDBP}) rbreak .
3483 @item rbreak @var{file}:@var{regex}
3484 If @code{rbreak} is called with a filename qualification, it limits
3485 the search for functions matching the given regular expression to the
3486 specified @var{file}. This can be used, for example, to set breakpoints on
3487 every function in a given file:
3490 (@value{GDBP}) rbreak file.c:.
3493 The colon separating the filename qualifier from the regex may
3494 optionally be surrounded by spaces.
3496 @kindex info breakpoints
3497 @cindex @code{$_} and @code{info breakpoints}
3498 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3499 @itemx info break @r{[}@var{n}@dots{}@r{]}
3500 Print a table of all breakpoints, watchpoints, and catchpoints set and
3501 not deleted. Optional argument @var{n} means print information only
3502 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3503 For each breakpoint, following columns are printed:
3506 @item Breakpoint Numbers
3508 Breakpoint, watchpoint, or catchpoint.
3510 Whether the breakpoint is marked to be disabled or deleted when hit.
3511 @item Enabled or Disabled
3512 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3513 that are not enabled.
3515 Where the breakpoint is in your program, as a memory address. For a
3516 pending breakpoint whose address is not yet known, this field will
3517 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3518 library that has the symbol or line referred by breakpoint is loaded.
3519 See below for details. A breakpoint with several locations will
3520 have @samp{<MULTIPLE>} in this field---see below for details.
3522 Where the breakpoint is in the source for your program, as a file and
3523 line number. For a pending breakpoint, the original string passed to
3524 the breakpoint command will be listed as it cannot be resolved until
3525 the appropriate shared library is loaded in the future.
3529 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3530 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3531 @value{GDBN} on the host's side. If it is ``target'', then the condition
3532 is evaluated by the target. The @code{info break} command shows
3533 the condition on the line following the affected breakpoint, together with
3534 its condition evaluation mode in between parentheses.
3536 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3537 allowed to have a condition specified for it. The condition is not parsed for
3538 validity until a shared library is loaded that allows the pending
3539 breakpoint to resolve to a valid location.
3542 @code{info break} with a breakpoint
3543 number @var{n} as argument lists only that breakpoint. The
3544 convenience variable @code{$_} and the default examining-address for
3545 the @code{x} command are set to the address of the last breakpoint
3546 listed (@pxref{Memory, ,Examining Memory}).
3549 @code{info break} displays a count of the number of times the breakpoint
3550 has been hit. This is especially useful in conjunction with the
3551 @code{ignore} command. You can ignore a large number of breakpoint
3552 hits, look at the breakpoint info to see how many times the breakpoint
3553 was hit, and then run again, ignoring one less than that number. This
3554 will get you quickly to the last hit of that breakpoint.
3557 For a breakpoints with an enable count (xref) greater than 1,
3558 @code{info break} also displays that count.
3562 @value{GDBN} allows you to set any number of breakpoints at the same place in
3563 your program. There is nothing silly or meaningless about this. When
3564 the breakpoints are conditional, this is even useful
3565 (@pxref{Conditions, ,Break Conditions}).
3567 @cindex multiple locations, breakpoints
3568 @cindex breakpoints, multiple locations
3569 It is possible that a breakpoint corresponds to several locations
3570 in your program. Examples of this situation are:
3574 Multiple functions in the program may have the same name.
3577 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3578 instances of the function body, used in different cases.
3581 For a C@t{++} template function, a given line in the function can
3582 correspond to any number of instantiations.
3585 For an inlined function, a given source line can correspond to
3586 several places where that function is inlined.
3589 In all those cases, @value{GDBN} will insert a breakpoint at all
3590 the relevant locations.
3592 A breakpoint with multiple locations is displayed in the breakpoint
3593 table using several rows---one header row, followed by one row for
3594 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3595 address column. The rows for individual locations contain the actual
3596 addresses for locations, and show the functions to which those
3597 locations belong. The number column for a location is of the form
3598 @var{breakpoint-number}.@var{location-number}.
3603 Num Type Disp Enb Address What
3604 1 breakpoint keep y <MULTIPLE>
3606 breakpoint already hit 1 time
3607 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3608 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3611 Each location can be individually enabled or disabled by passing
3612 @var{breakpoint-number}.@var{location-number} as argument to the
3613 @code{enable} and @code{disable} commands. Note that you cannot
3614 delete the individual locations from the list, you can only delete the
3615 entire list of locations that belong to their parent breakpoint (with
3616 the @kbd{delete @var{num}} command, where @var{num} is the number of
3617 the parent breakpoint, 1 in the above example). Disabling or enabling
3618 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3619 that belong to that breakpoint.
3621 @cindex pending breakpoints
3622 It's quite common to have a breakpoint inside a shared library.
3623 Shared libraries can be loaded and unloaded explicitly,
3624 and possibly repeatedly, as the program is executed. To support
3625 this use case, @value{GDBN} updates breakpoint locations whenever
3626 any shared library is loaded or unloaded. Typically, you would
3627 set a breakpoint in a shared library at the beginning of your
3628 debugging session, when the library is not loaded, and when the
3629 symbols from the library are not available. When you try to set
3630 breakpoint, @value{GDBN} will ask you if you want to set
3631 a so called @dfn{pending breakpoint}---breakpoint whose address
3632 is not yet resolved.
3634 After the program is run, whenever a new shared library is loaded,
3635 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3636 shared library contains the symbol or line referred to by some
3637 pending breakpoint, that breakpoint is resolved and becomes an
3638 ordinary breakpoint. When a library is unloaded, all breakpoints
3639 that refer to its symbols or source lines become pending again.
3641 This logic works for breakpoints with multiple locations, too. For
3642 example, if you have a breakpoint in a C@t{++} template function, and
3643 a newly loaded shared library has an instantiation of that template,
3644 a new location is added to the list of locations for the breakpoint.
3646 Except for having unresolved address, pending breakpoints do not
3647 differ from regular breakpoints. You can set conditions or commands,
3648 enable and disable them and perform other breakpoint operations.
3650 @value{GDBN} provides some additional commands for controlling what
3651 happens when the @samp{break} command cannot resolve breakpoint
3652 address specification to an address:
3654 @kindex set breakpoint pending
3655 @kindex show breakpoint pending
3657 @item set breakpoint pending auto
3658 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3659 location, it queries you whether a pending breakpoint should be created.
3661 @item set breakpoint pending on
3662 This indicates that an unrecognized breakpoint location should automatically
3663 result in a pending breakpoint being created.
3665 @item set breakpoint pending off
3666 This indicates that pending breakpoints are not to be created. Any
3667 unrecognized breakpoint location results in an error. This setting does
3668 not affect any pending breakpoints previously created.
3670 @item show breakpoint pending
3671 Show the current behavior setting for creating pending breakpoints.
3674 The settings above only affect the @code{break} command and its
3675 variants. Once breakpoint is set, it will be automatically updated
3676 as shared libraries are loaded and unloaded.
3678 @cindex automatic hardware breakpoints
3679 For some targets, @value{GDBN} can automatically decide if hardware or
3680 software breakpoints should be used, depending on whether the
3681 breakpoint address is read-only or read-write. This applies to
3682 breakpoints set with the @code{break} command as well as to internal
3683 breakpoints set by commands like @code{next} and @code{finish}. For
3684 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3687 You can control this automatic behaviour with the following commands::
3689 @kindex set breakpoint auto-hw
3690 @kindex show breakpoint auto-hw
3692 @item set breakpoint auto-hw on
3693 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3694 will try to use the target memory map to decide if software or hardware
3695 breakpoint must be used.
3697 @item set breakpoint auto-hw off
3698 This indicates @value{GDBN} should not automatically select breakpoint
3699 type. If the target provides a memory map, @value{GDBN} will warn when
3700 trying to set software breakpoint at a read-only address.
3703 @value{GDBN} normally implements breakpoints by replacing the program code
3704 at the breakpoint address with a special instruction, which, when
3705 executed, given control to the debugger. By default, the program
3706 code is so modified only when the program is resumed. As soon as
3707 the program stops, @value{GDBN} restores the original instructions. This
3708 behaviour guards against leaving breakpoints inserted in the
3709 target should gdb abrubptly disconnect. However, with slow remote
3710 targets, inserting and removing breakpoint can reduce the performance.
3711 This behavior can be controlled with the following commands::
3713 @kindex set breakpoint always-inserted
3714 @kindex show breakpoint always-inserted
3716 @item set breakpoint always-inserted off
3717 All breakpoints, including newly added by the user, are inserted in
3718 the target only when the target is resumed. All breakpoints are
3719 removed from the target when it stops.
3721 @item set breakpoint always-inserted on
3722 Causes all breakpoints to be inserted in the target at all times. If
3723 the user adds a new breakpoint, or changes an existing breakpoint, the
3724 breakpoints in the target are updated immediately. A breakpoint is
3725 removed from the target only when breakpoint itself is removed.
3727 @cindex non-stop mode, and @code{breakpoint always-inserted}
3728 @item set breakpoint always-inserted auto
3729 This is the default mode. If @value{GDBN} is controlling the inferior
3730 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3731 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3732 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3733 @code{breakpoint always-inserted} mode is off.
3736 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3737 when a breakpoint breaks. If the condition is true, then the process being
3738 debugged stops, otherwise the process is resumed.
3740 If the target supports evaluating conditions on its end, @value{GDBN} may
3741 download the breakpoint, together with its conditions, to it.
3743 This feature can be controlled via the following commands:
3745 @kindex set breakpoint condition-evaluation
3746 @kindex show breakpoint condition-evaluation
3748 @item set breakpoint condition-evaluation host
3749 This option commands @value{GDBN} to evaluate the breakpoint
3750 conditions on the host's side. Unconditional breakpoints are sent to
3751 the target which in turn receives the triggers and reports them back to GDB
3752 for condition evaluation. This is the standard evaluation mode.
3754 @item set breakpoint condition-evaluation target
3755 This option commands @value{GDBN} to download breakpoint conditions
3756 to the target at the moment of their insertion. The target
3757 is responsible for evaluating the conditional expression and reporting
3758 breakpoint stop events back to @value{GDBN} whenever the condition
3759 is true. Due to limitations of target-side evaluation, some conditions
3760 cannot be evaluated there, e.g., conditions that depend on local data
3761 that is only known to the host. Examples include
3762 conditional expressions involving convenience variables, complex types
3763 that cannot be handled by the agent expression parser and expressions
3764 that are too long to be sent over to the target, specially when the
3765 target is a remote system. In these cases, the conditions will be
3766 evaluated by @value{GDBN}.
3768 @item set breakpoint condition-evaluation auto
3769 This is the default mode. If the target supports evaluating breakpoint
3770 conditions on its end, @value{GDBN} will download breakpoint conditions to
3771 the target (limitations mentioned previously apply). If the target does
3772 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3773 to evaluating all these conditions on the host's side.
3777 @cindex negative breakpoint numbers
3778 @cindex internal @value{GDBN} breakpoints
3779 @value{GDBN} itself sometimes sets breakpoints in your program for
3780 special purposes, such as proper handling of @code{longjmp} (in C
3781 programs). These internal breakpoints are assigned negative numbers,
3782 starting with @code{-1}; @samp{info breakpoints} does not display them.
3783 You can see these breakpoints with the @value{GDBN} maintenance command
3784 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3787 @node Set Watchpoints
3788 @subsection Setting Watchpoints
3790 @cindex setting watchpoints
3791 You can use a watchpoint to stop execution whenever the value of an
3792 expression changes, without having to predict a particular place where
3793 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3794 The expression may be as simple as the value of a single variable, or
3795 as complex as many variables combined by operators. Examples include:
3799 A reference to the value of a single variable.
3802 An address cast to an appropriate data type. For example,
3803 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3804 address (assuming an @code{int} occupies 4 bytes).
3807 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3808 expression can use any operators valid in the program's native
3809 language (@pxref{Languages}).
3812 You can set a watchpoint on an expression even if the expression can
3813 not be evaluated yet. For instance, you can set a watchpoint on
3814 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3815 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3816 the expression produces a valid value. If the expression becomes
3817 valid in some other way than changing a variable (e.g.@: if the memory
3818 pointed to by @samp{*global_ptr} becomes readable as the result of a
3819 @code{malloc} call), @value{GDBN} may not stop until the next time
3820 the expression changes.
3822 @cindex software watchpoints
3823 @cindex hardware watchpoints
3824 Depending on your system, watchpoints may be implemented in software or
3825 hardware. @value{GDBN} does software watchpointing by single-stepping your
3826 program and testing the variable's value each time, which is hundreds of
3827 times slower than normal execution. (But this may still be worth it, to
3828 catch errors where you have no clue what part of your program is the
3831 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3832 x86-based targets, @value{GDBN} includes support for hardware
3833 watchpoints, which do not slow down the running of your program.
3837 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3838 Set a watchpoint for an expression. @value{GDBN} will break when the
3839 expression @var{expr} is written into by the program and its value
3840 changes. The simplest (and the most popular) use of this command is
3841 to watch the value of a single variable:
3844 (@value{GDBP}) watch foo
3847 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3848 argument, @value{GDBN} breaks only when the thread identified by
3849 @var{threadnum} changes the value of @var{expr}. If any other threads
3850 change the value of @var{expr}, @value{GDBN} will not break. Note
3851 that watchpoints restricted to a single thread in this way only work
3852 with Hardware Watchpoints.
3854 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3855 (see below). The @code{-location} argument tells @value{GDBN} to
3856 instead watch the memory referred to by @var{expr}. In this case,
3857 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3858 and watch the memory at that address. The type of the result is used
3859 to determine the size of the watched memory. If the expression's
3860 result does not have an address, then @value{GDBN} will print an
3863 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3864 of masked watchpoints, if the current architecture supports this
3865 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3866 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3867 to an address to watch. The mask specifies that some bits of an address
3868 (the bits which are reset in the mask) should be ignored when matching
3869 the address accessed by the inferior against the watchpoint address.
3870 Thus, a masked watchpoint watches many addresses simultaneously---those
3871 addresses whose unmasked bits are identical to the unmasked bits in the
3872 watchpoint address. The @code{mask} argument implies @code{-location}.
3876 (@value{GDBP}) watch foo mask 0xffff00ff
3877 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3881 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3882 Set a watchpoint that will break when the value of @var{expr} is read
3886 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3887 Set a watchpoint that will break when @var{expr} is either read from
3888 or written into by the program.
3890 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3891 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3892 This command prints a list of watchpoints, using the same format as
3893 @code{info break} (@pxref{Set Breaks}).
3896 If you watch for a change in a numerically entered address you need to
3897 dereference it, as the address itself is just a constant number which will
3898 never change. @value{GDBN} refuses to create a watchpoint that watches
3899 a never-changing value:
3902 (@value{GDBP}) watch 0x600850
3903 Cannot watch constant value 0x600850.
3904 (@value{GDBP}) watch *(int *) 0x600850
3905 Watchpoint 1: *(int *) 6293584
3908 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3909 watchpoints execute very quickly, and the debugger reports a change in
3910 value at the exact instruction where the change occurs. If @value{GDBN}
3911 cannot set a hardware watchpoint, it sets a software watchpoint, which
3912 executes more slowly and reports the change in value at the next
3913 @emph{statement}, not the instruction, after the change occurs.
3915 @cindex use only software watchpoints
3916 You can force @value{GDBN} to use only software watchpoints with the
3917 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3918 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3919 the underlying system supports them. (Note that hardware-assisted
3920 watchpoints that were set @emph{before} setting
3921 @code{can-use-hw-watchpoints} to zero will still use the hardware
3922 mechanism of watching expression values.)
3925 @item set can-use-hw-watchpoints
3926 @kindex set can-use-hw-watchpoints
3927 Set whether or not to use hardware watchpoints.
3929 @item show can-use-hw-watchpoints
3930 @kindex show can-use-hw-watchpoints
3931 Show the current mode of using hardware watchpoints.
3934 For remote targets, you can restrict the number of hardware
3935 watchpoints @value{GDBN} will use, see @ref{set remote
3936 hardware-breakpoint-limit}.
3938 When you issue the @code{watch} command, @value{GDBN} reports
3941 Hardware watchpoint @var{num}: @var{expr}
3945 if it was able to set a hardware watchpoint.
3947 Currently, the @code{awatch} and @code{rwatch} commands can only set
3948 hardware watchpoints, because accesses to data that don't change the
3949 value of the watched expression cannot be detected without examining
3950 every instruction as it is being executed, and @value{GDBN} does not do
3951 that currently. If @value{GDBN} finds that it is unable to set a
3952 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3953 will print a message like this:
3956 Expression cannot be implemented with read/access watchpoint.
3959 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3960 data type of the watched expression is wider than what a hardware
3961 watchpoint on the target machine can handle. For example, some systems
3962 can only watch regions that are up to 4 bytes wide; on such systems you
3963 cannot set hardware watchpoints for an expression that yields a
3964 double-precision floating-point number (which is typically 8 bytes
3965 wide). As a work-around, it might be possible to break the large region
3966 into a series of smaller ones and watch them with separate watchpoints.
3968 If you set too many hardware watchpoints, @value{GDBN} might be unable
3969 to insert all of them when you resume the execution of your program.
3970 Since the precise number of active watchpoints is unknown until such
3971 time as the program is about to be resumed, @value{GDBN} might not be
3972 able to warn you about this when you set the watchpoints, and the
3973 warning will be printed only when the program is resumed:
3976 Hardware watchpoint @var{num}: Could not insert watchpoint
3980 If this happens, delete or disable some of the watchpoints.
3982 Watching complex expressions that reference many variables can also
3983 exhaust the resources available for hardware-assisted watchpoints.
3984 That's because @value{GDBN} needs to watch every variable in the
3985 expression with separately allocated resources.
3987 If you call a function interactively using @code{print} or @code{call},
3988 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3989 kind of breakpoint or the call completes.
3991 @value{GDBN} automatically deletes watchpoints that watch local
3992 (automatic) variables, or expressions that involve such variables, when
3993 they go out of scope, that is, when the execution leaves the block in
3994 which these variables were defined. In particular, when the program
3995 being debugged terminates, @emph{all} local variables go out of scope,
3996 and so only watchpoints that watch global variables remain set. If you
3997 rerun the program, you will need to set all such watchpoints again. One
3998 way of doing that would be to set a code breakpoint at the entry to the
3999 @code{main} function and when it breaks, set all the watchpoints.
4001 @cindex watchpoints and threads
4002 @cindex threads and watchpoints
4003 In multi-threaded programs, watchpoints will detect changes to the
4004 watched expression from every thread.
4007 @emph{Warning:} In multi-threaded programs, software watchpoints
4008 have only limited usefulness. If @value{GDBN} creates a software
4009 watchpoint, it can only watch the value of an expression @emph{in a
4010 single thread}. If you are confident that the expression can only
4011 change due to the current thread's activity (and if you are also
4012 confident that no other thread can become current), then you can use
4013 software watchpoints as usual. However, @value{GDBN} may not notice
4014 when a non-current thread's activity changes the expression. (Hardware
4015 watchpoints, in contrast, watch an expression in all threads.)
4018 @xref{set remote hardware-watchpoint-limit}.
4020 @node Set Catchpoints
4021 @subsection Setting Catchpoints
4022 @cindex catchpoints, setting
4023 @cindex exception handlers
4024 @cindex event handling
4026 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4027 kinds of program events, such as C@t{++} exceptions or the loading of a
4028 shared library. Use the @code{catch} command to set a catchpoint.
4032 @item catch @var{event}
4033 Stop when @var{event} occurs. @var{event} can be any of the following:
4036 @cindex stop on C@t{++} exceptions
4037 The throwing of a C@t{++} exception.
4040 The catching of a C@t{++} exception.
4043 @cindex Ada exception catching
4044 @cindex catch Ada exceptions
4045 An Ada exception being raised. If an exception name is specified
4046 at the end of the command (eg @code{catch exception Program_Error}),
4047 the debugger will stop only when this specific exception is raised.
4048 Otherwise, the debugger stops execution when any Ada exception is raised.
4050 When inserting an exception catchpoint on a user-defined exception whose
4051 name is identical to one of the exceptions defined by the language, the
4052 fully qualified name must be used as the exception name. Otherwise,
4053 @value{GDBN} will assume that it should stop on the pre-defined exception
4054 rather than the user-defined one. For instance, assuming an exception
4055 called @code{Constraint_Error} is defined in package @code{Pck}, then
4056 the command to use to catch such exceptions is @kbd{catch exception
4057 Pck.Constraint_Error}.
4059 @item exception unhandled
4060 An exception that was raised but is not handled by the program.
4063 A failed Ada assertion.
4066 @cindex break on fork/exec
4067 A call to @code{exec}. This is currently only available for HP-UX
4071 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4072 @cindex break on a system call.
4073 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4074 syscall is a mechanism for application programs to request a service
4075 from the operating system (OS) or one of the OS system services.
4076 @value{GDBN} can catch some or all of the syscalls issued by the
4077 debuggee, and show the related information for each syscall. If no
4078 argument is specified, calls to and returns from all system calls
4081 @var{name} can be any system call name that is valid for the
4082 underlying OS. Just what syscalls are valid depends on the OS. On
4083 GNU and Unix systems, you can find the full list of valid syscall
4084 names on @file{/usr/include/asm/unistd.h}.
4086 @c For MS-Windows, the syscall names and the corresponding numbers
4087 @c can be found, e.g., on this URL:
4088 @c http://www.metasploit.com/users/opcode/syscalls.html
4089 @c but we don't support Windows syscalls yet.
4091 Normally, @value{GDBN} knows in advance which syscalls are valid for
4092 each OS, so you can use the @value{GDBN} command-line completion
4093 facilities (@pxref{Completion,, command completion}) to list the
4096 You may also specify the system call numerically. A syscall's
4097 number is the value passed to the OS's syscall dispatcher to
4098 identify the requested service. When you specify the syscall by its
4099 name, @value{GDBN} uses its database of syscalls to convert the name
4100 into the corresponding numeric code, but using the number directly
4101 may be useful if @value{GDBN}'s database does not have the complete
4102 list of syscalls on your system (e.g., because @value{GDBN} lags
4103 behind the OS upgrades).
4105 The example below illustrates how this command works if you don't provide
4109 (@value{GDBP}) catch syscall
4110 Catchpoint 1 (syscall)
4112 Starting program: /tmp/catch-syscall
4114 Catchpoint 1 (call to syscall 'close'), \
4115 0xffffe424 in __kernel_vsyscall ()
4119 Catchpoint 1 (returned from syscall 'close'), \
4120 0xffffe424 in __kernel_vsyscall ()
4124 Here is an example of catching a system call by name:
4127 (@value{GDBP}) catch syscall chroot
4128 Catchpoint 1 (syscall 'chroot' [61])
4130 Starting program: /tmp/catch-syscall
4132 Catchpoint 1 (call to syscall 'chroot'), \
4133 0xffffe424 in __kernel_vsyscall ()
4137 Catchpoint 1 (returned from syscall 'chroot'), \
4138 0xffffe424 in __kernel_vsyscall ()
4142 An example of specifying a system call numerically. In the case
4143 below, the syscall number has a corresponding entry in the XML
4144 file, so @value{GDBN} finds its name and prints it:
4147 (@value{GDBP}) catch syscall 252
4148 Catchpoint 1 (syscall(s) 'exit_group')
4150 Starting program: /tmp/catch-syscall
4152 Catchpoint 1 (call to syscall 'exit_group'), \
4153 0xffffe424 in __kernel_vsyscall ()
4157 Program exited normally.
4161 However, there can be situations when there is no corresponding name
4162 in XML file for that syscall number. In this case, @value{GDBN} prints
4163 a warning message saying that it was not able to find the syscall name,
4164 but the catchpoint will be set anyway. See the example below:
4167 (@value{GDBP}) catch syscall 764
4168 warning: The number '764' does not represent a known syscall.
4169 Catchpoint 2 (syscall 764)
4173 If you configure @value{GDBN} using the @samp{--without-expat} option,
4174 it will not be able to display syscall names. Also, if your
4175 architecture does not have an XML file describing its system calls,
4176 you will not be able to see the syscall names. It is important to
4177 notice that these two features are used for accessing the syscall
4178 name database. In either case, you will see a warning like this:
4181 (@value{GDBP}) catch syscall
4182 warning: Could not open "syscalls/i386-linux.xml"
4183 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4184 GDB will not be able to display syscall names.
4185 Catchpoint 1 (syscall)
4189 Of course, the file name will change depending on your architecture and system.
4191 Still using the example above, you can also try to catch a syscall by its
4192 number. In this case, you would see something like:
4195 (@value{GDBP}) catch syscall 252
4196 Catchpoint 1 (syscall(s) 252)
4199 Again, in this case @value{GDBN} would not be able to display syscall's names.
4202 A call to @code{fork}. This is currently only available for HP-UX
4206 A call to @code{vfork}. This is currently only available for HP-UX
4209 @item load @r{[}regexp@r{]}
4210 @itemx unload @r{[}regexp@r{]}
4211 The loading or unloading of a shared library. If @var{regexp} is
4212 given, then the catchpoint will stop only if the regular expression
4213 matches one of the affected libraries.
4217 @item tcatch @var{event}
4218 Set a catchpoint that is enabled only for one stop. The catchpoint is
4219 automatically deleted after the first time the event is caught.
4223 Use the @code{info break} command to list the current catchpoints.
4225 There are currently some limitations to C@t{++} exception handling
4226 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4230 If you call a function interactively, @value{GDBN} normally returns
4231 control to you when the function has finished executing. If the call
4232 raises an exception, however, the call may bypass the mechanism that
4233 returns control to you and cause your program either to abort or to
4234 simply continue running until it hits a breakpoint, catches a signal
4235 that @value{GDBN} is listening for, or exits. This is the case even if
4236 you set a catchpoint for the exception; catchpoints on exceptions are
4237 disabled within interactive calls.
4240 You cannot raise an exception interactively.
4243 You cannot install an exception handler interactively.
4246 @cindex raise exceptions
4247 Sometimes @code{catch} is not the best way to debug exception handling:
4248 if you need to know exactly where an exception is raised, it is better to
4249 stop @emph{before} the exception handler is called, since that way you
4250 can see the stack before any unwinding takes place. If you set a
4251 breakpoint in an exception handler instead, it may not be easy to find
4252 out where the exception was raised.
4254 To stop just before an exception handler is called, you need some
4255 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4256 raised by calling a library function named @code{__raise_exception}
4257 which has the following ANSI C interface:
4260 /* @var{addr} is where the exception identifier is stored.
4261 @var{id} is the exception identifier. */
4262 void __raise_exception (void **addr, void *id);
4266 To make the debugger catch all exceptions before any stack
4267 unwinding takes place, set a breakpoint on @code{__raise_exception}
4268 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4270 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4271 that depends on the value of @var{id}, you can stop your program when
4272 a specific exception is raised. You can use multiple conditional
4273 breakpoints to stop your program when any of a number of exceptions are
4278 @subsection Deleting Breakpoints
4280 @cindex clearing breakpoints, watchpoints, catchpoints
4281 @cindex deleting breakpoints, watchpoints, catchpoints
4282 It is often necessary to eliminate a breakpoint, watchpoint, or
4283 catchpoint once it has done its job and you no longer want your program
4284 to stop there. This is called @dfn{deleting} the breakpoint. A
4285 breakpoint that has been deleted no longer exists; it is forgotten.
4287 With the @code{clear} command you can delete breakpoints according to
4288 where they are in your program. With the @code{delete} command you can
4289 delete individual breakpoints, watchpoints, or catchpoints by specifying
4290 their breakpoint numbers.
4292 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4293 automatically ignores breakpoints on the first instruction to be executed
4294 when you continue execution without changing the execution address.
4299 Delete any breakpoints at the next instruction to be executed in the
4300 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4301 the innermost frame is selected, this is a good way to delete a
4302 breakpoint where your program just stopped.
4304 @item clear @var{location}
4305 Delete any breakpoints set at the specified @var{location}.
4306 @xref{Specify Location}, for the various forms of @var{location}; the
4307 most useful ones are listed below:
4310 @item clear @var{function}
4311 @itemx clear @var{filename}:@var{function}
4312 Delete any breakpoints set at entry to the named @var{function}.
4314 @item clear @var{linenum}
4315 @itemx clear @var{filename}:@var{linenum}
4316 Delete any breakpoints set at or within the code of the specified
4317 @var{linenum} of the specified @var{filename}.
4320 @cindex delete breakpoints
4322 @kindex d @r{(@code{delete})}
4323 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4324 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4325 ranges specified as arguments. If no argument is specified, delete all
4326 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4327 confirm off}). You can abbreviate this command as @code{d}.
4331 @subsection Disabling Breakpoints
4333 @cindex enable/disable a breakpoint
4334 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4335 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4336 it had been deleted, but remembers the information on the breakpoint so
4337 that you can @dfn{enable} it again later.
4339 You disable and enable breakpoints, watchpoints, and catchpoints with
4340 the @code{enable} and @code{disable} commands, optionally specifying
4341 one or more breakpoint numbers as arguments. Use @code{info break} to
4342 print a list of all breakpoints, watchpoints, and catchpoints if you
4343 do not know which numbers to use.
4345 Disabling and enabling a breakpoint that has multiple locations
4346 affects all of its locations.
4348 A breakpoint, watchpoint, or catchpoint can have any of several
4349 different states of enablement:
4353 Enabled. The breakpoint stops your program. A breakpoint set
4354 with the @code{break} command starts out in this state.
4356 Disabled. The breakpoint has no effect on your program.
4358 Enabled once. The breakpoint stops your program, but then becomes
4361 Enabled for a count. The breakpoint stops your program for the next
4362 N times, then becomes disabled.
4364 Enabled for deletion. The breakpoint stops your program, but
4365 immediately after it does so it is deleted permanently. A breakpoint
4366 set with the @code{tbreak} command starts out in this state.
4369 You can use the following commands to enable or disable breakpoints,
4370 watchpoints, and catchpoints:
4374 @kindex dis @r{(@code{disable})}
4375 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4376 Disable the specified breakpoints---or all breakpoints, if none are
4377 listed. A disabled breakpoint has no effect but is not forgotten. All
4378 options such as ignore-counts, conditions and commands are remembered in
4379 case the breakpoint is enabled again later. You may abbreviate
4380 @code{disable} as @code{dis}.
4383 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4384 Enable the specified breakpoints (or all defined breakpoints). They
4385 become effective once again in stopping your program.
4387 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4388 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4389 of these breakpoints immediately after stopping your program.
4391 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4392 Enable the specified breakpoints temporarily. @value{GDBN} records
4393 @var{count} with each of the specified breakpoints, and decrements a
4394 breakpoint's count when it is hit. When any count reaches 0,
4395 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4396 count (@pxref{Conditions, ,Break Conditions}), that will be
4397 decremented to 0 before @var{count} is affected.
4399 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4400 Enable the specified breakpoints to work once, then die. @value{GDBN}
4401 deletes any of these breakpoints as soon as your program stops there.
4402 Breakpoints set by the @code{tbreak} command start out in this state.
4405 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4406 @c confusing: tbreak is also initially enabled.
4407 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4408 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4409 subsequently, they become disabled or enabled only when you use one of
4410 the commands above. (The command @code{until} can set and delete a
4411 breakpoint of its own, but it does not change the state of your other
4412 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4416 @subsection Break Conditions
4417 @cindex conditional breakpoints
4418 @cindex breakpoint conditions
4420 @c FIXME what is scope of break condition expr? Context where wanted?
4421 @c in particular for a watchpoint?
4422 The simplest sort of breakpoint breaks every time your program reaches a
4423 specified place. You can also specify a @dfn{condition} for a
4424 breakpoint. A condition is just a Boolean expression in your
4425 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4426 a condition evaluates the expression each time your program reaches it,
4427 and your program stops only if the condition is @emph{true}.
4429 This is the converse of using assertions for program validation; in that
4430 situation, you want to stop when the assertion is violated---that is,
4431 when the condition is false. In C, if you want to test an assertion expressed
4432 by the condition @var{assert}, you should set the condition
4433 @samp{! @var{assert}} on the appropriate breakpoint.
4435 Conditions are also accepted for watchpoints; you may not need them,
4436 since a watchpoint is inspecting the value of an expression anyhow---but
4437 it might be simpler, say, to just set a watchpoint on a variable name,
4438 and specify a condition that tests whether the new value is an interesting
4441 Break conditions can have side effects, and may even call functions in
4442 your program. This can be useful, for example, to activate functions
4443 that log program progress, or to use your own print functions to
4444 format special data structures. The effects are completely predictable
4445 unless there is another enabled breakpoint at the same address. (In
4446 that case, @value{GDBN} might see the other breakpoint first and stop your
4447 program without checking the condition of this one.) Note that
4448 breakpoint commands are usually more convenient and flexible than break
4450 purpose of performing side effects when a breakpoint is reached
4451 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4453 Breakpoint conditions can also be evaluated on the target's side if
4454 the target supports it. Instead of evaluating the conditions locally,
4455 @value{GDBN} encodes the expression into an agent expression
4456 (@pxref{Agent Expressions}) suitable for execution on the target,
4457 independently of @value{GDBN}. Global variables become raw memory
4458 locations, locals become stack accesses, and so forth.
4460 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4461 when its condition evaluates to true. This mechanism may provide faster
4462 response times depending on the performance characteristics of the target
4463 since it does not need to keep @value{GDBN} informed about
4464 every breakpoint trigger, even those with false conditions.
4466 Break conditions can be specified when a breakpoint is set, by using
4467 @samp{if} in the arguments to the @code{break} command. @xref{Set
4468 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4469 with the @code{condition} command.
4471 You can also use the @code{if} keyword with the @code{watch} command.
4472 The @code{catch} command does not recognize the @code{if} keyword;
4473 @code{condition} is the only way to impose a further condition on a
4478 @item condition @var{bnum} @var{expression}
4479 Specify @var{expression} as the break condition for breakpoint,
4480 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4481 breakpoint @var{bnum} stops your program only if the value of
4482 @var{expression} is true (nonzero, in C). When you use
4483 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4484 syntactic correctness, and to determine whether symbols in it have
4485 referents in the context of your breakpoint. If @var{expression} uses
4486 symbols not referenced in the context of the breakpoint, @value{GDBN}
4487 prints an error message:
4490 No symbol "foo" in current context.
4495 not actually evaluate @var{expression} at the time the @code{condition}
4496 command (or a command that sets a breakpoint with a condition, like
4497 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4499 @item condition @var{bnum}
4500 Remove the condition from breakpoint number @var{bnum}. It becomes
4501 an ordinary unconditional breakpoint.
4504 @cindex ignore count (of breakpoint)
4505 A special case of a breakpoint condition is to stop only when the
4506 breakpoint has been reached a certain number of times. This is so
4507 useful that there is a special way to do it, using the @dfn{ignore
4508 count} of the breakpoint. Every breakpoint has an ignore count, which
4509 is an integer. Most of the time, the ignore count is zero, and
4510 therefore has no effect. But if your program reaches a breakpoint whose
4511 ignore count is positive, then instead of stopping, it just decrements
4512 the ignore count by one and continues. As a result, if the ignore count
4513 value is @var{n}, the breakpoint does not stop the next @var{n} times
4514 your program reaches it.
4518 @item ignore @var{bnum} @var{count}
4519 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4520 The next @var{count} times the breakpoint is reached, your program's
4521 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4524 To make the breakpoint stop the next time it is reached, specify
4527 When you use @code{continue} to resume execution of your program from a
4528 breakpoint, you can specify an ignore count directly as an argument to
4529 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4530 Stepping,,Continuing and Stepping}.
4532 If a breakpoint has a positive ignore count and a condition, the
4533 condition is not checked. Once the ignore count reaches zero,
4534 @value{GDBN} resumes checking the condition.
4536 You could achieve the effect of the ignore count with a condition such
4537 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4538 is decremented each time. @xref{Convenience Vars, ,Convenience
4542 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4545 @node Break Commands
4546 @subsection Breakpoint Command Lists
4548 @cindex breakpoint commands
4549 You can give any breakpoint (or watchpoint or catchpoint) a series of
4550 commands to execute when your program stops due to that breakpoint. For
4551 example, you might want to print the values of certain expressions, or
4552 enable other breakpoints.
4556 @kindex end@r{ (breakpoint commands)}
4557 @item commands @r{[}@var{range}@dots{}@r{]}
4558 @itemx @dots{} @var{command-list} @dots{}
4560 Specify a list of commands for the given breakpoints. The commands
4561 themselves appear on the following lines. Type a line containing just
4562 @code{end} to terminate the commands.
4564 To remove all commands from a breakpoint, type @code{commands} and
4565 follow it immediately with @code{end}; that is, give no commands.
4567 With no argument, @code{commands} refers to the last breakpoint,
4568 watchpoint, or catchpoint set (not to the breakpoint most recently
4569 encountered). If the most recent breakpoints were set with a single
4570 command, then the @code{commands} will apply to all the breakpoints
4571 set by that command. This applies to breakpoints set by
4572 @code{rbreak}, and also applies when a single @code{break} command
4573 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4577 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4578 disabled within a @var{command-list}.
4580 You can use breakpoint commands to start your program up again. Simply
4581 use the @code{continue} command, or @code{step}, or any other command
4582 that resumes execution.
4584 Any other commands in the command list, after a command that resumes
4585 execution, are ignored. This is because any time you resume execution
4586 (even with a simple @code{next} or @code{step}), you may encounter
4587 another breakpoint---which could have its own command list, leading to
4588 ambiguities about which list to execute.
4591 If the first command you specify in a command list is @code{silent}, the
4592 usual message about stopping at a breakpoint is not printed. This may
4593 be desirable for breakpoints that are to print a specific message and
4594 then continue. If none of the remaining commands print anything, you
4595 see no sign that the breakpoint was reached. @code{silent} is
4596 meaningful only at the beginning of a breakpoint command list.
4598 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4599 print precisely controlled output, and are often useful in silent
4600 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4602 For example, here is how you could use breakpoint commands to print the
4603 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4609 printf "x is %d\n",x
4614 One application for breakpoint commands is to compensate for one bug so
4615 you can test for another. Put a breakpoint just after the erroneous line
4616 of code, give it a condition to detect the case in which something
4617 erroneous has been done, and give it commands to assign correct values
4618 to any variables that need them. End with the @code{continue} command
4619 so that your program does not stop, and start with the @code{silent}
4620 command so that no output is produced. Here is an example:
4631 @node Save Breakpoints
4632 @subsection How to save breakpoints to a file
4634 To save breakpoint definitions to a file use the @w{@code{save
4635 breakpoints}} command.
4638 @kindex save breakpoints
4639 @cindex save breakpoints to a file for future sessions
4640 @item save breakpoints [@var{filename}]
4641 This command saves all current breakpoint definitions together with
4642 their commands and ignore counts, into a file @file{@var{filename}}
4643 suitable for use in a later debugging session. This includes all
4644 types of breakpoints (breakpoints, watchpoints, catchpoints,
4645 tracepoints). To read the saved breakpoint definitions, use the
4646 @code{source} command (@pxref{Command Files}). Note that watchpoints
4647 with expressions involving local variables may fail to be recreated
4648 because it may not be possible to access the context where the
4649 watchpoint is valid anymore. Because the saved breakpoint definitions
4650 are simply a sequence of @value{GDBN} commands that recreate the
4651 breakpoints, you can edit the file in your favorite editing program,
4652 and remove the breakpoint definitions you're not interested in, or
4653 that can no longer be recreated.
4656 @node Static Probe Points
4657 @subsection Static Probe Points
4659 @cindex static probe point, SystemTap
4660 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4661 for Statically Defined Tracing, and the probes are designed to have a tiny
4662 runtime code and data footprint, and no dynamic relocations. They are
4663 usable from assembly, C and C@t{++} languages. See
4664 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4665 for a good reference on how the @acronym{SDT} probes are implemented.
4667 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4668 @acronym{SDT} probes are supported on ELF-compatible systems. See
4669 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4670 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4671 in your applications.
4673 @cindex semaphores on static probe points
4674 Some probes have an associated semaphore variable; for instance, this
4675 happens automatically if you defined your probe using a DTrace-style
4676 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4677 automatically enable it when you specify a breakpoint using the
4678 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4679 location by some other method (e.g., @code{break file:line}), then
4680 @value{GDBN} will not automatically set the semaphore.
4682 You can examine the available static static probes using @code{info
4683 probes}, with optional arguments:
4687 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4688 If given, @var{provider} is a regular expression used to match against provider
4689 names when selecting which probes to list. If omitted, probes by all
4690 probes from all providers are listed.
4692 If given, @var{name} is a regular expression to match against probe names
4693 when selecting which probes to list. If omitted, probe names are not
4694 considered when deciding whether to display them.
4696 If given, @var{objfile} is a regular expression used to select which
4697 object files (executable or shared libraries) to examine. If not
4698 given, all object files are considered.
4700 @item info probes all
4701 List the available static probes, from all types.
4704 @vindex $_probe_arg@r{, convenience variable}
4705 A probe may specify up to twelve arguments. These are available at the
4706 point at which the probe is defined---that is, when the current PC is
4707 at the probe's location. The arguments are available using the
4708 convenience variables (@pxref{Convenience Vars})
4709 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4710 an integer of the appropriate size; types are not preserved. The
4711 convenience variable @code{$_probe_argc} holds the number of arguments
4712 at the current probe point.
4714 These variables are always available, but attempts to access them at
4715 any location other than a probe point will cause @value{GDBN} to give
4719 @c @ifclear BARETARGET
4720 @node Error in Breakpoints
4721 @subsection ``Cannot insert breakpoints''
4723 If you request too many active hardware-assisted breakpoints and
4724 watchpoints, you will see this error message:
4726 @c FIXME: the precise wording of this message may change; the relevant
4727 @c source change is not committed yet (Sep 3, 1999).
4729 Stopped; cannot insert breakpoints.
4730 You may have requested too many hardware breakpoints and watchpoints.
4734 This message is printed when you attempt to resume the program, since
4735 only then @value{GDBN} knows exactly how many hardware breakpoints and
4736 watchpoints it needs to insert.
4738 When this message is printed, you need to disable or remove some of the
4739 hardware-assisted breakpoints and watchpoints, and then continue.
4741 @node Breakpoint-related Warnings
4742 @subsection ``Breakpoint address adjusted...''
4743 @cindex breakpoint address adjusted
4745 Some processor architectures place constraints on the addresses at
4746 which breakpoints may be placed. For architectures thus constrained,
4747 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4748 with the constraints dictated by the architecture.
4750 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4751 a VLIW architecture in which a number of RISC-like instructions may be
4752 bundled together for parallel execution. The FR-V architecture
4753 constrains the location of a breakpoint instruction within such a
4754 bundle to the instruction with the lowest address. @value{GDBN}
4755 honors this constraint by adjusting a breakpoint's address to the
4756 first in the bundle.
4758 It is not uncommon for optimized code to have bundles which contain
4759 instructions from different source statements, thus it may happen that
4760 a breakpoint's address will be adjusted from one source statement to
4761 another. Since this adjustment may significantly alter @value{GDBN}'s
4762 breakpoint related behavior from what the user expects, a warning is
4763 printed when the breakpoint is first set and also when the breakpoint
4766 A warning like the one below is printed when setting a breakpoint
4767 that's been subject to address adjustment:
4770 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4773 Such warnings are printed both for user settable and @value{GDBN}'s
4774 internal breakpoints. If you see one of these warnings, you should
4775 verify that a breakpoint set at the adjusted address will have the
4776 desired affect. If not, the breakpoint in question may be removed and
4777 other breakpoints may be set which will have the desired behavior.
4778 E.g., it may be sufficient to place the breakpoint at a later
4779 instruction. A conditional breakpoint may also be useful in some
4780 cases to prevent the breakpoint from triggering too often.
4782 @value{GDBN} will also issue a warning when stopping at one of these
4783 adjusted breakpoints:
4786 warning: Breakpoint 1 address previously adjusted from 0x00010414
4790 When this warning is encountered, it may be too late to take remedial
4791 action except in cases where the breakpoint is hit earlier or more
4792 frequently than expected.
4794 @node Continuing and Stepping
4795 @section Continuing and Stepping
4799 @cindex resuming execution
4800 @dfn{Continuing} means resuming program execution until your program
4801 completes normally. In contrast, @dfn{stepping} means executing just
4802 one more ``step'' of your program, where ``step'' may mean either one
4803 line of source code, or one machine instruction (depending on what
4804 particular command you use). Either when continuing or when stepping,
4805 your program may stop even sooner, due to a breakpoint or a signal. (If
4806 it stops due to a signal, you may want to use @code{handle}, or use
4807 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4811 @kindex c @r{(@code{continue})}
4812 @kindex fg @r{(resume foreground execution)}
4813 @item continue @r{[}@var{ignore-count}@r{]}
4814 @itemx c @r{[}@var{ignore-count}@r{]}
4815 @itemx fg @r{[}@var{ignore-count}@r{]}
4816 Resume program execution, at the address where your program last stopped;
4817 any breakpoints set at that address are bypassed. The optional argument
4818 @var{ignore-count} allows you to specify a further number of times to
4819 ignore a breakpoint at this location; its effect is like that of
4820 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4822 The argument @var{ignore-count} is meaningful only when your program
4823 stopped due to a breakpoint. At other times, the argument to
4824 @code{continue} is ignored.
4826 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4827 debugged program is deemed to be the foreground program) are provided
4828 purely for convenience, and have exactly the same behavior as
4832 To resume execution at a different place, you can use @code{return}
4833 (@pxref{Returning, ,Returning from a Function}) to go back to the
4834 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4835 Different Address}) to go to an arbitrary location in your program.
4837 A typical technique for using stepping is to set a breakpoint
4838 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4839 beginning of the function or the section of your program where a problem
4840 is believed to lie, run your program until it stops at that breakpoint,
4841 and then step through the suspect area, examining the variables that are
4842 interesting, until you see the problem happen.
4846 @kindex s @r{(@code{step})}
4848 Continue running your program until control reaches a different source
4849 line, then stop it and return control to @value{GDBN}. This command is
4850 abbreviated @code{s}.
4853 @c "without debugging information" is imprecise; actually "without line
4854 @c numbers in the debugging information". (gcc -g1 has debugging info but
4855 @c not line numbers). But it seems complex to try to make that
4856 @c distinction here.
4857 @emph{Warning:} If you use the @code{step} command while control is
4858 within a function that was compiled without debugging information,
4859 execution proceeds until control reaches a function that does have
4860 debugging information. Likewise, it will not step into a function which
4861 is compiled without debugging information. To step through functions
4862 without debugging information, use the @code{stepi} command, described
4866 The @code{step} command only stops at the first instruction of a source
4867 line. This prevents the multiple stops that could otherwise occur in
4868 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4869 to stop if a function that has debugging information is called within
4870 the line. In other words, @code{step} @emph{steps inside} any functions
4871 called within the line.
4873 Also, the @code{step} command only enters a function if there is line
4874 number information for the function. Otherwise it acts like the
4875 @code{next} command. This avoids problems when using @code{cc -gl}
4876 on MIPS machines. Previously, @code{step} entered subroutines if there
4877 was any debugging information about the routine.
4879 @item step @var{count}
4880 Continue running as in @code{step}, but do so @var{count} times. If a
4881 breakpoint is reached, or a signal not related to stepping occurs before
4882 @var{count} steps, stepping stops right away.
4885 @kindex n @r{(@code{next})}
4886 @item next @r{[}@var{count}@r{]}
4887 Continue to the next source line in the current (innermost) stack frame.
4888 This is similar to @code{step}, but function calls that appear within
4889 the line of code are executed without stopping. Execution stops when
4890 control reaches a different line of code at the original stack level
4891 that was executing when you gave the @code{next} command. This command
4892 is abbreviated @code{n}.
4894 An argument @var{count} is a repeat count, as for @code{step}.
4897 @c FIX ME!! Do we delete this, or is there a way it fits in with
4898 @c the following paragraph? --- Vctoria
4900 @c @code{next} within a function that lacks debugging information acts like
4901 @c @code{step}, but any function calls appearing within the code of the
4902 @c function are executed without stopping.
4904 The @code{next} command only stops at the first instruction of a
4905 source line. This prevents multiple stops that could otherwise occur in
4906 @code{switch} statements, @code{for} loops, etc.
4908 @kindex set step-mode
4910 @cindex functions without line info, and stepping
4911 @cindex stepping into functions with no line info
4912 @itemx set step-mode on
4913 The @code{set step-mode on} command causes the @code{step} command to
4914 stop at the first instruction of a function which contains no debug line
4915 information rather than stepping over it.
4917 This is useful in cases where you may be interested in inspecting the
4918 machine instructions of a function which has no symbolic info and do not
4919 want @value{GDBN} to automatically skip over this function.
4921 @item set step-mode off
4922 Causes the @code{step} command to step over any functions which contains no
4923 debug information. This is the default.
4925 @item show step-mode
4926 Show whether @value{GDBN} will stop in or step over functions without
4927 source line debug information.
4930 @kindex fin @r{(@code{finish})}
4932 Continue running until just after function in the selected stack frame
4933 returns. Print the returned value (if any). This command can be
4934 abbreviated as @code{fin}.
4936 Contrast this with the @code{return} command (@pxref{Returning,
4937 ,Returning from a Function}).
4940 @kindex u @r{(@code{until})}
4941 @cindex run until specified location
4944 Continue running until a source line past the current line, in the
4945 current stack frame, is reached. This command is used to avoid single
4946 stepping through a loop more than once. It is like the @code{next}
4947 command, except that when @code{until} encounters a jump, it
4948 automatically continues execution until the program counter is greater
4949 than the address of the jump.
4951 This means that when you reach the end of a loop after single stepping
4952 though it, @code{until} makes your program continue execution until it
4953 exits the loop. In contrast, a @code{next} command at the end of a loop
4954 simply steps back to the beginning of the loop, which forces you to step
4955 through the next iteration.
4957 @code{until} always stops your program if it attempts to exit the current
4960 @code{until} may produce somewhat counterintuitive results if the order
4961 of machine code does not match the order of the source lines. For
4962 example, in the following excerpt from a debugging session, the @code{f}
4963 (@code{frame}) command shows that execution is stopped at line
4964 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4968 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4970 (@value{GDBP}) until
4971 195 for ( ; argc > 0; NEXTARG) @{
4974 This happened because, for execution efficiency, the compiler had
4975 generated code for the loop closure test at the end, rather than the
4976 start, of the loop---even though the test in a C @code{for}-loop is
4977 written before the body of the loop. The @code{until} command appeared
4978 to step back to the beginning of the loop when it advanced to this
4979 expression; however, it has not really gone to an earlier
4980 statement---not in terms of the actual machine code.
4982 @code{until} with no argument works by means of single
4983 instruction stepping, and hence is slower than @code{until} with an
4986 @item until @var{location}
4987 @itemx u @var{location}
4988 Continue running your program until either the specified location is
4989 reached, or the current stack frame returns. @var{location} is any of
4990 the forms described in @ref{Specify Location}.
4991 This form of the command uses temporary breakpoints, and
4992 hence is quicker than @code{until} without an argument. The specified
4993 location is actually reached only if it is in the current frame. This
4994 implies that @code{until} can be used to skip over recursive function
4995 invocations. For instance in the code below, if the current location is
4996 line @code{96}, issuing @code{until 99} will execute the program up to
4997 line @code{99} in the same invocation of factorial, i.e., after the inner
4998 invocations have returned.
5001 94 int factorial (int value)
5003 96 if (value > 1) @{
5004 97 value *= factorial (value - 1);
5011 @kindex advance @var{location}
5012 @itemx advance @var{location}
5013 Continue running the program up to the given @var{location}. An argument is
5014 required, which should be of one of the forms described in
5015 @ref{Specify Location}.
5016 Execution will also stop upon exit from the current stack
5017 frame. This command is similar to @code{until}, but @code{advance} will
5018 not skip over recursive function calls, and the target location doesn't
5019 have to be in the same frame as the current one.
5023 @kindex si @r{(@code{stepi})}
5025 @itemx stepi @var{arg}
5027 Execute one machine instruction, then stop and return to the debugger.
5029 It is often useful to do @samp{display/i $pc} when stepping by machine
5030 instructions. This makes @value{GDBN} automatically display the next
5031 instruction to be executed, each time your program stops. @xref{Auto
5032 Display,, Automatic Display}.
5034 An argument is a repeat count, as in @code{step}.
5038 @kindex ni @r{(@code{nexti})}
5040 @itemx nexti @var{arg}
5042 Execute one machine instruction, but if it is a function call,
5043 proceed until the function returns.
5045 An argument is a repeat count, as in @code{next}.
5048 @node Skipping Over Functions and Files
5049 @section Skipping Over Functions and Files
5050 @cindex skipping over functions and files
5052 The program you are debugging may contain some functions which are
5053 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5054 skip a function or all functions in a file when stepping.
5056 For example, consider the following C function:
5067 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5068 are not interested in stepping through @code{boring}. If you run @code{step}
5069 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5070 step over both @code{foo} and @code{boring}!
5072 One solution is to @code{step} into @code{boring} and use the @code{finish}
5073 command to immediately exit it. But this can become tedious if @code{boring}
5074 is called from many places.
5076 A more flexible solution is to execute @kbd{skip boring}. This instructs
5077 @value{GDBN} never to step into @code{boring}. Now when you execute
5078 @code{step} at line 103, you'll step over @code{boring} and directly into
5081 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5082 example, @code{skip file boring.c}.
5085 @kindex skip function
5086 @item skip @r{[}@var{linespec}@r{]}
5087 @itemx skip function @r{[}@var{linespec}@r{]}
5088 After running this command, the function named by @var{linespec} or the
5089 function containing the line named by @var{linespec} will be skipped over when
5090 stepping. @xref{Specify Location}.
5092 If you do not specify @var{linespec}, the function you're currently debugging
5095 (If you have a function called @code{file} that you want to skip, use
5096 @kbd{skip function file}.)
5099 @item skip file @r{[}@var{filename}@r{]}
5100 After running this command, any function whose source lives in @var{filename}
5101 will be skipped over when stepping.
5103 If you do not specify @var{filename}, functions whose source lives in the file
5104 you're currently debugging will be skipped.
5107 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5108 These are the commands for managing your list of skips:
5112 @item info skip @r{[}@var{range}@r{]}
5113 Print details about the specified skip(s). If @var{range} is not specified,
5114 print a table with details about all functions and files marked for skipping.
5115 @code{info skip} prints the following information about each skip:
5119 A number identifying this skip.
5121 The type of this skip, either @samp{function} or @samp{file}.
5122 @item Enabled or Disabled
5123 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5125 For function skips, this column indicates the address in memory of the function
5126 being skipped. If you've set a function skip on a function which has not yet
5127 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5128 which has the function is loaded, @code{info skip} will show the function's
5131 For file skips, this field contains the filename being skipped. For functions
5132 skips, this field contains the function name and its line number in the file
5133 where it is defined.
5137 @item skip delete @r{[}@var{range}@r{]}
5138 Delete the specified skip(s). If @var{range} is not specified, delete all
5142 @item skip enable @r{[}@var{range}@r{]}
5143 Enable the specified skip(s). If @var{range} is not specified, enable all
5146 @kindex skip disable
5147 @item skip disable @r{[}@var{range}@r{]}
5148 Disable the specified skip(s). If @var{range} is not specified, disable all
5157 A signal is an asynchronous event that can happen in a program. The
5158 operating system defines the possible kinds of signals, and gives each
5159 kind a name and a number. For example, in Unix @code{SIGINT} is the
5160 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5161 @code{SIGSEGV} is the signal a program gets from referencing a place in
5162 memory far away from all the areas in use; @code{SIGALRM} occurs when
5163 the alarm clock timer goes off (which happens only if your program has
5164 requested an alarm).
5166 @cindex fatal signals
5167 Some signals, including @code{SIGALRM}, are a normal part of the
5168 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5169 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5170 program has not specified in advance some other way to handle the signal.
5171 @code{SIGINT} does not indicate an error in your program, but it is normally
5172 fatal so it can carry out the purpose of the interrupt: to kill the program.
5174 @value{GDBN} has the ability to detect any occurrence of a signal in your
5175 program. You can tell @value{GDBN} in advance what to do for each kind of
5178 @cindex handling signals
5179 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5180 @code{SIGALRM} be silently passed to your program
5181 (so as not to interfere with their role in the program's functioning)
5182 but to stop your program immediately whenever an error signal happens.
5183 You can change these settings with the @code{handle} command.
5186 @kindex info signals
5190 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5191 handle each one. You can use this to see the signal numbers of all
5192 the defined types of signals.
5194 @item info signals @var{sig}
5195 Similar, but print information only about the specified signal number.
5197 @code{info handle} is an alias for @code{info signals}.
5200 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5201 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5202 can be the number of a signal or its name (with or without the
5203 @samp{SIG} at the beginning); a list of signal numbers of the form
5204 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5205 known signals. Optional arguments @var{keywords}, described below,
5206 say what change to make.
5210 The keywords allowed by the @code{handle} command can be abbreviated.
5211 Their full names are:
5215 @value{GDBN} should not stop your program when this signal happens. It may
5216 still print a message telling you that the signal has come in.
5219 @value{GDBN} should stop your program when this signal happens. This implies
5220 the @code{print} keyword as well.
5223 @value{GDBN} should print a message when this signal happens.
5226 @value{GDBN} should not mention the occurrence of the signal at all. This
5227 implies the @code{nostop} keyword as well.
5231 @value{GDBN} should allow your program to see this signal; your program
5232 can handle the signal, or else it may terminate if the signal is fatal
5233 and not handled. @code{pass} and @code{noignore} are synonyms.
5237 @value{GDBN} should not allow your program to see this signal.
5238 @code{nopass} and @code{ignore} are synonyms.
5242 When a signal stops your program, the signal is not visible to the
5244 continue. Your program sees the signal then, if @code{pass} is in
5245 effect for the signal in question @emph{at that time}. In other words,
5246 after @value{GDBN} reports a signal, you can use the @code{handle}
5247 command with @code{pass} or @code{nopass} to control whether your
5248 program sees that signal when you continue.
5250 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5251 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5252 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5255 You can also use the @code{signal} command to prevent your program from
5256 seeing a signal, or cause it to see a signal it normally would not see,
5257 or to give it any signal at any time. For example, if your program stopped
5258 due to some sort of memory reference error, you might store correct
5259 values into the erroneous variables and continue, hoping to see more
5260 execution; but your program would probably terminate immediately as
5261 a result of the fatal signal once it saw the signal. To prevent this,
5262 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5265 @cindex extra signal information
5266 @anchor{extra signal information}
5268 On some targets, @value{GDBN} can inspect extra signal information
5269 associated with the intercepted signal, before it is actually
5270 delivered to the program being debugged. This information is exported
5271 by the convenience variable @code{$_siginfo}, and consists of data
5272 that is passed by the kernel to the signal handler at the time of the
5273 receipt of a signal. The data type of the information itself is
5274 target dependent. You can see the data type using the @code{ptype
5275 $_siginfo} command. On Unix systems, it typically corresponds to the
5276 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5279 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5280 referenced address that raised a segmentation fault.
5284 (@value{GDBP}) continue
5285 Program received signal SIGSEGV, Segmentation fault.
5286 0x0000000000400766 in main ()
5288 (@value{GDBP}) ptype $_siginfo
5295 struct @{...@} _kill;
5296 struct @{...@} _timer;
5298 struct @{...@} _sigchld;
5299 struct @{...@} _sigfault;
5300 struct @{...@} _sigpoll;
5303 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5307 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5308 $1 = (void *) 0x7ffff7ff7000
5312 Depending on target support, @code{$_siginfo} may also be writable.
5315 @section Stopping and Starting Multi-thread Programs
5317 @cindex stopped threads
5318 @cindex threads, stopped
5320 @cindex continuing threads
5321 @cindex threads, continuing
5323 @value{GDBN} supports debugging programs with multiple threads
5324 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5325 are two modes of controlling execution of your program within the
5326 debugger. In the default mode, referred to as @dfn{all-stop mode},
5327 when any thread in your program stops (for example, at a breakpoint
5328 or while being stepped), all other threads in the program are also stopped by
5329 @value{GDBN}. On some targets, @value{GDBN} also supports
5330 @dfn{non-stop mode}, in which other threads can continue to run freely while
5331 you examine the stopped thread in the debugger.
5334 * All-Stop Mode:: All threads stop when GDB takes control
5335 * Non-Stop Mode:: Other threads continue to execute
5336 * Background Execution:: Running your program asynchronously
5337 * Thread-Specific Breakpoints:: Controlling breakpoints
5338 * Interrupted System Calls:: GDB may interfere with system calls
5339 * Observer Mode:: GDB does not alter program behavior
5343 @subsection All-Stop Mode
5345 @cindex all-stop mode
5347 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5348 @emph{all} threads of execution stop, not just the current thread. This
5349 allows you to examine the overall state of the program, including
5350 switching between threads, without worrying that things may change
5353 Conversely, whenever you restart the program, @emph{all} threads start
5354 executing. @emph{This is true even when single-stepping} with commands
5355 like @code{step} or @code{next}.
5357 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5358 Since thread scheduling is up to your debugging target's operating
5359 system (not controlled by @value{GDBN}), other threads may
5360 execute more than one statement while the current thread completes a
5361 single step. Moreover, in general other threads stop in the middle of a
5362 statement, rather than at a clean statement boundary, when the program
5365 You might even find your program stopped in another thread after
5366 continuing or even single-stepping. This happens whenever some other
5367 thread runs into a breakpoint, a signal, or an exception before the
5368 first thread completes whatever you requested.
5370 @cindex automatic thread selection
5371 @cindex switching threads automatically
5372 @cindex threads, automatic switching
5373 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5374 signal, it automatically selects the thread where that breakpoint or
5375 signal happened. @value{GDBN} alerts you to the context switch with a
5376 message such as @samp{[Switching to Thread @var{n}]} to identify the
5379 On some OSes, you can modify @value{GDBN}'s default behavior by
5380 locking the OS scheduler to allow only a single thread to run.
5383 @item set scheduler-locking @var{mode}
5384 @cindex scheduler locking mode
5385 @cindex lock scheduler
5386 Set the scheduler locking mode. If it is @code{off}, then there is no
5387 locking and any thread may run at any time. If @code{on}, then only the
5388 current thread may run when the inferior is resumed. The @code{step}
5389 mode optimizes for single-stepping; it prevents other threads
5390 from preempting the current thread while you are stepping, so that
5391 the focus of debugging does not change unexpectedly.
5392 Other threads only rarely (or never) get a chance to run
5393 when you step. They are more likely to run when you @samp{next} over a
5394 function call, and they are completely free to run when you use commands
5395 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5396 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5397 the current thread away from the thread that you are debugging.
5399 @item show scheduler-locking
5400 Display the current scheduler locking mode.
5403 @cindex resume threads of multiple processes simultaneously
5404 By default, when you issue one of the execution commands such as
5405 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5406 threads of the current inferior to run. For example, if @value{GDBN}
5407 is attached to two inferiors, each with two threads, the
5408 @code{continue} command resumes only the two threads of the current
5409 inferior. This is useful, for example, when you debug a program that
5410 forks and you want to hold the parent stopped (so that, for instance,
5411 it doesn't run to exit), while you debug the child. In other
5412 situations, you may not be interested in inspecting the current state
5413 of any of the processes @value{GDBN} is attached to, and you may want
5414 to resume them all until some breakpoint is hit. In the latter case,
5415 you can instruct @value{GDBN} to allow all threads of all the
5416 inferiors to run with the @w{@code{set schedule-multiple}} command.
5419 @kindex set schedule-multiple
5420 @item set schedule-multiple
5421 Set the mode for allowing threads of multiple processes to be resumed
5422 when an execution command is issued. When @code{on}, all threads of
5423 all processes are allowed to run. When @code{off}, only the threads
5424 of the current process are resumed. The default is @code{off}. The
5425 @code{scheduler-locking} mode takes precedence when set to @code{on},
5426 or while you are stepping and set to @code{step}.
5428 @item show schedule-multiple
5429 Display the current mode for resuming the execution of threads of
5434 @subsection Non-Stop Mode
5436 @cindex non-stop mode
5438 @c This section is really only a place-holder, and needs to be expanded
5439 @c with more details.
5441 For some multi-threaded targets, @value{GDBN} supports an optional
5442 mode of operation in which you can examine stopped program threads in
5443 the debugger while other threads continue to execute freely. This
5444 minimizes intrusion when debugging live systems, such as programs
5445 where some threads have real-time constraints or must continue to
5446 respond to external events. This is referred to as @dfn{non-stop} mode.
5448 In non-stop mode, when a thread stops to report a debugging event,
5449 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5450 threads as well, in contrast to the all-stop mode behavior. Additionally,
5451 execution commands such as @code{continue} and @code{step} apply by default
5452 only to the current thread in non-stop mode, rather than all threads as
5453 in all-stop mode. This allows you to control threads explicitly in
5454 ways that are not possible in all-stop mode --- for example, stepping
5455 one thread while allowing others to run freely, stepping
5456 one thread while holding all others stopped, or stepping several threads
5457 independently and simultaneously.
5459 To enter non-stop mode, use this sequence of commands before you run
5460 or attach to your program:
5463 # Enable the async interface.
5466 # If using the CLI, pagination breaks non-stop.
5469 # Finally, turn it on!
5473 You can use these commands to manipulate the non-stop mode setting:
5476 @kindex set non-stop
5477 @item set non-stop on
5478 Enable selection of non-stop mode.
5479 @item set non-stop off
5480 Disable selection of non-stop mode.
5481 @kindex show non-stop
5483 Show the current non-stop enablement setting.
5486 Note these commands only reflect whether non-stop mode is enabled,
5487 not whether the currently-executing program is being run in non-stop mode.
5488 In particular, the @code{set non-stop} preference is only consulted when
5489 @value{GDBN} starts or connects to the target program, and it is generally
5490 not possible to switch modes once debugging has started. Furthermore,
5491 since not all targets support non-stop mode, even when you have enabled
5492 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5495 In non-stop mode, all execution commands apply only to the current thread
5496 by default. That is, @code{continue} only continues one thread.
5497 To continue all threads, issue @code{continue -a} or @code{c -a}.
5499 You can use @value{GDBN}'s background execution commands
5500 (@pxref{Background Execution}) to run some threads in the background
5501 while you continue to examine or step others from @value{GDBN}.
5502 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5503 always executed asynchronously in non-stop mode.
5505 Suspending execution is done with the @code{interrupt} command when
5506 running in the background, or @kbd{Ctrl-c} during foreground execution.
5507 In all-stop mode, this stops the whole process;
5508 but in non-stop mode the interrupt applies only to the current thread.
5509 To stop the whole program, use @code{interrupt -a}.
5511 Other execution commands do not currently support the @code{-a} option.
5513 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5514 that thread current, as it does in all-stop mode. This is because the
5515 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5516 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5517 changed to a different thread just as you entered a command to operate on the
5518 previously current thread.
5520 @node Background Execution
5521 @subsection Background Execution
5523 @cindex foreground execution
5524 @cindex background execution
5525 @cindex asynchronous execution
5526 @cindex execution, foreground, background and asynchronous
5528 @value{GDBN}'s execution commands have two variants: the normal
5529 foreground (synchronous) behavior, and a background
5530 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5531 the program to report that some thread has stopped before prompting for
5532 another command. In background execution, @value{GDBN} immediately gives
5533 a command prompt so that you can issue other commands while your program runs.
5535 You need to explicitly enable asynchronous mode before you can use
5536 background execution commands. You can use these commands to
5537 manipulate the asynchronous mode setting:
5540 @kindex set target-async
5541 @item set target-async on
5542 Enable asynchronous mode.
5543 @item set target-async off
5544 Disable asynchronous mode.
5545 @kindex show target-async
5546 @item show target-async
5547 Show the current target-async setting.
5550 If the target doesn't support async mode, @value{GDBN} issues an error
5551 message if you attempt to use the background execution commands.
5553 To specify background execution, add a @code{&} to the command. For example,
5554 the background form of the @code{continue} command is @code{continue&}, or
5555 just @code{c&}. The execution commands that accept background execution
5561 @xref{Starting, , Starting your Program}.
5565 @xref{Attach, , Debugging an Already-running Process}.
5569 @xref{Continuing and Stepping, step}.
5573 @xref{Continuing and Stepping, stepi}.
5577 @xref{Continuing and Stepping, next}.
5581 @xref{Continuing and Stepping, nexti}.
5585 @xref{Continuing and Stepping, continue}.
5589 @xref{Continuing and Stepping, finish}.
5593 @xref{Continuing and Stepping, until}.
5597 Background execution is especially useful in conjunction with non-stop
5598 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5599 However, you can also use these commands in the normal all-stop mode with
5600 the restriction that you cannot issue another execution command until the
5601 previous one finishes. Examples of commands that are valid in all-stop
5602 mode while the program is running include @code{help} and @code{info break}.
5604 You can interrupt your program while it is running in the background by
5605 using the @code{interrupt} command.
5612 Suspend execution of the running program. In all-stop mode,
5613 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5614 only the current thread. To stop the whole program in non-stop mode,
5615 use @code{interrupt -a}.
5618 @node Thread-Specific Breakpoints
5619 @subsection Thread-Specific Breakpoints
5621 When your program has multiple threads (@pxref{Threads,, Debugging
5622 Programs with Multiple Threads}), you can choose whether to set
5623 breakpoints on all threads, or on a particular thread.
5626 @cindex breakpoints and threads
5627 @cindex thread breakpoints
5628 @kindex break @dots{} thread @var{threadno}
5629 @item break @var{linespec} thread @var{threadno}
5630 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5631 @var{linespec} specifies source lines; there are several ways of
5632 writing them (@pxref{Specify Location}), but the effect is always to
5633 specify some source line.
5635 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5636 to specify that you only want @value{GDBN} to stop the program when a
5637 particular thread reaches this breakpoint. @var{threadno} is one of the
5638 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5639 column of the @samp{info threads} display.
5641 If you do not specify @samp{thread @var{threadno}} when you set a
5642 breakpoint, the breakpoint applies to @emph{all} threads of your
5645 You can use the @code{thread} qualifier on conditional breakpoints as
5646 well; in this case, place @samp{thread @var{threadno}} before or
5647 after the breakpoint condition, like this:
5650 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5655 @node Interrupted System Calls
5656 @subsection Interrupted System Calls
5658 @cindex thread breakpoints and system calls
5659 @cindex system calls and thread breakpoints
5660 @cindex premature return from system calls
5661 There is an unfortunate side effect when using @value{GDBN} to debug
5662 multi-threaded programs. If one thread stops for a
5663 breakpoint, or for some other reason, and another thread is blocked in a
5664 system call, then the system call may return prematurely. This is a
5665 consequence of the interaction between multiple threads and the signals
5666 that @value{GDBN} uses to implement breakpoints and other events that
5669 To handle this problem, your program should check the return value of
5670 each system call and react appropriately. This is good programming
5673 For example, do not write code like this:
5679 The call to @code{sleep} will return early if a different thread stops
5680 at a breakpoint or for some other reason.
5682 Instead, write this:
5687 unslept = sleep (unslept);
5690 A system call is allowed to return early, so the system is still
5691 conforming to its specification. But @value{GDBN} does cause your
5692 multi-threaded program to behave differently than it would without
5695 Also, @value{GDBN} uses internal breakpoints in the thread library to
5696 monitor certain events such as thread creation and thread destruction.
5697 When such an event happens, a system call in another thread may return
5698 prematurely, even though your program does not appear to stop.
5701 @subsection Observer Mode
5703 If you want to build on non-stop mode and observe program behavior
5704 without any chance of disruption by @value{GDBN}, you can set
5705 variables to disable all of the debugger's attempts to modify state,
5706 whether by writing memory, inserting breakpoints, etc. These operate
5707 at a low level, intercepting operations from all commands.
5709 When all of these are set to @code{off}, then @value{GDBN} is said to
5710 be @dfn{observer mode}. As a convenience, the variable
5711 @code{observer} can be set to disable these, plus enable non-stop
5714 Note that @value{GDBN} will not prevent you from making nonsensical
5715 combinations of these settings. For instance, if you have enabled
5716 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5717 then breakpoints that work by writing trap instructions into the code
5718 stream will still not be able to be placed.
5723 @item set observer on
5724 @itemx set observer off
5725 When set to @code{on}, this disables all the permission variables
5726 below (except for @code{insert-fast-tracepoints}), plus enables
5727 non-stop debugging. Setting this to @code{off} switches back to
5728 normal debugging, though remaining in non-stop mode.
5731 Show whether observer mode is on or off.
5733 @kindex may-write-registers
5734 @item set may-write-registers on
5735 @itemx set may-write-registers off
5736 This controls whether @value{GDBN} will attempt to alter the values of
5737 registers, such as with assignment expressions in @code{print}, or the
5738 @code{jump} command. It defaults to @code{on}.
5740 @item show may-write-registers
5741 Show the current permission to write registers.
5743 @kindex may-write-memory
5744 @item set may-write-memory on
5745 @itemx set may-write-memory off
5746 This controls whether @value{GDBN} will attempt to alter the contents
5747 of memory, such as with assignment expressions in @code{print}. It
5748 defaults to @code{on}.
5750 @item show may-write-memory
5751 Show the current permission to write memory.
5753 @kindex may-insert-breakpoints
5754 @item set may-insert-breakpoints on
5755 @itemx set may-insert-breakpoints off
5756 This controls whether @value{GDBN} will attempt to insert breakpoints.
5757 This affects all breakpoints, including internal breakpoints defined
5758 by @value{GDBN}. It defaults to @code{on}.
5760 @item show may-insert-breakpoints
5761 Show the current permission to insert breakpoints.
5763 @kindex may-insert-tracepoints
5764 @item set may-insert-tracepoints on
5765 @itemx set may-insert-tracepoints off
5766 This controls whether @value{GDBN} will attempt to insert (regular)
5767 tracepoints at the beginning of a tracing experiment. It affects only
5768 non-fast tracepoints, fast tracepoints being under the control of
5769 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5771 @item show may-insert-tracepoints
5772 Show the current permission to insert tracepoints.
5774 @kindex may-insert-fast-tracepoints
5775 @item set may-insert-fast-tracepoints on
5776 @itemx set may-insert-fast-tracepoints off
5777 This controls whether @value{GDBN} will attempt to insert fast
5778 tracepoints at the beginning of a tracing experiment. It affects only
5779 fast tracepoints, regular (non-fast) tracepoints being under the
5780 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5782 @item show may-insert-fast-tracepoints
5783 Show the current permission to insert fast tracepoints.
5785 @kindex may-interrupt
5786 @item set may-interrupt on
5787 @itemx set may-interrupt off
5788 This controls whether @value{GDBN} will attempt to interrupt or stop
5789 program execution. When this variable is @code{off}, the
5790 @code{interrupt} command will have no effect, nor will
5791 @kbd{Ctrl-c}. It defaults to @code{on}.
5793 @item show may-interrupt
5794 Show the current permission to interrupt or stop the program.
5798 @node Reverse Execution
5799 @chapter Running programs backward
5800 @cindex reverse execution
5801 @cindex running programs backward
5803 When you are debugging a program, it is not unusual to realize that
5804 you have gone too far, and some event of interest has already happened.
5805 If the target environment supports it, @value{GDBN} can allow you to
5806 ``rewind'' the program by running it backward.
5808 A target environment that supports reverse execution should be able
5809 to ``undo'' the changes in machine state that have taken place as the
5810 program was executing normally. Variables, registers etc.@: should
5811 revert to their previous values. Obviously this requires a great
5812 deal of sophistication on the part of the target environment; not
5813 all target environments can support reverse execution.
5815 When a program is executed in reverse, the instructions that
5816 have most recently been executed are ``un-executed'', in reverse
5817 order. The program counter runs backward, following the previous
5818 thread of execution in reverse. As each instruction is ``un-executed'',
5819 the values of memory and/or registers that were changed by that
5820 instruction are reverted to their previous states. After executing
5821 a piece of source code in reverse, all side effects of that code
5822 should be ``undone'', and all variables should be returned to their
5823 prior values@footnote{
5824 Note that some side effects are easier to undo than others. For instance,
5825 memory and registers are relatively easy, but device I/O is hard. Some
5826 targets may be able undo things like device I/O, and some may not.
5828 The contract between @value{GDBN} and the reverse executing target
5829 requires only that the target do something reasonable when
5830 @value{GDBN} tells it to execute backwards, and then report the
5831 results back to @value{GDBN}. Whatever the target reports back to
5832 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5833 assumes that the memory and registers that the target reports are in a
5834 consistant state, but @value{GDBN} accepts whatever it is given.
5837 If you are debugging in a target environment that supports
5838 reverse execution, @value{GDBN} provides the following commands.
5841 @kindex reverse-continue
5842 @kindex rc @r{(@code{reverse-continue})}
5843 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5844 @itemx rc @r{[}@var{ignore-count}@r{]}
5845 Beginning at the point where your program last stopped, start executing
5846 in reverse. Reverse execution will stop for breakpoints and synchronous
5847 exceptions (signals), just like normal execution. Behavior of
5848 asynchronous signals depends on the target environment.
5850 @kindex reverse-step
5851 @kindex rs @r{(@code{step})}
5852 @item reverse-step @r{[}@var{count}@r{]}
5853 Run the program backward until control reaches the start of a
5854 different source line; then stop it, and return control to @value{GDBN}.
5856 Like the @code{step} command, @code{reverse-step} will only stop
5857 at the beginning of a source line. It ``un-executes'' the previously
5858 executed source line. If the previous source line included calls to
5859 debuggable functions, @code{reverse-step} will step (backward) into
5860 the called function, stopping at the beginning of the @emph{last}
5861 statement in the called function (typically a return statement).
5863 Also, as with the @code{step} command, if non-debuggable functions are
5864 called, @code{reverse-step} will run thru them backward without stopping.
5866 @kindex reverse-stepi
5867 @kindex rsi @r{(@code{reverse-stepi})}
5868 @item reverse-stepi @r{[}@var{count}@r{]}
5869 Reverse-execute one machine instruction. Note that the instruction
5870 to be reverse-executed is @emph{not} the one pointed to by the program
5871 counter, but the instruction executed prior to that one. For instance,
5872 if the last instruction was a jump, @code{reverse-stepi} will take you
5873 back from the destination of the jump to the jump instruction itself.
5875 @kindex reverse-next
5876 @kindex rn @r{(@code{reverse-next})}
5877 @item reverse-next @r{[}@var{count}@r{]}
5878 Run backward to the beginning of the previous line executed in
5879 the current (innermost) stack frame. If the line contains function
5880 calls, they will be ``un-executed'' without stopping. Starting from
5881 the first line of a function, @code{reverse-next} will take you back
5882 to the caller of that function, @emph{before} the function was called,
5883 just as the normal @code{next} command would take you from the last
5884 line of a function back to its return to its caller
5885 @footnote{Unless the code is too heavily optimized.}.
5887 @kindex reverse-nexti
5888 @kindex rni @r{(@code{reverse-nexti})}
5889 @item reverse-nexti @r{[}@var{count}@r{]}
5890 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5891 in reverse, except that called functions are ``un-executed'' atomically.
5892 That is, if the previously executed instruction was a return from
5893 another function, @code{reverse-nexti} will continue to execute
5894 in reverse until the call to that function (from the current stack
5897 @kindex reverse-finish
5898 @item reverse-finish
5899 Just as the @code{finish} command takes you to the point where the
5900 current function returns, @code{reverse-finish} takes you to the point
5901 where it was called. Instead of ending up at the end of the current
5902 function invocation, you end up at the beginning.
5904 @kindex set exec-direction
5905 @item set exec-direction
5906 Set the direction of target execution.
5907 @itemx set exec-direction reverse
5908 @cindex execute forward or backward in time
5909 @value{GDBN} will perform all execution commands in reverse, until the
5910 exec-direction mode is changed to ``forward''. Affected commands include
5911 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5912 command cannot be used in reverse mode.
5913 @item set exec-direction forward
5914 @value{GDBN} will perform all execution commands in the normal fashion.
5915 This is the default.
5919 @node Process Record and Replay
5920 @chapter Recording Inferior's Execution and Replaying It
5921 @cindex process record and replay
5922 @cindex recording inferior's execution and replaying it
5924 On some platforms, @value{GDBN} provides a special @dfn{process record
5925 and replay} target that can record a log of the process execution, and
5926 replay it later with both forward and reverse execution commands.
5929 When this target is in use, if the execution log includes the record
5930 for the next instruction, @value{GDBN} will debug in @dfn{replay
5931 mode}. In the replay mode, the inferior does not really execute code
5932 instructions. Instead, all the events that normally happen during
5933 code execution are taken from the execution log. While code is not
5934 really executed in replay mode, the values of registers (including the
5935 program counter register) and the memory of the inferior are still
5936 changed as they normally would. Their contents are taken from the
5940 If the record for the next instruction is not in the execution log,
5941 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5942 inferior executes normally, and @value{GDBN} records the execution log
5945 The process record and replay target supports reverse execution
5946 (@pxref{Reverse Execution}), even if the platform on which the
5947 inferior runs does not. However, the reverse execution is limited in
5948 this case by the range of the instructions recorded in the execution
5949 log. In other words, reverse execution on platforms that don't
5950 support it directly can only be done in the replay mode.
5952 When debugging in the reverse direction, @value{GDBN} will work in
5953 replay mode as long as the execution log includes the record for the
5954 previous instruction; otherwise, it will work in record mode, if the
5955 platform supports reverse execution, or stop if not.
5957 For architecture environments that support process record and replay,
5958 @value{GDBN} provides the following commands:
5961 @kindex target record
5965 This command starts the process record and replay target. The process
5966 record and replay target can only debug a process that is already
5967 running. Therefore, you need first to start the process with the
5968 @kbd{run} or @kbd{start} commands, and then start the recording with
5969 the @kbd{target record} command.
5971 Both @code{record} and @code{rec} are aliases of @code{target record}.
5973 @cindex displaced stepping, and process record and replay
5974 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5975 will be automatically disabled when process record and replay target
5976 is started. That's because the process record and replay target
5977 doesn't support displaced stepping.
5979 @cindex non-stop mode, and process record and replay
5980 @cindex asynchronous execution, and process record and replay
5981 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5982 the asynchronous execution mode (@pxref{Background Execution}), the
5983 process record and replay target cannot be started because it doesn't
5984 support these two modes.
5989 Stop the process record and replay target. When process record and
5990 replay target stops, the entire execution log will be deleted and the
5991 inferior will either be terminated, or will remain in its final state.
5993 When you stop the process record and replay target in record mode (at
5994 the end of the execution log), the inferior will be stopped at the
5995 next instruction that would have been recorded. In other words, if
5996 you record for a while and then stop recording, the inferior process
5997 will be left in the same state as if the recording never happened.
5999 On the other hand, if the process record and replay target is stopped
6000 while in replay mode (that is, not at the end of the execution log,
6001 but at some earlier point), the inferior process will become ``live''
6002 at that earlier state, and it will then be possible to continue the
6003 usual ``live'' debugging of the process from that state.
6005 When the inferior process exits, or @value{GDBN} detaches from it,
6006 process record and replay target will automatically stop itself.
6009 @item record save @var{filename}
6010 Save the execution log to a file @file{@var{filename}}.
6011 Default filename is @file{gdb_record.@var{process_id}}, where
6012 @var{process_id} is the process ID of the inferior.
6014 @kindex record restore
6015 @item record restore @var{filename}
6016 Restore the execution log from a file @file{@var{filename}}.
6017 File must have been created with @code{record save}.
6019 @kindex set record insn-number-max
6020 @item set record insn-number-max @var{limit}
6021 Set the limit of instructions to be recorded. Default value is 200000.
6023 If @var{limit} is a positive number, then @value{GDBN} will start
6024 deleting instructions from the log once the number of the record
6025 instructions becomes greater than @var{limit}. For every new recorded
6026 instruction, @value{GDBN} will delete the earliest recorded
6027 instruction to keep the number of recorded instructions at the limit.
6028 (Since deleting recorded instructions loses information, @value{GDBN}
6029 lets you control what happens when the limit is reached, by means of
6030 the @code{stop-at-limit} option, described below.)
6032 If @var{limit} is zero, @value{GDBN} will never delete recorded
6033 instructions from the execution log. The number of recorded
6034 instructions is unlimited in this case.
6036 @kindex show record insn-number-max
6037 @item show record insn-number-max
6038 Show the limit of instructions to be recorded.
6040 @kindex set record stop-at-limit
6041 @item set record stop-at-limit
6042 Control the behavior when the number of recorded instructions reaches
6043 the limit. If ON (the default), @value{GDBN} will stop when the limit
6044 is reached for the first time and ask you whether you want to stop the
6045 inferior or continue running it and recording the execution log. If
6046 you decide to continue recording, each new recorded instruction will
6047 cause the oldest one to be deleted.
6049 If this option is OFF, @value{GDBN} will automatically delete the
6050 oldest record to make room for each new one, without asking.
6052 @kindex show record stop-at-limit
6053 @item show record stop-at-limit
6054 Show the current setting of @code{stop-at-limit}.
6056 @kindex set record memory-query
6057 @item set record memory-query
6058 Control the behavior when @value{GDBN} is unable to record memory
6059 changes caused by an instruction. If ON, @value{GDBN} will query
6060 whether to stop the inferior in that case.
6062 If this option is OFF (the default), @value{GDBN} will automatically
6063 ignore the effect of such instructions on memory. Later, when
6064 @value{GDBN} replays this execution log, it will mark the log of this
6065 instruction as not accessible, and it will not affect the replay
6068 @kindex show record memory-query
6069 @item show record memory-query
6070 Show the current setting of @code{memory-query}.
6074 Show various statistics about the state of process record and its
6075 in-memory execution log buffer, including:
6079 Whether in record mode or replay mode.
6081 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6083 Highest recorded instruction number.
6085 Current instruction about to be replayed (if in replay mode).
6087 Number of instructions contained in the execution log.
6089 Maximum number of instructions that may be contained in the execution log.
6092 @kindex record delete
6095 When record target runs in replay mode (``in the past''), delete the
6096 subsequent execution log and begin to record a new execution log starting
6097 from the current address. This means you will abandon the previously
6098 recorded ``future'' and begin recording a new ``future''.
6103 @chapter Examining the Stack
6105 When your program has stopped, the first thing you need to know is where it
6106 stopped and how it got there.
6109 Each time your program performs a function call, information about the call
6111 That information includes the location of the call in your program,
6112 the arguments of the call,
6113 and the local variables of the function being called.
6114 The information is saved in a block of data called a @dfn{stack frame}.
6115 The stack frames are allocated in a region of memory called the @dfn{call
6118 When your program stops, the @value{GDBN} commands for examining the
6119 stack allow you to see all of this information.
6121 @cindex selected frame
6122 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6123 @value{GDBN} commands refer implicitly to the selected frame. In
6124 particular, whenever you ask @value{GDBN} for the value of a variable in
6125 your program, the value is found in the selected frame. There are
6126 special @value{GDBN} commands to select whichever frame you are
6127 interested in. @xref{Selection, ,Selecting a Frame}.
6129 When your program stops, @value{GDBN} automatically selects the
6130 currently executing frame and describes it briefly, similar to the
6131 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6134 * Frames:: Stack frames
6135 * Backtrace:: Backtraces
6136 * Selection:: Selecting a frame
6137 * Frame Info:: Information on a frame
6142 @section Stack Frames
6144 @cindex frame, definition
6146 The call stack is divided up into contiguous pieces called @dfn{stack
6147 frames}, or @dfn{frames} for short; each frame is the data associated
6148 with one call to one function. The frame contains the arguments given
6149 to the function, the function's local variables, and the address at
6150 which the function is executing.
6152 @cindex initial frame
6153 @cindex outermost frame
6154 @cindex innermost frame
6155 When your program is started, the stack has only one frame, that of the
6156 function @code{main}. This is called the @dfn{initial} frame or the
6157 @dfn{outermost} frame. Each time a function is called, a new frame is
6158 made. Each time a function returns, the frame for that function invocation
6159 is eliminated. If a function is recursive, there can be many frames for
6160 the same function. The frame for the function in which execution is
6161 actually occurring is called the @dfn{innermost} frame. This is the most
6162 recently created of all the stack frames that still exist.
6164 @cindex frame pointer
6165 Inside your program, stack frames are identified by their addresses. A
6166 stack frame consists of many bytes, each of which has its own address; each
6167 kind of computer has a convention for choosing one byte whose
6168 address serves as the address of the frame. Usually this address is kept
6169 in a register called the @dfn{frame pointer register}
6170 (@pxref{Registers, $fp}) while execution is going on in that frame.
6172 @cindex frame number
6173 @value{GDBN} assigns numbers to all existing stack frames, starting with
6174 zero for the innermost frame, one for the frame that called it,
6175 and so on upward. These numbers do not really exist in your program;
6176 they are assigned by @value{GDBN} to give you a way of designating stack
6177 frames in @value{GDBN} commands.
6179 @c The -fomit-frame-pointer below perennially causes hbox overflow
6180 @c underflow problems.
6181 @cindex frameless execution
6182 Some compilers provide a way to compile functions so that they operate
6183 without stack frames. (For example, the @value{NGCC} option
6185 @samp{-fomit-frame-pointer}
6187 generates functions without a frame.)
6188 This is occasionally done with heavily used library functions to save
6189 the frame setup time. @value{GDBN} has limited facilities for dealing
6190 with these function invocations. If the innermost function invocation
6191 has no stack frame, @value{GDBN} nevertheless regards it as though
6192 it had a separate frame, which is numbered zero as usual, allowing
6193 correct tracing of the function call chain. However, @value{GDBN} has
6194 no provision for frameless functions elsewhere in the stack.
6197 @kindex frame@r{, command}
6198 @cindex current stack frame
6199 @item frame @var{args}
6200 The @code{frame} command allows you to move from one stack frame to another,
6201 and to print the stack frame you select. @var{args} may be either the
6202 address of the frame or the stack frame number. Without an argument,
6203 @code{frame} prints the current stack frame.
6205 @kindex select-frame
6206 @cindex selecting frame silently
6208 The @code{select-frame} command allows you to move from one stack frame
6209 to another without printing the frame. This is the silent version of
6217 @cindex call stack traces
6218 A backtrace is a summary of how your program got where it is. It shows one
6219 line per frame, for many frames, starting with the currently executing
6220 frame (frame zero), followed by its caller (frame one), and on up the
6225 @kindex bt @r{(@code{backtrace})}
6228 Print a backtrace of the entire stack: one line per frame for all
6229 frames in the stack.
6231 You can stop the backtrace at any time by typing the system interrupt
6232 character, normally @kbd{Ctrl-c}.
6234 @item backtrace @var{n}
6236 Similar, but print only the innermost @var{n} frames.
6238 @item backtrace -@var{n}
6240 Similar, but print only the outermost @var{n} frames.
6242 @item backtrace full
6244 @itemx bt full @var{n}
6245 @itemx bt full -@var{n}
6246 Print the values of the local variables also. @var{n} specifies the
6247 number of frames to print, as described above.
6252 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6253 are additional aliases for @code{backtrace}.
6255 @cindex multiple threads, backtrace
6256 In a multi-threaded program, @value{GDBN} by default shows the
6257 backtrace only for the current thread. To display the backtrace for
6258 several or all of the threads, use the command @code{thread apply}
6259 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6260 apply all backtrace}, @value{GDBN} will display the backtrace for all
6261 the threads; this is handy when you debug a core dump of a
6262 multi-threaded program.
6264 Each line in the backtrace shows the frame number and the function name.
6265 The program counter value is also shown---unless you use @code{set
6266 print address off}. The backtrace also shows the source file name and
6267 line number, as well as the arguments to the function. The program
6268 counter value is omitted if it is at the beginning of the code for that
6271 Here is an example of a backtrace. It was made with the command
6272 @samp{bt 3}, so it shows the innermost three frames.
6276 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6278 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6279 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6281 (More stack frames follow...)
6286 The display for frame zero does not begin with a program counter
6287 value, indicating that your program has stopped at the beginning of the
6288 code for line @code{993} of @code{builtin.c}.
6291 The value of parameter @code{data} in frame 1 has been replaced by
6292 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6293 only if it is a scalar (integer, pointer, enumeration, etc). See command
6294 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6295 on how to configure the way function parameter values are printed.
6297 @cindex optimized out, in backtrace
6298 @cindex function call arguments, optimized out
6299 If your program was compiled with optimizations, some compilers will
6300 optimize away arguments passed to functions if those arguments are
6301 never used after the call. Such optimizations generate code that
6302 passes arguments through registers, but doesn't store those arguments
6303 in the stack frame. @value{GDBN} has no way of displaying such
6304 arguments in stack frames other than the innermost one. Here's what
6305 such a backtrace might look like:
6309 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6311 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6312 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6314 (More stack frames follow...)
6319 The values of arguments that were not saved in their stack frames are
6320 shown as @samp{<optimized out>}.
6322 If you need to display the values of such optimized-out arguments,
6323 either deduce that from other variables whose values depend on the one
6324 you are interested in, or recompile without optimizations.
6326 @cindex backtrace beyond @code{main} function
6327 @cindex program entry point
6328 @cindex startup code, and backtrace
6329 Most programs have a standard user entry point---a place where system
6330 libraries and startup code transition into user code. For C this is
6331 @code{main}@footnote{
6332 Note that embedded programs (the so-called ``free-standing''
6333 environment) are not required to have a @code{main} function as the
6334 entry point. They could even have multiple entry points.}.
6335 When @value{GDBN} finds the entry function in a backtrace
6336 it will terminate the backtrace, to avoid tracing into highly
6337 system-specific (and generally uninteresting) code.
6339 If you need to examine the startup code, or limit the number of levels
6340 in a backtrace, you can change this behavior:
6343 @item set backtrace past-main
6344 @itemx set backtrace past-main on
6345 @kindex set backtrace
6346 Backtraces will continue past the user entry point.
6348 @item set backtrace past-main off
6349 Backtraces will stop when they encounter the user entry point. This is the
6352 @item show backtrace past-main
6353 @kindex show backtrace
6354 Display the current user entry point backtrace policy.
6356 @item set backtrace past-entry
6357 @itemx set backtrace past-entry on
6358 Backtraces will continue past the internal entry point of an application.
6359 This entry point is encoded by the linker when the application is built,
6360 and is likely before the user entry point @code{main} (or equivalent) is called.
6362 @item set backtrace past-entry off
6363 Backtraces will stop when they encounter the internal entry point of an
6364 application. This is the default.
6366 @item show backtrace past-entry
6367 Display the current internal entry point backtrace policy.
6369 @item set backtrace limit @var{n}
6370 @itemx set backtrace limit 0
6371 @cindex backtrace limit
6372 Limit the backtrace to @var{n} levels. A value of zero means
6375 @item show backtrace limit
6376 Display the current limit on backtrace levels.
6380 @section Selecting a Frame
6382 Most commands for examining the stack and other data in your program work on
6383 whichever stack frame is selected at the moment. Here are the commands for
6384 selecting a stack frame; all of them finish by printing a brief description
6385 of the stack frame just selected.
6388 @kindex frame@r{, selecting}
6389 @kindex f @r{(@code{frame})}
6392 Select frame number @var{n}. Recall that frame zero is the innermost
6393 (currently executing) frame, frame one is the frame that called the
6394 innermost one, and so on. The highest-numbered frame is the one for
6397 @item frame @var{addr}
6399 Select the frame at address @var{addr}. This is useful mainly if the
6400 chaining of stack frames has been damaged by a bug, making it
6401 impossible for @value{GDBN} to assign numbers properly to all frames. In
6402 addition, this can be useful when your program has multiple stacks and
6403 switches between them.
6405 On the SPARC architecture, @code{frame} needs two addresses to
6406 select an arbitrary frame: a frame pointer and a stack pointer.
6408 On the MIPS and Alpha architecture, it needs two addresses: a stack
6409 pointer and a program counter.
6411 On the 29k architecture, it needs three addresses: a register stack
6412 pointer, a program counter, and a memory stack pointer.
6416 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6417 advances toward the outermost frame, to higher frame numbers, to frames
6418 that have existed longer. @var{n} defaults to one.
6421 @kindex do @r{(@code{down})}
6423 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6424 advances toward the innermost frame, to lower frame numbers, to frames
6425 that were created more recently. @var{n} defaults to one. You may
6426 abbreviate @code{down} as @code{do}.
6429 All of these commands end by printing two lines of output describing the
6430 frame. The first line shows the frame number, the function name, the
6431 arguments, and the source file and line number of execution in that
6432 frame. The second line shows the text of that source line.
6440 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6442 10 read_input_file (argv[i]);
6446 After such a printout, the @code{list} command with no arguments
6447 prints ten lines centered on the point of execution in the frame.
6448 You can also edit the program at the point of execution with your favorite
6449 editing program by typing @code{edit}.
6450 @xref{List, ,Printing Source Lines},
6454 @kindex down-silently
6456 @item up-silently @var{n}
6457 @itemx down-silently @var{n}
6458 These two commands are variants of @code{up} and @code{down},
6459 respectively; they differ in that they do their work silently, without
6460 causing display of the new frame. They are intended primarily for use
6461 in @value{GDBN} command scripts, where the output might be unnecessary and
6466 @section Information About a Frame
6468 There are several other commands to print information about the selected
6474 When used without any argument, this command does not change which
6475 frame is selected, but prints a brief description of the currently
6476 selected stack frame. It can be abbreviated @code{f}. With an
6477 argument, this command is used to select a stack frame.
6478 @xref{Selection, ,Selecting a Frame}.
6481 @kindex info f @r{(@code{info frame})}
6484 This command prints a verbose description of the selected stack frame,
6489 the address of the frame
6491 the address of the next frame down (called by this frame)
6493 the address of the next frame up (caller of this frame)
6495 the language in which the source code corresponding to this frame is written
6497 the address of the frame's arguments
6499 the address of the frame's local variables
6501 the program counter saved in it (the address of execution in the caller frame)
6503 which registers were saved in the frame
6506 @noindent The verbose description is useful when
6507 something has gone wrong that has made the stack format fail to fit
6508 the usual conventions.
6510 @item info frame @var{addr}
6511 @itemx info f @var{addr}
6512 Print a verbose description of the frame at address @var{addr}, without
6513 selecting that frame. The selected frame remains unchanged by this
6514 command. This requires the same kind of address (more than one for some
6515 architectures) that you specify in the @code{frame} command.
6516 @xref{Selection, ,Selecting a Frame}.
6520 Print the arguments of the selected frame, each on a separate line.
6524 Print the local variables of the selected frame, each on a separate
6525 line. These are all variables (declared either static or automatic)
6526 accessible at the point of execution of the selected frame.
6532 @chapter Examining Source Files
6534 @value{GDBN} can print parts of your program's source, since the debugging
6535 information recorded in the program tells @value{GDBN} what source files were
6536 used to build it. When your program stops, @value{GDBN} spontaneously prints
6537 the line where it stopped. Likewise, when you select a stack frame
6538 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6539 execution in that frame has stopped. You can print other portions of
6540 source files by explicit command.
6542 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6543 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6544 @value{GDBN} under @sc{gnu} Emacs}.
6547 * List:: Printing source lines
6548 * Specify Location:: How to specify code locations
6549 * Edit:: Editing source files
6550 * Search:: Searching source files
6551 * Source Path:: Specifying source directories
6552 * Machine Code:: Source and machine code
6556 @section Printing Source Lines
6559 @kindex l @r{(@code{list})}
6560 To print lines from a source file, use the @code{list} command
6561 (abbreviated @code{l}). By default, ten lines are printed.
6562 There are several ways to specify what part of the file you want to
6563 print; see @ref{Specify Location}, for the full list.
6565 Here are the forms of the @code{list} command most commonly used:
6568 @item list @var{linenum}
6569 Print lines centered around line number @var{linenum} in the
6570 current source file.
6572 @item list @var{function}
6573 Print lines centered around the beginning of function
6577 Print more lines. If the last lines printed were printed with a
6578 @code{list} command, this prints lines following the last lines
6579 printed; however, if the last line printed was a solitary line printed
6580 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6581 Stack}), this prints lines centered around that line.
6584 Print lines just before the lines last printed.
6587 @cindex @code{list}, how many lines to display
6588 By default, @value{GDBN} prints ten source lines with any of these forms of
6589 the @code{list} command. You can change this using @code{set listsize}:
6592 @kindex set listsize
6593 @item set listsize @var{count}
6594 Make the @code{list} command display @var{count} source lines (unless
6595 the @code{list} argument explicitly specifies some other number).
6597 @kindex show listsize
6599 Display the number of lines that @code{list} prints.
6602 Repeating a @code{list} command with @key{RET} discards the argument,
6603 so it is equivalent to typing just @code{list}. This is more useful
6604 than listing the same lines again. An exception is made for an
6605 argument of @samp{-}; that argument is preserved in repetition so that
6606 each repetition moves up in the source file.
6608 In general, the @code{list} command expects you to supply zero, one or two
6609 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6610 of writing them (@pxref{Specify Location}), but the effect is always
6611 to specify some source line.
6613 Here is a complete description of the possible arguments for @code{list}:
6616 @item list @var{linespec}
6617 Print lines centered around the line specified by @var{linespec}.
6619 @item list @var{first},@var{last}
6620 Print lines from @var{first} to @var{last}. Both arguments are
6621 linespecs. When a @code{list} command has two linespecs, and the
6622 source file of the second linespec is omitted, this refers to
6623 the same source file as the first linespec.
6625 @item list ,@var{last}
6626 Print lines ending with @var{last}.
6628 @item list @var{first},
6629 Print lines starting with @var{first}.
6632 Print lines just after the lines last printed.
6635 Print lines just before the lines last printed.
6638 As described in the preceding table.
6641 @node Specify Location
6642 @section Specifying a Location
6643 @cindex specifying location
6646 Several @value{GDBN} commands accept arguments that specify a location
6647 of your program's code. Since @value{GDBN} is a source-level
6648 debugger, a location usually specifies some line in the source code;
6649 for that reason, locations are also known as @dfn{linespecs}.
6651 Here are all the different ways of specifying a code location that
6652 @value{GDBN} understands:
6656 Specifies the line number @var{linenum} of the current source file.
6659 @itemx +@var{offset}
6660 Specifies the line @var{offset} lines before or after the @dfn{current
6661 line}. For the @code{list} command, the current line is the last one
6662 printed; for the breakpoint commands, this is the line at which
6663 execution stopped in the currently selected @dfn{stack frame}
6664 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6665 used as the second of the two linespecs in a @code{list} command,
6666 this specifies the line @var{offset} lines up or down from the first
6669 @item @var{filename}:@var{linenum}
6670 Specifies the line @var{linenum} in the source file @var{filename}.
6671 If @var{filename} is a relative file name, then it will match any
6672 source file name with the same trailing components. For example, if
6673 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6674 name of @file{/build/trunk/gcc/expr.c}, but not
6675 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6677 @item @var{function}
6678 Specifies the line that begins the body of the function @var{function}.
6679 For example, in C, this is the line with the open brace.
6681 @item @var{function}:@var{label}
6682 Specifies the line where @var{label} appears in @var{function}.
6684 @item @var{filename}:@var{function}
6685 Specifies the line that begins the body of the function @var{function}
6686 in the file @var{filename}. You only need the file name with a
6687 function name to avoid ambiguity when there are identically named
6688 functions in different source files.
6691 Specifies the line at which the label named @var{label} appears.
6692 @value{GDBN} searches for the label in the function corresponding to
6693 the currently selected stack frame. If there is no current selected
6694 stack frame (for instance, if the inferior is not running), then
6695 @value{GDBN} will not search for a label.
6697 @item *@var{address}
6698 Specifies the program address @var{address}. For line-oriented
6699 commands, such as @code{list} and @code{edit}, this specifies a source
6700 line that contains @var{address}. For @code{break} and other
6701 breakpoint oriented commands, this can be used to set breakpoints in
6702 parts of your program which do not have debugging information or
6705 Here @var{address} may be any expression valid in the current working
6706 language (@pxref{Languages, working language}) that specifies a code
6707 address. In addition, as a convenience, @value{GDBN} extends the
6708 semantics of expressions used in locations to cover the situations
6709 that frequently happen during debugging. Here are the various forms
6713 @item @var{expression}
6714 Any expression valid in the current working language.
6716 @item @var{funcaddr}
6717 An address of a function or procedure derived from its name. In C,
6718 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6719 simply the function's name @var{function} (and actually a special case
6720 of a valid expression). In Pascal and Modula-2, this is
6721 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6722 (although the Pascal form also works).
6724 This form specifies the address of the function's first instruction,
6725 before the stack frame and arguments have been set up.
6727 @item '@var{filename}'::@var{funcaddr}
6728 Like @var{funcaddr} above, but also specifies the name of the source
6729 file explicitly. This is useful if the name of the function does not
6730 specify the function unambiguously, e.g., if there are several
6731 functions with identical names in different source files.
6734 @cindex breakpoint at static probe point
6735 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
6736 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
6737 applications to embed static probes. @xref{Static Probe Points}, for more
6738 information on finding and using static probes. This form of linespec
6739 specifies the location of such a static probe.
6741 If @var{objfile} is given, only probes coming from that shared library
6742 or executable matching @var{objfile} as a regular expression are considered.
6743 If @var{provider} is given, then only probes from that provider are considered.
6744 If several probes match the spec, @value{GDBN} will insert a breakpoint at
6745 each one of those probes.
6751 @section Editing Source Files
6752 @cindex editing source files
6755 @kindex e @r{(@code{edit})}
6756 To edit the lines in a source file, use the @code{edit} command.
6757 The editing program of your choice
6758 is invoked with the current line set to
6759 the active line in the program.
6760 Alternatively, there are several ways to specify what part of the file you
6761 want to print if you want to see other parts of the program:
6764 @item edit @var{location}
6765 Edit the source file specified by @code{location}. Editing starts at
6766 that @var{location}, e.g., at the specified source line of the
6767 specified file. @xref{Specify Location}, for all the possible forms
6768 of the @var{location} argument; here are the forms of the @code{edit}
6769 command most commonly used:
6772 @item edit @var{number}
6773 Edit the current source file with @var{number} as the active line number.
6775 @item edit @var{function}
6776 Edit the file containing @var{function} at the beginning of its definition.
6781 @subsection Choosing your Editor
6782 You can customize @value{GDBN} to use any editor you want
6784 The only restriction is that your editor (say @code{ex}), recognizes the
6785 following command-line syntax:
6787 ex +@var{number} file
6789 The optional numeric value +@var{number} specifies the number of the line in
6790 the file where to start editing.}.
6791 By default, it is @file{@value{EDITOR}}, but you can change this
6792 by setting the environment variable @code{EDITOR} before using
6793 @value{GDBN}. For example, to configure @value{GDBN} to use the
6794 @code{vi} editor, you could use these commands with the @code{sh} shell:
6800 or in the @code{csh} shell,
6802 setenv EDITOR /usr/bin/vi
6807 @section Searching Source Files
6808 @cindex searching source files
6810 There are two commands for searching through the current source file for a
6815 @kindex forward-search
6816 @item forward-search @var{regexp}
6817 @itemx search @var{regexp}
6818 The command @samp{forward-search @var{regexp}} checks each line,
6819 starting with the one following the last line listed, for a match for
6820 @var{regexp}. It lists the line that is found. You can use the
6821 synonym @samp{search @var{regexp}} or abbreviate the command name as
6824 @kindex reverse-search
6825 @item reverse-search @var{regexp}
6826 The command @samp{reverse-search @var{regexp}} checks each line, starting
6827 with the one before the last line listed and going backward, for a match
6828 for @var{regexp}. It lists the line that is found. You can abbreviate
6829 this command as @code{rev}.
6833 @section Specifying Source Directories
6836 @cindex directories for source files
6837 Executable programs sometimes do not record the directories of the source
6838 files from which they were compiled, just the names. Even when they do,
6839 the directories could be moved between the compilation and your debugging
6840 session. @value{GDBN} has a list of directories to search for source files;
6841 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6842 it tries all the directories in the list, in the order they are present
6843 in the list, until it finds a file with the desired name.
6845 For example, suppose an executable references the file
6846 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6847 @file{/mnt/cross}. The file is first looked up literally; if this
6848 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6849 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6850 message is printed. @value{GDBN} does not look up the parts of the
6851 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6852 Likewise, the subdirectories of the source path are not searched: if
6853 the source path is @file{/mnt/cross}, and the binary refers to
6854 @file{foo.c}, @value{GDBN} would not find it under
6855 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6857 Plain file names, relative file names with leading directories, file
6858 names containing dots, etc.@: are all treated as described above; for
6859 instance, if the source path is @file{/mnt/cross}, and the source file
6860 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6861 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6862 that---@file{/mnt/cross/foo.c}.
6864 Note that the executable search path is @emph{not} used to locate the
6867 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6868 any information it has cached about where source files are found and where
6869 each line is in the file.
6873 When you start @value{GDBN}, its source path includes only @samp{cdir}
6874 and @samp{cwd}, in that order.
6875 To add other directories, use the @code{directory} command.
6877 The search path is used to find both program source files and @value{GDBN}
6878 script files (read using the @samp{-command} option and @samp{source} command).
6880 In addition to the source path, @value{GDBN} provides a set of commands
6881 that manage a list of source path substitution rules. A @dfn{substitution
6882 rule} specifies how to rewrite source directories stored in the program's
6883 debug information in case the sources were moved to a different
6884 directory between compilation and debugging. A rule is made of
6885 two strings, the first specifying what needs to be rewritten in
6886 the path, and the second specifying how it should be rewritten.
6887 In @ref{set substitute-path}, we name these two parts @var{from} and
6888 @var{to} respectively. @value{GDBN} does a simple string replacement
6889 of @var{from} with @var{to} at the start of the directory part of the
6890 source file name, and uses that result instead of the original file
6891 name to look up the sources.
6893 Using the previous example, suppose the @file{foo-1.0} tree has been
6894 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6895 @value{GDBN} to replace @file{/usr/src} in all source path names with
6896 @file{/mnt/cross}. The first lookup will then be
6897 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6898 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6899 substitution rule, use the @code{set substitute-path} command
6900 (@pxref{set substitute-path}).
6902 To avoid unexpected substitution results, a rule is applied only if the
6903 @var{from} part of the directory name ends at a directory separator.
6904 For instance, a rule substituting @file{/usr/source} into
6905 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6906 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6907 is applied only at the beginning of the directory name, this rule will
6908 not be applied to @file{/root/usr/source/baz.c} either.
6910 In many cases, you can achieve the same result using the @code{directory}
6911 command. However, @code{set substitute-path} can be more efficient in
6912 the case where the sources are organized in a complex tree with multiple
6913 subdirectories. With the @code{directory} command, you need to add each
6914 subdirectory of your project. If you moved the entire tree while
6915 preserving its internal organization, then @code{set substitute-path}
6916 allows you to direct the debugger to all the sources with one single
6919 @code{set substitute-path} is also more than just a shortcut command.
6920 The source path is only used if the file at the original location no
6921 longer exists. On the other hand, @code{set substitute-path} modifies
6922 the debugger behavior to look at the rewritten location instead. So, if
6923 for any reason a source file that is not relevant to your executable is
6924 located at the original location, a substitution rule is the only
6925 method available to point @value{GDBN} at the new location.
6927 @cindex @samp{--with-relocated-sources}
6928 @cindex default source path substitution
6929 You can configure a default source path substitution rule by
6930 configuring @value{GDBN} with the
6931 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6932 should be the name of a directory under @value{GDBN}'s configured
6933 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6934 directory names in debug information under @var{dir} will be adjusted
6935 automatically if the installed @value{GDBN} is moved to a new
6936 location. This is useful if @value{GDBN}, libraries or executables
6937 with debug information and corresponding source code are being moved
6941 @item directory @var{dirname} @dots{}
6942 @item dir @var{dirname} @dots{}
6943 Add directory @var{dirname} to the front of the source path. Several
6944 directory names may be given to this command, separated by @samp{:}
6945 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6946 part of absolute file names) or
6947 whitespace. You may specify a directory that is already in the source
6948 path; this moves it forward, so @value{GDBN} searches it sooner.
6952 @vindex $cdir@r{, convenience variable}
6953 @vindex $cwd@r{, convenience variable}
6954 @cindex compilation directory
6955 @cindex current directory
6956 @cindex working directory
6957 @cindex directory, current
6958 @cindex directory, compilation
6959 You can use the string @samp{$cdir} to refer to the compilation
6960 directory (if one is recorded), and @samp{$cwd} to refer to the current
6961 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6962 tracks the current working directory as it changes during your @value{GDBN}
6963 session, while the latter is immediately expanded to the current
6964 directory at the time you add an entry to the source path.
6967 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6969 @c RET-repeat for @code{directory} is explicitly disabled, but since
6970 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6972 @item set directories @var{path-list}
6973 @kindex set directories
6974 Set the source path to @var{path-list}.
6975 @samp{$cdir:$cwd} are added if missing.
6977 @item show directories
6978 @kindex show directories
6979 Print the source path: show which directories it contains.
6981 @anchor{set substitute-path}
6982 @item set substitute-path @var{from} @var{to}
6983 @kindex set substitute-path
6984 Define a source path substitution rule, and add it at the end of the
6985 current list of existing substitution rules. If a rule with the same
6986 @var{from} was already defined, then the old rule is also deleted.
6988 For example, if the file @file{/foo/bar/baz.c} was moved to
6989 @file{/mnt/cross/baz.c}, then the command
6992 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6996 will tell @value{GDBN} to replace @samp{/usr/src} with
6997 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6998 @file{baz.c} even though it was moved.
7000 In the case when more than one substitution rule have been defined,
7001 the rules are evaluated one by one in the order where they have been
7002 defined. The first one matching, if any, is selected to perform
7005 For instance, if we had entered the following commands:
7008 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7009 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7013 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7014 @file{/mnt/include/defs.h} by using the first rule. However, it would
7015 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7016 @file{/mnt/src/lib/foo.c}.
7019 @item unset substitute-path [path]
7020 @kindex unset substitute-path
7021 If a path is specified, search the current list of substitution rules
7022 for a rule that would rewrite that path. Delete that rule if found.
7023 A warning is emitted by the debugger if no rule could be found.
7025 If no path is specified, then all substitution rules are deleted.
7027 @item show substitute-path [path]
7028 @kindex show substitute-path
7029 If a path is specified, then print the source path substitution rule
7030 which would rewrite that path, if any.
7032 If no path is specified, then print all existing source path substitution
7037 If your source path is cluttered with directories that are no longer of
7038 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7039 versions of source. You can correct the situation as follows:
7043 Use @code{directory} with no argument to reset the source path to its default value.
7046 Use @code{directory} with suitable arguments to reinstall the
7047 directories you want in the source path. You can add all the
7048 directories in one command.
7052 @section Source and Machine Code
7053 @cindex source line and its code address
7055 You can use the command @code{info line} to map source lines to program
7056 addresses (and vice versa), and the command @code{disassemble} to display
7057 a range of addresses as machine instructions. You can use the command
7058 @code{set disassemble-next-line} to set whether to disassemble next
7059 source line when execution stops. When run under @sc{gnu} Emacs
7060 mode, the @code{info line} command causes the arrow to point to the
7061 line specified. Also, @code{info line} prints addresses in symbolic form as
7066 @item info line @var{linespec}
7067 Print the starting and ending addresses of the compiled code for
7068 source line @var{linespec}. You can specify source lines in any of
7069 the ways documented in @ref{Specify Location}.
7072 For example, we can use @code{info line} to discover the location of
7073 the object code for the first line of function
7074 @code{m4_changequote}:
7076 @c FIXME: I think this example should also show the addresses in
7077 @c symbolic form, as they usually would be displayed.
7079 (@value{GDBP}) info line m4_changequote
7080 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7084 @cindex code address and its source line
7085 We can also inquire (using @code{*@var{addr}} as the form for
7086 @var{linespec}) what source line covers a particular address:
7088 (@value{GDBP}) info line *0x63ff
7089 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7092 @cindex @code{$_} and @code{info line}
7093 @cindex @code{x} command, default address
7094 @kindex x@r{(examine), and} info line
7095 After @code{info line}, the default address for the @code{x} command
7096 is changed to the starting address of the line, so that @samp{x/i} is
7097 sufficient to begin examining the machine code (@pxref{Memory,
7098 ,Examining Memory}). Also, this address is saved as the value of the
7099 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7104 @cindex assembly instructions
7105 @cindex instructions, assembly
7106 @cindex machine instructions
7107 @cindex listing machine instructions
7109 @itemx disassemble /m
7110 @itemx disassemble /r
7111 This specialized command dumps a range of memory as machine
7112 instructions. It can also print mixed source+disassembly by specifying
7113 the @code{/m} modifier and print the raw instructions in hex as well as
7114 in symbolic form by specifying the @code{/r}.
7115 The default memory range is the function surrounding the
7116 program counter of the selected frame. A single argument to this
7117 command is a program counter value; @value{GDBN} dumps the function
7118 surrounding this value. When two arguments are given, they should
7119 be separated by a comma, possibly surrounded by whitespace. The
7120 arguments specify a range of addresses to dump, in one of two forms:
7123 @item @var{start},@var{end}
7124 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7125 @item @var{start},+@var{length}
7126 the addresses from @var{start} (inclusive) to
7127 @code{@var{start}+@var{length}} (exclusive).
7131 When 2 arguments are specified, the name of the function is also
7132 printed (since there could be several functions in the given range).
7134 The argument(s) can be any expression yielding a numeric value, such as
7135 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7137 If the range of memory being disassembled contains current program counter,
7138 the instruction at that location is shown with a @code{=>} marker.
7141 The following example shows the disassembly of a range of addresses of
7142 HP PA-RISC 2.0 code:
7145 (@value{GDBP}) disas 0x32c4, 0x32e4
7146 Dump of assembler code from 0x32c4 to 0x32e4:
7147 0x32c4 <main+204>: addil 0,dp
7148 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7149 0x32cc <main+212>: ldil 0x3000,r31
7150 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7151 0x32d4 <main+220>: ldo 0(r31),rp
7152 0x32d8 <main+224>: addil -0x800,dp
7153 0x32dc <main+228>: ldo 0x588(r1),r26
7154 0x32e0 <main+232>: ldil 0x3000,r31
7155 End of assembler dump.
7158 Here is an example showing mixed source+assembly for Intel x86, when the
7159 program is stopped just after function prologue:
7162 (@value{GDBP}) disas /m main
7163 Dump of assembler code for function main:
7165 0x08048330 <+0>: push %ebp
7166 0x08048331 <+1>: mov %esp,%ebp
7167 0x08048333 <+3>: sub $0x8,%esp
7168 0x08048336 <+6>: and $0xfffffff0,%esp
7169 0x08048339 <+9>: sub $0x10,%esp
7171 6 printf ("Hello.\n");
7172 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7173 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7177 0x08048348 <+24>: mov $0x0,%eax
7178 0x0804834d <+29>: leave
7179 0x0804834e <+30>: ret
7181 End of assembler dump.
7184 Here is another example showing raw instructions in hex for AMD x86-64,
7187 (gdb) disas /r 0x400281,+10
7188 Dump of assembler code from 0x400281 to 0x40028b:
7189 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7190 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7191 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7192 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7193 End of assembler dump.
7196 Some architectures have more than one commonly-used set of instruction
7197 mnemonics or other syntax.
7199 For programs that were dynamically linked and use shared libraries,
7200 instructions that call functions or branch to locations in the shared
7201 libraries might show a seemingly bogus location---it's actually a
7202 location of the relocation table. On some architectures, @value{GDBN}
7203 might be able to resolve these to actual function names.
7206 @kindex set disassembly-flavor
7207 @cindex Intel disassembly flavor
7208 @cindex AT&T disassembly flavor
7209 @item set disassembly-flavor @var{instruction-set}
7210 Select the instruction set to use when disassembling the
7211 program via the @code{disassemble} or @code{x/i} commands.
7213 Currently this command is only defined for the Intel x86 family. You
7214 can set @var{instruction-set} to either @code{intel} or @code{att}.
7215 The default is @code{att}, the AT&T flavor used by default by Unix
7216 assemblers for x86-based targets.
7218 @kindex show disassembly-flavor
7219 @item show disassembly-flavor
7220 Show the current setting of the disassembly flavor.
7224 @kindex set disassemble-next-line
7225 @kindex show disassemble-next-line
7226 @item set disassemble-next-line
7227 @itemx show disassemble-next-line
7228 Control whether or not @value{GDBN} will disassemble the next source
7229 line or instruction when execution stops. If ON, @value{GDBN} will
7230 display disassembly of the next source line when execution of the
7231 program being debugged stops. This is @emph{in addition} to
7232 displaying the source line itself, which @value{GDBN} always does if
7233 possible. If the next source line cannot be displayed for some reason
7234 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7235 info in the debug info), @value{GDBN} will display disassembly of the
7236 next @emph{instruction} instead of showing the next source line. If
7237 AUTO, @value{GDBN} will display disassembly of next instruction only
7238 if the source line cannot be displayed. This setting causes
7239 @value{GDBN} to display some feedback when you step through a function
7240 with no line info or whose source file is unavailable. The default is
7241 OFF, which means never display the disassembly of the next line or
7247 @chapter Examining Data
7249 @cindex printing data
7250 @cindex examining data
7253 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7254 @c document because it is nonstandard... Under Epoch it displays in a
7255 @c different window or something like that.
7256 The usual way to examine data in your program is with the @code{print}
7257 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7258 evaluates and prints the value of an expression of the language your
7259 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7260 Different Languages}). It may also print the expression using a
7261 Python-based pretty-printer (@pxref{Pretty Printing}).
7264 @item print @var{expr}
7265 @itemx print /@var{f} @var{expr}
7266 @var{expr} is an expression (in the source language). By default the
7267 value of @var{expr} is printed in a format appropriate to its data type;
7268 you can choose a different format by specifying @samp{/@var{f}}, where
7269 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7273 @itemx print /@var{f}
7274 @cindex reprint the last value
7275 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7276 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7277 conveniently inspect the same value in an alternative format.
7280 A more low-level way of examining data is with the @code{x} command.
7281 It examines data in memory at a specified address and prints it in a
7282 specified format. @xref{Memory, ,Examining Memory}.
7284 If you are interested in information about types, or about how the
7285 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7286 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7289 @cindex exploring hierarchical data structures
7291 Another way of examining values of expressions and type information is
7292 through the Python extension command @code{explore} (available only if
7293 the @value{GDBN} build is configured with @code{--with-python}). It
7294 offers an interactive way to start at the highest level (or, the most
7295 abstract level) of the data type of an expression (or, the data type
7296 itself) and explore all the way down to leaf scalar values/fields
7297 embedded in the higher level data types.
7300 @item explore @var{arg}
7301 @var{arg} is either an expression (in the source language), or a type
7302 visible in the current context of the program being debugged.
7305 The working of the @code{explore} command can be illustrated with an
7306 example. If a data type @code{struct ComplexStruct} is defined in your
7316 struct ComplexStruct
7318 struct SimpleStruct *ss_p;
7324 followed by variable declarations as
7327 struct SimpleStruct ss = @{ 10, 1.11 @};
7328 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7332 then, the value of the variable @code{cs} can be explored using the
7333 @code{explore} command as follows.
7337 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7338 the following fields:
7340 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7341 arr = <Enter 1 to explore this field of type `int [10]'>
7343 Enter the field number of choice:
7347 Since the fields of @code{cs} are not scalar values, you are being
7348 prompted to chose the field you want to explore. Let's say you choose
7349 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7350 pointer, you will be asked if it is pointing to a single value. From
7351 the declaration of @code{cs} above, it is indeed pointing to a single
7352 value, hence you enter @code{y}. If you enter @code{n}, then you will
7353 be asked if it were pointing to an array of values, in which case this
7354 field will be explored as if it were an array.
7357 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7358 Continue exploring it as a pointer to a single value [y/n]: y
7359 The value of `*(cs.ss_p)' is a struct/class of type `struct
7360 SimpleStruct' with the following fields:
7362 i = 10 .. (Value of type `int')
7363 d = 1.1100000000000001 .. (Value of type `double')
7365 Press enter to return to parent value:
7369 If the field @code{arr} of @code{cs} was chosen for exploration by
7370 entering @code{1} earlier, then since it is as array, you will be
7371 prompted to enter the index of the element in the array that you want
7375 `cs.arr' is an array of `int'.
7376 Enter the index of the element you want to explore in `cs.arr': 5
7378 `(cs.arr)[5]' is a scalar value of type `int'.
7382 Press enter to return to parent value:
7385 In general, at any stage of exploration, you can go deeper towards the
7386 leaf values by responding to the prompts appropriately, or hit the
7387 return key to return to the enclosing data structure (the @i{higher}
7388 level data structure).
7390 Similar to exploring values, you can use the @code{explore} command to
7391 explore types. Instead of specifying a value (which is typically a
7392 variable name or an expression valid in the current context of the
7393 program being debugged), you specify a type name. If you consider the
7394 same example as above, your can explore the type
7395 @code{struct ComplexStruct} by passing the argument
7396 @code{struct ComplexStruct} to the @code{explore} command.
7399 (gdb) explore struct ComplexStruct
7403 By responding to the prompts appropriately in the subsequent interactive
7404 session, you can explore the type @code{struct ComplexStruct} in a
7405 manner similar to how the value @code{cs} was explored in the above
7408 The @code{explore} command also has two sub-commands,
7409 @code{explore value} and @code{explore type}. The former sub-command is
7410 a way to explicitly specify that value exploration of the argument is
7411 being invoked, while the latter is a way to explicitly specify that type
7412 exploration of the argument is being invoked.
7415 @item explore value @var{expr}
7416 @cindex explore value
7417 This sub-command of @code{explore} explores the value of the
7418 expression @var{expr} (if @var{expr} is an expression valid in the
7419 current context of the program being debugged). The behavior of this
7420 command is identical to that of the behavior of the @code{explore}
7421 command being passed the argument @var{expr}.
7423 @item explore type @var{arg}
7424 @cindex explore type
7425 This sub-command of @code{explore} explores the type of @var{arg} (if
7426 @var{arg} is a type visible in the current context of program being
7427 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7428 is an expression valid in the current context of the program being
7429 debugged). If @var{arg} is a type, then the behavior of this command is
7430 identical to that of the @code{explore} command being passed the
7431 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7432 this command will be identical to that of the @code{explore} command
7433 being passed the type of @var{arg} as the argument.
7437 * Expressions:: Expressions
7438 * Ambiguous Expressions:: Ambiguous Expressions
7439 * Variables:: Program variables
7440 * Arrays:: Artificial arrays
7441 * Output Formats:: Output formats
7442 * Memory:: Examining memory
7443 * Auto Display:: Automatic display
7444 * Print Settings:: Print settings
7445 * Pretty Printing:: Python pretty printing
7446 * Value History:: Value history
7447 * Convenience Vars:: Convenience variables
7448 * Registers:: Registers
7449 * Floating Point Hardware:: Floating point hardware
7450 * Vector Unit:: Vector Unit
7451 * OS Information:: Auxiliary data provided by operating system
7452 * Memory Region Attributes:: Memory region attributes
7453 * Dump/Restore Files:: Copy between memory and a file
7454 * Core File Generation:: Cause a program dump its core
7455 * Character Sets:: Debugging programs that use a different
7456 character set than GDB does
7457 * Caching Remote Data:: Data caching for remote targets
7458 * Searching Memory:: Searching memory for a sequence of bytes
7462 @section Expressions
7465 @code{print} and many other @value{GDBN} commands accept an expression and
7466 compute its value. Any kind of constant, variable or operator defined
7467 by the programming language you are using is valid in an expression in
7468 @value{GDBN}. This includes conditional expressions, function calls,
7469 casts, and string constants. It also includes preprocessor macros, if
7470 you compiled your program to include this information; see
7473 @cindex arrays in expressions
7474 @value{GDBN} supports array constants in expressions input by
7475 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7476 you can use the command @code{print @{1, 2, 3@}} to create an array
7477 of three integers. If you pass an array to a function or assign it
7478 to a program variable, @value{GDBN} copies the array to memory that
7479 is @code{malloc}ed in the target program.
7481 Because C is so widespread, most of the expressions shown in examples in
7482 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7483 Languages}, for information on how to use expressions in other
7486 In this section, we discuss operators that you can use in @value{GDBN}
7487 expressions regardless of your programming language.
7489 @cindex casts, in expressions
7490 Casts are supported in all languages, not just in C, because it is so
7491 useful to cast a number into a pointer in order to examine a structure
7492 at that address in memory.
7493 @c FIXME: casts supported---Mod2 true?
7495 @value{GDBN} supports these operators, in addition to those common
7496 to programming languages:
7500 @samp{@@} is a binary operator for treating parts of memory as arrays.
7501 @xref{Arrays, ,Artificial Arrays}, for more information.
7504 @samp{::} allows you to specify a variable in terms of the file or
7505 function where it is defined. @xref{Variables, ,Program Variables}.
7507 @cindex @{@var{type}@}
7508 @cindex type casting memory
7509 @cindex memory, viewing as typed object
7510 @cindex casts, to view memory
7511 @item @{@var{type}@} @var{addr}
7512 Refers to an object of type @var{type} stored at address @var{addr} in
7513 memory. @var{addr} may be any expression whose value is an integer or
7514 pointer (but parentheses are required around binary operators, just as in
7515 a cast). This construct is allowed regardless of what kind of data is
7516 normally supposed to reside at @var{addr}.
7519 @node Ambiguous Expressions
7520 @section Ambiguous Expressions
7521 @cindex ambiguous expressions
7523 Expressions can sometimes contain some ambiguous elements. For instance,
7524 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7525 a single function name to be defined several times, for application in
7526 different contexts. This is called @dfn{overloading}. Another example
7527 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7528 templates and is typically instantiated several times, resulting in
7529 the same function name being defined in different contexts.
7531 In some cases and depending on the language, it is possible to adjust
7532 the expression to remove the ambiguity. For instance in C@t{++}, you
7533 can specify the signature of the function you want to break on, as in
7534 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7535 qualified name of your function often makes the expression unambiguous
7538 When an ambiguity that needs to be resolved is detected, the debugger
7539 has the capability to display a menu of numbered choices for each
7540 possibility, and then waits for the selection with the prompt @samp{>}.
7541 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7542 aborts the current command. If the command in which the expression was
7543 used allows more than one choice to be selected, the next option in the
7544 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7547 For example, the following session excerpt shows an attempt to set a
7548 breakpoint at the overloaded symbol @code{String::after}.
7549 We choose three particular definitions of that function name:
7551 @c FIXME! This is likely to change to show arg type lists, at least
7554 (@value{GDBP}) b String::after
7557 [2] file:String.cc; line number:867
7558 [3] file:String.cc; line number:860
7559 [4] file:String.cc; line number:875
7560 [5] file:String.cc; line number:853
7561 [6] file:String.cc; line number:846
7562 [7] file:String.cc; line number:735
7564 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7565 Breakpoint 2 at 0xb344: file String.cc, line 875.
7566 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7567 Multiple breakpoints were set.
7568 Use the "delete" command to delete unwanted
7575 @kindex set multiple-symbols
7576 @item set multiple-symbols @var{mode}
7577 @cindex multiple-symbols menu
7579 This option allows you to adjust the debugger behavior when an expression
7582 By default, @var{mode} is set to @code{all}. If the command with which
7583 the expression is used allows more than one choice, then @value{GDBN}
7584 automatically selects all possible choices. For instance, inserting
7585 a breakpoint on a function using an ambiguous name results in a breakpoint
7586 inserted on each possible match. However, if a unique choice must be made,
7587 then @value{GDBN} uses the menu to help you disambiguate the expression.
7588 For instance, printing the address of an overloaded function will result
7589 in the use of the menu.
7591 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7592 when an ambiguity is detected.
7594 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7595 an error due to the ambiguity and the command is aborted.
7597 @kindex show multiple-symbols
7598 @item show multiple-symbols
7599 Show the current value of the @code{multiple-symbols} setting.
7603 @section Program Variables
7605 The most common kind of expression to use is the name of a variable
7608 Variables in expressions are understood in the selected stack frame
7609 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7613 global (or file-static)
7620 visible according to the scope rules of the
7621 programming language from the point of execution in that frame
7624 @noindent This means that in the function
7639 you can examine and use the variable @code{a} whenever your program is
7640 executing within the function @code{foo}, but you can only use or
7641 examine the variable @code{b} while your program is executing inside
7642 the block where @code{b} is declared.
7644 @cindex variable name conflict
7645 There is an exception: you can refer to a variable or function whose
7646 scope is a single source file even if the current execution point is not
7647 in this file. But it is possible to have more than one such variable or
7648 function with the same name (in different source files). If that
7649 happens, referring to that name has unpredictable effects. If you wish,
7650 you can specify a static variable in a particular function or file by
7651 using the colon-colon (@code{::}) notation:
7653 @cindex colon-colon, context for variables/functions
7655 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7656 @cindex @code{::}, context for variables/functions
7659 @var{file}::@var{variable}
7660 @var{function}::@var{variable}
7664 Here @var{file} or @var{function} is the name of the context for the
7665 static @var{variable}. In the case of file names, you can use quotes to
7666 make sure @value{GDBN} parses the file name as a single word---for example,
7667 to print a global value of @code{x} defined in @file{f2.c}:
7670 (@value{GDBP}) p 'f2.c'::x
7673 The @code{::} notation is normally used for referring to
7674 static variables, since you typically disambiguate uses of local variables
7675 in functions by selecting the appropriate frame and using the
7676 simple name of the variable. However, you may also use this notation
7677 to refer to local variables in frames enclosing the selected frame:
7686 process (a); /* Stop here */
7697 For example, if there is a breakpoint at the commented line,
7698 here is what you might see
7699 when the program stops after executing the call @code{bar(0)}:
7704 (@value{GDBP}) p bar::a
7707 #2 0x080483d0 in foo (a=5) at foobar.c:12
7710 (@value{GDBP}) p bar::a
7714 @cindex C@t{++} scope resolution
7715 These uses of @samp{::} are very rarely in conflict with the very similar
7716 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7717 scope resolution operator in @value{GDBN} expressions.
7718 @c FIXME: Um, so what happens in one of those rare cases where it's in
7721 @cindex wrong values
7722 @cindex variable values, wrong
7723 @cindex function entry/exit, wrong values of variables
7724 @cindex optimized code, wrong values of variables
7726 @emph{Warning:} Occasionally, a local variable may appear to have the
7727 wrong value at certain points in a function---just after entry to a new
7728 scope, and just before exit.
7730 You may see this problem when you are stepping by machine instructions.
7731 This is because, on most machines, it takes more than one instruction to
7732 set up a stack frame (including local variable definitions); if you are
7733 stepping by machine instructions, variables may appear to have the wrong
7734 values until the stack frame is completely built. On exit, it usually
7735 also takes more than one machine instruction to destroy a stack frame;
7736 after you begin stepping through that group of instructions, local
7737 variable definitions may be gone.
7739 This may also happen when the compiler does significant optimizations.
7740 To be sure of always seeing accurate values, turn off all optimization
7743 @cindex ``No symbol "foo" in current context''
7744 Another possible effect of compiler optimizations is to optimize
7745 unused variables out of existence, or assign variables to registers (as
7746 opposed to memory addresses). Depending on the support for such cases
7747 offered by the debug info format used by the compiler, @value{GDBN}
7748 might not be able to display values for such local variables. If that
7749 happens, @value{GDBN} will print a message like this:
7752 No symbol "foo" in current context.
7755 To solve such problems, either recompile without optimizations, or use a
7756 different debug info format, if the compiler supports several such
7757 formats. @xref{Compilation}, for more information on choosing compiler
7758 options. @xref{C, ,C and C@t{++}}, for more information about debug
7759 info formats that are best suited to C@t{++} programs.
7761 If you ask to print an object whose contents are unknown to
7762 @value{GDBN}, e.g., because its data type is not completely specified
7763 by the debug information, @value{GDBN} will say @samp{<incomplete
7764 type>}. @xref{Symbols, incomplete type}, for more about this.
7766 If you append @kbd{@@entry} string to a function parameter name you get its
7767 value at the time the function got called. If the value is not available an
7768 error message is printed. Entry values are available only with some compilers.
7769 Entry values are normally also printed at the function parameter list according
7770 to @ref{set print entry-values}.
7773 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7779 (gdb) print i@@entry
7783 Strings are identified as arrays of @code{char} values without specified
7784 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7785 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7786 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7787 defines literal string type @code{"char"} as @code{char} without a sign.
7792 signed char var1[] = "A";
7795 You get during debugging
7800 $2 = @{65 'A', 0 '\0'@}
7804 @section Artificial Arrays
7806 @cindex artificial array
7808 @kindex @@@r{, referencing memory as an array}
7809 It is often useful to print out several successive objects of the
7810 same type in memory; a section of an array, or an array of
7811 dynamically determined size for which only a pointer exists in the
7814 You can do this by referring to a contiguous span of memory as an
7815 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7816 operand of @samp{@@} should be the first element of the desired array
7817 and be an individual object. The right operand should be the desired length
7818 of the array. The result is an array value whose elements are all of
7819 the type of the left argument. The first element is actually the left
7820 argument; the second element comes from bytes of memory immediately
7821 following those that hold the first element, and so on. Here is an
7822 example. If a program says
7825 int *array = (int *) malloc (len * sizeof (int));
7829 you can print the contents of @code{array} with
7835 The left operand of @samp{@@} must reside in memory. Array values made
7836 with @samp{@@} in this way behave just like other arrays in terms of
7837 subscripting, and are coerced to pointers when used in expressions.
7838 Artificial arrays most often appear in expressions via the value history
7839 (@pxref{Value History, ,Value History}), after printing one out.
7841 Another way to create an artificial array is to use a cast.
7842 This re-interprets a value as if it were an array.
7843 The value need not be in memory:
7845 (@value{GDBP}) p/x (short[2])0x12345678
7846 $1 = @{0x1234, 0x5678@}
7849 As a convenience, if you leave the array length out (as in
7850 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7851 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7853 (@value{GDBP}) p/x (short[])0x12345678
7854 $2 = @{0x1234, 0x5678@}
7857 Sometimes the artificial array mechanism is not quite enough; in
7858 moderately complex data structures, the elements of interest may not
7859 actually be adjacent---for example, if you are interested in the values
7860 of pointers in an array. One useful work-around in this situation is
7861 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7862 Variables}) as a counter in an expression that prints the first
7863 interesting value, and then repeat that expression via @key{RET}. For
7864 instance, suppose you have an array @code{dtab} of pointers to
7865 structures, and you are interested in the values of a field @code{fv}
7866 in each structure. Here is an example of what you might type:
7876 @node Output Formats
7877 @section Output Formats
7879 @cindex formatted output
7880 @cindex output formats
7881 By default, @value{GDBN} prints a value according to its data type. Sometimes
7882 this is not what you want. For example, you might want to print a number
7883 in hex, or a pointer in decimal. Or you might want to view data in memory
7884 at a certain address as a character string or as an instruction. To do
7885 these things, specify an @dfn{output format} when you print a value.
7887 The simplest use of output formats is to say how to print a value
7888 already computed. This is done by starting the arguments of the
7889 @code{print} command with a slash and a format letter. The format
7890 letters supported are:
7894 Regard the bits of the value as an integer, and print the integer in
7898 Print as integer in signed decimal.
7901 Print as integer in unsigned decimal.
7904 Print as integer in octal.
7907 Print as integer in binary. The letter @samp{t} stands for ``two''.
7908 @footnote{@samp{b} cannot be used because these format letters are also
7909 used with the @code{x} command, where @samp{b} stands for ``byte'';
7910 see @ref{Memory,,Examining Memory}.}
7913 @cindex unknown address, locating
7914 @cindex locate address
7915 Print as an address, both absolute in hexadecimal and as an offset from
7916 the nearest preceding symbol. You can use this format used to discover
7917 where (in what function) an unknown address is located:
7920 (@value{GDBP}) p/a 0x54320
7921 $3 = 0x54320 <_initialize_vx+396>
7925 The command @code{info symbol 0x54320} yields similar results.
7926 @xref{Symbols, info symbol}.
7929 Regard as an integer and print it as a character constant. This
7930 prints both the numerical value and its character representation. The
7931 character representation is replaced with the octal escape @samp{\nnn}
7932 for characters outside the 7-bit @sc{ascii} range.
7934 Without this format, @value{GDBN} displays @code{char},
7935 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7936 constants. Single-byte members of vectors are displayed as integer
7940 Regard the bits of the value as a floating point number and print
7941 using typical floating point syntax.
7944 @cindex printing strings
7945 @cindex printing byte arrays
7946 Regard as a string, if possible. With this format, pointers to single-byte
7947 data are displayed as null-terminated strings and arrays of single-byte data
7948 are displayed as fixed-length strings. Other values are displayed in their
7951 Without this format, @value{GDBN} displays pointers to and arrays of
7952 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7953 strings. Single-byte members of a vector are displayed as an integer
7957 @cindex raw printing
7958 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7959 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7960 Printing}). This typically results in a higher-level display of the
7961 value's contents. The @samp{r} format bypasses any Python
7962 pretty-printer which might exist.
7965 For example, to print the program counter in hex (@pxref{Registers}), type
7972 Note that no space is required before the slash; this is because command
7973 names in @value{GDBN} cannot contain a slash.
7975 To reprint the last value in the value history with a different format,
7976 you can use the @code{print} command with just a format and no
7977 expression. For example, @samp{p/x} reprints the last value in hex.
7980 @section Examining Memory
7982 You can use the command @code{x} (for ``examine'') to examine memory in
7983 any of several formats, independently of your program's data types.
7985 @cindex examining memory
7987 @kindex x @r{(examine memory)}
7988 @item x/@var{nfu} @var{addr}
7991 Use the @code{x} command to examine memory.
7994 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7995 much memory to display and how to format it; @var{addr} is an
7996 expression giving the address where you want to start displaying memory.
7997 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7998 Several commands set convenient defaults for @var{addr}.
8001 @item @var{n}, the repeat count
8002 The repeat count is a decimal integer; the default is 1. It specifies
8003 how much memory (counting by units @var{u}) to display.
8004 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8007 @item @var{f}, the display format
8008 The display format is one of the formats used by @code{print}
8009 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8010 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8011 The default is @samp{x} (hexadecimal) initially. The default changes
8012 each time you use either @code{x} or @code{print}.
8014 @item @var{u}, the unit size
8015 The unit size is any of
8021 Halfwords (two bytes).
8023 Words (four bytes). This is the initial default.
8025 Giant words (eight bytes).
8028 Each time you specify a unit size with @code{x}, that size becomes the
8029 default unit the next time you use @code{x}. For the @samp{i} format,
8030 the unit size is ignored and is normally not written. For the @samp{s} format,
8031 the unit size defaults to @samp{b}, unless it is explicitly given.
8032 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8033 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8034 Note that the results depend on the programming language of the
8035 current compilation unit. If the language is C, the @samp{s}
8036 modifier will use the UTF-16 encoding while @samp{w} will use
8037 UTF-32. The encoding is set by the programming language and cannot
8040 @item @var{addr}, starting display address
8041 @var{addr} is the address where you want @value{GDBN} to begin displaying
8042 memory. The expression need not have a pointer value (though it may);
8043 it is always interpreted as an integer address of a byte of memory.
8044 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8045 @var{addr} is usually just after the last address examined---but several
8046 other commands also set the default address: @code{info breakpoints} (to
8047 the address of the last breakpoint listed), @code{info line} (to the
8048 starting address of a line), and @code{print} (if you use it to display
8049 a value from memory).
8052 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8053 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8054 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8055 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8056 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8058 Since the letters indicating unit sizes are all distinct from the
8059 letters specifying output formats, you do not have to remember whether
8060 unit size or format comes first; either order works. The output
8061 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8062 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8064 Even though the unit size @var{u} is ignored for the formats @samp{s}
8065 and @samp{i}, you might still want to use a count @var{n}; for example,
8066 @samp{3i} specifies that you want to see three machine instructions,
8067 including any operands. For convenience, especially when used with
8068 the @code{display} command, the @samp{i} format also prints branch delay
8069 slot instructions, if any, beyond the count specified, which immediately
8070 follow the last instruction that is within the count. The command
8071 @code{disassemble} gives an alternative way of inspecting machine
8072 instructions; see @ref{Machine Code,,Source and Machine Code}.
8074 All the defaults for the arguments to @code{x} are designed to make it
8075 easy to continue scanning memory with minimal specifications each time
8076 you use @code{x}. For example, after you have inspected three machine
8077 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8078 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8079 the repeat count @var{n} is used again; the other arguments default as
8080 for successive uses of @code{x}.
8082 When examining machine instructions, the instruction at current program
8083 counter is shown with a @code{=>} marker. For example:
8086 (@value{GDBP}) x/5i $pc-6
8087 0x804837f <main+11>: mov %esp,%ebp
8088 0x8048381 <main+13>: push %ecx
8089 0x8048382 <main+14>: sub $0x4,%esp
8090 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8091 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8094 @cindex @code{$_}, @code{$__}, and value history
8095 The addresses and contents printed by the @code{x} command are not saved
8096 in the value history because there is often too much of them and they
8097 would get in the way. Instead, @value{GDBN} makes these values available for
8098 subsequent use in expressions as values of the convenience variables
8099 @code{$_} and @code{$__}. After an @code{x} command, the last address
8100 examined is available for use in expressions in the convenience variable
8101 @code{$_}. The contents of that address, as examined, are available in
8102 the convenience variable @code{$__}.
8104 If the @code{x} command has a repeat count, the address and contents saved
8105 are from the last memory unit printed; this is not the same as the last
8106 address printed if several units were printed on the last line of output.
8108 @cindex remote memory comparison
8109 @cindex verify remote memory image
8110 When you are debugging a program running on a remote target machine
8111 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8112 remote machine's memory against the executable file you downloaded to
8113 the target. The @code{compare-sections} command is provided for such
8117 @kindex compare-sections
8118 @item compare-sections @r{[}@var{section-name}@r{]}
8119 Compare the data of a loadable section @var{section-name} in the
8120 executable file of the program being debugged with the same section in
8121 the remote machine's memory, and report any mismatches. With no
8122 arguments, compares all loadable sections. This command's
8123 availability depends on the target's support for the @code{"qCRC"}
8128 @section Automatic Display
8129 @cindex automatic display
8130 @cindex display of expressions
8132 If you find that you want to print the value of an expression frequently
8133 (to see how it changes), you might want to add it to the @dfn{automatic
8134 display list} so that @value{GDBN} prints its value each time your program stops.
8135 Each expression added to the list is given a number to identify it;
8136 to remove an expression from the list, you specify that number.
8137 The automatic display looks like this:
8141 3: bar[5] = (struct hack *) 0x3804
8145 This display shows item numbers, expressions and their current values. As with
8146 displays you request manually using @code{x} or @code{print}, you can
8147 specify the output format you prefer; in fact, @code{display} decides
8148 whether to use @code{print} or @code{x} depending your format
8149 specification---it uses @code{x} if you specify either the @samp{i}
8150 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8154 @item display @var{expr}
8155 Add the expression @var{expr} to the list of expressions to display
8156 each time your program stops. @xref{Expressions, ,Expressions}.
8158 @code{display} does not repeat if you press @key{RET} again after using it.
8160 @item display/@var{fmt} @var{expr}
8161 For @var{fmt} specifying only a display format and not a size or
8162 count, add the expression @var{expr} to the auto-display list but
8163 arrange to display it each time in the specified format @var{fmt}.
8164 @xref{Output Formats,,Output Formats}.
8166 @item display/@var{fmt} @var{addr}
8167 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8168 number of units, add the expression @var{addr} as a memory address to
8169 be examined each time your program stops. Examining means in effect
8170 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8173 For example, @samp{display/i $pc} can be helpful, to see the machine
8174 instruction about to be executed each time execution stops (@samp{$pc}
8175 is a common name for the program counter; @pxref{Registers, ,Registers}).
8178 @kindex delete display
8180 @item undisplay @var{dnums}@dots{}
8181 @itemx delete display @var{dnums}@dots{}
8182 Remove items from the list of expressions to display. Specify the
8183 numbers of the displays that you want affected with the command
8184 argument @var{dnums}. It can be a single display number, one of the
8185 numbers shown in the first field of the @samp{info display} display;
8186 or it could be a range of display numbers, as in @code{2-4}.
8188 @code{undisplay} does not repeat if you press @key{RET} after using it.
8189 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8191 @kindex disable display
8192 @item disable display @var{dnums}@dots{}
8193 Disable the display of item numbers @var{dnums}. A disabled display
8194 item is not printed automatically, but is not forgotten. It may be
8195 enabled again later. Specify the numbers of the displays that you
8196 want affected with the command argument @var{dnums}. It can be a
8197 single display number, one of the numbers shown in the first field of
8198 the @samp{info display} display; or it could be a range of display
8199 numbers, as in @code{2-4}.
8201 @kindex enable display
8202 @item enable display @var{dnums}@dots{}
8203 Enable display of item numbers @var{dnums}. It becomes effective once
8204 again in auto display of its expression, until you specify otherwise.
8205 Specify the numbers of the displays that you want affected with the
8206 command argument @var{dnums}. It can be a single display number, one
8207 of the numbers shown in the first field of the @samp{info display}
8208 display; or it could be a range of display numbers, as in @code{2-4}.
8211 Display the current values of the expressions on the list, just as is
8212 done when your program stops.
8214 @kindex info display
8216 Print the list of expressions previously set up to display
8217 automatically, each one with its item number, but without showing the
8218 values. This includes disabled expressions, which are marked as such.
8219 It also includes expressions which would not be displayed right now
8220 because they refer to automatic variables not currently available.
8223 @cindex display disabled out of scope
8224 If a display expression refers to local variables, then it does not make
8225 sense outside the lexical context for which it was set up. Such an
8226 expression is disabled when execution enters a context where one of its
8227 variables is not defined. For example, if you give the command
8228 @code{display last_char} while inside a function with an argument
8229 @code{last_char}, @value{GDBN} displays this argument while your program
8230 continues to stop inside that function. When it stops elsewhere---where
8231 there is no variable @code{last_char}---the display is disabled
8232 automatically. The next time your program stops where @code{last_char}
8233 is meaningful, you can enable the display expression once again.
8235 @node Print Settings
8236 @section Print Settings
8238 @cindex format options
8239 @cindex print settings
8240 @value{GDBN} provides the following ways to control how arrays, structures,
8241 and symbols are printed.
8244 These settings are useful for debugging programs in any language:
8248 @item set print address
8249 @itemx set print address on
8250 @cindex print/don't print memory addresses
8251 @value{GDBN} prints memory addresses showing the location of stack
8252 traces, structure values, pointer values, breakpoints, and so forth,
8253 even when it also displays the contents of those addresses. The default
8254 is @code{on}. For example, this is what a stack frame display looks like with
8255 @code{set print address on}:
8260 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8262 530 if (lquote != def_lquote)
8266 @item set print address off
8267 Do not print addresses when displaying their contents. For example,
8268 this is the same stack frame displayed with @code{set print address off}:
8272 (@value{GDBP}) set print addr off
8274 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8275 530 if (lquote != def_lquote)
8279 You can use @samp{set print address off} to eliminate all machine
8280 dependent displays from the @value{GDBN} interface. For example, with
8281 @code{print address off}, you should get the same text for backtraces on
8282 all machines---whether or not they involve pointer arguments.
8285 @item show print address
8286 Show whether or not addresses are to be printed.
8289 When @value{GDBN} prints a symbolic address, it normally prints the
8290 closest earlier symbol plus an offset. If that symbol does not uniquely
8291 identify the address (for example, it is a name whose scope is a single
8292 source file), you may need to clarify. One way to do this is with
8293 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8294 you can set @value{GDBN} to print the source file and line number when
8295 it prints a symbolic address:
8298 @item set print symbol-filename on
8299 @cindex source file and line of a symbol
8300 @cindex symbol, source file and line
8301 Tell @value{GDBN} to print the source file name and line number of a
8302 symbol in the symbolic form of an address.
8304 @item set print symbol-filename off
8305 Do not print source file name and line number of a symbol. This is the
8308 @item show print symbol-filename
8309 Show whether or not @value{GDBN} will print the source file name and
8310 line number of a symbol in the symbolic form of an address.
8313 Another situation where it is helpful to show symbol filenames and line
8314 numbers is when disassembling code; @value{GDBN} shows you the line
8315 number and source file that corresponds to each instruction.
8317 Also, you may wish to see the symbolic form only if the address being
8318 printed is reasonably close to the closest earlier symbol:
8321 @item set print max-symbolic-offset @var{max-offset}
8322 @cindex maximum value for offset of closest symbol
8323 Tell @value{GDBN} to only display the symbolic form of an address if the
8324 offset between the closest earlier symbol and the address is less than
8325 @var{max-offset}. The default is 0, which tells @value{GDBN}
8326 to always print the symbolic form of an address if any symbol precedes it.
8328 @item show print max-symbolic-offset
8329 Ask how large the maximum offset is that @value{GDBN} prints in a
8333 @cindex wild pointer, interpreting
8334 @cindex pointer, finding referent
8335 If you have a pointer and you are not sure where it points, try
8336 @samp{set print symbol-filename on}. Then you can determine the name
8337 and source file location of the variable where it points, using
8338 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8339 For example, here @value{GDBN} shows that a variable @code{ptt} points
8340 at another variable @code{t}, defined in @file{hi2.c}:
8343 (@value{GDBP}) set print symbol-filename on
8344 (@value{GDBP}) p/a ptt
8345 $4 = 0xe008 <t in hi2.c>
8349 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8350 does not show the symbol name and filename of the referent, even with
8351 the appropriate @code{set print} options turned on.
8354 Other settings control how different kinds of objects are printed:
8357 @item set print array
8358 @itemx set print array on
8359 @cindex pretty print arrays
8360 Pretty print arrays. This format is more convenient to read,
8361 but uses more space. The default is off.
8363 @item set print array off
8364 Return to compressed format for arrays.
8366 @item show print array
8367 Show whether compressed or pretty format is selected for displaying
8370 @cindex print array indexes
8371 @item set print array-indexes
8372 @itemx set print array-indexes on
8373 Print the index of each element when displaying arrays. May be more
8374 convenient to locate a given element in the array or quickly find the
8375 index of a given element in that printed array. The default is off.
8377 @item set print array-indexes off
8378 Stop printing element indexes when displaying arrays.
8380 @item show print array-indexes
8381 Show whether the index of each element is printed when displaying
8384 @item set print elements @var{number-of-elements}
8385 @cindex number of array elements to print
8386 @cindex limit on number of printed array elements
8387 Set a limit on how many elements of an array @value{GDBN} will print.
8388 If @value{GDBN} is printing a large array, it stops printing after it has
8389 printed the number of elements set by the @code{set print elements} command.
8390 This limit also applies to the display of strings.
8391 When @value{GDBN} starts, this limit is set to 200.
8392 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8394 @item show print elements
8395 Display the number of elements of a large array that @value{GDBN} will print.
8396 If the number is 0, then the printing is unlimited.
8398 @item set print frame-arguments @var{value}
8399 @kindex set print frame-arguments
8400 @cindex printing frame argument values
8401 @cindex print all frame argument values
8402 @cindex print frame argument values for scalars only
8403 @cindex do not print frame argument values
8404 This command allows to control how the values of arguments are printed
8405 when the debugger prints a frame (@pxref{Frames}). The possible
8410 The values of all arguments are printed.
8413 Print the value of an argument only if it is a scalar. The value of more
8414 complex arguments such as arrays, structures, unions, etc, is replaced
8415 by @code{@dots{}}. This is the default. Here is an example where
8416 only scalar arguments are shown:
8419 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8424 None of the argument values are printed. Instead, the value of each argument
8425 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8428 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8433 By default, only scalar arguments are printed. This command can be used
8434 to configure the debugger to print the value of all arguments, regardless
8435 of their type. However, it is often advantageous to not print the value
8436 of more complex parameters. For instance, it reduces the amount of
8437 information printed in each frame, making the backtrace more readable.
8438 Also, it improves performance when displaying Ada frames, because
8439 the computation of large arguments can sometimes be CPU-intensive,
8440 especially in large applications. Setting @code{print frame-arguments}
8441 to @code{scalars} (the default) or @code{none} avoids this computation,
8442 thus speeding up the display of each Ada frame.
8444 @item show print frame-arguments
8445 Show how the value of arguments should be displayed when printing a frame.
8447 @anchor{set print entry-values}
8448 @item set print entry-values @var{value}
8449 @kindex set print entry-values
8450 Set printing of frame argument values at function entry. In some cases
8451 @value{GDBN} can determine the value of function argument which was passed by
8452 the function caller, even if the value was modified inside the called function
8453 and therefore is different. With optimized code, the current value could be
8454 unavailable, but the entry value may still be known.
8456 The default value is @code{default} (see below for its description). Older
8457 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8458 this feature will behave in the @code{default} setting the same way as with the
8461 This functionality is currently supported only by DWARF 2 debugging format and
8462 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8463 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8466 The @var{value} parameter can be one of the following:
8470 Print only actual parameter values, never print values from function entry
8474 #0 different (val=6)
8475 #0 lost (val=<optimized out>)
8477 #0 invalid (val=<optimized out>)
8481 Print only parameter values from function entry point. The actual parameter
8482 values are never printed.
8484 #0 equal (val@@entry=5)
8485 #0 different (val@@entry=5)
8486 #0 lost (val@@entry=5)
8487 #0 born (val@@entry=<optimized out>)
8488 #0 invalid (val@@entry=<optimized out>)
8492 Print only parameter values from function entry point. If value from function
8493 entry point is not known while the actual value is known, print the actual
8494 value for such parameter.
8496 #0 equal (val@@entry=5)
8497 #0 different (val@@entry=5)
8498 #0 lost (val@@entry=5)
8500 #0 invalid (val@@entry=<optimized out>)
8504 Print actual parameter values. If actual parameter value is not known while
8505 value from function entry point is known, print the entry point value for such
8509 #0 different (val=6)
8510 #0 lost (val@@entry=5)
8512 #0 invalid (val=<optimized out>)
8516 Always print both the actual parameter value and its value from function entry
8517 point, even if values of one or both are not available due to compiler
8520 #0 equal (val=5, val@@entry=5)
8521 #0 different (val=6, val@@entry=5)
8522 #0 lost (val=<optimized out>, val@@entry=5)
8523 #0 born (val=10, val@@entry=<optimized out>)
8524 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8528 Print the actual parameter value if it is known and also its value from
8529 function entry point if it is known. If neither is known, print for the actual
8530 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8531 values are known and identical, print the shortened
8532 @code{param=param@@entry=VALUE} notation.
8534 #0 equal (val=val@@entry=5)
8535 #0 different (val=6, val@@entry=5)
8536 #0 lost (val@@entry=5)
8538 #0 invalid (val=<optimized out>)
8542 Always print the actual parameter value. Print also its value from function
8543 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8544 if both values are known and identical, print the shortened
8545 @code{param=param@@entry=VALUE} notation.
8547 #0 equal (val=val@@entry=5)
8548 #0 different (val=6, val@@entry=5)
8549 #0 lost (val=<optimized out>, val@@entry=5)
8551 #0 invalid (val=<optimized out>)
8555 For analysis messages on possible failures of frame argument values at function
8556 entry resolution see @ref{set debug entry-values}.
8558 @item show print entry-values
8559 Show the method being used for printing of frame argument values at function
8562 @item set print repeats
8563 @cindex repeated array elements
8564 Set the threshold for suppressing display of repeated array
8565 elements. When the number of consecutive identical elements of an
8566 array exceeds the threshold, @value{GDBN} prints the string
8567 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8568 identical repetitions, instead of displaying the identical elements
8569 themselves. Setting the threshold to zero will cause all elements to
8570 be individually printed. The default threshold is 10.
8572 @item show print repeats
8573 Display the current threshold for printing repeated identical
8576 @item set print null-stop
8577 @cindex @sc{null} elements in arrays
8578 Cause @value{GDBN} to stop printing the characters of an array when the first
8579 @sc{null} is encountered. This is useful when large arrays actually
8580 contain only short strings.
8583 @item show print null-stop
8584 Show whether @value{GDBN} stops printing an array on the first
8585 @sc{null} character.
8587 @item set print pretty on
8588 @cindex print structures in indented form
8589 @cindex indentation in structure display
8590 Cause @value{GDBN} to print structures in an indented format with one member
8591 per line, like this:
8606 @item set print pretty off
8607 Cause @value{GDBN} to print structures in a compact format, like this:
8611 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8612 meat = 0x54 "Pork"@}
8617 This is the default format.
8619 @item show print pretty
8620 Show which format @value{GDBN} is using to print structures.
8622 @item set print sevenbit-strings on
8623 @cindex eight-bit characters in strings
8624 @cindex octal escapes in strings
8625 Print using only seven-bit characters; if this option is set,
8626 @value{GDBN} displays any eight-bit characters (in strings or
8627 character values) using the notation @code{\}@var{nnn}. This setting is
8628 best if you are working in English (@sc{ascii}) and you use the
8629 high-order bit of characters as a marker or ``meta'' bit.
8631 @item set print sevenbit-strings off
8632 Print full eight-bit characters. This allows the use of more
8633 international character sets, and is the default.
8635 @item show print sevenbit-strings
8636 Show whether or not @value{GDBN} is printing only seven-bit characters.
8638 @item set print union on
8639 @cindex unions in structures, printing
8640 Tell @value{GDBN} to print unions which are contained in structures
8641 and other unions. This is the default setting.
8643 @item set print union off
8644 Tell @value{GDBN} not to print unions which are contained in
8645 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8648 @item show print union
8649 Ask @value{GDBN} whether or not it will print unions which are contained in
8650 structures and other unions.
8652 For example, given the declarations
8655 typedef enum @{Tree, Bug@} Species;
8656 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8657 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8668 struct thing foo = @{Tree, @{Acorn@}@};
8672 with @code{set print union on} in effect @samp{p foo} would print
8675 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8679 and with @code{set print union off} in effect it would print
8682 $1 = @{it = Tree, form = @{...@}@}
8686 @code{set print union} affects programs written in C-like languages
8692 These settings are of interest when debugging C@t{++} programs:
8695 @cindex demangling C@t{++} names
8696 @item set print demangle
8697 @itemx set print demangle on
8698 Print C@t{++} names in their source form rather than in the encoded
8699 (``mangled'') form passed to the assembler and linker for type-safe
8700 linkage. The default is on.
8702 @item show print demangle
8703 Show whether C@t{++} names are printed in mangled or demangled form.
8705 @item set print asm-demangle
8706 @itemx set print asm-demangle on
8707 Print C@t{++} names in their source form rather than their mangled form, even
8708 in assembler code printouts such as instruction disassemblies.
8711 @item show print asm-demangle
8712 Show whether C@t{++} names in assembly listings are printed in mangled
8715 @cindex C@t{++} symbol decoding style
8716 @cindex symbol decoding style, C@t{++}
8717 @kindex set demangle-style
8718 @item set demangle-style @var{style}
8719 Choose among several encoding schemes used by different compilers to
8720 represent C@t{++} names. The choices for @var{style} are currently:
8724 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8727 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8728 This is the default.
8731 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8734 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8737 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8738 @strong{Warning:} this setting alone is not sufficient to allow
8739 debugging @code{cfront}-generated executables. @value{GDBN} would
8740 require further enhancement to permit that.
8743 If you omit @var{style}, you will see a list of possible formats.
8745 @item show demangle-style
8746 Display the encoding style currently in use for decoding C@t{++} symbols.
8748 @item set print object
8749 @itemx set print object on
8750 @cindex derived type of an object, printing
8751 @cindex display derived types
8752 When displaying a pointer to an object, identify the @emph{actual}
8753 (derived) type of the object rather than the @emph{declared} type, using
8754 the virtual function table. Note that the virtual function table is
8755 required---this feature can only work for objects that have run-time
8756 type identification; a single virtual method in the object's declared
8757 type is sufficient. Note that this setting is also taken into account when
8758 working with variable objects via MI (@pxref{GDB/MI}).
8760 @item set print object off
8761 Display only the declared type of objects, without reference to the
8762 virtual function table. This is the default setting.
8764 @item show print object
8765 Show whether actual, or declared, object types are displayed.
8767 @item set print static-members
8768 @itemx set print static-members on
8769 @cindex static members of C@t{++} objects
8770 Print static members when displaying a C@t{++} object. The default is on.
8772 @item set print static-members off
8773 Do not print static members when displaying a C@t{++} object.
8775 @item show print static-members
8776 Show whether C@t{++} static members are printed or not.
8778 @item set print pascal_static-members
8779 @itemx set print pascal_static-members on
8780 @cindex static members of Pascal objects
8781 @cindex Pascal objects, static members display
8782 Print static members when displaying a Pascal object. The default is on.
8784 @item set print pascal_static-members off
8785 Do not print static members when displaying a Pascal object.
8787 @item show print pascal_static-members
8788 Show whether Pascal static members are printed or not.
8790 @c These don't work with HP ANSI C++ yet.
8791 @item set print vtbl
8792 @itemx set print vtbl on
8793 @cindex pretty print C@t{++} virtual function tables
8794 @cindex virtual functions (C@t{++}) display
8795 @cindex VTBL display
8796 Pretty print C@t{++} virtual function tables. The default is off.
8797 (The @code{vtbl} commands do not work on programs compiled with the HP
8798 ANSI C@t{++} compiler (@code{aCC}).)
8800 @item set print vtbl off
8801 Do not pretty print C@t{++} virtual function tables.
8803 @item show print vtbl
8804 Show whether C@t{++} virtual function tables are pretty printed, or not.
8807 @node Pretty Printing
8808 @section Pretty Printing
8810 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8811 Python code. It greatly simplifies the display of complex objects. This
8812 mechanism works for both MI and the CLI.
8815 * Pretty-Printer Introduction:: Introduction to pretty-printers
8816 * Pretty-Printer Example:: An example pretty-printer
8817 * Pretty-Printer Commands:: Pretty-printer commands
8820 @node Pretty-Printer Introduction
8821 @subsection Pretty-Printer Introduction
8823 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8824 registered for the value. If there is then @value{GDBN} invokes the
8825 pretty-printer to print the value. Otherwise the value is printed normally.
8827 Pretty-printers are normally named. This makes them easy to manage.
8828 The @samp{info pretty-printer} command will list all the installed
8829 pretty-printers with their names.
8830 If a pretty-printer can handle multiple data types, then its
8831 @dfn{subprinters} are the printers for the individual data types.
8832 Each such subprinter has its own name.
8833 The format of the name is @var{printer-name};@var{subprinter-name}.
8835 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8836 Typically they are automatically loaded and registered when the corresponding
8837 debug information is loaded, thus making them available without having to
8838 do anything special.
8840 There are three places where a pretty-printer can be registered.
8844 Pretty-printers registered globally are available when debugging
8848 Pretty-printers registered with a program space are available only
8849 when debugging that program.
8850 @xref{Progspaces In Python}, for more details on program spaces in Python.
8853 Pretty-printers registered with an objfile are loaded and unloaded
8854 with the corresponding objfile (e.g., shared library).
8855 @xref{Objfiles In Python}, for more details on objfiles in Python.
8858 @xref{Selecting Pretty-Printers}, for further information on how
8859 pretty-printers are selected,
8861 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8864 @node Pretty-Printer Example
8865 @subsection Pretty-Printer Example
8867 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8870 (@value{GDBP}) print s
8872 static npos = 4294967295,
8874 <std::allocator<char>> = @{
8875 <__gnu_cxx::new_allocator<char>> = @{
8876 <No data fields>@}, <No data fields>
8878 members of std::basic_string<char, std::char_traits<char>,
8879 std::allocator<char> >::_Alloc_hider:
8880 _M_p = 0x804a014 "abcd"
8885 With a pretty-printer for @code{std::string} only the contents are printed:
8888 (@value{GDBP}) print s
8892 @node Pretty-Printer Commands
8893 @subsection Pretty-Printer Commands
8894 @cindex pretty-printer commands
8897 @kindex info pretty-printer
8898 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8899 Print the list of installed pretty-printers.
8900 This includes disabled pretty-printers, which are marked as such.
8902 @var{object-regexp} is a regular expression matching the objects
8903 whose pretty-printers to list.
8904 Objects can be @code{global}, the program space's file
8905 (@pxref{Progspaces In Python}),
8906 and the object files within that program space (@pxref{Objfiles In Python}).
8907 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8908 looks up a printer from these three objects.
8910 @var{name-regexp} is a regular expression matching the name of the printers
8913 @kindex disable pretty-printer
8914 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8915 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8916 A disabled pretty-printer is not forgotten, it may be enabled again later.
8918 @kindex enable pretty-printer
8919 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8920 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8925 Suppose we have three pretty-printers installed: one from library1.so
8926 named @code{foo} that prints objects of type @code{foo}, and
8927 another from library2.so named @code{bar} that prints two types of objects,
8928 @code{bar1} and @code{bar2}.
8931 (gdb) info pretty-printer
8938 (gdb) info pretty-printer library2
8943 (gdb) disable pretty-printer library1
8945 2 of 3 printers enabled
8946 (gdb) info pretty-printer
8953 (gdb) disable pretty-printer library2 bar:bar1
8955 1 of 3 printers enabled
8956 (gdb) info pretty-printer library2
8963 (gdb) disable pretty-printer library2 bar
8965 0 of 3 printers enabled
8966 (gdb) info pretty-printer library2
8975 Note that for @code{bar} the entire printer can be disabled,
8976 as can each individual subprinter.
8979 @section Value History
8981 @cindex value history
8982 @cindex history of values printed by @value{GDBN}
8983 Values printed by the @code{print} command are saved in the @value{GDBN}
8984 @dfn{value history}. This allows you to refer to them in other expressions.
8985 Values are kept until the symbol table is re-read or discarded
8986 (for example with the @code{file} or @code{symbol-file} commands).
8987 When the symbol table changes, the value history is discarded,
8988 since the values may contain pointers back to the types defined in the
8993 @cindex history number
8994 The values printed are given @dfn{history numbers} by which you can
8995 refer to them. These are successive integers starting with one.
8996 @code{print} shows you the history number assigned to a value by
8997 printing @samp{$@var{num} = } before the value; here @var{num} is the
9000 To refer to any previous value, use @samp{$} followed by the value's
9001 history number. The way @code{print} labels its output is designed to
9002 remind you of this. Just @code{$} refers to the most recent value in
9003 the history, and @code{$$} refers to the value before that.
9004 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9005 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9006 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9008 For example, suppose you have just printed a pointer to a structure and
9009 want to see the contents of the structure. It suffices to type
9015 If you have a chain of structures where the component @code{next} points
9016 to the next one, you can print the contents of the next one with this:
9023 You can print successive links in the chain by repeating this
9024 command---which you can do by just typing @key{RET}.
9026 Note that the history records values, not expressions. If the value of
9027 @code{x} is 4 and you type these commands:
9035 then the value recorded in the value history by the @code{print} command
9036 remains 4 even though the value of @code{x} has changed.
9041 Print the last ten values in the value history, with their item numbers.
9042 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9043 values} does not change the history.
9045 @item show values @var{n}
9046 Print ten history values centered on history item number @var{n}.
9049 Print ten history values just after the values last printed. If no more
9050 values are available, @code{show values +} produces no display.
9053 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9054 same effect as @samp{show values +}.
9056 @node Convenience Vars
9057 @section Convenience Variables
9059 @cindex convenience variables
9060 @cindex user-defined variables
9061 @value{GDBN} provides @dfn{convenience variables} that you can use within
9062 @value{GDBN} to hold on to a value and refer to it later. These variables
9063 exist entirely within @value{GDBN}; they are not part of your program, and
9064 setting a convenience variable has no direct effect on further execution
9065 of your program. That is why you can use them freely.
9067 Convenience variables are prefixed with @samp{$}. Any name preceded by
9068 @samp{$} can be used for a convenience variable, unless it is one of
9069 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9070 (Value history references, in contrast, are @emph{numbers} preceded
9071 by @samp{$}. @xref{Value History, ,Value History}.)
9073 You can save a value in a convenience variable with an assignment
9074 expression, just as you would set a variable in your program.
9078 set $foo = *object_ptr
9082 would save in @code{$foo} the value contained in the object pointed to by
9085 Using a convenience variable for the first time creates it, but its
9086 value is @code{void} until you assign a new value. You can alter the
9087 value with another assignment at any time.
9089 Convenience variables have no fixed types. You can assign a convenience
9090 variable any type of value, including structures and arrays, even if
9091 that variable already has a value of a different type. The convenience
9092 variable, when used as an expression, has the type of its current value.
9095 @kindex show convenience
9096 @cindex show all user variables
9097 @item show convenience
9098 Print a list of convenience variables used so far, and their values.
9099 Abbreviated @code{show conv}.
9101 @kindex init-if-undefined
9102 @cindex convenience variables, initializing
9103 @item init-if-undefined $@var{variable} = @var{expression}
9104 Set a convenience variable if it has not already been set. This is useful
9105 for user-defined commands that keep some state. It is similar, in concept,
9106 to using local static variables with initializers in C (except that
9107 convenience variables are global). It can also be used to allow users to
9108 override default values used in a command script.
9110 If the variable is already defined then the expression is not evaluated so
9111 any side-effects do not occur.
9114 One of the ways to use a convenience variable is as a counter to be
9115 incremented or a pointer to be advanced. For example, to print
9116 a field from successive elements of an array of structures:
9120 print bar[$i++]->contents
9124 Repeat that command by typing @key{RET}.
9126 Some convenience variables are created automatically by @value{GDBN} and given
9127 values likely to be useful.
9130 @vindex $_@r{, convenience variable}
9132 The variable @code{$_} is automatically set by the @code{x} command to
9133 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9134 commands which provide a default address for @code{x} to examine also
9135 set @code{$_} to that address; these commands include @code{info line}
9136 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9137 except when set by the @code{x} command, in which case it is a pointer
9138 to the type of @code{$__}.
9140 @vindex $__@r{, convenience variable}
9142 The variable @code{$__} is automatically set by the @code{x} command
9143 to the value found in the last address examined. Its type is chosen
9144 to match the format in which the data was printed.
9147 @vindex $_exitcode@r{, convenience variable}
9148 The variable @code{$_exitcode} is automatically set to the exit code when
9149 the program being debugged terminates.
9152 @itemx $_probe_arg0@dots{}$_probe_arg11
9153 Arguments to a static probe. @xref{Static Probe Points}.
9156 @vindex $_sdata@r{, inspect, convenience variable}
9157 The variable @code{$_sdata} contains extra collected static tracepoint
9158 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9159 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9160 if extra static tracepoint data has not been collected.
9163 @vindex $_siginfo@r{, convenience variable}
9164 The variable @code{$_siginfo} contains extra signal information
9165 (@pxref{extra signal information}). Note that @code{$_siginfo}
9166 could be empty, if the application has not yet received any signals.
9167 For example, it will be empty before you execute the @code{run} command.
9170 @vindex $_tlb@r{, convenience variable}
9171 The variable @code{$_tlb} is automatically set when debugging
9172 applications running on MS-Windows in native mode or connected to
9173 gdbserver that supports the @code{qGetTIBAddr} request.
9174 @xref{General Query Packets}.
9175 This variable contains the address of the thread information block.
9179 On HP-UX systems, if you refer to a function or variable name that
9180 begins with a dollar sign, @value{GDBN} searches for a user or system
9181 name first, before it searches for a convenience variable.
9183 @cindex convenience functions
9184 @value{GDBN} also supplies some @dfn{convenience functions}. These
9185 have a syntax similar to convenience variables. A convenience
9186 function can be used in an expression just like an ordinary function;
9187 however, a convenience function is implemented internally to
9192 @kindex help function
9193 @cindex show all convenience functions
9194 Print a list of all convenience functions.
9201 You can refer to machine register contents, in expressions, as variables
9202 with names starting with @samp{$}. The names of registers are different
9203 for each machine; use @code{info registers} to see the names used on
9207 @kindex info registers
9208 @item info registers
9209 Print the names and values of all registers except floating-point
9210 and vector registers (in the selected stack frame).
9212 @kindex info all-registers
9213 @cindex floating point registers
9214 @item info all-registers
9215 Print the names and values of all registers, including floating-point
9216 and vector registers (in the selected stack frame).
9218 @item info registers @var{regname} @dots{}
9219 Print the @dfn{relativized} value of each specified register @var{regname}.
9220 As discussed in detail below, register values are normally relative to
9221 the selected stack frame. @var{regname} may be any register name valid on
9222 the machine you are using, with or without the initial @samp{$}.
9225 @cindex stack pointer register
9226 @cindex program counter register
9227 @cindex process status register
9228 @cindex frame pointer register
9229 @cindex standard registers
9230 @value{GDBN} has four ``standard'' register names that are available (in
9231 expressions) on most machines---whenever they do not conflict with an
9232 architecture's canonical mnemonics for registers. The register names
9233 @code{$pc} and @code{$sp} are used for the program counter register and
9234 the stack pointer. @code{$fp} is used for a register that contains a
9235 pointer to the current stack frame, and @code{$ps} is used for a
9236 register that contains the processor status. For example,
9237 you could print the program counter in hex with
9244 or print the instruction to be executed next with
9251 or add four to the stack pointer@footnote{This is a way of removing
9252 one word from the stack, on machines where stacks grow downward in
9253 memory (most machines, nowadays). This assumes that the innermost
9254 stack frame is selected; setting @code{$sp} is not allowed when other
9255 stack frames are selected. To pop entire frames off the stack,
9256 regardless of machine architecture, use @code{return};
9257 see @ref{Returning, ,Returning from a Function}.} with
9263 Whenever possible, these four standard register names are available on
9264 your machine even though the machine has different canonical mnemonics,
9265 so long as there is no conflict. The @code{info registers} command
9266 shows the canonical names. For example, on the SPARC, @code{info
9267 registers} displays the processor status register as @code{$psr} but you
9268 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9269 is an alias for the @sc{eflags} register.
9271 @value{GDBN} always considers the contents of an ordinary register as an
9272 integer when the register is examined in this way. Some machines have
9273 special registers which can hold nothing but floating point; these
9274 registers are considered to have floating point values. There is no way
9275 to refer to the contents of an ordinary register as floating point value
9276 (although you can @emph{print} it as a floating point value with
9277 @samp{print/f $@var{regname}}).
9279 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9280 means that the data format in which the register contents are saved by
9281 the operating system is not the same one that your program normally
9282 sees. For example, the registers of the 68881 floating point
9283 coprocessor are always saved in ``extended'' (raw) format, but all C
9284 programs expect to work with ``double'' (virtual) format. In such
9285 cases, @value{GDBN} normally works with the virtual format only (the format
9286 that makes sense for your program), but the @code{info registers} command
9287 prints the data in both formats.
9289 @cindex SSE registers (x86)
9290 @cindex MMX registers (x86)
9291 Some machines have special registers whose contents can be interpreted
9292 in several different ways. For example, modern x86-based machines
9293 have SSE and MMX registers that can hold several values packed
9294 together in several different formats. @value{GDBN} refers to such
9295 registers in @code{struct} notation:
9298 (@value{GDBP}) print $xmm1
9300 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9301 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9302 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9303 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9304 v4_int32 = @{0, 20657912, 11, 13@},
9305 v2_int64 = @{88725056443645952, 55834574859@},
9306 uint128 = 0x0000000d0000000b013b36f800000000
9311 To set values of such registers, you need to tell @value{GDBN} which
9312 view of the register you wish to change, as if you were assigning
9313 value to a @code{struct} member:
9316 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9319 Normally, register values are relative to the selected stack frame
9320 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9321 value that the register would contain if all stack frames farther in
9322 were exited and their saved registers restored. In order to see the
9323 true contents of hardware registers, you must select the innermost
9324 frame (with @samp{frame 0}).
9326 However, @value{GDBN} must deduce where registers are saved, from the machine
9327 code generated by your compiler. If some registers are not saved, or if
9328 @value{GDBN} is unable to locate the saved registers, the selected stack
9329 frame makes no difference.
9331 @node Floating Point Hardware
9332 @section Floating Point Hardware
9333 @cindex floating point
9335 Depending on the configuration, @value{GDBN} may be able to give
9336 you more information about the status of the floating point hardware.
9341 Display hardware-dependent information about the floating
9342 point unit. The exact contents and layout vary depending on the
9343 floating point chip. Currently, @samp{info float} is supported on
9344 the ARM and x86 machines.
9348 @section Vector Unit
9351 Depending on the configuration, @value{GDBN} may be able to give you
9352 more information about the status of the vector unit.
9357 Display information about the vector unit. The exact contents and
9358 layout vary depending on the hardware.
9361 @node OS Information
9362 @section Operating System Auxiliary Information
9363 @cindex OS information
9365 @value{GDBN} provides interfaces to useful OS facilities that can help
9366 you debug your program.
9368 @cindex @code{ptrace} system call
9369 @cindex @code{struct user} contents
9370 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9371 machines), it interfaces with the inferior via the @code{ptrace}
9372 system call. The operating system creates a special sata structure,
9373 called @code{struct user}, for this interface. You can use the
9374 command @code{info udot} to display the contents of this data
9380 Display the contents of the @code{struct user} maintained by the OS
9381 kernel for the program being debugged. @value{GDBN} displays the
9382 contents of @code{struct user} as a list of hex numbers, similar to
9383 the @code{examine} command.
9386 @cindex auxiliary vector
9387 @cindex vector, auxiliary
9388 Some operating systems supply an @dfn{auxiliary vector} to programs at
9389 startup. This is akin to the arguments and environment that you
9390 specify for a program, but contains a system-dependent variety of
9391 binary values that tell system libraries important details about the
9392 hardware, operating system, and process. Each value's purpose is
9393 identified by an integer tag; the meanings are well-known but system-specific.
9394 Depending on the configuration and operating system facilities,
9395 @value{GDBN} may be able to show you this information. For remote
9396 targets, this functionality may further depend on the remote stub's
9397 support of the @samp{qXfer:auxv:read} packet, see
9398 @ref{qXfer auxiliary vector read}.
9403 Display the auxiliary vector of the inferior, which can be either a
9404 live process or a core dump file. @value{GDBN} prints each tag value
9405 numerically, and also shows names and text descriptions for recognized
9406 tags. Some values in the vector are numbers, some bit masks, and some
9407 pointers to strings or other data. @value{GDBN} displays each value in the
9408 most appropriate form for a recognized tag, and in hexadecimal for
9409 an unrecognized tag.
9412 On some targets, @value{GDBN} can access operating-system-specific information
9413 and display it to user, without interpretation. For remote targets,
9414 this functionality depends on the remote stub's support of the
9415 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9420 List the types of OS information available for the target. If the
9421 target does not return a list of possible types, this command will
9424 @kindex info os processes
9425 @item info os processes
9426 Display the list of processes on the target. For each process,
9427 @value{GDBN} prints the process identifier, the name of the user, and
9428 the command corresponding to the process.
9431 @node Memory Region Attributes
9432 @section Memory Region Attributes
9433 @cindex memory region attributes
9435 @dfn{Memory region attributes} allow you to describe special handling
9436 required by regions of your target's memory. @value{GDBN} uses
9437 attributes to determine whether to allow certain types of memory
9438 accesses; whether to use specific width accesses; and whether to cache
9439 target memory. By default the description of memory regions is
9440 fetched from the target (if the current target supports this), but the
9441 user can override the fetched regions.
9443 Defined memory regions can be individually enabled and disabled. When a
9444 memory region is disabled, @value{GDBN} uses the default attributes when
9445 accessing memory in that region. Similarly, if no memory regions have
9446 been defined, @value{GDBN} uses the default attributes when accessing
9449 When a memory region is defined, it is given a number to identify it;
9450 to enable, disable, or remove a memory region, you specify that number.
9454 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9455 Define a memory region bounded by @var{lower} and @var{upper} with
9456 attributes @var{attributes}@dots{}, and add it to the list of regions
9457 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9458 case: it is treated as the target's maximum memory address.
9459 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9462 Discard any user changes to the memory regions and use target-supplied
9463 regions, if available, or no regions if the target does not support.
9466 @item delete mem @var{nums}@dots{}
9467 Remove memory regions @var{nums}@dots{} from the list of regions
9468 monitored by @value{GDBN}.
9471 @item disable mem @var{nums}@dots{}
9472 Disable monitoring of memory regions @var{nums}@dots{}.
9473 A disabled memory region is not forgotten.
9474 It may be enabled again later.
9477 @item enable mem @var{nums}@dots{}
9478 Enable monitoring of memory regions @var{nums}@dots{}.
9482 Print a table of all defined memory regions, with the following columns
9486 @item Memory Region Number
9487 @item Enabled or Disabled.
9488 Enabled memory regions are marked with @samp{y}.
9489 Disabled memory regions are marked with @samp{n}.
9492 The address defining the inclusive lower bound of the memory region.
9495 The address defining the exclusive upper bound of the memory region.
9498 The list of attributes set for this memory region.
9503 @subsection Attributes
9505 @subsubsection Memory Access Mode
9506 The access mode attributes set whether @value{GDBN} may make read or
9507 write accesses to a memory region.
9509 While these attributes prevent @value{GDBN} from performing invalid
9510 memory accesses, they do nothing to prevent the target system, I/O DMA,
9511 etc.@: from accessing memory.
9515 Memory is read only.
9517 Memory is write only.
9519 Memory is read/write. This is the default.
9522 @subsubsection Memory Access Size
9523 The access size attribute tells @value{GDBN} to use specific sized
9524 accesses in the memory region. Often memory mapped device registers
9525 require specific sized accesses. If no access size attribute is
9526 specified, @value{GDBN} may use accesses of any size.
9530 Use 8 bit memory accesses.
9532 Use 16 bit memory accesses.
9534 Use 32 bit memory accesses.
9536 Use 64 bit memory accesses.
9539 @c @subsubsection Hardware/Software Breakpoints
9540 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9541 @c will use hardware or software breakpoints for the internal breakpoints
9542 @c used by the step, next, finish, until, etc. commands.
9546 @c Always use hardware breakpoints
9547 @c @item swbreak (default)
9550 @subsubsection Data Cache
9551 The data cache attributes set whether @value{GDBN} will cache target
9552 memory. While this generally improves performance by reducing debug
9553 protocol overhead, it can lead to incorrect results because @value{GDBN}
9554 does not know about volatile variables or memory mapped device
9559 Enable @value{GDBN} to cache target memory.
9561 Disable @value{GDBN} from caching target memory. This is the default.
9564 @subsection Memory Access Checking
9565 @value{GDBN} can be instructed to refuse accesses to memory that is
9566 not explicitly described. This can be useful if accessing such
9567 regions has undesired effects for a specific target, or to provide
9568 better error checking. The following commands control this behaviour.
9571 @kindex set mem inaccessible-by-default
9572 @item set mem inaccessible-by-default [on|off]
9573 If @code{on} is specified, make @value{GDBN} treat memory not
9574 explicitly described by the memory ranges as non-existent and refuse accesses
9575 to such memory. The checks are only performed if there's at least one
9576 memory range defined. If @code{off} is specified, make @value{GDBN}
9577 treat the memory not explicitly described by the memory ranges as RAM.
9578 The default value is @code{on}.
9579 @kindex show mem inaccessible-by-default
9580 @item show mem inaccessible-by-default
9581 Show the current handling of accesses to unknown memory.
9585 @c @subsubsection Memory Write Verification
9586 @c The memory write verification attributes set whether @value{GDBN}
9587 @c will re-reads data after each write to verify the write was successful.
9591 @c @item noverify (default)
9594 @node Dump/Restore Files
9595 @section Copy Between Memory and a File
9596 @cindex dump/restore files
9597 @cindex append data to a file
9598 @cindex dump data to a file
9599 @cindex restore data from a file
9601 You can use the commands @code{dump}, @code{append}, and
9602 @code{restore} to copy data between target memory and a file. The
9603 @code{dump} and @code{append} commands write data to a file, and the
9604 @code{restore} command reads data from a file back into the inferior's
9605 memory. Files may be in binary, Motorola S-record, Intel hex, or
9606 Tektronix Hex format; however, @value{GDBN} can only append to binary
9612 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9613 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9614 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9615 or the value of @var{expr}, to @var{filename} in the given format.
9617 The @var{format} parameter may be any one of:
9624 Motorola S-record format.
9626 Tektronix Hex format.
9629 @value{GDBN} uses the same definitions of these formats as the
9630 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9631 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9635 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9636 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9637 Append the contents of memory from @var{start_addr} to @var{end_addr},
9638 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9639 (@value{GDBN} can only append data to files in raw binary form.)
9642 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9643 Restore the contents of file @var{filename} into memory. The
9644 @code{restore} command can automatically recognize any known @sc{bfd}
9645 file format, except for raw binary. To restore a raw binary file you
9646 must specify the optional keyword @code{binary} after the filename.
9648 If @var{bias} is non-zero, its value will be added to the addresses
9649 contained in the file. Binary files always start at address zero, so
9650 they will be restored at address @var{bias}. Other bfd files have
9651 a built-in location; they will be restored at offset @var{bias}
9654 If @var{start} and/or @var{end} are non-zero, then only data between
9655 file offset @var{start} and file offset @var{end} will be restored.
9656 These offsets are relative to the addresses in the file, before
9657 the @var{bias} argument is applied.
9661 @node Core File Generation
9662 @section How to Produce a Core File from Your Program
9663 @cindex dump core from inferior
9665 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9666 image of a running process and its process status (register values
9667 etc.). Its primary use is post-mortem debugging of a program that
9668 crashed while it ran outside a debugger. A program that crashes
9669 automatically produces a core file, unless this feature is disabled by
9670 the user. @xref{Files}, for information on invoking @value{GDBN} in
9671 the post-mortem debugging mode.
9673 Occasionally, you may wish to produce a core file of the program you
9674 are debugging in order to preserve a snapshot of its state.
9675 @value{GDBN} has a special command for that.
9679 @kindex generate-core-file
9680 @item generate-core-file [@var{file}]
9681 @itemx gcore [@var{file}]
9682 Produce a core dump of the inferior process. The optional argument
9683 @var{file} specifies the file name where to put the core dump. If not
9684 specified, the file name defaults to @file{core.@var{pid}}, where
9685 @var{pid} is the inferior process ID.
9687 Note that this command is implemented only for some systems (as of
9688 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9691 @node Character Sets
9692 @section Character Sets
9693 @cindex character sets
9695 @cindex translating between character sets
9696 @cindex host character set
9697 @cindex target character set
9699 If the program you are debugging uses a different character set to
9700 represent characters and strings than the one @value{GDBN} uses itself,
9701 @value{GDBN} can automatically translate between the character sets for
9702 you. The character set @value{GDBN} uses we call the @dfn{host
9703 character set}; the one the inferior program uses we call the
9704 @dfn{target character set}.
9706 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9707 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9708 remote protocol (@pxref{Remote Debugging}) to debug a program
9709 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9710 then the host character set is Latin-1, and the target character set is
9711 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9712 target-charset EBCDIC-US}, then @value{GDBN} translates between
9713 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9714 character and string literals in expressions.
9716 @value{GDBN} has no way to automatically recognize which character set
9717 the inferior program uses; you must tell it, using the @code{set
9718 target-charset} command, described below.
9720 Here are the commands for controlling @value{GDBN}'s character set
9724 @item set target-charset @var{charset}
9725 @kindex set target-charset
9726 Set the current target character set to @var{charset}. To display the
9727 list of supported target character sets, type
9728 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9730 @item set host-charset @var{charset}
9731 @kindex set host-charset
9732 Set the current host character set to @var{charset}.
9734 By default, @value{GDBN} uses a host character set appropriate to the
9735 system it is running on; you can override that default using the
9736 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9737 automatically determine the appropriate host character set. In this
9738 case, @value{GDBN} uses @samp{UTF-8}.
9740 @value{GDBN} can only use certain character sets as its host character
9741 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9742 @value{GDBN} will list the host character sets it supports.
9744 @item set charset @var{charset}
9746 Set the current host and target character sets to @var{charset}. As
9747 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9748 @value{GDBN} will list the names of the character sets that can be used
9749 for both host and target.
9752 @kindex show charset
9753 Show the names of the current host and target character sets.
9755 @item show host-charset
9756 @kindex show host-charset
9757 Show the name of the current host character set.
9759 @item show target-charset
9760 @kindex show target-charset
9761 Show the name of the current target character set.
9763 @item set target-wide-charset @var{charset}
9764 @kindex set target-wide-charset
9765 Set the current target's wide character set to @var{charset}. This is
9766 the character set used by the target's @code{wchar_t} type. To
9767 display the list of supported wide character sets, type
9768 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9770 @item show target-wide-charset
9771 @kindex show target-wide-charset
9772 Show the name of the current target's wide character set.
9775 Here is an example of @value{GDBN}'s character set support in action.
9776 Assume that the following source code has been placed in the file
9777 @file{charset-test.c}:
9783 = @{72, 101, 108, 108, 111, 44, 32, 119,
9784 111, 114, 108, 100, 33, 10, 0@};
9785 char ibm1047_hello[]
9786 = @{200, 133, 147, 147, 150, 107, 64, 166,
9787 150, 153, 147, 132, 90, 37, 0@};
9791 printf ("Hello, world!\n");
9795 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9796 containing the string @samp{Hello, world!} followed by a newline,
9797 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9799 We compile the program, and invoke the debugger on it:
9802 $ gcc -g charset-test.c -o charset-test
9803 $ gdb -nw charset-test
9804 GNU gdb 2001-12-19-cvs
9805 Copyright 2001 Free Software Foundation, Inc.
9810 We can use the @code{show charset} command to see what character sets
9811 @value{GDBN} is currently using to interpret and display characters and
9815 (@value{GDBP}) show charset
9816 The current host and target character set is `ISO-8859-1'.
9820 For the sake of printing this manual, let's use @sc{ascii} as our
9821 initial character set:
9823 (@value{GDBP}) set charset ASCII
9824 (@value{GDBP}) show charset
9825 The current host and target character set is `ASCII'.
9829 Let's assume that @sc{ascii} is indeed the correct character set for our
9830 host system --- in other words, let's assume that if @value{GDBN} prints
9831 characters using the @sc{ascii} character set, our terminal will display
9832 them properly. Since our current target character set is also
9833 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9836 (@value{GDBP}) print ascii_hello
9837 $1 = 0x401698 "Hello, world!\n"
9838 (@value{GDBP}) print ascii_hello[0]
9843 @value{GDBN} uses the target character set for character and string
9844 literals you use in expressions:
9847 (@value{GDBP}) print '+'
9852 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9855 @value{GDBN} relies on the user to tell it which character set the
9856 target program uses. If we print @code{ibm1047_hello} while our target
9857 character set is still @sc{ascii}, we get jibberish:
9860 (@value{GDBP}) print ibm1047_hello
9861 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9862 (@value{GDBP}) print ibm1047_hello[0]
9867 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9868 @value{GDBN} tells us the character sets it supports:
9871 (@value{GDBP}) set target-charset
9872 ASCII EBCDIC-US IBM1047 ISO-8859-1
9873 (@value{GDBP}) set target-charset
9876 We can select @sc{ibm1047} as our target character set, and examine the
9877 program's strings again. Now the @sc{ascii} string is wrong, but
9878 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9879 target character set, @sc{ibm1047}, to the host character set,
9880 @sc{ascii}, and they display correctly:
9883 (@value{GDBP}) set target-charset IBM1047
9884 (@value{GDBP}) show charset
9885 The current host character set is `ASCII'.
9886 The current target character set is `IBM1047'.
9887 (@value{GDBP}) print ascii_hello
9888 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9889 (@value{GDBP}) print ascii_hello[0]
9891 (@value{GDBP}) print ibm1047_hello
9892 $8 = 0x4016a8 "Hello, world!\n"
9893 (@value{GDBP}) print ibm1047_hello[0]
9898 As above, @value{GDBN} uses the target character set for character and
9899 string literals you use in expressions:
9902 (@value{GDBP}) print '+'
9907 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9910 @node Caching Remote Data
9911 @section Caching Data of Remote Targets
9912 @cindex caching data of remote targets
9914 @value{GDBN} caches data exchanged between the debugger and a
9915 remote target (@pxref{Remote Debugging}). Such caching generally improves
9916 performance, because it reduces the overhead of the remote protocol by
9917 bundling memory reads and writes into large chunks. Unfortunately, simply
9918 caching everything would lead to incorrect results, since @value{GDBN}
9919 does not necessarily know anything about volatile values, memory-mapped I/O
9920 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9921 memory can be changed @emph{while} a gdb command is executing.
9922 Therefore, by default, @value{GDBN} only caches data
9923 known to be on the stack@footnote{In non-stop mode, it is moderately
9924 rare for a running thread to modify the stack of a stopped thread
9925 in a way that would interfere with a backtrace, and caching of
9926 stack reads provides a significant speed up of remote backtraces.}.
9927 Other regions of memory can be explicitly marked as
9928 cacheable; see @pxref{Memory Region Attributes}.
9931 @kindex set remotecache
9932 @item set remotecache on
9933 @itemx set remotecache off
9934 This option no longer does anything; it exists for compatibility
9937 @kindex show remotecache
9938 @item show remotecache
9939 Show the current state of the obsolete remotecache flag.
9941 @kindex set stack-cache
9942 @item set stack-cache on
9943 @itemx set stack-cache off
9944 Enable or disable caching of stack accesses. When @code{ON}, use
9945 caching. By default, this option is @code{ON}.
9947 @kindex show stack-cache
9948 @item show stack-cache
9949 Show the current state of data caching for memory accesses.
9952 @item info dcache @r{[}line@r{]}
9953 Print the information about the data cache performance. The
9954 information displayed includes the dcache width and depth, and for
9955 each cache line, its number, address, and how many times it was
9956 referenced. This command is useful for debugging the data cache
9959 If a line number is specified, the contents of that line will be
9962 @item set dcache size @var{size}
9964 @kindex set dcache size
9965 Set maximum number of entries in dcache (dcache depth above).
9967 @item set dcache line-size @var{line-size}
9968 @cindex dcache line-size
9969 @kindex set dcache line-size
9970 Set number of bytes each dcache entry caches (dcache width above).
9971 Must be a power of 2.
9973 @item show dcache size
9974 @kindex show dcache size
9975 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9977 @item show dcache line-size
9978 @kindex show dcache line-size
9979 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9983 @node Searching Memory
9984 @section Search Memory
9985 @cindex searching memory
9987 Memory can be searched for a particular sequence of bytes with the
9988 @code{find} command.
9992 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9993 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9994 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9995 etc. The search begins at address @var{start_addr} and continues for either
9996 @var{len} bytes or through to @var{end_addr} inclusive.
9999 @var{s} and @var{n} are optional parameters.
10000 They may be specified in either order, apart or together.
10003 @item @var{s}, search query size
10004 The size of each search query value.
10010 halfwords (two bytes)
10014 giant words (eight bytes)
10017 All values are interpreted in the current language.
10018 This means, for example, that if the current source language is C/C@t{++}
10019 then searching for the string ``hello'' includes the trailing '\0'.
10021 If the value size is not specified, it is taken from the
10022 value's type in the current language.
10023 This is useful when one wants to specify the search
10024 pattern as a mixture of types.
10025 Note that this means, for example, that in the case of C-like languages
10026 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10027 which is typically four bytes.
10029 @item @var{n}, maximum number of finds
10030 The maximum number of matches to print. The default is to print all finds.
10033 You can use strings as search values. Quote them with double-quotes
10035 The string value is copied into the search pattern byte by byte,
10036 regardless of the endianness of the target and the size specification.
10038 The address of each match found is printed as well as a count of the
10039 number of matches found.
10041 The address of the last value found is stored in convenience variable
10043 A count of the number of matches is stored in @samp{$numfound}.
10045 For example, if stopped at the @code{printf} in this function:
10051 static char hello[] = "hello-hello";
10052 static struct @{ char c; short s; int i; @}
10053 __attribute__ ((packed)) mixed
10054 = @{ 'c', 0x1234, 0x87654321 @};
10055 printf ("%s\n", hello);
10060 you get during debugging:
10063 (gdb) find &hello[0], +sizeof(hello), "hello"
10064 0x804956d <hello.1620+6>
10066 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10067 0x8049567 <hello.1620>
10068 0x804956d <hello.1620+6>
10070 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10071 0x8049567 <hello.1620>
10073 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10074 0x8049560 <mixed.1625>
10076 (gdb) print $numfound
10079 $2 = (void *) 0x8049560
10082 @node Optimized Code
10083 @chapter Debugging Optimized Code
10084 @cindex optimized code, debugging
10085 @cindex debugging optimized code
10087 Almost all compilers support optimization. With optimization
10088 disabled, the compiler generates assembly code that corresponds
10089 directly to your source code, in a simplistic way. As the compiler
10090 applies more powerful optimizations, the generated assembly code
10091 diverges from your original source code. With help from debugging
10092 information generated by the compiler, @value{GDBN} can map from
10093 the running program back to constructs from your original source.
10095 @value{GDBN} is more accurate with optimization disabled. If you
10096 can recompile without optimization, it is easier to follow the
10097 progress of your program during debugging. But, there are many cases
10098 where you may need to debug an optimized version.
10100 When you debug a program compiled with @samp{-g -O}, remember that the
10101 optimizer has rearranged your code; the debugger shows you what is
10102 really there. Do not be too surprised when the execution path does not
10103 exactly match your source file! An extreme example: if you define a
10104 variable, but never use it, @value{GDBN} never sees that
10105 variable---because the compiler optimizes it out of existence.
10107 Some things do not work as well with @samp{-g -O} as with just
10108 @samp{-g}, particularly on machines with instruction scheduling. If in
10109 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10110 please report it to us as a bug (including a test case!).
10111 @xref{Variables}, for more information about debugging optimized code.
10114 * Inline Functions:: How @value{GDBN} presents inlining
10115 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10118 @node Inline Functions
10119 @section Inline Functions
10120 @cindex inline functions, debugging
10122 @dfn{Inlining} is an optimization that inserts a copy of the function
10123 body directly at each call site, instead of jumping to a shared
10124 routine. @value{GDBN} displays inlined functions just like
10125 non-inlined functions. They appear in backtraces. You can view their
10126 arguments and local variables, step into them with @code{step}, skip
10127 them with @code{next}, and escape from them with @code{finish}.
10128 You can check whether a function was inlined by using the
10129 @code{info frame} command.
10131 For @value{GDBN} to support inlined functions, the compiler must
10132 record information about inlining in the debug information ---
10133 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10134 other compilers do also. @value{GDBN} only supports inlined functions
10135 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10136 do not emit two required attributes (@samp{DW_AT_call_file} and
10137 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10138 function calls with earlier versions of @value{NGCC}. It instead
10139 displays the arguments and local variables of inlined functions as
10140 local variables in the caller.
10142 The body of an inlined function is directly included at its call site;
10143 unlike a non-inlined function, there are no instructions devoted to
10144 the call. @value{GDBN} still pretends that the call site and the
10145 start of the inlined function are different instructions. Stepping to
10146 the call site shows the call site, and then stepping again shows
10147 the first line of the inlined function, even though no additional
10148 instructions are executed.
10150 This makes source-level debugging much clearer; you can see both the
10151 context of the call and then the effect of the call. Only stepping by
10152 a single instruction using @code{stepi} or @code{nexti} does not do
10153 this; single instruction steps always show the inlined body.
10155 There are some ways that @value{GDBN} does not pretend that inlined
10156 function calls are the same as normal calls:
10160 Setting breakpoints at the call site of an inlined function may not
10161 work, because the call site does not contain any code. @value{GDBN}
10162 may incorrectly move the breakpoint to the next line of the enclosing
10163 function, after the call. This limitation will be removed in a future
10164 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10165 or inside the inlined function instead.
10168 @value{GDBN} cannot locate the return value of inlined calls after
10169 using the @code{finish} command. This is a limitation of compiler-generated
10170 debugging information; after @code{finish}, you can step to the next line
10171 and print a variable where your program stored the return value.
10175 @node Tail Call Frames
10176 @section Tail Call Frames
10177 @cindex tail call frames, debugging
10179 Function @code{B} can call function @code{C} in its very last statement. In
10180 unoptimized compilation the call of @code{C} is immediately followed by return
10181 instruction at the end of @code{B} code. Optimizing compiler may replace the
10182 call and return in function @code{B} into one jump to function @code{C}
10183 instead. Such use of a jump instruction is called @dfn{tail call}.
10185 During execution of function @code{C}, there will be no indication in the
10186 function call stack frames that it was tail-called from @code{B}. If function
10187 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10188 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10189 some cases @value{GDBN} can determine that @code{C} was tail-called from
10190 @code{B}, and it will then create fictitious call frame for that, with the
10191 return address set up as if @code{B} called @code{C} normally.
10193 This functionality is currently supported only by DWARF 2 debugging format and
10194 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10195 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10198 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10199 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10203 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10205 Stack level 1, frame at 0x7fffffffda30:
10206 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10207 tail call frame, caller of frame at 0x7fffffffda30
10208 source language c++.
10209 Arglist at unknown address.
10210 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10213 The detection of all the possible code path executions can find them ambiguous.
10214 There is no execution history stored (possible @ref{Reverse Execution} is never
10215 used for this purpose) and the last known caller could have reached the known
10216 callee by multiple different jump sequences. In such case @value{GDBN} still
10217 tries to show at least all the unambiguous top tail callers and all the
10218 unambiguous bottom tail calees, if any.
10221 @anchor{set debug entry-values}
10222 @item set debug entry-values
10223 @kindex set debug entry-values
10224 When set to on, enables printing of analysis messages for both frame argument
10225 values at function entry and tail calls. It will show all the possible valid
10226 tail calls code paths it has considered. It will also print the intersection
10227 of them with the final unambiguous (possibly partial or even empty) code path
10230 @item show debug entry-values
10231 @kindex show debug entry-values
10232 Show the current state of analysis messages printing for both frame argument
10233 values at function entry and tail calls.
10236 The analysis messages for tail calls can for example show why the virtual tail
10237 call frame for function @code{c} has not been recognized (due to the indirect
10238 reference by variable @code{x}):
10241 static void __attribute__((noinline, noclone)) c (void);
10242 void (*x) (void) = c;
10243 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10244 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10245 int main (void) @{ x (); return 0; @}
10247 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10248 DW_TAG_GNU_call_site 0x40039a in main
10250 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10253 #1 0x000000000040039a in main () at t.c:5
10256 Another possibility is an ambiguous virtual tail call frames resolution:
10260 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10261 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10262 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10263 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10264 static void __attribute__((noinline, noclone)) b (void)
10265 @{ if (i) c (); else e (); @}
10266 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10267 int main (void) @{ a (); return 0; @}
10269 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10270 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10271 tailcall: reduced: 0x4004d2(a) |
10274 #1 0x00000000004004d2 in a () at t.c:8
10275 #2 0x0000000000400395 in main () at t.c:9
10278 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10279 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10281 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10282 @ifset HAVE_MAKEINFO_CLICK
10283 @set ARROW @click{}
10284 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10285 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10287 @ifclear HAVE_MAKEINFO_CLICK
10289 @set CALLSEQ1B @value{CALLSEQ1A}
10290 @set CALLSEQ2B @value{CALLSEQ2A}
10293 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10294 The code can have possible execution paths @value{CALLSEQ1B} or
10295 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10297 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10298 has found. It then finds another possible calling sequcen - that one is
10299 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10300 printed as the @code{reduced:} calling sequence. That one could have many
10301 futher @code{compare:} and @code{reduced:} statements as long as there remain
10302 any non-ambiguous sequence entries.
10304 For the frame of function @code{b} in both cases there are different possible
10305 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10306 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10307 therefore this one is displayed to the user while the ambiguous frames are
10310 There can be also reasons why printing of frame argument values at function
10315 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10316 static void __attribute__((noinline, noclone)) a (int i);
10317 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10318 static void __attribute__((noinline, noclone)) a (int i)
10319 @{ if (i) b (i - 1); else c (0); @}
10320 int main (void) @{ a (5); return 0; @}
10323 #0 c (i=i@@entry=0) at t.c:2
10324 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10325 function "a" at 0x400420 can call itself via tail calls
10326 i=<optimized out>) at t.c:6
10327 #2 0x000000000040036e in main () at t.c:7
10330 @value{GDBN} cannot find out from the inferior state if and how many times did
10331 function @code{a} call itself (via function @code{b}) as these calls would be
10332 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10333 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10334 prints @code{<optimized out>} instead.
10337 @chapter C Preprocessor Macros
10339 Some languages, such as C and C@t{++}, provide a way to define and invoke
10340 ``preprocessor macros'' which expand into strings of tokens.
10341 @value{GDBN} can evaluate expressions containing macro invocations, show
10342 the result of macro expansion, and show a macro's definition, including
10343 where it was defined.
10345 You may need to compile your program specially to provide @value{GDBN}
10346 with information about preprocessor macros. Most compilers do not
10347 include macros in their debugging information, even when you compile
10348 with the @option{-g} flag. @xref{Compilation}.
10350 A program may define a macro at one point, remove that definition later,
10351 and then provide a different definition after that. Thus, at different
10352 points in the program, a macro may have different definitions, or have
10353 no definition at all. If there is a current stack frame, @value{GDBN}
10354 uses the macros in scope at that frame's source code line. Otherwise,
10355 @value{GDBN} uses the macros in scope at the current listing location;
10358 Whenever @value{GDBN} evaluates an expression, it always expands any
10359 macro invocations present in the expression. @value{GDBN} also provides
10360 the following commands for working with macros explicitly.
10364 @kindex macro expand
10365 @cindex macro expansion, showing the results of preprocessor
10366 @cindex preprocessor macro expansion, showing the results of
10367 @cindex expanding preprocessor macros
10368 @item macro expand @var{expression}
10369 @itemx macro exp @var{expression}
10370 Show the results of expanding all preprocessor macro invocations in
10371 @var{expression}. Since @value{GDBN} simply expands macros, but does
10372 not parse the result, @var{expression} need not be a valid expression;
10373 it can be any string of tokens.
10376 @item macro expand-once @var{expression}
10377 @itemx macro exp1 @var{expression}
10378 @cindex expand macro once
10379 @i{(This command is not yet implemented.)} Show the results of
10380 expanding those preprocessor macro invocations that appear explicitly in
10381 @var{expression}. Macro invocations appearing in that expansion are
10382 left unchanged. This command allows you to see the effect of a
10383 particular macro more clearly, without being confused by further
10384 expansions. Since @value{GDBN} simply expands macros, but does not
10385 parse the result, @var{expression} need not be a valid expression; it
10386 can be any string of tokens.
10389 @cindex macro definition, showing
10390 @cindex definition of a macro, showing
10391 @cindex macros, from debug info
10392 @item info macro [-a|-all] [--] @var{macro}
10393 Show the current definition or all definitions of the named @var{macro},
10394 and describe the source location or compiler command-line where that
10395 definition was established. The optional double dash is to signify the end of
10396 argument processing and the beginning of @var{macro} for non C-like macros where
10397 the macro may begin with a hyphen.
10399 @kindex info macros
10400 @item info macros @var{linespec}
10401 Show all macro definitions that are in effect at the location specified
10402 by @var{linespec}, and describe the source location or compiler
10403 command-line where those definitions were established.
10405 @kindex macro define
10406 @cindex user-defined macros
10407 @cindex defining macros interactively
10408 @cindex macros, user-defined
10409 @item macro define @var{macro} @var{replacement-list}
10410 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10411 Introduce a definition for a preprocessor macro named @var{macro},
10412 invocations of which are replaced by the tokens given in
10413 @var{replacement-list}. The first form of this command defines an
10414 ``object-like'' macro, which takes no arguments; the second form
10415 defines a ``function-like'' macro, which takes the arguments given in
10418 A definition introduced by this command is in scope in every
10419 expression evaluated in @value{GDBN}, until it is removed with the
10420 @code{macro undef} command, described below. The definition overrides
10421 all definitions for @var{macro} present in the program being debugged,
10422 as well as any previous user-supplied definition.
10424 @kindex macro undef
10425 @item macro undef @var{macro}
10426 Remove any user-supplied definition for the macro named @var{macro}.
10427 This command only affects definitions provided with the @code{macro
10428 define} command, described above; it cannot remove definitions present
10429 in the program being debugged.
10433 List all the macros defined using the @code{macro define} command.
10436 @cindex macros, example of debugging with
10437 Here is a transcript showing the above commands in action. First, we
10438 show our source files:
10443 #include "sample.h"
10446 #define ADD(x) (M + x)
10451 printf ("Hello, world!\n");
10453 printf ("We're so creative.\n");
10455 printf ("Goodbye, world!\n");
10462 Now, we compile the program using the @sc{gnu} C compiler,
10463 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10464 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10465 and @option{-gdwarf-4}; we recommend always choosing the most recent
10466 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10467 includes information about preprocessor macros in the debugging
10471 $ gcc -gdwarf-2 -g3 sample.c -o sample
10475 Now, we start @value{GDBN} on our sample program:
10479 GNU gdb 2002-05-06-cvs
10480 Copyright 2002 Free Software Foundation, Inc.
10481 GDB is free software, @dots{}
10485 We can expand macros and examine their definitions, even when the
10486 program is not running. @value{GDBN} uses the current listing position
10487 to decide which macro definitions are in scope:
10490 (@value{GDBP}) list main
10493 5 #define ADD(x) (M + x)
10498 10 printf ("Hello, world!\n");
10500 12 printf ("We're so creative.\n");
10501 (@value{GDBP}) info macro ADD
10502 Defined at /home/jimb/gdb/macros/play/sample.c:5
10503 #define ADD(x) (M + x)
10504 (@value{GDBP}) info macro Q
10505 Defined at /home/jimb/gdb/macros/play/sample.h:1
10506 included at /home/jimb/gdb/macros/play/sample.c:2
10508 (@value{GDBP}) macro expand ADD(1)
10509 expands to: (42 + 1)
10510 (@value{GDBP}) macro expand-once ADD(1)
10511 expands to: once (M + 1)
10515 In the example above, note that @code{macro expand-once} expands only
10516 the macro invocation explicit in the original text --- the invocation of
10517 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10518 which was introduced by @code{ADD}.
10520 Once the program is running, @value{GDBN} uses the macro definitions in
10521 force at the source line of the current stack frame:
10524 (@value{GDBP}) break main
10525 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10527 Starting program: /home/jimb/gdb/macros/play/sample
10529 Breakpoint 1, main () at sample.c:10
10530 10 printf ("Hello, world!\n");
10534 At line 10, the definition of the macro @code{N} at line 9 is in force:
10537 (@value{GDBP}) info macro N
10538 Defined at /home/jimb/gdb/macros/play/sample.c:9
10540 (@value{GDBP}) macro expand N Q M
10541 expands to: 28 < 42
10542 (@value{GDBP}) print N Q M
10547 As we step over directives that remove @code{N}'s definition, and then
10548 give it a new definition, @value{GDBN} finds the definition (or lack
10549 thereof) in force at each point:
10552 (@value{GDBP}) next
10554 12 printf ("We're so creative.\n");
10555 (@value{GDBP}) info macro N
10556 The symbol `N' has no definition as a C/C++ preprocessor macro
10557 at /home/jimb/gdb/macros/play/sample.c:12
10558 (@value{GDBP}) next
10560 14 printf ("Goodbye, world!\n");
10561 (@value{GDBP}) info macro N
10562 Defined at /home/jimb/gdb/macros/play/sample.c:13
10564 (@value{GDBP}) macro expand N Q M
10565 expands to: 1729 < 42
10566 (@value{GDBP}) print N Q M
10571 In addition to source files, macros can be defined on the compilation command
10572 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10573 such a way, @value{GDBN} displays the location of their definition as line zero
10574 of the source file submitted to the compiler.
10577 (@value{GDBP}) info macro __STDC__
10578 Defined at /home/jimb/gdb/macros/play/sample.c:0
10585 @chapter Tracepoints
10586 @c This chapter is based on the documentation written by Michael
10587 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10589 @cindex tracepoints
10590 In some applications, it is not feasible for the debugger to interrupt
10591 the program's execution long enough for the developer to learn
10592 anything helpful about its behavior. If the program's correctness
10593 depends on its real-time behavior, delays introduced by a debugger
10594 might cause the program to change its behavior drastically, or perhaps
10595 fail, even when the code itself is correct. It is useful to be able
10596 to observe the program's behavior without interrupting it.
10598 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10599 specify locations in the program, called @dfn{tracepoints}, and
10600 arbitrary expressions to evaluate when those tracepoints are reached.
10601 Later, using the @code{tfind} command, you can examine the values
10602 those expressions had when the program hit the tracepoints. The
10603 expressions may also denote objects in memory---structures or arrays,
10604 for example---whose values @value{GDBN} should record; while visiting
10605 a particular tracepoint, you may inspect those objects as if they were
10606 in memory at that moment. However, because @value{GDBN} records these
10607 values without interacting with you, it can do so quickly and
10608 unobtrusively, hopefully not disturbing the program's behavior.
10610 The tracepoint facility is currently available only for remote
10611 targets. @xref{Targets}. In addition, your remote target must know
10612 how to collect trace data. This functionality is implemented in the
10613 remote stub; however, none of the stubs distributed with @value{GDBN}
10614 support tracepoints as of this writing. The format of the remote
10615 packets used to implement tracepoints are described in @ref{Tracepoint
10618 It is also possible to get trace data from a file, in a manner reminiscent
10619 of corefiles; you specify the filename, and use @code{tfind} to search
10620 through the file. @xref{Trace Files}, for more details.
10622 This chapter describes the tracepoint commands and features.
10625 * Set Tracepoints::
10626 * Analyze Collected Data::
10627 * Tracepoint Variables::
10631 @node Set Tracepoints
10632 @section Commands to Set Tracepoints
10634 Before running such a @dfn{trace experiment}, an arbitrary number of
10635 tracepoints can be set. A tracepoint is actually a special type of
10636 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10637 standard breakpoint commands. For instance, as with breakpoints,
10638 tracepoint numbers are successive integers starting from one, and many
10639 of the commands associated with tracepoints take the tracepoint number
10640 as their argument, to identify which tracepoint to work on.
10642 For each tracepoint, you can specify, in advance, some arbitrary set
10643 of data that you want the target to collect in the trace buffer when
10644 it hits that tracepoint. The collected data can include registers,
10645 local variables, or global data. Later, you can use @value{GDBN}
10646 commands to examine the values these data had at the time the
10647 tracepoint was hit.
10649 Tracepoints do not support every breakpoint feature. Ignore counts on
10650 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10651 commands when they are hit. Tracepoints may not be thread-specific
10654 @cindex fast tracepoints
10655 Some targets may support @dfn{fast tracepoints}, which are inserted in
10656 a different way (such as with a jump instead of a trap), that is
10657 faster but possibly restricted in where they may be installed.
10659 @cindex static tracepoints
10660 @cindex markers, static tracepoints
10661 @cindex probing markers, static tracepoints
10662 Regular and fast tracepoints are dynamic tracing facilities, meaning
10663 that they can be used to insert tracepoints at (almost) any location
10664 in the target. Some targets may also support controlling @dfn{static
10665 tracepoints} from @value{GDBN}. With static tracing, a set of
10666 instrumentation points, also known as @dfn{markers}, are embedded in
10667 the target program, and can be activated or deactivated by name or
10668 address. These are usually placed at locations which facilitate
10669 investigating what the target is actually doing. @value{GDBN}'s
10670 support for static tracing includes being able to list instrumentation
10671 points, and attach them with @value{GDBN} defined high level
10672 tracepoints that expose the whole range of convenience of
10673 @value{GDBN}'s tracepoints support. Namely, support for collecting
10674 registers values and values of global or local (to the instrumentation
10675 point) variables; tracepoint conditions and trace state variables.
10676 The act of installing a @value{GDBN} static tracepoint on an
10677 instrumentation point, or marker, is referred to as @dfn{probing} a
10678 static tracepoint marker.
10680 @code{gdbserver} supports tracepoints on some target systems.
10681 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10683 This section describes commands to set tracepoints and associated
10684 conditions and actions.
10687 * Create and Delete Tracepoints::
10688 * Enable and Disable Tracepoints::
10689 * Tracepoint Passcounts::
10690 * Tracepoint Conditions::
10691 * Trace State Variables::
10692 * Tracepoint Actions::
10693 * Listing Tracepoints::
10694 * Listing Static Tracepoint Markers::
10695 * Starting and Stopping Trace Experiments::
10696 * Tracepoint Restrictions::
10699 @node Create and Delete Tracepoints
10700 @subsection Create and Delete Tracepoints
10703 @cindex set tracepoint
10705 @item trace @var{location}
10706 The @code{trace} command is very similar to the @code{break} command.
10707 Its argument @var{location} can be a source line, a function name, or
10708 an address in the target program. @xref{Specify Location}. The
10709 @code{trace} command defines a tracepoint, which is a point in the
10710 target program where the debugger will briefly stop, collect some
10711 data, and then allow the program to continue. Setting a tracepoint or
10712 changing its actions takes effect immediately if the remote stub
10713 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10715 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10716 these changes don't take effect until the next @code{tstart}
10717 command, and once a trace experiment is running, further changes will
10718 not have any effect until the next trace experiment starts. In addition,
10719 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10720 address is not yet resolved. (This is similar to pending breakpoints.)
10721 Pending tracepoints are not downloaded to the target and not installed
10722 until they are resolved. The resolution of pending tracepoints requires
10723 @value{GDBN} support---when debugging with the remote target, and
10724 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10725 tracing}), pending tracepoints can not be resolved (and downloaded to
10726 the remote stub) while @value{GDBN} is disconnected.
10728 Here are some examples of using the @code{trace} command:
10731 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10733 (@value{GDBP}) @b{trace +2} // 2 lines forward
10735 (@value{GDBP}) @b{trace my_function} // first source line of function
10737 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10739 (@value{GDBP}) @b{trace *0x2117c4} // an address
10743 You can abbreviate @code{trace} as @code{tr}.
10745 @item trace @var{location} if @var{cond}
10746 Set a tracepoint with condition @var{cond}; evaluate the expression
10747 @var{cond} each time the tracepoint is reached, and collect data only
10748 if the value is nonzero---that is, if @var{cond} evaluates as true.
10749 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10750 information on tracepoint conditions.
10752 @item ftrace @var{location} [ if @var{cond} ]
10753 @cindex set fast tracepoint
10754 @cindex fast tracepoints, setting
10756 The @code{ftrace} command sets a fast tracepoint. For targets that
10757 support them, fast tracepoints will use a more efficient but possibly
10758 less general technique to trigger data collection, such as a jump
10759 instruction instead of a trap, or some sort of hardware support. It
10760 may not be possible to create a fast tracepoint at the desired
10761 location, in which case the command will exit with an explanatory
10764 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10767 On 32-bit x86-architecture systems, fast tracepoints normally need to
10768 be placed at an instruction that is 5 bytes or longer, but can be
10769 placed at 4-byte instructions if the low 64K of memory of the target
10770 program is available to install trampolines. Some Unix-type systems,
10771 such as @sc{gnu}/Linux, exclude low addresses from the program's
10772 address space; but for instance with the Linux kernel it is possible
10773 to let @value{GDBN} use this area by doing a @command{sysctl} command
10774 to set the @code{mmap_min_addr} kernel parameter, as in
10777 sudo sysctl -w vm.mmap_min_addr=32768
10781 which sets the low address to 32K, which leaves plenty of room for
10782 trampolines. The minimum address should be set to a page boundary.
10784 @item strace @var{location} [ if @var{cond} ]
10785 @cindex set static tracepoint
10786 @cindex static tracepoints, setting
10787 @cindex probe static tracepoint marker
10789 The @code{strace} command sets a static tracepoint. For targets that
10790 support it, setting a static tracepoint probes a static
10791 instrumentation point, or marker, found at @var{location}. It may not
10792 be possible to set a static tracepoint at the desired location, in
10793 which case the command will exit with an explanatory message.
10795 @value{GDBN} handles arguments to @code{strace} exactly as for
10796 @code{trace}, with the addition that the user can also specify
10797 @code{-m @var{marker}} as @var{location}. This probes the marker
10798 identified by the @var{marker} string identifier. This identifier
10799 depends on the static tracepoint backend library your program is
10800 using. You can find all the marker identifiers in the @samp{ID} field
10801 of the @code{info static-tracepoint-markers} command output.
10802 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10803 Markers}. For example, in the following small program using the UST
10809 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10814 the marker id is composed of joining the first two arguments to the
10815 @code{trace_mark} call with a slash, which translates to:
10818 (@value{GDBP}) info static-tracepoint-markers
10819 Cnt Enb ID Address What
10820 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10826 so you may probe the marker above with:
10829 (@value{GDBP}) strace -m ust/bar33
10832 Static tracepoints accept an extra collect action --- @code{collect
10833 $_sdata}. This collects arbitrary user data passed in the probe point
10834 call to the tracing library. In the UST example above, you'll see
10835 that the third argument to @code{trace_mark} is a printf-like format
10836 string. The user data is then the result of running that formating
10837 string against the following arguments. Note that @code{info
10838 static-tracepoint-markers} command output lists that format string in
10839 the @samp{Data:} field.
10841 You can inspect this data when analyzing the trace buffer, by printing
10842 the $_sdata variable like any other variable available to
10843 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10846 @cindex last tracepoint number
10847 @cindex recent tracepoint number
10848 @cindex tracepoint number
10849 The convenience variable @code{$tpnum} records the tracepoint number
10850 of the most recently set tracepoint.
10852 @kindex delete tracepoint
10853 @cindex tracepoint deletion
10854 @item delete tracepoint @r{[}@var{num}@r{]}
10855 Permanently delete one or more tracepoints. With no argument, the
10856 default is to delete all tracepoints. Note that the regular
10857 @code{delete} command can remove tracepoints also.
10862 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10864 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10868 You can abbreviate this command as @code{del tr}.
10871 @node Enable and Disable Tracepoints
10872 @subsection Enable and Disable Tracepoints
10874 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10877 @kindex disable tracepoint
10878 @item disable tracepoint @r{[}@var{num}@r{]}
10879 Disable tracepoint @var{num}, or all tracepoints if no argument
10880 @var{num} is given. A disabled tracepoint will have no effect during
10881 a trace experiment, but it is not forgotten. You can re-enable
10882 a disabled tracepoint using the @code{enable tracepoint} command.
10883 If the command is issued during a trace experiment and the debug target
10884 has support for disabling tracepoints during a trace experiment, then the
10885 change will be effective immediately. Otherwise, it will be applied to the
10886 next trace experiment.
10888 @kindex enable tracepoint
10889 @item enable tracepoint @r{[}@var{num}@r{]}
10890 Enable tracepoint @var{num}, or all tracepoints. If this command is
10891 issued during a trace experiment and the debug target supports enabling
10892 tracepoints during a trace experiment, then the enabled tracepoints will
10893 become effective immediately. Otherwise, they will become effective the
10894 next time a trace experiment is run.
10897 @node Tracepoint Passcounts
10898 @subsection Tracepoint Passcounts
10902 @cindex tracepoint pass count
10903 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10904 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10905 automatically stop a trace experiment. If a tracepoint's passcount is
10906 @var{n}, then the trace experiment will be automatically stopped on
10907 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10908 @var{num} is not specified, the @code{passcount} command sets the
10909 passcount of the most recently defined tracepoint. If no passcount is
10910 given, the trace experiment will run until stopped explicitly by the
10916 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10917 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10919 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10920 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10921 (@value{GDBP}) @b{trace foo}
10922 (@value{GDBP}) @b{pass 3}
10923 (@value{GDBP}) @b{trace bar}
10924 (@value{GDBP}) @b{pass 2}
10925 (@value{GDBP}) @b{trace baz}
10926 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10927 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10928 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10929 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10933 @node Tracepoint Conditions
10934 @subsection Tracepoint Conditions
10935 @cindex conditional tracepoints
10936 @cindex tracepoint conditions
10938 The simplest sort of tracepoint collects data every time your program
10939 reaches a specified place. You can also specify a @dfn{condition} for
10940 a tracepoint. A condition is just a Boolean expression in your
10941 programming language (@pxref{Expressions, ,Expressions}). A
10942 tracepoint with a condition evaluates the expression each time your
10943 program reaches it, and data collection happens only if the condition
10946 Tracepoint conditions can be specified when a tracepoint is set, by
10947 using @samp{if} in the arguments to the @code{trace} command.
10948 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10949 also be set or changed at any time with the @code{condition} command,
10950 just as with breakpoints.
10952 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10953 the conditional expression itself. Instead, @value{GDBN} encodes the
10954 expression into an agent expression (@pxref{Agent Expressions})
10955 suitable for execution on the target, independently of @value{GDBN}.
10956 Global variables become raw memory locations, locals become stack
10957 accesses, and so forth.
10959 For instance, suppose you have a function that is usually called
10960 frequently, but should not be called after an error has occurred. You
10961 could use the following tracepoint command to collect data about calls
10962 of that function that happen while the error code is propagating
10963 through the program; an unconditional tracepoint could end up
10964 collecting thousands of useless trace frames that you would have to
10968 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10971 @node Trace State Variables
10972 @subsection Trace State Variables
10973 @cindex trace state variables
10975 A @dfn{trace state variable} is a special type of variable that is
10976 created and managed by target-side code. The syntax is the same as
10977 that for GDB's convenience variables (a string prefixed with ``$''),
10978 but they are stored on the target. They must be created explicitly,
10979 using a @code{tvariable} command. They are always 64-bit signed
10982 Trace state variables are remembered by @value{GDBN}, and downloaded
10983 to the target along with tracepoint information when the trace
10984 experiment starts. There are no intrinsic limits on the number of
10985 trace state variables, beyond memory limitations of the target.
10987 @cindex convenience variables, and trace state variables
10988 Although trace state variables are managed by the target, you can use
10989 them in print commands and expressions as if they were convenience
10990 variables; @value{GDBN} will get the current value from the target
10991 while the trace experiment is running. Trace state variables share
10992 the same namespace as other ``$'' variables, which means that you
10993 cannot have trace state variables with names like @code{$23} or
10994 @code{$pc}, nor can you have a trace state variable and a convenience
10995 variable with the same name.
10999 @item tvariable $@var{name} [ = @var{expression} ]
11001 The @code{tvariable} command creates a new trace state variable named
11002 @code{$@var{name}}, and optionally gives it an initial value of
11003 @var{expression}. @var{expression} is evaluated when this command is
11004 entered; the result will be converted to an integer if possible,
11005 otherwise @value{GDBN} will report an error. A subsequent
11006 @code{tvariable} command specifying the same name does not create a
11007 variable, but instead assigns the supplied initial value to the
11008 existing variable of that name, overwriting any previous initial
11009 value. The default initial value is 0.
11011 @item info tvariables
11012 @kindex info tvariables
11013 List all the trace state variables along with their initial values.
11014 Their current values may also be displayed, if the trace experiment is
11017 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11018 @kindex delete tvariable
11019 Delete the given trace state variables, or all of them if no arguments
11024 @node Tracepoint Actions
11025 @subsection Tracepoint Action Lists
11029 @cindex tracepoint actions
11030 @item actions @r{[}@var{num}@r{]}
11031 This command will prompt for a list of actions to be taken when the
11032 tracepoint is hit. If the tracepoint number @var{num} is not
11033 specified, this command sets the actions for the one that was most
11034 recently defined (so that you can define a tracepoint and then say
11035 @code{actions} without bothering about its number). You specify the
11036 actions themselves on the following lines, one action at a time, and
11037 terminate the actions list with a line containing just @code{end}. So
11038 far, the only defined actions are @code{collect}, @code{teval}, and
11039 @code{while-stepping}.
11041 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11042 Commands, ,Breakpoint Command Lists}), except that only the defined
11043 actions are allowed; any other @value{GDBN} command is rejected.
11045 @cindex remove actions from a tracepoint
11046 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11047 and follow it immediately with @samp{end}.
11050 (@value{GDBP}) @b{collect @var{data}} // collect some data
11052 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11054 (@value{GDBP}) @b{end} // signals the end of actions.
11057 In the following example, the action list begins with @code{collect}
11058 commands indicating the things to be collected when the tracepoint is
11059 hit. Then, in order to single-step and collect additional data
11060 following the tracepoint, a @code{while-stepping} command is used,
11061 followed by the list of things to be collected after each step in a
11062 sequence of single steps. The @code{while-stepping} command is
11063 terminated by its own separate @code{end} command. Lastly, the action
11064 list is terminated by an @code{end} command.
11067 (@value{GDBP}) @b{trace foo}
11068 (@value{GDBP}) @b{actions}
11069 Enter actions for tracepoint 1, one per line:
11072 > while-stepping 12
11073 > collect $pc, arr[i]
11078 @kindex collect @r{(tracepoints)}
11079 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11080 Collect values of the given expressions when the tracepoint is hit.
11081 This command accepts a comma-separated list of any valid expressions.
11082 In addition to global, static, or local variables, the following
11083 special arguments are supported:
11087 Collect all registers.
11090 Collect all function arguments.
11093 Collect all local variables.
11096 Collect the return address. This is helpful if you want to see more
11100 Collects the number of arguments from the static probe at which the
11101 tracepoint is located.
11102 @xref{Static Probe Points}.
11104 @item $_probe_arg@var{n}
11105 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11106 from the static probe at which the tracepoint is located.
11107 @xref{Static Probe Points}.
11110 @vindex $_sdata@r{, collect}
11111 Collect static tracepoint marker specific data. Only available for
11112 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11113 Lists}. On the UST static tracepoints library backend, an
11114 instrumentation point resembles a @code{printf} function call. The
11115 tracing library is able to collect user specified data formatted to a
11116 character string using the format provided by the programmer that
11117 instrumented the program. Other backends have similar mechanisms.
11118 Here's an example of a UST marker call:
11121 const char master_name[] = "$your_name";
11122 trace_mark(channel1, marker1, "hello %s", master_name)
11125 In this case, collecting @code{$_sdata} collects the string
11126 @samp{hello $yourname}. When analyzing the trace buffer, you can
11127 inspect @samp{$_sdata} like any other variable available to
11131 You can give several consecutive @code{collect} commands, each one
11132 with a single argument, or one @code{collect} command with several
11133 arguments separated by commas; the effect is the same.
11135 The optional @var{mods} changes the usual handling of the arguments.
11136 @code{s} requests that pointers to chars be handled as strings, in
11137 particular collecting the contents of the memory being pointed at, up
11138 to the first zero. The upper bound is by default the value of the
11139 @code{print elements} variable; if @code{s} is followed by a decimal
11140 number, that is the upper bound instead. So for instance
11141 @samp{collect/s25 mystr} collects as many as 25 characters at
11144 The command @code{info scope} (@pxref{Symbols, info scope}) is
11145 particularly useful for figuring out what data to collect.
11147 @kindex teval @r{(tracepoints)}
11148 @item teval @var{expr1}, @var{expr2}, @dots{}
11149 Evaluate the given expressions when the tracepoint is hit. This
11150 command accepts a comma-separated list of expressions. The results
11151 are discarded, so this is mainly useful for assigning values to trace
11152 state variables (@pxref{Trace State Variables}) without adding those
11153 values to the trace buffer, as would be the case if the @code{collect}
11156 @kindex while-stepping @r{(tracepoints)}
11157 @item while-stepping @var{n}
11158 Perform @var{n} single-step instruction traces after the tracepoint,
11159 collecting new data after each step. The @code{while-stepping}
11160 command is followed by the list of what to collect while stepping
11161 (followed by its own @code{end} command):
11164 > while-stepping 12
11165 > collect $regs, myglobal
11171 Note that @code{$pc} is not automatically collected by
11172 @code{while-stepping}; you need to explicitly collect that register if
11173 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11176 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11177 @kindex set default-collect
11178 @cindex default collection action
11179 This variable is a list of expressions to collect at each tracepoint
11180 hit. It is effectively an additional @code{collect} action prepended
11181 to every tracepoint action list. The expressions are parsed
11182 individually for each tracepoint, so for instance a variable named
11183 @code{xyz} may be interpreted as a global for one tracepoint, and a
11184 local for another, as appropriate to the tracepoint's location.
11186 @item show default-collect
11187 @kindex show default-collect
11188 Show the list of expressions that are collected by default at each
11193 @node Listing Tracepoints
11194 @subsection Listing Tracepoints
11197 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11198 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11199 @cindex information about tracepoints
11200 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11201 Display information about the tracepoint @var{num}. If you don't
11202 specify a tracepoint number, displays information about all the
11203 tracepoints defined so far. The format is similar to that used for
11204 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11205 command, simply restricting itself to tracepoints.
11207 A tracepoint's listing may include additional information specific to
11212 its passcount as given by the @code{passcount @var{n}} command
11216 (@value{GDBP}) @b{info trace}
11217 Num Type Disp Enb Address What
11218 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11220 collect globfoo, $regs
11229 This command can be abbreviated @code{info tp}.
11232 @node Listing Static Tracepoint Markers
11233 @subsection Listing Static Tracepoint Markers
11236 @kindex info static-tracepoint-markers
11237 @cindex information about static tracepoint markers
11238 @item info static-tracepoint-markers
11239 Display information about all static tracepoint markers defined in the
11242 For each marker, the following columns are printed:
11246 An incrementing counter, output to help readability. This is not a
11249 The marker ID, as reported by the target.
11250 @item Enabled or Disabled
11251 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11252 that are not enabled.
11254 Where the marker is in your program, as a memory address.
11256 Where the marker is in the source for your program, as a file and line
11257 number. If the debug information included in the program does not
11258 allow @value{GDBN} to locate the source of the marker, this column
11259 will be left blank.
11263 In addition, the following information may be printed for each marker:
11267 User data passed to the tracing library by the marker call. In the
11268 UST backend, this is the format string passed as argument to the
11270 @item Static tracepoints probing the marker
11271 The list of static tracepoints attached to the marker.
11275 (@value{GDBP}) info static-tracepoint-markers
11276 Cnt ID Enb Address What
11277 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11278 Data: number1 %d number2 %d
11279 Probed by static tracepoints: #2
11280 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11286 @node Starting and Stopping Trace Experiments
11287 @subsection Starting and Stopping Trace Experiments
11290 @kindex tstart [ @var{notes} ]
11291 @cindex start a new trace experiment
11292 @cindex collected data discarded
11294 This command starts the trace experiment, and begins collecting data.
11295 It has the side effect of discarding all the data collected in the
11296 trace buffer during the previous trace experiment. If any arguments
11297 are supplied, they are taken as a note and stored with the trace
11298 experiment's state. The notes may be arbitrary text, and are
11299 especially useful with disconnected tracing in a multi-user context;
11300 the notes can explain what the trace is doing, supply user contact
11301 information, and so forth.
11303 @kindex tstop [ @var{notes} ]
11304 @cindex stop a running trace experiment
11306 This command stops the trace experiment. If any arguments are
11307 supplied, they are recorded with the experiment as a note. This is
11308 useful if you are stopping a trace started by someone else, for
11309 instance if the trace is interfering with the system's behavior and
11310 needs to be stopped quickly.
11312 @strong{Note}: a trace experiment and data collection may stop
11313 automatically if any tracepoint's passcount is reached
11314 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11317 @cindex status of trace data collection
11318 @cindex trace experiment, status of
11320 This command displays the status of the current trace data
11324 Here is an example of the commands we described so far:
11327 (@value{GDBP}) @b{trace gdb_c_test}
11328 (@value{GDBP}) @b{actions}
11329 Enter actions for tracepoint #1, one per line.
11330 > collect $regs,$locals,$args
11331 > while-stepping 11
11335 (@value{GDBP}) @b{tstart}
11336 [time passes @dots{}]
11337 (@value{GDBP}) @b{tstop}
11340 @anchor{disconnected tracing}
11341 @cindex disconnected tracing
11342 You can choose to continue running the trace experiment even if
11343 @value{GDBN} disconnects from the target, voluntarily or
11344 involuntarily. For commands such as @code{detach}, the debugger will
11345 ask what you want to do with the trace. But for unexpected
11346 terminations (@value{GDBN} crash, network outage), it would be
11347 unfortunate to lose hard-won trace data, so the variable
11348 @code{disconnected-tracing} lets you decide whether the trace should
11349 continue running without @value{GDBN}.
11352 @item set disconnected-tracing on
11353 @itemx set disconnected-tracing off
11354 @kindex set disconnected-tracing
11355 Choose whether a tracing run should continue to run if @value{GDBN}
11356 has disconnected from the target. Note that @code{detach} or
11357 @code{quit} will ask you directly what to do about a running trace no
11358 matter what this variable's setting, so the variable is mainly useful
11359 for handling unexpected situations, such as loss of the network.
11361 @item show disconnected-tracing
11362 @kindex show disconnected-tracing
11363 Show the current choice for disconnected tracing.
11367 When you reconnect to the target, the trace experiment may or may not
11368 still be running; it might have filled the trace buffer in the
11369 meantime, or stopped for one of the other reasons. If it is running,
11370 it will continue after reconnection.
11372 Upon reconnection, the target will upload information about the
11373 tracepoints in effect. @value{GDBN} will then compare that
11374 information to the set of tracepoints currently defined, and attempt
11375 to match them up, allowing for the possibility that the numbers may
11376 have changed due to creation and deletion in the meantime. If one of
11377 the target's tracepoints does not match any in @value{GDBN}, the
11378 debugger will create a new tracepoint, so that you have a number with
11379 which to specify that tracepoint. This matching-up process is
11380 necessarily heuristic, and it may result in useless tracepoints being
11381 created; you may simply delete them if they are of no use.
11383 @cindex circular trace buffer
11384 If your target agent supports a @dfn{circular trace buffer}, then you
11385 can run a trace experiment indefinitely without filling the trace
11386 buffer; when space runs out, the agent deletes already-collected trace
11387 frames, oldest first, until there is enough room to continue
11388 collecting. This is especially useful if your tracepoints are being
11389 hit too often, and your trace gets terminated prematurely because the
11390 buffer is full. To ask for a circular trace buffer, simply set
11391 @samp{circular-trace-buffer} to on. You can set this at any time,
11392 including during tracing; if the agent can do it, it will change
11393 buffer handling on the fly, otherwise it will not take effect until
11397 @item set circular-trace-buffer on
11398 @itemx set circular-trace-buffer off
11399 @kindex set circular-trace-buffer
11400 Choose whether a tracing run should use a linear or circular buffer
11401 for trace data. A linear buffer will not lose any trace data, but may
11402 fill up prematurely, while a circular buffer will discard old trace
11403 data, but it will have always room for the latest tracepoint hits.
11405 @item show circular-trace-buffer
11406 @kindex show circular-trace-buffer
11407 Show the current choice for the trace buffer. Note that this may not
11408 match the agent's current buffer handling, nor is it guaranteed to
11409 match the setting that might have been in effect during a past run,
11410 for instance if you are looking at frames from a trace file.
11415 @item set trace-user @var{text}
11416 @kindex set trace-user
11418 @item show trace-user
11419 @kindex show trace-user
11421 @item set trace-notes @var{text}
11422 @kindex set trace-notes
11423 Set the trace run's notes.
11425 @item show trace-notes
11426 @kindex show trace-notes
11427 Show the trace run's notes.
11429 @item set trace-stop-notes @var{text}
11430 @kindex set trace-stop-notes
11431 Set the trace run's stop notes. The handling of the note is as for
11432 @code{tstop} arguments; the set command is convenient way to fix a
11433 stop note that is mistaken or incomplete.
11435 @item show trace-stop-notes
11436 @kindex show trace-stop-notes
11437 Show the trace run's stop notes.
11441 @node Tracepoint Restrictions
11442 @subsection Tracepoint Restrictions
11444 @cindex tracepoint restrictions
11445 There are a number of restrictions on the use of tracepoints. As
11446 described above, tracepoint data gathering occurs on the target
11447 without interaction from @value{GDBN}. Thus the full capabilities of
11448 the debugger are not available during data gathering, and then at data
11449 examination time, you will be limited by only having what was
11450 collected. The following items describe some common problems, but it
11451 is not exhaustive, and you may run into additional difficulties not
11457 Tracepoint expressions are intended to gather objects (lvalues). Thus
11458 the full flexibility of GDB's expression evaluator is not available.
11459 You cannot call functions, cast objects to aggregate types, access
11460 convenience variables or modify values (except by assignment to trace
11461 state variables). Some language features may implicitly call
11462 functions (for instance Objective-C fields with accessors), and therefore
11463 cannot be collected either.
11466 Collection of local variables, either individually or in bulk with
11467 @code{$locals} or @code{$args}, during @code{while-stepping} may
11468 behave erratically. The stepping action may enter a new scope (for
11469 instance by stepping into a function), or the location of the variable
11470 may change (for instance it is loaded into a register). The
11471 tracepoint data recorded uses the location information for the
11472 variables that is correct for the tracepoint location. When the
11473 tracepoint is created, it is not possible, in general, to determine
11474 where the steps of a @code{while-stepping} sequence will advance the
11475 program---particularly if a conditional branch is stepped.
11478 Collection of an incompletely-initialized or partially-destroyed object
11479 may result in something that @value{GDBN} cannot display, or displays
11480 in a misleading way.
11483 When @value{GDBN} displays a pointer to character it automatically
11484 dereferences the pointer to also display characters of the string
11485 being pointed to. However, collecting the pointer during tracing does
11486 not automatically collect the string. You need to explicitly
11487 dereference the pointer and provide size information if you want to
11488 collect not only the pointer, but the memory pointed to. For example,
11489 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11493 It is not possible to collect a complete stack backtrace at a
11494 tracepoint. Instead, you may collect the registers and a few hundred
11495 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11496 (adjust to use the name of the actual stack pointer register on your
11497 target architecture, and the amount of stack you wish to capture).
11498 Then the @code{backtrace} command will show a partial backtrace when
11499 using a trace frame. The number of stack frames that can be examined
11500 depends on the sizes of the frames in the collected stack. Note that
11501 if you ask for a block so large that it goes past the bottom of the
11502 stack, the target agent may report an error trying to read from an
11506 If you do not collect registers at a tracepoint, @value{GDBN} can
11507 infer that the value of @code{$pc} must be the same as the address of
11508 the tracepoint and use that when you are looking at a trace frame
11509 for that tracepoint. However, this cannot work if the tracepoint has
11510 multiple locations (for instance if it was set in a function that was
11511 inlined), or if it has a @code{while-stepping} loop. In those cases
11512 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11517 @node Analyze Collected Data
11518 @section Using the Collected Data
11520 After the tracepoint experiment ends, you use @value{GDBN} commands
11521 for examining the trace data. The basic idea is that each tracepoint
11522 collects a trace @dfn{snapshot} every time it is hit and another
11523 snapshot every time it single-steps. All these snapshots are
11524 consecutively numbered from zero and go into a buffer, and you can
11525 examine them later. The way you examine them is to @dfn{focus} on a
11526 specific trace snapshot. When the remote stub is focused on a trace
11527 snapshot, it will respond to all @value{GDBN} requests for memory and
11528 registers by reading from the buffer which belongs to that snapshot,
11529 rather than from @emph{real} memory or registers of the program being
11530 debugged. This means that @strong{all} @value{GDBN} commands
11531 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11532 behave as if we were currently debugging the program state as it was
11533 when the tracepoint occurred. Any requests for data that are not in
11534 the buffer will fail.
11537 * tfind:: How to select a trace snapshot
11538 * tdump:: How to display all data for a snapshot
11539 * save tracepoints:: How to save tracepoints for a future run
11543 @subsection @code{tfind @var{n}}
11546 @cindex select trace snapshot
11547 @cindex find trace snapshot
11548 The basic command for selecting a trace snapshot from the buffer is
11549 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11550 counting from zero. If no argument @var{n} is given, the next
11551 snapshot is selected.
11553 Here are the various forms of using the @code{tfind} command.
11557 Find the first snapshot in the buffer. This is a synonym for
11558 @code{tfind 0} (since 0 is the number of the first snapshot).
11561 Stop debugging trace snapshots, resume @emph{live} debugging.
11564 Same as @samp{tfind none}.
11567 No argument means find the next trace snapshot.
11570 Find the previous trace snapshot before the current one. This permits
11571 retracing earlier steps.
11573 @item tfind tracepoint @var{num}
11574 Find the next snapshot associated with tracepoint @var{num}. Search
11575 proceeds forward from the last examined trace snapshot. If no
11576 argument @var{num} is given, it means find the next snapshot collected
11577 for the same tracepoint as the current snapshot.
11579 @item tfind pc @var{addr}
11580 Find the next snapshot associated with the value @var{addr} of the
11581 program counter. Search proceeds forward from the last examined trace
11582 snapshot. If no argument @var{addr} is given, it means find the next
11583 snapshot with the same value of PC as the current snapshot.
11585 @item tfind outside @var{addr1}, @var{addr2}
11586 Find the next snapshot whose PC is outside the given range of
11587 addresses (exclusive).
11589 @item tfind range @var{addr1}, @var{addr2}
11590 Find the next snapshot whose PC is between @var{addr1} and
11591 @var{addr2} (inclusive).
11593 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11594 Find the next snapshot associated with the source line @var{n}. If
11595 the optional argument @var{file} is given, refer to line @var{n} in
11596 that source file. Search proceeds forward from the last examined
11597 trace snapshot. If no argument @var{n} is given, it means find the
11598 next line other than the one currently being examined; thus saying
11599 @code{tfind line} repeatedly can appear to have the same effect as
11600 stepping from line to line in a @emph{live} debugging session.
11603 The default arguments for the @code{tfind} commands are specifically
11604 designed to make it easy to scan through the trace buffer. For
11605 instance, @code{tfind} with no argument selects the next trace
11606 snapshot, and @code{tfind -} with no argument selects the previous
11607 trace snapshot. So, by giving one @code{tfind} command, and then
11608 simply hitting @key{RET} repeatedly you can examine all the trace
11609 snapshots in order. Or, by saying @code{tfind -} and then hitting
11610 @key{RET} repeatedly you can examine the snapshots in reverse order.
11611 The @code{tfind line} command with no argument selects the snapshot
11612 for the next source line executed. The @code{tfind pc} command with
11613 no argument selects the next snapshot with the same program counter
11614 (PC) as the current frame. The @code{tfind tracepoint} command with
11615 no argument selects the next trace snapshot collected by the same
11616 tracepoint as the current one.
11618 In addition to letting you scan through the trace buffer manually,
11619 these commands make it easy to construct @value{GDBN} scripts that
11620 scan through the trace buffer and print out whatever collected data
11621 you are interested in. Thus, if we want to examine the PC, FP, and SP
11622 registers from each trace frame in the buffer, we can say this:
11625 (@value{GDBP}) @b{tfind start}
11626 (@value{GDBP}) @b{while ($trace_frame != -1)}
11627 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11628 $trace_frame, $pc, $sp, $fp
11632 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11633 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11634 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11635 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11636 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11637 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11638 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11639 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11640 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11641 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11642 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11645 Or, if we want to examine the variable @code{X} at each source line in
11649 (@value{GDBP}) @b{tfind start}
11650 (@value{GDBP}) @b{while ($trace_frame != -1)}
11651 > printf "Frame %d, X == %d\n", $trace_frame, X
11661 @subsection @code{tdump}
11663 @cindex dump all data collected at tracepoint
11664 @cindex tracepoint data, display
11666 This command takes no arguments. It prints all the data collected at
11667 the current trace snapshot.
11670 (@value{GDBP}) @b{trace 444}
11671 (@value{GDBP}) @b{actions}
11672 Enter actions for tracepoint #2, one per line:
11673 > collect $regs, $locals, $args, gdb_long_test
11676 (@value{GDBP}) @b{tstart}
11678 (@value{GDBP}) @b{tfind line 444}
11679 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11681 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11683 (@value{GDBP}) @b{tdump}
11684 Data collected at tracepoint 2, trace frame 1:
11685 d0 0xc4aa0085 -995491707
11689 d4 0x71aea3d 119204413
11692 d7 0x380035 3670069
11693 a0 0x19e24a 1696330
11694 a1 0x3000668 50333288
11696 a3 0x322000 3284992
11697 a4 0x3000698 50333336
11698 a5 0x1ad3cc 1758156
11699 fp 0x30bf3c 0x30bf3c
11700 sp 0x30bf34 0x30bf34
11702 pc 0x20b2c8 0x20b2c8
11706 p = 0x20e5b4 "gdb-test"
11713 gdb_long_test = 17 '\021'
11718 @code{tdump} works by scanning the tracepoint's current collection
11719 actions and printing the value of each expression listed. So
11720 @code{tdump} can fail, if after a run, you change the tracepoint's
11721 actions to mention variables that were not collected during the run.
11723 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11724 uses the collected value of @code{$pc} to distinguish between trace
11725 frames that were collected at the tracepoint hit, and frames that were
11726 collected while stepping. This allows it to correctly choose whether
11727 to display the basic list of collections, or the collections from the
11728 body of the while-stepping loop. However, if @code{$pc} was not collected,
11729 then @code{tdump} will always attempt to dump using the basic collection
11730 list, and may fail if a while-stepping frame does not include all the
11731 same data that is collected at the tracepoint hit.
11732 @c This is getting pretty arcane, example would be good.
11734 @node save tracepoints
11735 @subsection @code{save tracepoints @var{filename}}
11736 @kindex save tracepoints
11737 @kindex save-tracepoints
11738 @cindex save tracepoints for future sessions
11740 This command saves all current tracepoint definitions together with
11741 their actions and passcounts, into a file @file{@var{filename}}
11742 suitable for use in a later debugging session. To read the saved
11743 tracepoint definitions, use the @code{source} command (@pxref{Command
11744 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11745 alias for @w{@code{save tracepoints}}
11747 @node Tracepoint Variables
11748 @section Convenience Variables for Tracepoints
11749 @cindex tracepoint variables
11750 @cindex convenience variables for tracepoints
11753 @vindex $trace_frame
11754 @item (int) $trace_frame
11755 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11756 snapshot is selected.
11758 @vindex $tracepoint
11759 @item (int) $tracepoint
11760 The tracepoint for the current trace snapshot.
11762 @vindex $trace_line
11763 @item (int) $trace_line
11764 The line number for the current trace snapshot.
11766 @vindex $trace_file
11767 @item (char []) $trace_file
11768 The source file for the current trace snapshot.
11770 @vindex $trace_func
11771 @item (char []) $trace_func
11772 The name of the function containing @code{$tracepoint}.
11775 Note: @code{$trace_file} is not suitable for use in @code{printf},
11776 use @code{output} instead.
11778 Here's a simple example of using these convenience variables for
11779 stepping through all the trace snapshots and printing some of their
11780 data. Note that these are not the same as trace state variables,
11781 which are managed by the target.
11784 (@value{GDBP}) @b{tfind start}
11786 (@value{GDBP}) @b{while $trace_frame != -1}
11787 > output $trace_file
11788 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11794 @section Using Trace Files
11795 @cindex trace files
11797 In some situations, the target running a trace experiment may no
11798 longer be available; perhaps it crashed, or the hardware was needed
11799 for a different activity. To handle these cases, you can arrange to
11800 dump the trace data into a file, and later use that file as a source
11801 of trace data, via the @code{target tfile} command.
11806 @item tsave [ -r ] @var{filename}
11807 Save the trace data to @var{filename}. By default, this command
11808 assumes that @var{filename} refers to the host filesystem, so if
11809 necessary @value{GDBN} will copy raw trace data up from the target and
11810 then save it. If the target supports it, you can also supply the
11811 optional argument @code{-r} (``remote'') to direct the target to save
11812 the data directly into @var{filename} in its own filesystem, which may be
11813 more efficient if the trace buffer is very large. (Note, however, that
11814 @code{target tfile} can only read from files accessible to the host.)
11816 @kindex target tfile
11818 @item target tfile @var{filename}
11819 Use the file named @var{filename} as a source of trace data. Commands
11820 that examine data work as they do with a live target, but it is not
11821 possible to run any new trace experiments. @code{tstatus} will report
11822 the state of the trace run at the moment the data was saved, as well
11823 as the current trace frame you are examining. @var{filename} must be
11824 on a filesystem accessible to the host.
11829 @chapter Debugging Programs That Use Overlays
11832 If your program is too large to fit completely in your target system's
11833 memory, you can sometimes use @dfn{overlays} to work around this
11834 problem. @value{GDBN} provides some support for debugging programs that
11838 * How Overlays Work:: A general explanation of overlays.
11839 * Overlay Commands:: Managing overlays in @value{GDBN}.
11840 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11841 mapped by asking the inferior.
11842 * Overlay Sample Program:: A sample program using overlays.
11845 @node How Overlays Work
11846 @section How Overlays Work
11847 @cindex mapped overlays
11848 @cindex unmapped overlays
11849 @cindex load address, overlay's
11850 @cindex mapped address
11851 @cindex overlay area
11853 Suppose you have a computer whose instruction address space is only 64
11854 kilobytes long, but which has much more memory which can be accessed by
11855 other means: special instructions, segment registers, or memory
11856 management hardware, for example. Suppose further that you want to
11857 adapt a program which is larger than 64 kilobytes to run on this system.
11859 One solution is to identify modules of your program which are relatively
11860 independent, and need not call each other directly; call these modules
11861 @dfn{overlays}. Separate the overlays from the main program, and place
11862 their machine code in the larger memory. Place your main program in
11863 instruction memory, but leave at least enough space there to hold the
11864 largest overlay as well.
11866 Now, to call a function located in an overlay, you must first copy that
11867 overlay's machine code from the large memory into the space set aside
11868 for it in the instruction memory, and then jump to its entry point
11871 @c NB: In the below the mapped area's size is greater or equal to the
11872 @c size of all overlays. This is intentional to remind the developer
11873 @c that overlays don't necessarily need to be the same size.
11877 Data Instruction Larger
11878 Address Space Address Space Address Space
11879 +-----------+ +-----------+ +-----------+
11881 +-----------+ +-----------+ +-----------+<-- overlay 1
11882 | program | | main | .----| overlay 1 | load address
11883 | variables | | program | | +-----------+
11884 | and heap | | | | | |
11885 +-----------+ | | | +-----------+<-- overlay 2
11886 | | +-----------+ | | | load address
11887 +-----------+ | | | .-| overlay 2 |
11889 mapped --->+-----------+ | | +-----------+
11890 address | | | | | |
11891 | overlay | <-' | | |
11892 | area | <---' +-----------+<-- overlay 3
11893 | | <---. | | load address
11894 +-----------+ `--| overlay 3 |
11901 @anchor{A code overlay}A code overlay
11905 The diagram (@pxref{A code overlay}) shows a system with separate data
11906 and instruction address spaces. To map an overlay, the program copies
11907 its code from the larger address space to the instruction address space.
11908 Since the overlays shown here all use the same mapped address, only one
11909 may be mapped at a time. For a system with a single address space for
11910 data and instructions, the diagram would be similar, except that the
11911 program variables and heap would share an address space with the main
11912 program and the overlay area.
11914 An overlay loaded into instruction memory and ready for use is called a
11915 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11916 instruction memory. An overlay not present (or only partially present)
11917 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11918 is its address in the larger memory. The mapped address is also called
11919 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11920 called the @dfn{load memory address}, or @dfn{LMA}.
11922 Unfortunately, overlays are not a completely transparent way to adapt a
11923 program to limited instruction memory. They introduce a new set of
11924 global constraints you must keep in mind as you design your program:
11929 Before calling or returning to a function in an overlay, your program
11930 must make sure that overlay is actually mapped. Otherwise, the call or
11931 return will transfer control to the right address, but in the wrong
11932 overlay, and your program will probably crash.
11935 If the process of mapping an overlay is expensive on your system, you
11936 will need to choose your overlays carefully to minimize their effect on
11937 your program's performance.
11940 The executable file you load onto your system must contain each
11941 overlay's instructions, appearing at the overlay's load address, not its
11942 mapped address. However, each overlay's instructions must be relocated
11943 and its symbols defined as if the overlay were at its mapped address.
11944 You can use GNU linker scripts to specify different load and relocation
11945 addresses for pieces of your program; see @ref{Overlay Description,,,
11946 ld.info, Using ld: the GNU linker}.
11949 The procedure for loading executable files onto your system must be able
11950 to load their contents into the larger address space as well as the
11951 instruction and data spaces.
11955 The overlay system described above is rather simple, and could be
11956 improved in many ways:
11961 If your system has suitable bank switch registers or memory management
11962 hardware, you could use those facilities to make an overlay's load area
11963 contents simply appear at their mapped address in instruction space.
11964 This would probably be faster than copying the overlay to its mapped
11965 area in the usual way.
11968 If your overlays are small enough, you could set aside more than one
11969 overlay area, and have more than one overlay mapped at a time.
11972 You can use overlays to manage data, as well as instructions. In
11973 general, data overlays are even less transparent to your design than
11974 code overlays: whereas code overlays only require care when you call or
11975 return to functions, data overlays require care every time you access
11976 the data. Also, if you change the contents of a data overlay, you
11977 must copy its contents back out to its load address before you can copy a
11978 different data overlay into the same mapped area.
11983 @node Overlay Commands
11984 @section Overlay Commands
11986 To use @value{GDBN}'s overlay support, each overlay in your program must
11987 correspond to a separate section of the executable file. The section's
11988 virtual memory address and load memory address must be the overlay's
11989 mapped and load addresses. Identifying overlays with sections allows
11990 @value{GDBN} to determine the appropriate address of a function or
11991 variable, depending on whether the overlay is mapped or not.
11993 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11994 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11999 Disable @value{GDBN}'s overlay support. When overlay support is
12000 disabled, @value{GDBN} assumes that all functions and variables are
12001 always present at their mapped addresses. By default, @value{GDBN}'s
12002 overlay support is disabled.
12004 @item overlay manual
12005 @cindex manual overlay debugging
12006 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12007 relies on you to tell it which overlays are mapped, and which are not,
12008 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12009 commands described below.
12011 @item overlay map-overlay @var{overlay}
12012 @itemx overlay map @var{overlay}
12013 @cindex map an overlay
12014 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12015 be the name of the object file section containing the overlay. When an
12016 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12017 functions and variables at their mapped addresses. @value{GDBN} assumes
12018 that any other overlays whose mapped ranges overlap that of
12019 @var{overlay} are now unmapped.
12021 @item overlay unmap-overlay @var{overlay}
12022 @itemx overlay unmap @var{overlay}
12023 @cindex unmap an overlay
12024 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12025 must be the name of the object file section containing the overlay.
12026 When an overlay is unmapped, @value{GDBN} assumes it can find the
12027 overlay's functions and variables at their load addresses.
12030 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12031 consults a data structure the overlay manager maintains in the inferior
12032 to see which overlays are mapped. For details, see @ref{Automatic
12033 Overlay Debugging}.
12035 @item overlay load-target
12036 @itemx overlay load
12037 @cindex reloading the overlay table
12038 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12039 re-reads the table @value{GDBN} automatically each time the inferior
12040 stops, so this command should only be necessary if you have changed the
12041 overlay mapping yourself using @value{GDBN}. This command is only
12042 useful when using automatic overlay debugging.
12044 @item overlay list-overlays
12045 @itemx overlay list
12046 @cindex listing mapped overlays
12047 Display a list of the overlays currently mapped, along with their mapped
12048 addresses, load addresses, and sizes.
12052 Normally, when @value{GDBN} prints a code address, it includes the name
12053 of the function the address falls in:
12056 (@value{GDBP}) print main
12057 $3 = @{int ()@} 0x11a0 <main>
12060 When overlay debugging is enabled, @value{GDBN} recognizes code in
12061 unmapped overlays, and prints the names of unmapped functions with
12062 asterisks around them. For example, if @code{foo} is a function in an
12063 unmapped overlay, @value{GDBN} prints it this way:
12066 (@value{GDBP}) overlay list
12067 No sections are mapped.
12068 (@value{GDBP}) print foo
12069 $5 = @{int (int)@} 0x100000 <*foo*>
12072 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12076 (@value{GDBP}) overlay list
12077 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12078 mapped at 0x1016 - 0x104a
12079 (@value{GDBP}) print foo
12080 $6 = @{int (int)@} 0x1016 <foo>
12083 When overlay debugging is enabled, @value{GDBN} can find the correct
12084 address for functions and variables in an overlay, whether or not the
12085 overlay is mapped. This allows most @value{GDBN} commands, like
12086 @code{break} and @code{disassemble}, to work normally, even on unmapped
12087 code. However, @value{GDBN}'s breakpoint support has some limitations:
12091 @cindex breakpoints in overlays
12092 @cindex overlays, setting breakpoints in
12093 You can set breakpoints in functions in unmapped overlays, as long as
12094 @value{GDBN} can write to the overlay at its load address.
12096 @value{GDBN} can not set hardware or simulator-based breakpoints in
12097 unmapped overlays. However, if you set a breakpoint at the end of your
12098 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12099 you are using manual overlay management), @value{GDBN} will re-set its
12100 breakpoints properly.
12104 @node Automatic Overlay Debugging
12105 @section Automatic Overlay Debugging
12106 @cindex automatic overlay debugging
12108 @value{GDBN} can automatically track which overlays are mapped and which
12109 are not, given some simple co-operation from the overlay manager in the
12110 inferior. If you enable automatic overlay debugging with the
12111 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12112 looks in the inferior's memory for certain variables describing the
12113 current state of the overlays.
12115 Here are the variables your overlay manager must define to support
12116 @value{GDBN}'s automatic overlay debugging:
12120 @item @code{_ovly_table}:
12121 This variable must be an array of the following structures:
12126 /* The overlay's mapped address. */
12129 /* The size of the overlay, in bytes. */
12130 unsigned long size;
12132 /* The overlay's load address. */
12135 /* Non-zero if the overlay is currently mapped;
12137 unsigned long mapped;
12141 @item @code{_novlys}:
12142 This variable must be a four-byte signed integer, holding the total
12143 number of elements in @code{_ovly_table}.
12147 To decide whether a particular overlay is mapped or not, @value{GDBN}
12148 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12149 @code{lma} members equal the VMA and LMA of the overlay's section in the
12150 executable file. When @value{GDBN} finds a matching entry, it consults
12151 the entry's @code{mapped} member to determine whether the overlay is
12154 In addition, your overlay manager may define a function called
12155 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12156 will silently set a breakpoint there. If the overlay manager then
12157 calls this function whenever it has changed the overlay table, this
12158 will enable @value{GDBN} to accurately keep track of which overlays
12159 are in program memory, and update any breakpoints that may be set
12160 in overlays. This will allow breakpoints to work even if the
12161 overlays are kept in ROM or other non-writable memory while they
12162 are not being executed.
12164 @node Overlay Sample Program
12165 @section Overlay Sample Program
12166 @cindex overlay example program
12168 When linking a program which uses overlays, you must place the overlays
12169 at their load addresses, while relocating them to run at their mapped
12170 addresses. To do this, you must write a linker script (@pxref{Overlay
12171 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12172 since linker scripts are specific to a particular host system, target
12173 architecture, and target memory layout, this manual cannot provide
12174 portable sample code demonstrating @value{GDBN}'s overlay support.
12176 However, the @value{GDBN} source distribution does contain an overlaid
12177 program, with linker scripts for a few systems, as part of its test
12178 suite. The program consists of the following files from
12179 @file{gdb/testsuite/gdb.base}:
12183 The main program file.
12185 A simple overlay manager, used by @file{overlays.c}.
12190 Overlay modules, loaded and used by @file{overlays.c}.
12193 Linker scripts for linking the test program on the @code{d10v-elf}
12194 and @code{m32r-elf} targets.
12197 You can build the test program using the @code{d10v-elf} GCC
12198 cross-compiler like this:
12201 $ d10v-elf-gcc -g -c overlays.c
12202 $ d10v-elf-gcc -g -c ovlymgr.c
12203 $ d10v-elf-gcc -g -c foo.c
12204 $ d10v-elf-gcc -g -c bar.c
12205 $ d10v-elf-gcc -g -c baz.c
12206 $ d10v-elf-gcc -g -c grbx.c
12207 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12208 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12211 The build process is identical for any other architecture, except that
12212 you must substitute the appropriate compiler and linker script for the
12213 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12217 @chapter Using @value{GDBN} with Different Languages
12220 Although programming languages generally have common aspects, they are
12221 rarely expressed in the same manner. For instance, in ANSI C,
12222 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12223 Modula-2, it is accomplished by @code{p^}. Values can also be
12224 represented (and displayed) differently. Hex numbers in C appear as
12225 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12227 @cindex working language
12228 Language-specific information is built into @value{GDBN} for some languages,
12229 allowing you to express operations like the above in your program's
12230 native language, and allowing @value{GDBN} to output values in a manner
12231 consistent with the syntax of your program's native language. The
12232 language you use to build expressions is called the @dfn{working
12236 * Setting:: Switching between source languages
12237 * Show:: Displaying the language
12238 * Checks:: Type and range checks
12239 * Supported Languages:: Supported languages
12240 * Unsupported Languages:: Unsupported languages
12244 @section Switching Between Source Languages
12246 There are two ways to control the working language---either have @value{GDBN}
12247 set it automatically, or select it manually yourself. You can use the
12248 @code{set language} command for either purpose. On startup, @value{GDBN}
12249 defaults to setting the language automatically. The working language is
12250 used to determine how expressions you type are interpreted, how values
12253 In addition to the working language, every source file that
12254 @value{GDBN} knows about has its own working language. For some object
12255 file formats, the compiler might indicate which language a particular
12256 source file is in. However, most of the time @value{GDBN} infers the
12257 language from the name of the file. The language of a source file
12258 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12259 show each frame appropriately for its own language. There is no way to
12260 set the language of a source file from within @value{GDBN}, but you can
12261 set the language associated with a filename extension. @xref{Show, ,
12262 Displaying the Language}.
12264 This is most commonly a problem when you use a program, such
12265 as @code{cfront} or @code{f2c}, that generates C but is written in
12266 another language. In that case, make the
12267 program use @code{#line} directives in its C output; that way
12268 @value{GDBN} will know the correct language of the source code of the original
12269 program, and will display that source code, not the generated C code.
12272 * Filenames:: Filename extensions and languages.
12273 * Manually:: Setting the working language manually
12274 * Automatically:: Having @value{GDBN} infer the source language
12278 @subsection List of Filename Extensions and Languages
12280 If a source file name ends in one of the following extensions, then
12281 @value{GDBN} infers that its language is the one indicated.
12299 C@t{++} source file
12305 Objective-C source file
12309 Fortran source file
12312 Modula-2 source file
12316 Assembler source file. This actually behaves almost like C, but
12317 @value{GDBN} does not skip over function prologues when stepping.
12320 In addition, you may set the language associated with a filename
12321 extension. @xref{Show, , Displaying the Language}.
12324 @subsection Setting the Working Language
12326 If you allow @value{GDBN} to set the language automatically,
12327 expressions are interpreted the same way in your debugging session and
12330 @kindex set language
12331 If you wish, you may set the language manually. To do this, issue the
12332 command @samp{set language @var{lang}}, where @var{lang} is the name of
12333 a language, such as
12334 @code{c} or @code{modula-2}.
12335 For a list of the supported languages, type @samp{set language}.
12337 Setting the language manually prevents @value{GDBN} from updating the working
12338 language automatically. This can lead to confusion if you try
12339 to debug a program when the working language is not the same as the
12340 source language, when an expression is acceptable to both
12341 languages---but means different things. For instance, if the current
12342 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12350 might not have the effect you intended. In C, this means to add
12351 @code{b} and @code{c} and place the result in @code{a}. The result
12352 printed would be the value of @code{a}. In Modula-2, this means to compare
12353 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12355 @node Automatically
12356 @subsection Having @value{GDBN} Infer the Source Language
12358 To have @value{GDBN} set the working language automatically, use
12359 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12360 then infers the working language. That is, when your program stops in a
12361 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12362 working language to the language recorded for the function in that
12363 frame. If the language for a frame is unknown (that is, if the function
12364 or block corresponding to the frame was defined in a source file that
12365 does not have a recognized extension), the current working language is
12366 not changed, and @value{GDBN} issues a warning.
12368 This may not seem necessary for most programs, which are written
12369 entirely in one source language. However, program modules and libraries
12370 written in one source language can be used by a main program written in
12371 a different source language. Using @samp{set language auto} in this
12372 case frees you from having to set the working language manually.
12375 @section Displaying the Language
12377 The following commands help you find out which language is the
12378 working language, and also what language source files were written in.
12381 @item show language
12382 @kindex show language
12383 Display the current working language. This is the
12384 language you can use with commands such as @code{print} to
12385 build and compute expressions that may involve variables in your program.
12388 @kindex info frame@r{, show the source language}
12389 Display the source language for this frame. This language becomes the
12390 working language if you use an identifier from this frame.
12391 @xref{Frame Info, ,Information about a Frame}, to identify the other
12392 information listed here.
12395 @kindex info source@r{, show the source language}
12396 Display the source language of this source file.
12397 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12398 information listed here.
12401 In unusual circumstances, you may have source files with extensions
12402 not in the standard list. You can then set the extension associated
12403 with a language explicitly:
12406 @item set extension-language @var{ext} @var{language}
12407 @kindex set extension-language
12408 Tell @value{GDBN} that source files with extension @var{ext} are to be
12409 assumed as written in the source language @var{language}.
12411 @item info extensions
12412 @kindex info extensions
12413 List all the filename extensions and the associated languages.
12417 @section Type and Range Checking
12420 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12421 checking are included, but they do not yet have any effect. This
12422 section documents the intended facilities.
12424 @c FIXME remove warning when type/range code added
12426 Some languages are designed to guard you against making seemingly common
12427 errors through a series of compile- and run-time checks. These include
12428 checking the type of arguments to functions and operators, and making
12429 sure mathematical overflows are caught at run time. Checks such as
12430 these help to ensure a program's correctness once it has been compiled
12431 by eliminating type mismatches, and providing active checks for range
12432 errors when your program is running.
12434 @value{GDBN} can check for conditions like the above if you wish.
12435 Although @value{GDBN} does not check the statements in your program,
12436 it can check expressions entered directly into @value{GDBN} for
12437 evaluation via the @code{print} command, for example. As with the
12438 working language, @value{GDBN} can also decide whether or not to check
12439 automatically based on your program's source language.
12440 @xref{Supported Languages, ,Supported Languages}, for the default
12441 settings of supported languages.
12444 * Type Checking:: An overview of type checking
12445 * Range Checking:: An overview of range checking
12448 @cindex type checking
12449 @cindex checks, type
12450 @node Type Checking
12451 @subsection An Overview of Type Checking
12453 Some languages, such as Modula-2, are strongly typed, meaning that the
12454 arguments to operators and functions have to be of the correct type,
12455 otherwise an error occurs. These checks prevent type mismatch
12456 errors from ever causing any run-time problems. For example,
12464 The second example fails because the @code{CARDINAL} 1 is not
12465 type-compatible with the @code{REAL} 2.3.
12467 For the expressions you use in @value{GDBN} commands, you can tell the
12468 @value{GDBN} type checker to skip checking;
12469 to treat any mismatches as errors and abandon the expression;
12470 or to only issue warnings when type mismatches occur,
12471 but evaluate the expression anyway. When you choose the last of
12472 these, @value{GDBN} evaluates expressions like the second example above, but
12473 also issues a warning.
12475 Even if you turn type checking off, there may be other reasons
12476 related to type that prevent @value{GDBN} from evaluating an expression.
12477 For instance, @value{GDBN} does not know how to add an @code{int} and
12478 a @code{struct foo}. These particular type errors have nothing to do
12479 with the language in use, and usually arise from expressions, such as
12480 the one described above, which make little sense to evaluate anyway.
12482 Each language defines to what degree it is strict about type. For
12483 instance, both Modula-2 and C require the arguments to arithmetical
12484 operators to be numbers. In C, enumerated types and pointers can be
12485 represented as numbers, so that they are valid arguments to mathematical
12486 operators. @xref{Supported Languages, ,Supported Languages}, for further
12487 details on specific languages.
12489 @value{GDBN} provides some additional commands for controlling the type checker:
12491 @kindex set check type
12492 @kindex show check type
12494 @item set check type auto
12495 Set type checking on or off based on the current working language.
12496 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12499 @item set check type on
12500 @itemx set check type off
12501 Set type checking on or off, overriding the default setting for the
12502 current working language. Issue a warning if the setting does not
12503 match the language default. If any type mismatches occur in
12504 evaluating an expression while type checking is on, @value{GDBN} prints a
12505 message and aborts evaluation of the expression.
12507 @item set check type warn
12508 Cause the type checker to issue warnings, but to always attempt to
12509 evaluate the expression. Evaluating the expression may still
12510 be impossible for other reasons. For example, @value{GDBN} cannot add
12511 numbers and structures.
12514 Show the current setting of the type checker, and whether or not @value{GDBN}
12515 is setting it automatically.
12518 @cindex range checking
12519 @cindex checks, range
12520 @node Range Checking
12521 @subsection An Overview of Range Checking
12523 In some languages (such as Modula-2), it is an error to exceed the
12524 bounds of a type; this is enforced with run-time checks. Such range
12525 checking is meant to ensure program correctness by making sure
12526 computations do not overflow, or indices on an array element access do
12527 not exceed the bounds of the array.
12529 For expressions you use in @value{GDBN} commands, you can tell
12530 @value{GDBN} to treat range errors in one of three ways: ignore them,
12531 always treat them as errors and abandon the expression, or issue
12532 warnings but evaluate the expression anyway.
12534 A range error can result from numerical overflow, from exceeding an
12535 array index bound, or when you type a constant that is not a member
12536 of any type. Some languages, however, do not treat overflows as an
12537 error. In many implementations of C, mathematical overflow causes the
12538 result to ``wrap around'' to lower values---for example, if @var{m} is
12539 the largest integer value, and @var{s} is the smallest, then
12542 @var{m} + 1 @result{} @var{s}
12545 This, too, is specific to individual languages, and in some cases
12546 specific to individual compilers or machines. @xref{Supported Languages, ,
12547 Supported Languages}, for further details on specific languages.
12549 @value{GDBN} provides some additional commands for controlling the range checker:
12551 @kindex set check range
12552 @kindex show check range
12554 @item set check range auto
12555 Set range checking on or off based on the current working language.
12556 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12559 @item set check range on
12560 @itemx set check range off
12561 Set range checking on or off, overriding the default setting for the
12562 current working language. A warning is issued if the setting does not
12563 match the language default. If a range error occurs and range checking is on,
12564 then a message is printed and evaluation of the expression is aborted.
12566 @item set check range warn
12567 Output messages when the @value{GDBN} range checker detects a range error,
12568 but attempt to evaluate the expression anyway. Evaluating the
12569 expression may still be impossible for other reasons, such as accessing
12570 memory that the process does not own (a typical example from many Unix
12574 Show the current setting of the range checker, and whether or not it is
12575 being set automatically by @value{GDBN}.
12578 @node Supported Languages
12579 @section Supported Languages
12581 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
12582 OpenCL C, Pascal, assembly, Modula-2, and Ada.
12583 @c This is false ...
12584 Some @value{GDBN} features may be used in expressions regardless of the
12585 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12586 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12587 ,Expressions}) can be used with the constructs of any supported
12590 The following sections detail to what degree each source language is
12591 supported by @value{GDBN}. These sections are not meant to be language
12592 tutorials or references, but serve only as a reference guide to what the
12593 @value{GDBN} expression parser accepts, and what input and output
12594 formats should look like for different languages. There are many good
12595 books written on each of these languages; please look to these for a
12596 language reference or tutorial.
12599 * C:: C and C@t{++}
12602 * Objective-C:: Objective-C
12603 * OpenCL C:: OpenCL C
12604 * Fortran:: Fortran
12606 * Modula-2:: Modula-2
12611 @subsection C and C@t{++}
12613 @cindex C and C@t{++}
12614 @cindex expressions in C or C@t{++}
12616 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12617 to both languages. Whenever this is the case, we discuss those languages
12621 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12622 @cindex @sc{gnu} C@t{++}
12623 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12624 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12625 effectively, you must compile your C@t{++} programs with a supported
12626 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12627 compiler (@code{aCC}).
12630 * C Operators:: C and C@t{++} operators
12631 * C Constants:: C and C@t{++} constants
12632 * C Plus Plus Expressions:: C@t{++} expressions
12633 * C Defaults:: Default settings for C and C@t{++}
12634 * C Checks:: C and C@t{++} type and range checks
12635 * Debugging C:: @value{GDBN} and C
12636 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12637 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12641 @subsubsection C and C@t{++} Operators
12643 @cindex C and C@t{++} operators
12645 Operators must be defined on values of specific types. For instance,
12646 @code{+} is defined on numbers, but not on structures. Operators are
12647 often defined on groups of types.
12649 For the purposes of C and C@t{++}, the following definitions hold:
12654 @emph{Integral types} include @code{int} with any of its storage-class
12655 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12658 @emph{Floating-point types} include @code{float}, @code{double}, and
12659 @code{long double} (if supported by the target platform).
12662 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12665 @emph{Scalar types} include all of the above.
12670 The following operators are supported. They are listed here
12671 in order of increasing precedence:
12675 The comma or sequencing operator. Expressions in a comma-separated list
12676 are evaluated from left to right, with the result of the entire
12677 expression being the last expression evaluated.
12680 Assignment. The value of an assignment expression is the value
12681 assigned. Defined on scalar types.
12684 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12685 and translated to @w{@code{@var{a} = @var{a op b}}}.
12686 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12687 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12688 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12691 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12692 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12696 Logical @sc{or}. Defined on integral types.
12699 Logical @sc{and}. Defined on integral types.
12702 Bitwise @sc{or}. Defined on integral types.
12705 Bitwise exclusive-@sc{or}. Defined on integral types.
12708 Bitwise @sc{and}. Defined on integral types.
12711 Equality and inequality. Defined on scalar types. The value of these
12712 expressions is 0 for false and non-zero for true.
12714 @item <@r{, }>@r{, }<=@r{, }>=
12715 Less than, greater than, less than or equal, greater than or equal.
12716 Defined on scalar types. The value of these expressions is 0 for false
12717 and non-zero for true.
12720 left shift, and right shift. Defined on integral types.
12723 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12726 Addition and subtraction. Defined on integral types, floating-point types and
12729 @item *@r{, }/@r{, }%
12730 Multiplication, division, and modulus. Multiplication and division are
12731 defined on integral and floating-point types. Modulus is defined on
12735 Increment and decrement. When appearing before a variable, the
12736 operation is performed before the variable is used in an expression;
12737 when appearing after it, the variable's value is used before the
12738 operation takes place.
12741 Pointer dereferencing. Defined on pointer types. Same precedence as
12745 Address operator. Defined on variables. Same precedence as @code{++}.
12747 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12748 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12749 to examine the address
12750 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12754 Negative. Defined on integral and floating-point types. Same
12755 precedence as @code{++}.
12758 Logical negation. Defined on integral types. Same precedence as
12762 Bitwise complement operator. Defined on integral types. Same precedence as
12767 Structure member, and pointer-to-structure member. For convenience,
12768 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12769 pointer based on the stored type information.
12770 Defined on @code{struct} and @code{union} data.
12773 Dereferences of pointers to members.
12776 Array indexing. @code{@var{a}[@var{i}]} is defined as
12777 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12780 Function parameter list. Same precedence as @code{->}.
12783 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12784 and @code{class} types.
12787 Doubled colons also represent the @value{GDBN} scope operator
12788 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12792 If an operator is redefined in the user code, @value{GDBN} usually
12793 attempts to invoke the redefined version instead of using the operator's
12794 predefined meaning.
12797 @subsubsection C and C@t{++} Constants
12799 @cindex C and C@t{++} constants
12801 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12806 Integer constants are a sequence of digits. Octal constants are
12807 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12808 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12809 @samp{l}, specifying that the constant should be treated as a
12813 Floating point constants are a sequence of digits, followed by a decimal
12814 point, followed by a sequence of digits, and optionally followed by an
12815 exponent. An exponent is of the form:
12816 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12817 sequence of digits. The @samp{+} is optional for positive exponents.
12818 A floating-point constant may also end with a letter @samp{f} or
12819 @samp{F}, specifying that the constant should be treated as being of
12820 the @code{float} (as opposed to the default @code{double}) type; or with
12821 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12825 Enumerated constants consist of enumerated identifiers, or their
12826 integral equivalents.
12829 Character constants are a single character surrounded by single quotes
12830 (@code{'}), or a number---the ordinal value of the corresponding character
12831 (usually its @sc{ascii} value). Within quotes, the single character may
12832 be represented by a letter or by @dfn{escape sequences}, which are of
12833 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12834 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12835 @samp{@var{x}} is a predefined special character---for example,
12836 @samp{\n} for newline.
12838 Wide character constants can be written by prefixing a character
12839 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12840 form of @samp{x}. The target wide character set is used when
12841 computing the value of this constant (@pxref{Character Sets}).
12844 String constants are a sequence of character constants surrounded by
12845 double quotes (@code{"}). Any valid character constant (as described
12846 above) may appear. Double quotes within the string must be preceded by
12847 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12850 Wide string constants can be written by prefixing a string constant
12851 with @samp{L}, as in C. The target wide character set is used when
12852 computing the value of this constant (@pxref{Character Sets}).
12855 Pointer constants are an integral value. You can also write pointers
12856 to constants using the C operator @samp{&}.
12859 Array constants are comma-separated lists surrounded by braces @samp{@{}
12860 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12861 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12862 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12865 @node C Plus Plus Expressions
12866 @subsubsection C@t{++} Expressions
12868 @cindex expressions in C@t{++}
12869 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12871 @cindex debugging C@t{++} programs
12872 @cindex C@t{++} compilers
12873 @cindex debug formats and C@t{++}
12874 @cindex @value{NGCC} and C@t{++}
12876 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12877 the proper compiler and the proper debug format. Currently,
12878 @value{GDBN} works best when debugging C@t{++} code that is compiled
12879 with the most recent version of @value{NGCC} possible. The DWARF
12880 debugging format is preferred; @value{NGCC} defaults to this on most
12881 popular platforms. Other compilers and/or debug formats are likely to
12882 work badly or not at all when using @value{GDBN} to debug C@t{++}
12883 code. @xref{Compilation}.
12888 @cindex member functions
12890 Member function calls are allowed; you can use expressions like
12893 count = aml->GetOriginal(x, y)
12896 @vindex this@r{, inside C@t{++} member functions}
12897 @cindex namespace in C@t{++}
12899 While a member function is active (in the selected stack frame), your
12900 expressions have the same namespace available as the member function;
12901 that is, @value{GDBN} allows implicit references to the class instance
12902 pointer @code{this} following the same rules as C@t{++}. @code{using}
12903 declarations in the current scope are also respected by @value{GDBN}.
12905 @cindex call overloaded functions
12906 @cindex overloaded functions, calling
12907 @cindex type conversions in C@t{++}
12909 You can call overloaded functions; @value{GDBN} resolves the function
12910 call to the right definition, with some restrictions. @value{GDBN} does not
12911 perform overload resolution involving user-defined type conversions,
12912 calls to constructors, or instantiations of templates that do not exist
12913 in the program. It also cannot handle ellipsis argument lists or
12916 It does perform integral conversions and promotions, floating-point
12917 promotions, arithmetic conversions, pointer conversions, conversions of
12918 class objects to base classes, and standard conversions such as those of
12919 functions or arrays to pointers; it requires an exact match on the
12920 number of function arguments.
12922 Overload resolution is always performed, unless you have specified
12923 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12924 ,@value{GDBN} Features for C@t{++}}.
12926 You must specify @code{set overload-resolution off} in order to use an
12927 explicit function signature to call an overloaded function, as in
12929 p 'foo(char,int)'('x', 13)
12932 The @value{GDBN} command-completion facility can simplify this;
12933 see @ref{Completion, ,Command Completion}.
12935 @cindex reference declarations
12937 @value{GDBN} understands variables declared as C@t{++} references; you can use
12938 them in expressions just as you do in C@t{++} source---they are automatically
12941 In the parameter list shown when @value{GDBN} displays a frame, the values of
12942 reference variables are not displayed (unlike other variables); this
12943 avoids clutter, since references are often used for large structures.
12944 The @emph{address} of a reference variable is always shown, unless
12945 you have specified @samp{set print address off}.
12948 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12949 expressions can use it just as expressions in your program do. Since
12950 one scope may be defined in another, you can use @code{::} repeatedly if
12951 necessary, for example in an expression like
12952 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12953 resolving name scope by reference to source files, in both C and C@t{++}
12954 debugging (@pxref{Variables, ,Program Variables}).
12957 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12962 @subsubsection C and C@t{++} Defaults
12964 @cindex C and C@t{++} defaults
12966 If you allow @value{GDBN} to set type and range checking automatically, they
12967 both default to @code{off} whenever the working language changes to
12968 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12969 selects the working language.
12971 If you allow @value{GDBN} to set the language automatically, it
12972 recognizes source files whose names end with @file{.c}, @file{.C}, or
12973 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12974 these files, it sets the working language to C or C@t{++}.
12975 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12976 for further details.
12978 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12979 @c unimplemented. If (b) changes, it might make sense to let this node
12980 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12983 @subsubsection C and C@t{++} Type and Range Checks
12985 @cindex C and C@t{++} checks
12987 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12988 is not used. However, if you turn type checking on, @value{GDBN}
12989 considers two variables type equivalent if:
12993 The two variables are structured and have the same structure, union, or
12997 The two variables have the same type name, or types that have been
12998 declared equivalent through @code{typedef}.
13001 @c leaving this out because neither J Gilmore nor R Pesch understand it.
13004 The two @code{struct}, @code{union}, or @code{enum} variables are
13005 declared in the same declaration. (Note: this may not be true for all C
13010 Range checking, if turned on, is done on mathematical operations. Array
13011 indices are not checked, since they are often used to index a pointer
13012 that is not itself an array.
13015 @subsubsection @value{GDBN} and C
13017 The @code{set print union} and @code{show print union} commands apply to
13018 the @code{union} type. When set to @samp{on}, any @code{union} that is
13019 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13020 appears as @samp{@{...@}}.
13022 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13023 with pointers and a memory allocation function. @xref{Expressions,
13026 @node Debugging C Plus Plus
13027 @subsubsection @value{GDBN} Features for C@t{++}
13029 @cindex commands for C@t{++}
13031 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13032 designed specifically for use with C@t{++}. Here is a summary:
13035 @cindex break in overloaded functions
13036 @item @r{breakpoint menus}
13037 When you want a breakpoint in a function whose name is overloaded,
13038 @value{GDBN} has the capability to display a menu of possible breakpoint
13039 locations to help you specify which function definition you want.
13040 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13042 @cindex overloading in C@t{++}
13043 @item rbreak @var{regex}
13044 Setting breakpoints using regular expressions is helpful for setting
13045 breakpoints on overloaded functions that are not members of any special
13047 @xref{Set Breaks, ,Setting Breakpoints}.
13049 @cindex C@t{++} exception handling
13052 Debug C@t{++} exception handling using these commands. @xref{Set
13053 Catchpoints, , Setting Catchpoints}.
13055 @cindex inheritance
13056 @item ptype @var{typename}
13057 Print inheritance relationships as well as other information for type
13059 @xref{Symbols, ,Examining the Symbol Table}.
13061 @item info vtbl @var{expression}.
13062 The @code{info vtbl} command can be used to display the virtual
13063 method tables of the object computed by @var{expression}. This shows
13064 one entry per virtual table; there may be multiple virtual tables when
13065 multiple inheritance is in use.
13067 @cindex C@t{++} symbol display
13068 @item set print demangle
13069 @itemx show print demangle
13070 @itemx set print asm-demangle
13071 @itemx show print asm-demangle
13072 Control whether C@t{++} symbols display in their source form, both when
13073 displaying code as C@t{++} source and when displaying disassemblies.
13074 @xref{Print Settings, ,Print Settings}.
13076 @item set print object
13077 @itemx show print object
13078 Choose whether to print derived (actual) or declared types of objects.
13079 @xref{Print Settings, ,Print Settings}.
13081 @item set print vtbl
13082 @itemx show print vtbl
13083 Control the format for printing virtual function tables.
13084 @xref{Print Settings, ,Print Settings}.
13085 (The @code{vtbl} commands do not work on programs compiled with the HP
13086 ANSI C@t{++} compiler (@code{aCC}).)
13088 @kindex set overload-resolution
13089 @cindex overloaded functions, overload resolution
13090 @item set overload-resolution on
13091 Enable overload resolution for C@t{++} expression evaluation. The default
13092 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13093 and searches for a function whose signature matches the argument types,
13094 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13095 Expressions, ,C@t{++} Expressions}, for details).
13096 If it cannot find a match, it emits a message.
13098 @item set overload-resolution off
13099 Disable overload resolution for C@t{++} expression evaluation. For
13100 overloaded functions that are not class member functions, @value{GDBN}
13101 chooses the first function of the specified name that it finds in the
13102 symbol table, whether or not its arguments are of the correct type. For
13103 overloaded functions that are class member functions, @value{GDBN}
13104 searches for a function whose signature @emph{exactly} matches the
13107 @kindex show overload-resolution
13108 @item show overload-resolution
13109 Show the current setting of overload resolution.
13111 @item @r{Overloaded symbol names}
13112 You can specify a particular definition of an overloaded symbol, using
13113 the same notation that is used to declare such symbols in C@t{++}: type
13114 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13115 also use the @value{GDBN} command-line word completion facilities to list the
13116 available choices, or to finish the type list for you.
13117 @xref{Completion,, Command Completion}, for details on how to do this.
13120 @node Decimal Floating Point
13121 @subsubsection Decimal Floating Point format
13122 @cindex decimal floating point format
13124 @value{GDBN} can examine, set and perform computations with numbers in
13125 decimal floating point format, which in the C language correspond to the
13126 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13127 specified by the extension to support decimal floating-point arithmetic.
13129 There are two encodings in use, depending on the architecture: BID (Binary
13130 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13131 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13134 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13135 to manipulate decimal floating point numbers, it is not possible to convert
13136 (using a cast, for example) integers wider than 32-bit to decimal float.
13138 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13139 point computations, error checking in decimal float operations ignores
13140 underflow, overflow and divide by zero exceptions.
13142 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13143 to inspect @code{_Decimal128} values stored in floating point registers.
13144 See @ref{PowerPC,,PowerPC} for more details.
13150 @value{GDBN} can be used to debug programs written in D and compiled with
13151 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13152 specific feature --- dynamic arrays.
13157 @cindex Go (programming language)
13158 @value{GDBN} can be used to debug programs written in Go and compiled with
13159 @file{gccgo} or @file{6g} compilers.
13161 Here is a summary of the Go-specific features and restrictions:
13164 @cindex current Go package
13165 @item The current Go package
13166 The name of the current package does not need to be specified when
13167 specifying global variables and functions.
13169 For example, given the program:
13173 var myglob = "Shall we?"
13179 When stopped inside @code{main} either of these work:
13183 (gdb) p main.myglob
13186 @cindex builtin Go types
13187 @item Builtin Go types
13188 The @code{string} type is recognized by @value{GDBN} and is printed
13191 @cindex builtin Go functions
13192 @item Builtin Go functions
13193 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13194 function and handles it internally.
13196 @cindex restrictions on Go expressions
13197 @item Restrictions on Go expressions
13198 All Go operators are supported except @code{&^}.
13199 The Go @code{_} ``blank identifier'' is not supported.
13200 Automatic dereferencing of pointers is not supported.
13204 @subsection Objective-C
13206 @cindex Objective-C
13207 This section provides information about some commands and command
13208 options that are useful for debugging Objective-C code. See also
13209 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13210 few more commands specific to Objective-C support.
13213 * Method Names in Commands::
13214 * The Print Command with Objective-C::
13217 @node Method Names in Commands
13218 @subsubsection Method Names in Commands
13220 The following commands have been extended to accept Objective-C method
13221 names as line specifications:
13223 @kindex clear@r{, and Objective-C}
13224 @kindex break@r{, and Objective-C}
13225 @kindex info line@r{, and Objective-C}
13226 @kindex jump@r{, and Objective-C}
13227 @kindex list@r{, and Objective-C}
13231 @item @code{info line}
13236 A fully qualified Objective-C method name is specified as
13239 -[@var{Class} @var{methodName}]
13242 where the minus sign is used to indicate an instance method and a
13243 plus sign (not shown) is used to indicate a class method. The class
13244 name @var{Class} and method name @var{methodName} are enclosed in
13245 brackets, similar to the way messages are specified in Objective-C
13246 source code. For example, to set a breakpoint at the @code{create}
13247 instance method of class @code{Fruit} in the program currently being
13251 break -[Fruit create]
13254 To list ten program lines around the @code{initialize} class method,
13258 list +[NSText initialize]
13261 In the current version of @value{GDBN}, the plus or minus sign is
13262 required. In future versions of @value{GDBN}, the plus or minus
13263 sign will be optional, but you can use it to narrow the search. It
13264 is also possible to specify just a method name:
13270 You must specify the complete method name, including any colons. If
13271 your program's source files contain more than one @code{create} method,
13272 you'll be presented with a numbered list of classes that implement that
13273 method. Indicate your choice by number, or type @samp{0} to exit if
13276 As another example, to clear a breakpoint established at the
13277 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13280 clear -[NSWindow makeKeyAndOrderFront:]
13283 @node The Print Command with Objective-C
13284 @subsubsection The Print Command With Objective-C
13285 @cindex Objective-C, print objects
13286 @kindex print-object
13287 @kindex po @r{(@code{print-object})}
13289 The print command has also been extended to accept methods. For example:
13292 print -[@var{object} hash]
13295 @cindex print an Objective-C object description
13296 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13298 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13299 and print the result. Also, an additional command has been added,
13300 @code{print-object} or @code{po} for short, which is meant to print
13301 the description of an object. However, this command may only work
13302 with certain Objective-C libraries that have a particular hook
13303 function, @code{_NSPrintForDebugger}, defined.
13306 @subsection OpenCL C
13309 This section provides information about @value{GDBN}s OpenCL C support.
13312 * OpenCL C Datatypes::
13313 * OpenCL C Expressions::
13314 * OpenCL C Operators::
13317 @node OpenCL C Datatypes
13318 @subsubsection OpenCL C Datatypes
13320 @cindex OpenCL C Datatypes
13321 @value{GDBN} supports the builtin scalar and vector datatypes specified
13322 by OpenCL 1.1. In addition the half- and double-precision floating point
13323 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13324 extensions are also known to @value{GDBN}.
13326 @node OpenCL C Expressions
13327 @subsubsection OpenCL C Expressions
13329 @cindex OpenCL C Expressions
13330 @value{GDBN} supports accesses to vector components including the access as
13331 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13332 supported by @value{GDBN} can be used as well.
13334 @node OpenCL C Operators
13335 @subsubsection OpenCL C Operators
13337 @cindex OpenCL C Operators
13338 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13342 @subsection Fortran
13343 @cindex Fortran-specific support in @value{GDBN}
13345 @value{GDBN} can be used to debug programs written in Fortran, but it
13346 currently supports only the features of Fortran 77 language.
13348 @cindex trailing underscore, in Fortran symbols
13349 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13350 among them) append an underscore to the names of variables and
13351 functions. When you debug programs compiled by those compilers, you
13352 will need to refer to variables and functions with a trailing
13356 * Fortran Operators:: Fortran operators and expressions
13357 * Fortran Defaults:: Default settings for Fortran
13358 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13361 @node Fortran Operators
13362 @subsubsection Fortran Operators and Expressions
13364 @cindex Fortran operators and expressions
13366 Operators must be defined on values of specific types. For instance,
13367 @code{+} is defined on numbers, but not on characters or other non-
13368 arithmetic types. Operators are often defined on groups of types.
13372 The exponentiation operator. It raises the first operand to the power
13376 The range operator. Normally used in the form of array(low:high) to
13377 represent a section of array.
13380 The access component operator. Normally used to access elements in derived
13381 types. Also suitable for unions. As unions aren't part of regular Fortran,
13382 this can only happen when accessing a register that uses a gdbarch-defined
13386 @node Fortran Defaults
13387 @subsubsection Fortran Defaults
13389 @cindex Fortran Defaults
13391 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13392 default uses case-insensitive matches for Fortran symbols. You can
13393 change that with the @samp{set case-insensitive} command, see
13394 @ref{Symbols}, for the details.
13396 @node Special Fortran Commands
13397 @subsubsection Special Fortran Commands
13399 @cindex Special Fortran commands
13401 @value{GDBN} has some commands to support Fortran-specific features,
13402 such as displaying common blocks.
13405 @cindex @code{COMMON} blocks, Fortran
13406 @kindex info common
13407 @item info common @r{[}@var{common-name}@r{]}
13408 This command prints the values contained in the Fortran @code{COMMON}
13409 block whose name is @var{common-name}. With no argument, the names of
13410 all @code{COMMON} blocks visible at the current program location are
13417 @cindex Pascal support in @value{GDBN}, limitations
13418 Debugging Pascal programs which use sets, subranges, file variables, or
13419 nested functions does not currently work. @value{GDBN} does not support
13420 entering expressions, printing values, or similar features using Pascal
13423 The Pascal-specific command @code{set print pascal_static-members}
13424 controls whether static members of Pascal objects are displayed.
13425 @xref{Print Settings, pascal_static-members}.
13428 @subsection Modula-2
13430 @cindex Modula-2, @value{GDBN} support
13432 The extensions made to @value{GDBN} to support Modula-2 only support
13433 output from the @sc{gnu} Modula-2 compiler (which is currently being
13434 developed). Other Modula-2 compilers are not currently supported, and
13435 attempting to debug executables produced by them is most likely
13436 to give an error as @value{GDBN} reads in the executable's symbol
13439 @cindex expressions in Modula-2
13441 * M2 Operators:: Built-in operators
13442 * Built-In Func/Proc:: Built-in functions and procedures
13443 * M2 Constants:: Modula-2 constants
13444 * M2 Types:: Modula-2 types
13445 * M2 Defaults:: Default settings for Modula-2
13446 * Deviations:: Deviations from standard Modula-2
13447 * M2 Checks:: Modula-2 type and range checks
13448 * M2 Scope:: The scope operators @code{::} and @code{.}
13449 * GDB/M2:: @value{GDBN} and Modula-2
13453 @subsubsection Operators
13454 @cindex Modula-2 operators
13456 Operators must be defined on values of specific types. For instance,
13457 @code{+} is defined on numbers, but not on structures. Operators are
13458 often defined on groups of types. For the purposes of Modula-2, the
13459 following definitions hold:
13464 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13468 @emph{Character types} consist of @code{CHAR} and its subranges.
13471 @emph{Floating-point types} consist of @code{REAL}.
13474 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13478 @emph{Scalar types} consist of all of the above.
13481 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13484 @emph{Boolean types} consist of @code{BOOLEAN}.
13488 The following operators are supported, and appear in order of
13489 increasing precedence:
13493 Function argument or array index separator.
13496 Assignment. The value of @var{var} @code{:=} @var{value} is
13500 Less than, greater than on integral, floating-point, or enumerated
13504 Less than or equal to, greater than or equal to
13505 on integral, floating-point and enumerated types, or set inclusion on
13506 set types. Same precedence as @code{<}.
13508 @item =@r{, }<>@r{, }#
13509 Equality and two ways of expressing inequality, valid on scalar types.
13510 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13511 available for inequality, since @code{#} conflicts with the script
13515 Set membership. Defined on set types and the types of their members.
13516 Same precedence as @code{<}.
13519 Boolean disjunction. Defined on boolean types.
13522 Boolean conjunction. Defined on boolean types.
13525 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13528 Addition and subtraction on integral and floating-point types, or union
13529 and difference on set types.
13532 Multiplication on integral and floating-point types, or set intersection
13536 Division on floating-point types, or symmetric set difference on set
13537 types. Same precedence as @code{*}.
13540 Integer division and remainder. Defined on integral types. Same
13541 precedence as @code{*}.
13544 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13547 Pointer dereferencing. Defined on pointer types.
13550 Boolean negation. Defined on boolean types. Same precedence as
13554 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13555 precedence as @code{^}.
13558 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13561 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13565 @value{GDBN} and Modula-2 scope operators.
13569 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13570 treats the use of the operator @code{IN}, or the use of operators
13571 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13572 @code{<=}, and @code{>=} on sets as an error.
13576 @node Built-In Func/Proc
13577 @subsubsection Built-in Functions and Procedures
13578 @cindex Modula-2 built-ins
13580 Modula-2 also makes available several built-in procedures and functions.
13581 In describing these, the following metavariables are used:
13586 represents an @code{ARRAY} variable.
13589 represents a @code{CHAR} constant or variable.
13592 represents a variable or constant of integral type.
13595 represents an identifier that belongs to a set. Generally used in the
13596 same function with the metavariable @var{s}. The type of @var{s} should
13597 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13600 represents a variable or constant of integral or floating-point type.
13603 represents a variable or constant of floating-point type.
13609 represents a variable.
13612 represents a variable or constant of one of many types. See the
13613 explanation of the function for details.
13616 All Modula-2 built-in procedures also return a result, described below.
13620 Returns the absolute value of @var{n}.
13623 If @var{c} is a lower case letter, it returns its upper case
13624 equivalent, otherwise it returns its argument.
13627 Returns the character whose ordinal value is @var{i}.
13630 Decrements the value in the variable @var{v} by one. Returns the new value.
13632 @item DEC(@var{v},@var{i})
13633 Decrements the value in the variable @var{v} by @var{i}. Returns the
13636 @item EXCL(@var{m},@var{s})
13637 Removes the element @var{m} from the set @var{s}. Returns the new
13640 @item FLOAT(@var{i})
13641 Returns the floating point equivalent of the integer @var{i}.
13643 @item HIGH(@var{a})
13644 Returns the index of the last member of @var{a}.
13647 Increments the value in the variable @var{v} by one. Returns the new value.
13649 @item INC(@var{v},@var{i})
13650 Increments the value in the variable @var{v} by @var{i}. Returns the
13653 @item INCL(@var{m},@var{s})
13654 Adds the element @var{m} to the set @var{s} if it is not already
13655 there. Returns the new set.
13658 Returns the maximum value of the type @var{t}.
13661 Returns the minimum value of the type @var{t}.
13664 Returns boolean TRUE if @var{i} is an odd number.
13667 Returns the ordinal value of its argument. For example, the ordinal
13668 value of a character is its @sc{ascii} value (on machines supporting the
13669 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13670 integral, character and enumerated types.
13672 @item SIZE(@var{x})
13673 Returns the size of its argument. @var{x} can be a variable or a type.
13675 @item TRUNC(@var{r})
13676 Returns the integral part of @var{r}.
13678 @item TSIZE(@var{x})
13679 Returns the size of its argument. @var{x} can be a variable or a type.
13681 @item VAL(@var{t},@var{i})
13682 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13686 @emph{Warning:} Sets and their operations are not yet supported, so
13687 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13691 @cindex Modula-2 constants
13693 @subsubsection Constants
13695 @value{GDBN} allows you to express the constants of Modula-2 in the following
13701 Integer constants are simply a sequence of digits. When used in an
13702 expression, a constant is interpreted to be type-compatible with the
13703 rest of the expression. Hexadecimal integers are specified by a
13704 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13707 Floating point constants appear as a sequence of digits, followed by a
13708 decimal point and another sequence of digits. An optional exponent can
13709 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13710 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13711 digits of the floating point constant must be valid decimal (base 10)
13715 Character constants consist of a single character enclosed by a pair of
13716 like quotes, either single (@code{'}) or double (@code{"}). They may
13717 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13718 followed by a @samp{C}.
13721 String constants consist of a sequence of characters enclosed by a
13722 pair of like quotes, either single (@code{'}) or double (@code{"}).
13723 Escape sequences in the style of C are also allowed. @xref{C
13724 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13728 Enumerated constants consist of an enumerated identifier.
13731 Boolean constants consist of the identifiers @code{TRUE} and
13735 Pointer constants consist of integral values only.
13738 Set constants are not yet supported.
13742 @subsubsection Modula-2 Types
13743 @cindex Modula-2 types
13745 Currently @value{GDBN} can print the following data types in Modula-2
13746 syntax: array types, record types, set types, pointer types, procedure
13747 types, enumerated types, subrange types and base types. You can also
13748 print the contents of variables declared using these type.
13749 This section gives a number of simple source code examples together with
13750 sample @value{GDBN} sessions.
13752 The first example contains the following section of code:
13761 and you can request @value{GDBN} to interrogate the type and value of
13762 @code{r} and @code{s}.
13765 (@value{GDBP}) print s
13767 (@value{GDBP}) ptype s
13769 (@value{GDBP}) print r
13771 (@value{GDBP}) ptype r
13776 Likewise if your source code declares @code{s} as:
13780 s: SET ['A'..'Z'] ;
13784 then you may query the type of @code{s} by:
13787 (@value{GDBP}) ptype s
13788 type = SET ['A'..'Z']
13792 Note that at present you cannot interactively manipulate set
13793 expressions using the debugger.
13795 The following example shows how you might declare an array in Modula-2
13796 and how you can interact with @value{GDBN} to print its type and contents:
13800 s: ARRAY [-10..10] OF CHAR ;
13804 (@value{GDBP}) ptype s
13805 ARRAY [-10..10] OF CHAR
13808 Note that the array handling is not yet complete and although the type
13809 is printed correctly, expression handling still assumes that all
13810 arrays have a lower bound of zero and not @code{-10} as in the example
13813 Here are some more type related Modula-2 examples:
13817 colour = (blue, red, yellow, green) ;
13818 t = [blue..yellow] ;
13826 The @value{GDBN} interaction shows how you can query the data type
13827 and value of a variable.
13830 (@value{GDBP}) print s
13832 (@value{GDBP}) ptype t
13833 type = [blue..yellow]
13837 In this example a Modula-2 array is declared and its contents
13838 displayed. Observe that the contents are written in the same way as
13839 their @code{C} counterparts.
13843 s: ARRAY [1..5] OF CARDINAL ;
13849 (@value{GDBP}) print s
13850 $1 = @{1, 0, 0, 0, 0@}
13851 (@value{GDBP}) ptype s
13852 type = ARRAY [1..5] OF CARDINAL
13855 The Modula-2 language interface to @value{GDBN} also understands
13856 pointer types as shown in this example:
13860 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13867 and you can request that @value{GDBN} describes the type of @code{s}.
13870 (@value{GDBP}) ptype s
13871 type = POINTER TO ARRAY [1..5] OF CARDINAL
13874 @value{GDBN} handles compound types as we can see in this example.
13875 Here we combine array types, record types, pointer types and subrange
13886 myarray = ARRAY myrange OF CARDINAL ;
13887 myrange = [-2..2] ;
13889 s: POINTER TO ARRAY myrange OF foo ;
13893 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13897 (@value{GDBP}) ptype s
13898 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13901 f3 : ARRAY [-2..2] OF CARDINAL;
13906 @subsubsection Modula-2 Defaults
13907 @cindex Modula-2 defaults
13909 If type and range checking are set automatically by @value{GDBN}, they
13910 both default to @code{on} whenever the working language changes to
13911 Modula-2. This happens regardless of whether you or @value{GDBN}
13912 selected the working language.
13914 If you allow @value{GDBN} to set the language automatically, then entering
13915 code compiled from a file whose name ends with @file{.mod} sets the
13916 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13917 Infer the Source Language}, for further details.
13920 @subsubsection Deviations from Standard Modula-2
13921 @cindex Modula-2, deviations from
13923 A few changes have been made to make Modula-2 programs easier to debug.
13924 This is done primarily via loosening its type strictness:
13928 Unlike in standard Modula-2, pointer constants can be formed by
13929 integers. This allows you to modify pointer variables during
13930 debugging. (In standard Modula-2, the actual address contained in a
13931 pointer variable is hidden from you; it can only be modified
13932 through direct assignment to another pointer variable or expression that
13933 returned a pointer.)
13936 C escape sequences can be used in strings and characters to represent
13937 non-printable characters. @value{GDBN} prints out strings with these
13938 escape sequences embedded. Single non-printable characters are
13939 printed using the @samp{CHR(@var{nnn})} format.
13942 The assignment operator (@code{:=}) returns the value of its right-hand
13946 All built-in procedures both modify @emph{and} return their argument.
13950 @subsubsection Modula-2 Type and Range Checks
13951 @cindex Modula-2 checks
13954 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13957 @c FIXME remove warning when type/range checks added
13959 @value{GDBN} considers two Modula-2 variables type equivalent if:
13963 They are of types that have been declared equivalent via a @code{TYPE
13964 @var{t1} = @var{t2}} statement
13967 They have been declared on the same line. (Note: This is true of the
13968 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13971 As long as type checking is enabled, any attempt to combine variables
13972 whose types are not equivalent is an error.
13974 Range checking is done on all mathematical operations, assignment, array
13975 index bounds, and all built-in functions and procedures.
13978 @subsubsection The Scope Operators @code{::} and @code{.}
13980 @cindex @code{.}, Modula-2 scope operator
13981 @cindex colon, doubled as scope operator
13983 @vindex colon-colon@r{, in Modula-2}
13984 @c Info cannot handle :: but TeX can.
13987 @vindex ::@r{, in Modula-2}
13990 There are a few subtle differences between the Modula-2 scope operator
13991 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13996 @var{module} . @var{id}
13997 @var{scope} :: @var{id}
14001 where @var{scope} is the name of a module or a procedure,
14002 @var{module} the name of a module, and @var{id} is any declared
14003 identifier within your program, except another module.
14005 Using the @code{::} operator makes @value{GDBN} search the scope
14006 specified by @var{scope} for the identifier @var{id}. If it is not
14007 found in the specified scope, then @value{GDBN} searches all scopes
14008 enclosing the one specified by @var{scope}.
14010 Using the @code{.} operator makes @value{GDBN} search the current scope for
14011 the identifier specified by @var{id} that was imported from the
14012 definition module specified by @var{module}. With this operator, it is
14013 an error if the identifier @var{id} was not imported from definition
14014 module @var{module}, or if @var{id} is not an identifier in
14018 @subsubsection @value{GDBN} and Modula-2
14020 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14021 Five subcommands of @code{set print} and @code{show print} apply
14022 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14023 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14024 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14025 analogue in Modula-2.
14027 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14028 with any language, is not useful with Modula-2. Its
14029 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14030 created in Modula-2 as they can in C or C@t{++}. However, because an
14031 address can be specified by an integral constant, the construct
14032 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14034 @cindex @code{#} in Modula-2
14035 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14036 interpreted as the beginning of a comment. Use @code{<>} instead.
14042 The extensions made to @value{GDBN} for Ada only support
14043 output from the @sc{gnu} Ada (GNAT) compiler.
14044 Other Ada compilers are not currently supported, and
14045 attempting to debug executables produced by them is most likely
14049 @cindex expressions in Ada
14051 * Ada Mode Intro:: General remarks on the Ada syntax
14052 and semantics supported by Ada mode
14054 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14055 * Additions to Ada:: Extensions of the Ada expression syntax.
14056 * Stopping Before Main Program:: Debugging the program during elaboration.
14057 * Ada Tasks:: Listing and setting breakpoints in tasks.
14058 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14059 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14061 * Ada Glitches:: Known peculiarities of Ada mode.
14064 @node Ada Mode Intro
14065 @subsubsection Introduction
14066 @cindex Ada mode, general
14068 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14069 syntax, with some extensions.
14070 The philosophy behind the design of this subset is
14074 That @value{GDBN} should provide basic literals and access to operations for
14075 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14076 leaving more sophisticated computations to subprograms written into the
14077 program (which therefore may be called from @value{GDBN}).
14080 That type safety and strict adherence to Ada language restrictions
14081 are not particularly important to the @value{GDBN} user.
14084 That brevity is important to the @value{GDBN} user.
14087 Thus, for brevity, the debugger acts as if all names declared in
14088 user-written packages are directly visible, even if they are not visible
14089 according to Ada rules, thus making it unnecessary to fully qualify most
14090 names with their packages, regardless of context. Where this causes
14091 ambiguity, @value{GDBN} asks the user's intent.
14093 The debugger will start in Ada mode if it detects an Ada main program.
14094 As for other languages, it will enter Ada mode when stopped in a program that
14095 was translated from an Ada source file.
14097 While in Ada mode, you may use `@t{--}' for comments. This is useful
14098 mostly for documenting command files. The standard @value{GDBN} comment
14099 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14100 middle (to allow based literals).
14102 The debugger supports limited overloading. Given a subprogram call in which
14103 the function symbol has multiple definitions, it will use the number of
14104 actual parameters and some information about their types to attempt to narrow
14105 the set of definitions. It also makes very limited use of context, preferring
14106 procedures to functions in the context of the @code{call} command, and
14107 functions to procedures elsewhere.
14109 @node Omissions from Ada
14110 @subsubsection Omissions from Ada
14111 @cindex Ada, omissions from
14113 Here are the notable omissions from the subset:
14117 Only a subset of the attributes are supported:
14121 @t{'First}, @t{'Last}, and @t{'Length}
14122 on array objects (not on types and subtypes).
14125 @t{'Min} and @t{'Max}.
14128 @t{'Pos} and @t{'Val}.
14134 @t{'Range} on array objects (not subtypes), but only as the right
14135 operand of the membership (@code{in}) operator.
14138 @t{'Access}, @t{'Unchecked_Access}, and
14139 @t{'Unrestricted_Access} (a GNAT extension).
14147 @code{Characters.Latin_1} are not available and
14148 concatenation is not implemented. Thus, escape characters in strings are
14149 not currently available.
14152 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14153 equality of representations. They will generally work correctly
14154 for strings and arrays whose elements have integer or enumeration types.
14155 They may not work correctly for arrays whose element
14156 types have user-defined equality, for arrays of real values
14157 (in particular, IEEE-conformant floating point, because of negative
14158 zeroes and NaNs), and for arrays whose elements contain unused bits with
14159 indeterminate values.
14162 The other component-by-component array operations (@code{and}, @code{or},
14163 @code{xor}, @code{not}, and relational tests other than equality)
14164 are not implemented.
14167 @cindex array aggregates (Ada)
14168 @cindex record aggregates (Ada)
14169 @cindex aggregates (Ada)
14170 There is limited support for array and record aggregates. They are
14171 permitted only on the right sides of assignments, as in these examples:
14174 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14175 (@value{GDBP}) set An_Array := (1, others => 0)
14176 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14177 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14178 (@value{GDBP}) set A_Record := (1, "Peter", True);
14179 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14183 discriminant's value by assigning an aggregate has an
14184 undefined effect if that discriminant is used within the record.
14185 However, you can first modify discriminants by directly assigning to
14186 them (which normally would not be allowed in Ada), and then performing an
14187 aggregate assignment. For example, given a variable @code{A_Rec}
14188 declared to have a type such as:
14191 type Rec (Len : Small_Integer := 0) is record
14193 Vals : IntArray (1 .. Len);
14197 you can assign a value with a different size of @code{Vals} with two
14201 (@value{GDBP}) set A_Rec.Len := 4
14202 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14205 As this example also illustrates, @value{GDBN} is very loose about the usual
14206 rules concerning aggregates. You may leave out some of the
14207 components of an array or record aggregate (such as the @code{Len}
14208 component in the assignment to @code{A_Rec} above); they will retain their
14209 original values upon assignment. You may freely use dynamic values as
14210 indices in component associations. You may even use overlapping or
14211 redundant component associations, although which component values are
14212 assigned in such cases is not defined.
14215 Calls to dispatching subprograms are not implemented.
14218 The overloading algorithm is much more limited (i.e., less selective)
14219 than that of real Ada. It makes only limited use of the context in
14220 which a subexpression appears to resolve its meaning, and it is much
14221 looser in its rules for allowing type matches. As a result, some
14222 function calls will be ambiguous, and the user will be asked to choose
14223 the proper resolution.
14226 The @code{new} operator is not implemented.
14229 Entry calls are not implemented.
14232 Aside from printing, arithmetic operations on the native VAX floating-point
14233 formats are not supported.
14236 It is not possible to slice a packed array.
14239 The names @code{True} and @code{False}, when not part of a qualified name,
14240 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14242 Should your program
14243 redefine these names in a package or procedure (at best a dubious practice),
14244 you will have to use fully qualified names to access their new definitions.
14247 @node Additions to Ada
14248 @subsubsection Additions to Ada
14249 @cindex Ada, deviations from
14251 As it does for other languages, @value{GDBN} makes certain generic
14252 extensions to Ada (@pxref{Expressions}):
14256 If the expression @var{E} is a variable residing in memory (typically
14257 a local variable or array element) and @var{N} is a positive integer,
14258 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14259 @var{N}-1 adjacent variables following it in memory as an array. In
14260 Ada, this operator is generally not necessary, since its prime use is
14261 in displaying parts of an array, and slicing will usually do this in
14262 Ada. However, there are occasional uses when debugging programs in
14263 which certain debugging information has been optimized away.
14266 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14267 appears in function or file @var{B}.'' When @var{B} is a file name,
14268 you must typically surround it in single quotes.
14271 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14272 @var{type} that appears at address @var{addr}.''
14275 A name starting with @samp{$} is a convenience variable
14276 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14279 In addition, @value{GDBN} provides a few other shortcuts and outright
14280 additions specific to Ada:
14284 The assignment statement is allowed as an expression, returning
14285 its right-hand operand as its value. Thus, you may enter
14288 (@value{GDBP}) set x := y + 3
14289 (@value{GDBP}) print A(tmp := y + 1)
14293 The semicolon is allowed as an ``operator,'' returning as its value
14294 the value of its right-hand operand.
14295 This allows, for example,
14296 complex conditional breaks:
14299 (@value{GDBP}) break f
14300 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14304 Rather than use catenation and symbolic character names to introduce special
14305 characters into strings, one may instead use a special bracket notation,
14306 which is also used to print strings. A sequence of characters of the form
14307 @samp{["@var{XX}"]} within a string or character literal denotes the
14308 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14309 sequence of characters @samp{["""]} also denotes a single quotation mark
14310 in strings. For example,
14312 "One line.["0a"]Next line.["0a"]"
14315 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14319 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14320 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14324 (@value{GDBP}) print 'max(x, y)
14328 When printing arrays, @value{GDBN} uses positional notation when the
14329 array has a lower bound of 1, and uses a modified named notation otherwise.
14330 For example, a one-dimensional array of three integers with a lower bound
14331 of 3 might print as
14338 That is, in contrast to valid Ada, only the first component has a @code{=>}
14342 You may abbreviate attributes in expressions with any unique,
14343 multi-character subsequence of
14344 their names (an exact match gets preference).
14345 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14346 in place of @t{a'length}.
14349 @cindex quoting Ada internal identifiers
14350 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14351 to lower case. The GNAT compiler uses upper-case characters for
14352 some of its internal identifiers, which are normally of no interest to users.
14353 For the rare occasions when you actually have to look at them,
14354 enclose them in angle brackets to avoid the lower-case mapping.
14357 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14361 Printing an object of class-wide type or dereferencing an
14362 access-to-class-wide value will display all the components of the object's
14363 specific type (as indicated by its run-time tag). Likewise, component
14364 selection on such a value will operate on the specific type of the
14369 @node Stopping Before Main Program
14370 @subsubsection Stopping at the Very Beginning
14372 @cindex breakpointing Ada elaboration code
14373 It is sometimes necessary to debug the program during elaboration, and
14374 before reaching the main procedure.
14375 As defined in the Ada Reference
14376 Manual, the elaboration code is invoked from a procedure called
14377 @code{adainit}. To run your program up to the beginning of
14378 elaboration, simply use the following two commands:
14379 @code{tbreak adainit} and @code{run}.
14382 @subsubsection Extensions for Ada Tasks
14383 @cindex Ada, tasking
14385 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14386 @value{GDBN} provides the following task-related commands:
14391 This command shows a list of current Ada tasks, as in the following example:
14398 (@value{GDBP}) info tasks
14399 ID TID P-ID Pri State Name
14400 1 8088000 0 15 Child Activation Wait main_task
14401 2 80a4000 1 15 Accept Statement b
14402 3 809a800 1 15 Child Activation Wait a
14403 * 4 80ae800 3 15 Runnable c
14408 In this listing, the asterisk before the last task indicates it to be the
14409 task currently being inspected.
14413 Represents @value{GDBN}'s internal task number.
14419 The parent's task ID (@value{GDBN}'s internal task number).
14422 The base priority of the task.
14425 Current state of the task.
14429 The task has been created but has not been activated. It cannot be
14433 The task is not blocked for any reason known to Ada. (It may be waiting
14434 for a mutex, though.) It is conceptually "executing" in normal mode.
14437 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14438 that were waiting on terminate alternatives have been awakened and have
14439 terminated themselves.
14441 @item Child Activation Wait
14442 The task is waiting for created tasks to complete activation.
14444 @item Accept Statement
14445 The task is waiting on an accept or selective wait statement.
14447 @item Waiting on entry call
14448 The task is waiting on an entry call.
14450 @item Async Select Wait
14451 The task is waiting to start the abortable part of an asynchronous
14455 The task is waiting on a select statement with only a delay
14458 @item Child Termination Wait
14459 The task is sleeping having completed a master within itself, and is
14460 waiting for the tasks dependent on that master to become terminated or
14461 waiting on a terminate Phase.
14463 @item Wait Child in Term Alt
14464 The task is sleeping waiting for tasks on terminate alternatives to
14465 finish terminating.
14467 @item Accepting RV with @var{taskno}
14468 The task is accepting a rendez-vous with the task @var{taskno}.
14472 Name of the task in the program.
14476 @kindex info task @var{taskno}
14477 @item info task @var{taskno}
14478 This command shows detailled informations on the specified task, as in
14479 the following example:
14484 (@value{GDBP}) info tasks
14485 ID TID P-ID Pri State Name
14486 1 8077880 0 15 Child Activation Wait main_task
14487 * 2 807c468 1 15 Runnable task_1
14488 (@value{GDBP}) info task 2
14489 Ada Task: 0x807c468
14492 Parent: 1 (main_task)
14498 @kindex task@r{ (Ada)}
14499 @cindex current Ada task ID
14500 This command prints the ID of the current task.
14506 (@value{GDBP}) info tasks
14507 ID TID P-ID Pri State Name
14508 1 8077870 0 15 Child Activation Wait main_task
14509 * 2 807c458 1 15 Runnable t
14510 (@value{GDBP}) task
14511 [Current task is 2]
14514 @item task @var{taskno}
14515 @cindex Ada task switching
14516 This command is like the @code{thread @var{threadno}}
14517 command (@pxref{Threads}). It switches the context of debugging
14518 from the current task to the given task.
14524 (@value{GDBP}) info tasks
14525 ID TID P-ID Pri State Name
14526 1 8077870 0 15 Child Activation Wait main_task
14527 * 2 807c458 1 15 Runnable t
14528 (@value{GDBP}) task 1
14529 [Switching to task 1]
14530 #0 0x8067726 in pthread_cond_wait ()
14532 #0 0x8067726 in pthread_cond_wait ()
14533 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14534 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14535 #3 0x806153e in system.tasking.stages.activate_tasks ()
14536 #4 0x804aacc in un () at un.adb:5
14539 @item break @var{linespec} task @var{taskno}
14540 @itemx break @var{linespec} task @var{taskno} if @dots{}
14541 @cindex breakpoints and tasks, in Ada
14542 @cindex task breakpoints, in Ada
14543 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14544 These commands are like the @code{break @dots{} thread @dots{}}
14545 command (@pxref{Thread Stops}).
14546 @var{linespec} specifies source lines, as described
14547 in @ref{Specify Location}.
14549 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14550 to specify that you only want @value{GDBN} to stop the program when a
14551 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14552 numeric task identifiers assigned by @value{GDBN}, shown in the first
14553 column of the @samp{info tasks} display.
14555 If you do not specify @samp{task @var{taskno}} when you set a
14556 breakpoint, the breakpoint applies to @emph{all} tasks of your
14559 You can use the @code{task} qualifier on conditional breakpoints as
14560 well; in this case, place @samp{task @var{taskno}} before the
14561 breakpoint condition (before the @code{if}).
14569 (@value{GDBP}) info tasks
14570 ID TID P-ID Pri State Name
14571 1 140022020 0 15 Child Activation Wait main_task
14572 2 140045060 1 15 Accept/Select Wait t2
14573 3 140044840 1 15 Runnable t1
14574 * 4 140056040 1 15 Runnable t3
14575 (@value{GDBP}) b 15 task 2
14576 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14577 (@value{GDBP}) cont
14582 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14584 (@value{GDBP}) info tasks
14585 ID TID P-ID Pri State Name
14586 1 140022020 0 15 Child Activation Wait main_task
14587 * 2 140045060 1 15 Runnable t2
14588 3 140044840 1 15 Runnable t1
14589 4 140056040 1 15 Delay Sleep t3
14593 @node Ada Tasks and Core Files
14594 @subsubsection Tasking Support when Debugging Core Files
14595 @cindex Ada tasking and core file debugging
14597 When inspecting a core file, as opposed to debugging a live program,
14598 tasking support may be limited or even unavailable, depending on
14599 the platform being used.
14600 For instance, on x86-linux, the list of tasks is available, but task
14601 switching is not supported. On Tru64, however, task switching will work
14604 On certain platforms, including Tru64, the debugger needs to perform some
14605 memory writes in order to provide Ada tasking support. When inspecting
14606 a core file, this means that the core file must be opened with read-write
14607 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14608 Under these circumstances, you should make a backup copy of the core
14609 file before inspecting it with @value{GDBN}.
14611 @node Ravenscar Profile
14612 @subsubsection Tasking Support when using the Ravenscar Profile
14613 @cindex Ravenscar Profile
14615 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14616 specifically designed for systems with safety-critical real-time
14620 @kindex set ravenscar task-switching on
14621 @cindex task switching with program using Ravenscar Profile
14622 @item set ravenscar task-switching on
14623 Allows task switching when debugging a program that uses the Ravenscar
14624 Profile. This is the default.
14626 @kindex set ravenscar task-switching off
14627 @item set ravenscar task-switching off
14628 Turn off task switching when debugging a program that uses the Ravenscar
14629 Profile. This is mostly intended to disable the code that adds support
14630 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14631 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14632 To be effective, this command should be run before the program is started.
14634 @kindex show ravenscar task-switching
14635 @item show ravenscar task-switching
14636 Show whether it is possible to switch from task to task in a program
14637 using the Ravenscar Profile.
14642 @subsubsection Known Peculiarities of Ada Mode
14643 @cindex Ada, problems
14645 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14646 we know of several problems with and limitations of Ada mode in
14648 some of which will be fixed with planned future releases of the debugger
14649 and the GNU Ada compiler.
14653 Static constants that the compiler chooses not to materialize as objects in
14654 storage are invisible to the debugger.
14657 Named parameter associations in function argument lists are ignored (the
14658 argument lists are treated as positional).
14661 Many useful library packages are currently invisible to the debugger.
14664 Fixed-point arithmetic, conversions, input, and output is carried out using
14665 floating-point arithmetic, and may give results that only approximate those on
14669 The GNAT compiler never generates the prefix @code{Standard} for any of
14670 the standard symbols defined by the Ada language. @value{GDBN} knows about
14671 this: it will strip the prefix from names when you use it, and will never
14672 look for a name you have so qualified among local symbols, nor match against
14673 symbols in other packages or subprograms. If you have
14674 defined entities anywhere in your program other than parameters and
14675 local variables whose simple names match names in @code{Standard},
14676 GNAT's lack of qualification here can cause confusion. When this happens,
14677 you can usually resolve the confusion
14678 by qualifying the problematic names with package
14679 @code{Standard} explicitly.
14682 Older versions of the compiler sometimes generate erroneous debugging
14683 information, resulting in the debugger incorrectly printing the value
14684 of affected entities. In some cases, the debugger is able to work
14685 around an issue automatically. In other cases, the debugger is able
14686 to work around the issue, but the work-around has to be specifically
14689 @kindex set ada trust-PAD-over-XVS
14690 @kindex show ada trust-PAD-over-XVS
14693 @item set ada trust-PAD-over-XVS on
14694 Configure GDB to strictly follow the GNAT encoding when computing the
14695 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14696 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14697 a complete description of the encoding used by the GNAT compiler).
14698 This is the default.
14700 @item set ada trust-PAD-over-XVS off
14701 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14702 sometimes prints the wrong value for certain entities, changing @code{ada
14703 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14704 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14705 @code{off}, but this incurs a slight performance penalty, so it is
14706 recommended to leave this setting to @code{on} unless necessary.
14710 @node Unsupported Languages
14711 @section Unsupported Languages
14713 @cindex unsupported languages
14714 @cindex minimal language
14715 In addition to the other fully-supported programming languages,
14716 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14717 It does not represent a real programming language, but provides a set
14718 of capabilities close to what the C or assembly languages provide.
14719 This should allow most simple operations to be performed while debugging
14720 an application that uses a language currently not supported by @value{GDBN}.
14722 If the language is set to @code{auto}, @value{GDBN} will automatically
14723 select this language if the current frame corresponds to an unsupported
14727 @chapter Examining the Symbol Table
14729 The commands described in this chapter allow you to inquire about the
14730 symbols (names of variables, functions and types) defined in your
14731 program. This information is inherent in the text of your program and
14732 does not change as your program executes. @value{GDBN} finds it in your
14733 program's symbol table, in the file indicated when you started @value{GDBN}
14734 (@pxref{File Options, ,Choosing Files}), or by one of the
14735 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14737 @cindex symbol names
14738 @cindex names of symbols
14739 @cindex quoting names
14740 Occasionally, you may need to refer to symbols that contain unusual
14741 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14742 most frequent case is in referring to static variables in other
14743 source files (@pxref{Variables,,Program Variables}). File names
14744 are recorded in object files as debugging symbols, but @value{GDBN} would
14745 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14746 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14747 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14754 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14757 @cindex case-insensitive symbol names
14758 @cindex case sensitivity in symbol names
14759 @kindex set case-sensitive
14760 @item set case-sensitive on
14761 @itemx set case-sensitive off
14762 @itemx set case-sensitive auto
14763 Normally, when @value{GDBN} looks up symbols, it matches their names
14764 with case sensitivity determined by the current source language.
14765 Occasionally, you may wish to control that. The command @code{set
14766 case-sensitive} lets you do that by specifying @code{on} for
14767 case-sensitive matches or @code{off} for case-insensitive ones. If
14768 you specify @code{auto}, case sensitivity is reset to the default
14769 suitable for the source language. The default is case-sensitive
14770 matches for all languages except for Fortran, for which the default is
14771 case-insensitive matches.
14773 @kindex show case-sensitive
14774 @item show case-sensitive
14775 This command shows the current setting of case sensitivity for symbols
14778 @kindex info address
14779 @cindex address of a symbol
14780 @item info address @var{symbol}
14781 Describe where the data for @var{symbol} is stored. For a register
14782 variable, this says which register it is kept in. For a non-register
14783 local variable, this prints the stack-frame offset at which the variable
14786 Note the contrast with @samp{print &@var{symbol}}, which does not work
14787 at all for a register variable, and for a stack local variable prints
14788 the exact address of the current instantiation of the variable.
14790 @kindex info symbol
14791 @cindex symbol from address
14792 @cindex closest symbol and offset for an address
14793 @item info symbol @var{addr}
14794 Print the name of a symbol which is stored at the address @var{addr}.
14795 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14796 nearest symbol and an offset from it:
14799 (@value{GDBP}) info symbol 0x54320
14800 _initialize_vx + 396 in section .text
14804 This is the opposite of the @code{info address} command. You can use
14805 it to find out the name of a variable or a function given its address.
14807 For dynamically linked executables, the name of executable or shared
14808 library containing the symbol is also printed:
14811 (@value{GDBP}) info symbol 0x400225
14812 _start + 5 in section .text of /tmp/a.out
14813 (@value{GDBP}) info symbol 0x2aaaac2811cf
14814 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14818 @item whatis [@var{arg}]
14819 Print the data type of @var{arg}, which can be either an expression
14820 or a name of a data type. With no argument, print the data type of
14821 @code{$}, the last value in the value history.
14823 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14824 is not actually evaluated, and any side-effecting operations (such as
14825 assignments or function calls) inside it do not take place.
14827 If @var{arg} is a variable or an expression, @code{whatis} prints its
14828 literal type as it is used in the source code. If the type was
14829 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14830 the data type underlying the @code{typedef}. If the type of the
14831 variable or the expression is a compound data type, such as
14832 @code{struct} or @code{class}, @code{whatis} never prints their
14833 fields or methods. It just prints the @code{struct}/@code{class}
14834 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14835 such a compound data type, use @code{ptype}.
14837 If @var{arg} is a type name that was defined using @code{typedef},
14838 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14839 Unrolling means that @code{whatis} will show the underlying type used
14840 in the @code{typedef} declaration of @var{arg}. However, if that
14841 underlying type is also a @code{typedef}, @code{whatis} will not
14844 For C code, the type names may also have the form @samp{class
14845 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14846 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14849 @item ptype [@var{arg}]
14850 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14851 detailed description of the type, instead of just the name of the type.
14852 @xref{Expressions, ,Expressions}.
14854 Contrary to @code{whatis}, @code{ptype} always unrolls any
14855 @code{typedef}s in its argument declaration, whether the argument is
14856 a variable, expression, or a data type. This means that @code{ptype}
14857 of a variable or an expression will not print literally its type as
14858 present in the source code---use @code{whatis} for that. @code{typedef}s at
14859 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14860 fields, methods and inner @code{class typedef}s of @code{struct}s,
14861 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14863 For example, for this variable declaration:
14866 typedef double real_t;
14867 struct complex @{ real_t real; double imag; @};
14868 typedef struct complex complex_t;
14870 real_t *real_pointer_var;
14874 the two commands give this output:
14878 (@value{GDBP}) whatis var
14880 (@value{GDBP}) ptype var
14881 type = struct complex @{
14885 (@value{GDBP}) whatis complex_t
14886 type = struct complex
14887 (@value{GDBP}) whatis struct complex
14888 type = struct complex
14889 (@value{GDBP}) ptype struct complex
14890 type = struct complex @{
14894 (@value{GDBP}) whatis real_pointer_var
14896 (@value{GDBP}) ptype real_pointer_var
14902 As with @code{whatis}, using @code{ptype} without an argument refers to
14903 the type of @code{$}, the last value in the value history.
14905 @cindex incomplete type
14906 Sometimes, programs use opaque data types or incomplete specifications
14907 of complex data structure. If the debug information included in the
14908 program does not allow @value{GDBN} to display a full declaration of
14909 the data type, it will say @samp{<incomplete type>}. For example,
14910 given these declarations:
14914 struct foo *fooptr;
14918 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14921 (@value{GDBP}) ptype foo
14922 $1 = <incomplete type>
14926 ``Incomplete type'' is C terminology for data types that are not
14927 completely specified.
14930 @item info types @var{regexp}
14932 Print a brief description of all types whose names match the regular
14933 expression @var{regexp} (or all types in your program, if you supply
14934 no argument). Each complete typename is matched as though it were a
14935 complete line; thus, @samp{i type value} gives information on all
14936 types in your program whose names include the string @code{value}, but
14937 @samp{i type ^value$} gives information only on types whose complete
14938 name is @code{value}.
14940 This command differs from @code{ptype} in two ways: first, like
14941 @code{whatis}, it does not print a detailed description; second, it
14942 lists all source files where a type is defined.
14945 @cindex local variables
14946 @item info scope @var{location}
14947 List all the variables local to a particular scope. This command
14948 accepts a @var{location} argument---a function name, a source line, or
14949 an address preceded by a @samp{*}, and prints all the variables local
14950 to the scope defined by that location. (@xref{Specify Location}, for
14951 details about supported forms of @var{location}.) For example:
14954 (@value{GDBP}) @b{info scope command_line_handler}
14955 Scope for command_line_handler:
14956 Symbol rl is an argument at stack/frame offset 8, length 4.
14957 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14958 Symbol linelength is in static storage at address 0x150a1c, length 4.
14959 Symbol p is a local variable in register $esi, length 4.
14960 Symbol p1 is a local variable in register $ebx, length 4.
14961 Symbol nline is a local variable in register $edx, length 4.
14962 Symbol repeat is a local variable at frame offset -8, length 4.
14966 This command is especially useful for determining what data to collect
14967 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14970 @kindex info source
14972 Show information about the current source file---that is, the source file for
14973 the function containing the current point of execution:
14976 the name of the source file, and the directory containing it,
14978 the directory it was compiled in,
14980 its length, in lines,
14982 which programming language it is written in,
14984 whether the executable includes debugging information for that file, and
14985 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14987 whether the debugging information includes information about
14988 preprocessor macros.
14992 @kindex info sources
14994 Print the names of all source files in your program for which there is
14995 debugging information, organized into two lists: files whose symbols
14996 have already been read, and files whose symbols will be read when needed.
14998 @kindex info functions
14999 @item info functions
15000 Print the names and data types of all defined functions.
15002 @item info functions @var{regexp}
15003 Print the names and data types of all defined functions
15004 whose names contain a match for regular expression @var{regexp}.
15005 Thus, @samp{info fun step} finds all functions whose names
15006 include @code{step}; @samp{info fun ^step} finds those whose names
15007 start with @code{step}. If a function name contains characters
15008 that conflict with the regular expression language (e.g.@:
15009 @samp{operator*()}), they may be quoted with a backslash.
15011 @kindex info variables
15012 @item info variables
15013 Print the names and data types of all variables that are defined
15014 outside of functions (i.e.@: excluding local variables).
15016 @item info variables @var{regexp}
15017 Print the names and data types of all variables (except for local
15018 variables) whose names contain a match for regular expression
15021 @kindex info classes
15022 @cindex Objective-C, classes and selectors
15024 @itemx info classes @var{regexp}
15025 Display all Objective-C classes in your program, or
15026 (with the @var{regexp} argument) all those matching a particular regular
15029 @kindex info selectors
15030 @item info selectors
15031 @itemx info selectors @var{regexp}
15032 Display all Objective-C selectors in your program, or
15033 (with the @var{regexp} argument) all those matching a particular regular
15037 This was never implemented.
15038 @kindex info methods
15040 @itemx info methods @var{regexp}
15041 The @code{info methods} command permits the user to examine all defined
15042 methods within C@t{++} program, or (with the @var{regexp} argument) a
15043 specific set of methods found in the various C@t{++} classes. Many
15044 C@t{++} classes provide a large number of methods. Thus, the output
15045 from the @code{ptype} command can be overwhelming and hard to use. The
15046 @code{info-methods} command filters the methods, printing only those
15047 which match the regular-expression @var{regexp}.
15050 @cindex opaque data types
15051 @kindex set opaque-type-resolution
15052 @item set opaque-type-resolution on
15053 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15054 declared as a pointer to a @code{struct}, @code{class}, or
15055 @code{union}---for example, @code{struct MyType *}---that is used in one
15056 source file although the full declaration of @code{struct MyType} is in
15057 another source file. The default is on.
15059 A change in the setting of this subcommand will not take effect until
15060 the next time symbols for a file are loaded.
15062 @item set opaque-type-resolution off
15063 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15064 is printed as follows:
15066 @{<no data fields>@}
15069 @kindex show opaque-type-resolution
15070 @item show opaque-type-resolution
15071 Show whether opaque types are resolved or not.
15073 @kindex maint print symbols
15074 @cindex symbol dump
15075 @kindex maint print psymbols
15076 @cindex partial symbol dump
15077 @item maint print symbols @var{filename}
15078 @itemx maint print psymbols @var{filename}
15079 @itemx maint print msymbols @var{filename}
15080 Write a dump of debugging symbol data into the file @var{filename}.
15081 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15082 symbols with debugging data are included. If you use @samp{maint print
15083 symbols}, @value{GDBN} includes all the symbols for which it has already
15084 collected full details: that is, @var{filename} reflects symbols for
15085 only those files whose symbols @value{GDBN} has read. You can use the
15086 command @code{info sources} to find out which files these are. If you
15087 use @samp{maint print psymbols} instead, the dump shows information about
15088 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15089 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15090 @samp{maint print msymbols} dumps just the minimal symbol information
15091 required for each object file from which @value{GDBN} has read some symbols.
15092 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15093 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15095 @kindex maint info symtabs
15096 @kindex maint info psymtabs
15097 @cindex listing @value{GDBN}'s internal symbol tables
15098 @cindex symbol tables, listing @value{GDBN}'s internal
15099 @cindex full symbol tables, listing @value{GDBN}'s internal
15100 @cindex partial symbol tables, listing @value{GDBN}'s internal
15101 @item maint info symtabs @r{[} @var{regexp} @r{]}
15102 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15104 List the @code{struct symtab} or @code{struct partial_symtab}
15105 structures whose names match @var{regexp}. If @var{regexp} is not
15106 given, list them all. The output includes expressions which you can
15107 copy into a @value{GDBN} debugging this one to examine a particular
15108 structure in more detail. For example:
15111 (@value{GDBP}) maint info psymtabs dwarf2read
15112 @{ objfile /home/gnu/build/gdb/gdb
15113 ((struct objfile *) 0x82e69d0)
15114 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15115 ((struct partial_symtab *) 0x8474b10)
15118 text addresses 0x814d3c8 -- 0x8158074
15119 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15120 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15121 dependencies (none)
15124 (@value{GDBP}) maint info symtabs
15128 We see that there is one partial symbol table whose filename contains
15129 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15130 and we see that @value{GDBN} has not read in any symtabs yet at all.
15131 If we set a breakpoint on a function, that will cause @value{GDBN} to
15132 read the symtab for the compilation unit containing that function:
15135 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15136 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15138 (@value{GDBP}) maint info symtabs
15139 @{ objfile /home/gnu/build/gdb/gdb
15140 ((struct objfile *) 0x82e69d0)
15141 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15142 ((struct symtab *) 0x86c1f38)
15145 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15146 linetable ((struct linetable *) 0x8370fa0)
15147 debugformat DWARF 2
15156 @chapter Altering Execution
15158 Once you think you have found an error in your program, you might want to
15159 find out for certain whether correcting the apparent error would lead to
15160 correct results in the rest of the run. You can find the answer by
15161 experiment, using the @value{GDBN} features for altering execution of the
15164 For example, you can store new values into variables or memory
15165 locations, give your program a signal, restart it at a different
15166 address, or even return prematurely from a function.
15169 * Assignment:: Assignment to variables
15170 * Jumping:: Continuing at a different address
15171 * Signaling:: Giving your program a signal
15172 * Returning:: Returning from a function
15173 * Calling:: Calling your program's functions
15174 * Patching:: Patching your program
15178 @section Assignment to Variables
15181 @cindex setting variables
15182 To alter the value of a variable, evaluate an assignment expression.
15183 @xref{Expressions, ,Expressions}. For example,
15190 stores the value 4 into the variable @code{x}, and then prints the
15191 value of the assignment expression (which is 4).
15192 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15193 information on operators in supported languages.
15195 @kindex set variable
15196 @cindex variables, setting
15197 If you are not interested in seeing the value of the assignment, use the
15198 @code{set} command instead of the @code{print} command. @code{set} is
15199 really the same as @code{print} except that the expression's value is
15200 not printed and is not put in the value history (@pxref{Value History,
15201 ,Value History}). The expression is evaluated only for its effects.
15203 If the beginning of the argument string of the @code{set} command
15204 appears identical to a @code{set} subcommand, use the @code{set
15205 variable} command instead of just @code{set}. This command is identical
15206 to @code{set} except for its lack of subcommands. For example, if your
15207 program has a variable @code{width}, you get an error if you try to set
15208 a new value with just @samp{set width=13}, because @value{GDBN} has the
15209 command @code{set width}:
15212 (@value{GDBP}) whatis width
15214 (@value{GDBP}) p width
15216 (@value{GDBP}) set width=47
15217 Invalid syntax in expression.
15221 The invalid expression, of course, is @samp{=47}. In
15222 order to actually set the program's variable @code{width}, use
15225 (@value{GDBP}) set var width=47
15228 Because the @code{set} command has many subcommands that can conflict
15229 with the names of program variables, it is a good idea to use the
15230 @code{set variable} command instead of just @code{set}. For example, if
15231 your program has a variable @code{g}, you run into problems if you try
15232 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15233 the command @code{set gnutarget}, abbreviated @code{set g}:
15237 (@value{GDBP}) whatis g
15241 (@value{GDBP}) set g=4
15245 The program being debugged has been started already.
15246 Start it from the beginning? (y or n) y
15247 Starting program: /home/smith/cc_progs/a.out
15248 "/home/smith/cc_progs/a.out": can't open to read symbols:
15249 Invalid bfd target.
15250 (@value{GDBP}) show g
15251 The current BFD target is "=4".
15256 The program variable @code{g} did not change, and you silently set the
15257 @code{gnutarget} to an invalid value. In order to set the variable
15261 (@value{GDBP}) set var g=4
15264 @value{GDBN} allows more implicit conversions in assignments than C; you can
15265 freely store an integer value into a pointer variable or vice versa,
15266 and you can convert any structure to any other structure that is the
15267 same length or shorter.
15268 @comment FIXME: how do structs align/pad in these conversions?
15269 @comment /doc@cygnus.com 18dec1990
15271 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15272 construct to generate a value of specified type at a specified address
15273 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15274 to memory location @code{0x83040} as an integer (which implies a certain size
15275 and representation in memory), and
15278 set @{int@}0x83040 = 4
15282 stores the value 4 into that memory location.
15285 @section Continuing at a Different Address
15287 Ordinarily, when you continue your program, you do so at the place where
15288 it stopped, with the @code{continue} command. You can instead continue at
15289 an address of your own choosing, with the following commands:
15293 @item jump @var{linespec}
15294 @itemx jump @var{location}
15295 Resume execution at line @var{linespec} or at address given by
15296 @var{location}. Execution stops again immediately if there is a
15297 breakpoint there. @xref{Specify Location}, for a description of the
15298 different forms of @var{linespec} and @var{location}. It is common
15299 practice to use the @code{tbreak} command in conjunction with
15300 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15302 The @code{jump} command does not change the current stack frame, or
15303 the stack pointer, or the contents of any memory location or any
15304 register other than the program counter. If line @var{linespec} is in
15305 a different function from the one currently executing, the results may
15306 be bizarre if the two functions expect different patterns of arguments or
15307 of local variables. For this reason, the @code{jump} command requests
15308 confirmation if the specified line is not in the function currently
15309 executing. However, even bizarre results are predictable if you are
15310 well acquainted with the machine-language code of your program.
15313 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15314 On many systems, you can get much the same effect as the @code{jump}
15315 command by storing a new value into the register @code{$pc}. The
15316 difference is that this does not start your program running; it only
15317 changes the address of where it @emph{will} run when you continue. For
15325 makes the next @code{continue} command or stepping command execute at
15326 address @code{0x485}, rather than at the address where your program stopped.
15327 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15329 The most common occasion to use the @code{jump} command is to back
15330 up---perhaps with more breakpoints set---over a portion of a program
15331 that has already executed, in order to examine its execution in more
15336 @section Giving your Program a Signal
15337 @cindex deliver a signal to a program
15341 @item signal @var{signal}
15342 Resume execution where your program stopped, but immediately give it the
15343 signal @var{signal}. @var{signal} can be the name or the number of a
15344 signal. For example, on many systems @code{signal 2} and @code{signal
15345 SIGINT} are both ways of sending an interrupt signal.
15347 Alternatively, if @var{signal} is zero, continue execution without
15348 giving a signal. This is useful when your program stopped on account of
15349 a signal and would ordinary see the signal when resumed with the
15350 @code{continue} command; @samp{signal 0} causes it to resume without a
15353 @code{signal} does not repeat when you press @key{RET} a second time
15354 after executing the command.
15358 Invoking the @code{signal} command is not the same as invoking the
15359 @code{kill} utility from the shell. Sending a signal with @code{kill}
15360 causes @value{GDBN} to decide what to do with the signal depending on
15361 the signal handling tables (@pxref{Signals}). The @code{signal} command
15362 passes the signal directly to your program.
15366 @section Returning from a Function
15369 @cindex returning from a function
15372 @itemx return @var{expression}
15373 You can cancel execution of a function call with the @code{return}
15374 command. If you give an
15375 @var{expression} argument, its value is used as the function's return
15379 When you use @code{return}, @value{GDBN} discards the selected stack frame
15380 (and all frames within it). You can think of this as making the
15381 discarded frame return prematurely. If you wish to specify a value to
15382 be returned, give that value as the argument to @code{return}.
15384 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15385 Frame}), and any other frames inside of it, leaving its caller as the
15386 innermost remaining frame. That frame becomes selected. The
15387 specified value is stored in the registers used for returning values
15390 The @code{return} command does not resume execution; it leaves the
15391 program stopped in the state that would exist if the function had just
15392 returned. In contrast, the @code{finish} command (@pxref{Continuing
15393 and Stepping, ,Continuing and Stepping}) resumes execution until the
15394 selected stack frame returns naturally.
15396 @value{GDBN} needs to know how the @var{expression} argument should be set for
15397 the inferior. The concrete registers assignment depends on the OS ABI and the
15398 type being returned by the selected stack frame. For example it is common for
15399 OS ABI to return floating point values in FPU registers while integer values in
15400 CPU registers. Still some ABIs return even floating point values in CPU
15401 registers. Larger integer widths (such as @code{long long int}) also have
15402 specific placement rules. @value{GDBN} already knows the OS ABI from its
15403 current target so it needs to find out also the type being returned to make the
15404 assignment into the right register(s).
15406 Normally, the selected stack frame has debug info. @value{GDBN} will always
15407 use the debug info instead of the implicit type of @var{expression} when the
15408 debug info is available. For example, if you type @kbd{return -1}, and the
15409 function in the current stack frame is declared to return a @code{long long
15410 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15411 into a @code{long long int}:
15414 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15416 (@value{GDBP}) return -1
15417 Make func return now? (y or n) y
15418 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15419 43 printf ("result=%lld\n", func ());
15423 However, if the selected stack frame does not have a debug info, e.g., if the
15424 function was compiled without debug info, @value{GDBN} has to find out the type
15425 to return from user. Specifying a different type by mistake may set the value
15426 in different inferior registers than the caller code expects. For example,
15427 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15428 of a @code{long long int} result for a debug info less function (on 32-bit
15429 architectures). Therefore the user is required to specify the return type by
15430 an appropriate cast explicitly:
15433 Breakpoint 2, 0x0040050b in func ()
15434 (@value{GDBP}) return -1
15435 Return value type not available for selected stack frame.
15436 Please use an explicit cast of the value to return.
15437 (@value{GDBP}) return (long long int) -1
15438 Make selected stack frame return now? (y or n) y
15439 #0 0x00400526 in main ()
15444 @section Calling Program Functions
15447 @cindex calling functions
15448 @cindex inferior functions, calling
15449 @item print @var{expr}
15450 Evaluate the expression @var{expr} and display the resulting value.
15451 @var{expr} may include calls to functions in the program being
15455 @item call @var{expr}
15456 Evaluate the expression @var{expr} without displaying @code{void}
15459 You can use this variant of the @code{print} command if you want to
15460 execute a function from your program that does not return anything
15461 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15462 with @code{void} returned values that @value{GDBN} will otherwise
15463 print. If the result is not void, it is printed and saved in the
15467 It is possible for the function you call via the @code{print} or
15468 @code{call} command to generate a signal (e.g., if there's a bug in
15469 the function, or if you passed it incorrect arguments). What happens
15470 in that case is controlled by the @code{set unwindonsignal} command.
15472 Similarly, with a C@t{++} program it is possible for the function you
15473 call via the @code{print} or @code{call} command to generate an
15474 exception that is not handled due to the constraints of the dummy
15475 frame. In this case, any exception that is raised in the frame, but has
15476 an out-of-frame exception handler will not be found. GDB builds a
15477 dummy-frame for the inferior function call, and the unwinder cannot
15478 seek for exception handlers outside of this dummy-frame. What happens
15479 in that case is controlled by the
15480 @code{set unwind-on-terminating-exception} command.
15483 @item set unwindonsignal
15484 @kindex set unwindonsignal
15485 @cindex unwind stack in called functions
15486 @cindex call dummy stack unwinding
15487 Set unwinding of the stack if a signal is received while in a function
15488 that @value{GDBN} called in the program being debugged. If set to on,
15489 @value{GDBN} unwinds the stack it created for the call and restores
15490 the context to what it was before the call. If set to off (the
15491 default), @value{GDBN} stops in the frame where the signal was
15494 @item show unwindonsignal
15495 @kindex show unwindonsignal
15496 Show the current setting of stack unwinding in the functions called by
15499 @item set unwind-on-terminating-exception
15500 @kindex set unwind-on-terminating-exception
15501 @cindex unwind stack in called functions with unhandled exceptions
15502 @cindex call dummy stack unwinding on unhandled exception.
15503 Set unwinding of the stack if a C@t{++} exception is raised, but left
15504 unhandled while in a function that @value{GDBN} called in the program being
15505 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15506 it created for the call and restores the context to what it was before
15507 the call. If set to off, @value{GDBN} the exception is delivered to
15508 the default C@t{++} exception handler and the inferior terminated.
15510 @item show unwind-on-terminating-exception
15511 @kindex show unwind-on-terminating-exception
15512 Show the current setting of stack unwinding in the functions called by
15517 @cindex weak alias functions
15518 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15519 for another function. In such case, @value{GDBN} might not pick up
15520 the type information, including the types of the function arguments,
15521 which causes @value{GDBN} to call the inferior function incorrectly.
15522 As a result, the called function will function erroneously and may
15523 even crash. A solution to that is to use the name of the aliased
15527 @section Patching Programs
15529 @cindex patching binaries
15530 @cindex writing into executables
15531 @cindex writing into corefiles
15533 By default, @value{GDBN} opens the file containing your program's
15534 executable code (or the corefile) read-only. This prevents accidental
15535 alterations to machine code; but it also prevents you from intentionally
15536 patching your program's binary.
15538 If you'd like to be able to patch the binary, you can specify that
15539 explicitly with the @code{set write} command. For example, you might
15540 want to turn on internal debugging flags, or even to make emergency
15546 @itemx set write off
15547 If you specify @samp{set write on}, @value{GDBN} opens executable and
15548 core files for both reading and writing; if you specify @kbd{set write
15549 off} (the default), @value{GDBN} opens them read-only.
15551 If you have already loaded a file, you must load it again (using the
15552 @code{exec-file} or @code{core-file} command) after changing @code{set
15553 write}, for your new setting to take effect.
15557 Display whether executable files and core files are opened for writing
15558 as well as reading.
15562 @chapter @value{GDBN} Files
15564 @value{GDBN} needs to know the file name of the program to be debugged,
15565 both in order to read its symbol table and in order to start your
15566 program. To debug a core dump of a previous run, you must also tell
15567 @value{GDBN} the name of the core dump file.
15570 * Files:: Commands to specify files
15571 * Separate Debug Files:: Debugging information in separate files
15572 * Index Files:: Index files speed up GDB
15573 * Symbol Errors:: Errors reading symbol files
15574 * Data Files:: GDB data files
15578 @section Commands to Specify Files
15580 @cindex symbol table
15581 @cindex core dump file
15583 You may want to specify executable and core dump file names. The usual
15584 way to do this is at start-up time, using the arguments to
15585 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15586 Out of @value{GDBN}}).
15588 Occasionally it is necessary to change to a different file during a
15589 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15590 specify a file you want to use. Or you are debugging a remote target
15591 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15592 Program}). In these situations the @value{GDBN} commands to specify
15593 new files are useful.
15596 @cindex executable file
15598 @item file @var{filename}
15599 Use @var{filename} as the program to be debugged. It is read for its
15600 symbols and for the contents of pure memory. It is also the program
15601 executed when you use the @code{run} command. If you do not specify a
15602 directory and the file is not found in the @value{GDBN} working directory,
15603 @value{GDBN} uses the environment variable @code{PATH} as a list of
15604 directories to search, just as the shell does when looking for a program
15605 to run. You can change the value of this variable, for both @value{GDBN}
15606 and your program, using the @code{path} command.
15608 @cindex unlinked object files
15609 @cindex patching object files
15610 You can load unlinked object @file{.o} files into @value{GDBN} using
15611 the @code{file} command. You will not be able to ``run'' an object
15612 file, but you can disassemble functions and inspect variables. Also,
15613 if the underlying BFD functionality supports it, you could use
15614 @kbd{gdb -write} to patch object files using this technique. Note
15615 that @value{GDBN} can neither interpret nor modify relocations in this
15616 case, so branches and some initialized variables will appear to go to
15617 the wrong place. But this feature is still handy from time to time.
15620 @code{file} with no argument makes @value{GDBN} discard any information it
15621 has on both executable file and the symbol table.
15624 @item exec-file @r{[} @var{filename} @r{]}
15625 Specify that the program to be run (but not the symbol table) is found
15626 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15627 if necessary to locate your program. Omitting @var{filename} means to
15628 discard information on the executable file.
15630 @kindex symbol-file
15631 @item symbol-file @r{[} @var{filename} @r{]}
15632 Read symbol table information from file @var{filename}. @code{PATH} is
15633 searched when necessary. Use the @code{file} command to get both symbol
15634 table and program to run from the same file.
15636 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15637 program's symbol table.
15639 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15640 some breakpoints and auto-display expressions. This is because they may
15641 contain pointers to the internal data recording symbols and data types,
15642 which are part of the old symbol table data being discarded inside
15645 @code{symbol-file} does not repeat if you press @key{RET} again after
15648 When @value{GDBN} is configured for a particular environment, it
15649 understands debugging information in whatever format is the standard
15650 generated for that environment; you may use either a @sc{gnu} compiler, or
15651 other compilers that adhere to the local conventions.
15652 Best results are usually obtained from @sc{gnu} compilers; for example,
15653 using @code{@value{NGCC}} you can generate debugging information for
15656 For most kinds of object files, with the exception of old SVR3 systems
15657 using COFF, the @code{symbol-file} command does not normally read the
15658 symbol table in full right away. Instead, it scans the symbol table
15659 quickly to find which source files and which symbols are present. The
15660 details are read later, one source file at a time, as they are needed.
15662 The purpose of this two-stage reading strategy is to make @value{GDBN}
15663 start up faster. For the most part, it is invisible except for
15664 occasional pauses while the symbol table details for a particular source
15665 file are being read. (The @code{set verbose} command can turn these
15666 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15667 Warnings and Messages}.)
15669 We have not implemented the two-stage strategy for COFF yet. When the
15670 symbol table is stored in COFF format, @code{symbol-file} reads the
15671 symbol table data in full right away. Note that ``stabs-in-COFF''
15672 still does the two-stage strategy, since the debug info is actually
15676 @cindex reading symbols immediately
15677 @cindex symbols, reading immediately
15678 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15679 @itemx file @r{[} -readnow @r{]} @var{filename}
15680 You can override the @value{GDBN} two-stage strategy for reading symbol
15681 tables by using the @samp{-readnow} option with any of the commands that
15682 load symbol table information, if you want to be sure @value{GDBN} has the
15683 entire symbol table available.
15685 @c FIXME: for now no mention of directories, since this seems to be in
15686 @c flux. 13mar1992 status is that in theory GDB would look either in
15687 @c current dir or in same dir as myprog; but issues like competing
15688 @c GDB's, or clutter in system dirs, mean that in practice right now
15689 @c only current dir is used. FFish says maybe a special GDB hierarchy
15690 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15694 @item core-file @r{[}@var{filename}@r{]}
15696 Specify the whereabouts of a core dump file to be used as the ``contents
15697 of memory''. Traditionally, core files contain only some parts of the
15698 address space of the process that generated them; @value{GDBN} can access the
15699 executable file itself for other parts.
15701 @code{core-file} with no argument specifies that no core file is
15704 Note that the core file is ignored when your program is actually running
15705 under @value{GDBN}. So, if you have been running your program and you
15706 wish to debug a core file instead, you must kill the subprocess in which
15707 the program is running. To do this, use the @code{kill} command
15708 (@pxref{Kill Process, ,Killing the Child Process}).
15710 @kindex add-symbol-file
15711 @cindex dynamic linking
15712 @item add-symbol-file @var{filename} @var{address}
15713 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15714 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15715 The @code{add-symbol-file} command reads additional symbol table
15716 information from the file @var{filename}. You would use this command
15717 when @var{filename} has been dynamically loaded (by some other means)
15718 into the program that is running. @var{address} should be the memory
15719 address at which the file has been loaded; @value{GDBN} cannot figure
15720 this out for itself. You can additionally specify an arbitrary number
15721 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15722 section name and base address for that section. You can specify any
15723 @var{address} as an expression.
15725 The symbol table of the file @var{filename} is added to the symbol table
15726 originally read with the @code{symbol-file} command. You can use the
15727 @code{add-symbol-file} command any number of times; the new symbol data
15728 thus read keeps adding to the old. To discard all old symbol data
15729 instead, use the @code{symbol-file} command without any arguments.
15731 @cindex relocatable object files, reading symbols from
15732 @cindex object files, relocatable, reading symbols from
15733 @cindex reading symbols from relocatable object files
15734 @cindex symbols, reading from relocatable object files
15735 @cindex @file{.o} files, reading symbols from
15736 Although @var{filename} is typically a shared library file, an
15737 executable file, or some other object file which has been fully
15738 relocated for loading into a process, you can also load symbolic
15739 information from relocatable @file{.o} files, as long as:
15743 the file's symbolic information refers only to linker symbols defined in
15744 that file, not to symbols defined by other object files,
15746 every section the file's symbolic information refers to has actually
15747 been loaded into the inferior, as it appears in the file, and
15749 you can determine the address at which every section was loaded, and
15750 provide these to the @code{add-symbol-file} command.
15754 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15755 relocatable files into an already running program; such systems
15756 typically make the requirements above easy to meet. However, it's
15757 important to recognize that many native systems use complex link
15758 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15759 assembly, for example) that make the requirements difficult to meet. In
15760 general, one cannot assume that using @code{add-symbol-file} to read a
15761 relocatable object file's symbolic information will have the same effect
15762 as linking the relocatable object file into the program in the normal
15765 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15767 @kindex add-symbol-file-from-memory
15768 @cindex @code{syscall DSO}
15769 @cindex load symbols from memory
15770 @item add-symbol-file-from-memory @var{address}
15771 Load symbols from the given @var{address} in a dynamically loaded
15772 object file whose image is mapped directly into the inferior's memory.
15773 For example, the Linux kernel maps a @code{syscall DSO} into each
15774 process's address space; this DSO provides kernel-specific code for
15775 some system calls. The argument can be any expression whose
15776 evaluation yields the address of the file's shared object file header.
15777 For this command to work, you must have used @code{symbol-file} or
15778 @code{exec-file} commands in advance.
15780 @kindex add-shared-symbol-files
15782 @item add-shared-symbol-files @var{library-file}
15783 @itemx assf @var{library-file}
15784 The @code{add-shared-symbol-files} command can currently be used only
15785 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15786 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15787 @value{GDBN} automatically looks for shared libraries, however if
15788 @value{GDBN} does not find yours, you can invoke
15789 @code{add-shared-symbol-files}. It takes one argument: the shared
15790 library's file name. @code{assf} is a shorthand alias for
15791 @code{add-shared-symbol-files}.
15794 @item section @var{section} @var{addr}
15795 The @code{section} command changes the base address of the named
15796 @var{section} of the exec file to @var{addr}. This can be used if the
15797 exec file does not contain section addresses, (such as in the
15798 @code{a.out} format), or when the addresses specified in the file
15799 itself are wrong. Each section must be changed separately. The
15800 @code{info files} command, described below, lists all the sections and
15804 @kindex info target
15807 @code{info files} and @code{info target} are synonymous; both print the
15808 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15809 including the names of the executable and core dump files currently in
15810 use by @value{GDBN}, and the files from which symbols were loaded. The
15811 command @code{help target} lists all possible targets rather than
15814 @kindex maint info sections
15815 @item maint info sections
15816 Another command that can give you extra information about program sections
15817 is @code{maint info sections}. In addition to the section information
15818 displayed by @code{info files}, this command displays the flags and file
15819 offset of each section in the executable and core dump files. In addition,
15820 @code{maint info sections} provides the following command options (which
15821 may be arbitrarily combined):
15825 Display sections for all loaded object files, including shared libraries.
15826 @item @var{sections}
15827 Display info only for named @var{sections}.
15828 @item @var{section-flags}
15829 Display info only for sections for which @var{section-flags} are true.
15830 The section flags that @value{GDBN} currently knows about are:
15833 Section will have space allocated in the process when loaded.
15834 Set for all sections except those containing debug information.
15836 Section will be loaded from the file into the child process memory.
15837 Set for pre-initialized code and data, clear for @code{.bss} sections.
15839 Section needs to be relocated before loading.
15841 Section cannot be modified by the child process.
15843 Section contains executable code only.
15845 Section contains data only (no executable code).
15847 Section will reside in ROM.
15849 Section contains data for constructor/destructor lists.
15851 Section is not empty.
15853 An instruction to the linker to not output the section.
15854 @item COFF_SHARED_LIBRARY
15855 A notification to the linker that the section contains
15856 COFF shared library information.
15858 Section contains common symbols.
15861 @kindex set trust-readonly-sections
15862 @cindex read-only sections
15863 @item set trust-readonly-sections on
15864 Tell @value{GDBN} that readonly sections in your object file
15865 really are read-only (i.e.@: that their contents will not change).
15866 In that case, @value{GDBN} can fetch values from these sections
15867 out of the object file, rather than from the target program.
15868 For some targets (notably embedded ones), this can be a significant
15869 enhancement to debugging performance.
15871 The default is off.
15873 @item set trust-readonly-sections off
15874 Tell @value{GDBN} not to trust readonly sections. This means that
15875 the contents of the section might change while the program is running,
15876 and must therefore be fetched from the target when needed.
15878 @item show trust-readonly-sections
15879 Show the current setting of trusting readonly sections.
15882 All file-specifying commands allow both absolute and relative file names
15883 as arguments. @value{GDBN} always converts the file name to an absolute file
15884 name and remembers it that way.
15886 @cindex shared libraries
15887 @anchor{Shared Libraries}
15888 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15889 and IBM RS/6000 AIX shared libraries.
15891 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15892 shared libraries. @xref{Expat}.
15894 @value{GDBN} automatically loads symbol definitions from shared libraries
15895 when you use the @code{run} command, or when you examine a core file.
15896 (Before you issue the @code{run} command, @value{GDBN} does not understand
15897 references to a function in a shared library, however---unless you are
15898 debugging a core file).
15900 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15901 automatically loads the symbols at the time of the @code{shl_load} call.
15903 @c FIXME: some @value{GDBN} release may permit some refs to undef
15904 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15905 @c FIXME...lib; check this from time to time when updating manual
15907 There are times, however, when you may wish to not automatically load
15908 symbol definitions from shared libraries, such as when they are
15909 particularly large or there are many of them.
15911 To control the automatic loading of shared library symbols, use the
15915 @kindex set auto-solib-add
15916 @item set auto-solib-add @var{mode}
15917 If @var{mode} is @code{on}, symbols from all shared object libraries
15918 will be loaded automatically when the inferior begins execution, you
15919 attach to an independently started inferior, or when the dynamic linker
15920 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15921 is @code{off}, symbols must be loaded manually, using the
15922 @code{sharedlibrary} command. The default value is @code{on}.
15924 @cindex memory used for symbol tables
15925 If your program uses lots of shared libraries with debug info that
15926 takes large amounts of memory, you can decrease the @value{GDBN}
15927 memory footprint by preventing it from automatically loading the
15928 symbols from shared libraries. To that end, type @kbd{set
15929 auto-solib-add off} before running the inferior, then load each
15930 library whose debug symbols you do need with @kbd{sharedlibrary
15931 @var{regexp}}, where @var{regexp} is a regular expression that matches
15932 the libraries whose symbols you want to be loaded.
15934 @kindex show auto-solib-add
15935 @item show auto-solib-add
15936 Display the current autoloading mode.
15939 @cindex load shared library
15940 To explicitly load shared library symbols, use the @code{sharedlibrary}
15944 @kindex info sharedlibrary
15946 @item info share @var{regex}
15947 @itemx info sharedlibrary @var{regex}
15948 Print the names of the shared libraries which are currently loaded
15949 that match @var{regex}. If @var{regex} is omitted then print
15950 all shared libraries that are loaded.
15952 @kindex sharedlibrary
15954 @item sharedlibrary @var{regex}
15955 @itemx share @var{regex}
15956 Load shared object library symbols for files matching a
15957 Unix regular expression.
15958 As with files loaded automatically, it only loads shared libraries
15959 required by your program for a core file or after typing @code{run}. If
15960 @var{regex} is omitted all shared libraries required by your program are
15963 @item nosharedlibrary
15964 @kindex nosharedlibrary
15965 @cindex unload symbols from shared libraries
15966 Unload all shared object library symbols. This discards all symbols
15967 that have been loaded from all shared libraries. Symbols from shared
15968 libraries that were loaded by explicit user requests are not
15972 Sometimes you may wish that @value{GDBN} stops and gives you control
15973 when any of shared library events happen. The best way to do this is
15974 to use @code{catch load} and @code{catch unload} (@pxref{Set
15977 @value{GDBN} also supports the the @code{set stop-on-solib-events}
15978 command for this. This command exists for historical reasons. It is
15979 less useful than setting a catchpoint, because it does not allow for
15980 conditions or commands as a catchpoint does.
15983 @item set stop-on-solib-events
15984 @kindex set stop-on-solib-events
15985 This command controls whether @value{GDBN} should give you control
15986 when the dynamic linker notifies it about some shared library event.
15987 The most common event of interest is loading or unloading of a new
15990 @item show stop-on-solib-events
15991 @kindex show stop-on-solib-events
15992 Show whether @value{GDBN} stops and gives you control when shared
15993 library events happen.
15996 Shared libraries are also supported in many cross or remote debugging
15997 configurations. @value{GDBN} needs to have access to the target's libraries;
15998 this can be accomplished either by providing copies of the libraries
15999 on the host system, or by asking @value{GDBN} to automatically retrieve the
16000 libraries from the target. If copies of the target libraries are
16001 provided, they need to be the same as the target libraries, although the
16002 copies on the target can be stripped as long as the copies on the host are
16005 @cindex where to look for shared libraries
16006 For remote debugging, you need to tell @value{GDBN} where the target
16007 libraries are, so that it can load the correct copies---otherwise, it
16008 may try to load the host's libraries. @value{GDBN} has two variables
16009 to specify the search directories for target libraries.
16012 @cindex prefix for shared library file names
16013 @cindex system root, alternate
16014 @kindex set solib-absolute-prefix
16015 @kindex set sysroot
16016 @item set sysroot @var{path}
16017 Use @var{path} as the system root for the program being debugged. Any
16018 absolute shared library paths will be prefixed with @var{path}; many
16019 runtime loaders store the absolute paths to the shared library in the
16020 target program's memory. If you use @code{set sysroot} to find shared
16021 libraries, they need to be laid out in the same way that they are on
16022 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16025 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16026 retrieve the target libraries from the remote system. This is only
16027 supported when using a remote target that supports the @code{remote get}
16028 command (@pxref{File Transfer,,Sending files to a remote system}).
16029 The part of @var{path} following the initial @file{remote:}
16030 (if present) is used as system root prefix on the remote file system.
16031 @footnote{If you want to specify a local system root using a directory
16032 that happens to be named @file{remote:}, you need to use some equivalent
16033 variant of the name like @file{./remote:}.}
16035 For targets with an MS-DOS based filesystem, such as MS-Windows and
16036 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16037 absolute file name with @var{path}. But first, on Unix hosts,
16038 @value{GDBN} converts all backslash directory separators into forward
16039 slashes, because the backslash is not a directory separator on Unix:
16042 c:\foo\bar.dll @result{} c:/foo/bar.dll
16045 Then, @value{GDBN} attempts prefixing the target file name with
16046 @var{path}, and looks for the resulting file name in the host file
16050 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16053 If that does not find the shared library, @value{GDBN} tries removing
16054 the @samp{:} character from the drive spec, both for convenience, and,
16055 for the case of the host file system not supporting file names with
16059 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16062 This makes it possible to have a system root that mirrors a target
16063 with more than one drive. E.g., you may want to setup your local
16064 copies of the target system shared libraries like so (note @samp{c} vs
16068 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16069 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16070 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16074 and point the system root at @file{/path/to/sysroot}, so that
16075 @value{GDBN} can find the correct copies of both
16076 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16078 If that still does not find the shared library, @value{GDBN} tries
16079 removing the whole drive spec from the target file name:
16082 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16085 This last lookup makes it possible to not care about the drive name,
16086 if you don't want or need to.
16088 The @code{set solib-absolute-prefix} command is an alias for @code{set
16091 @cindex default system root
16092 @cindex @samp{--with-sysroot}
16093 You can set the default system root by using the configure-time
16094 @samp{--with-sysroot} option. If the system root is inside
16095 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16096 @samp{--exec-prefix}), then the default system root will be updated
16097 automatically if the installed @value{GDBN} is moved to a new
16100 @kindex show sysroot
16102 Display the current shared library prefix.
16104 @kindex set solib-search-path
16105 @item set solib-search-path @var{path}
16106 If this variable is set, @var{path} is a colon-separated list of
16107 directories to search for shared libraries. @samp{solib-search-path}
16108 is used after @samp{sysroot} fails to locate the library, or if the
16109 path to the library is relative instead of absolute. If you want to
16110 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16111 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16112 finding your host's libraries. @samp{sysroot} is preferred; setting
16113 it to a nonexistent directory may interfere with automatic loading
16114 of shared library symbols.
16116 @kindex show solib-search-path
16117 @item show solib-search-path
16118 Display the current shared library search path.
16120 @cindex DOS file-name semantics of file names.
16121 @kindex set target-file-system-kind (unix|dos-based|auto)
16122 @kindex show target-file-system-kind
16123 @item set target-file-system-kind @var{kind}
16124 Set assumed file system kind for target reported file names.
16126 Shared library file names as reported by the target system may not
16127 make sense as is on the system @value{GDBN} is running on. For
16128 example, when remote debugging a target that has MS-DOS based file
16129 system semantics, from a Unix host, the target may be reporting to
16130 @value{GDBN} a list of loaded shared libraries with file names such as
16131 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16132 drive letters, so the @samp{c:\} prefix is not normally understood as
16133 indicating an absolute file name, and neither is the backslash
16134 normally considered a directory separator character. In that case,
16135 the native file system would interpret this whole absolute file name
16136 as a relative file name with no directory components. This would make
16137 it impossible to point @value{GDBN} at a copy of the remote target's
16138 shared libraries on the host using @code{set sysroot}, and impractical
16139 with @code{set solib-search-path}. Setting
16140 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16141 to interpret such file names similarly to how the target would, and to
16142 map them to file names valid on @value{GDBN}'s native file system
16143 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16144 to one of the supported file system kinds. In that case, @value{GDBN}
16145 tries to determine the appropriate file system variant based on the
16146 current target's operating system (@pxref{ABI, ,Configuring the
16147 Current ABI}). The supported file system settings are:
16151 Instruct @value{GDBN} to assume the target file system is of Unix
16152 kind. Only file names starting the forward slash (@samp{/}) character
16153 are considered absolute, and the directory separator character is also
16157 Instruct @value{GDBN} to assume the target file system is DOS based.
16158 File names starting with either a forward slash, or a drive letter
16159 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16160 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16161 considered directory separators.
16164 Instruct @value{GDBN} to use the file system kind associated with the
16165 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16166 This is the default.
16170 @cindex file name canonicalization
16171 @cindex base name differences
16172 When processing file names provided by the user, @value{GDBN}
16173 frequently needs to compare them to the file names recorded in the
16174 program's debug info. Normally, @value{GDBN} compares just the
16175 @dfn{base names} of the files as strings, which is reasonably fast
16176 even for very large programs. (The base name of a file is the last
16177 portion of its name, after stripping all the leading directories.)
16178 This shortcut in comparison is based upon the assumption that files
16179 cannot have more than one base name. This is usually true, but
16180 references to files that use symlinks or similar filesystem
16181 facilities violate that assumption. If your program records files
16182 using such facilities, or if you provide file names to @value{GDBN}
16183 using symlinks etc., you can set @code{basenames-may-differ} to
16184 @code{true} to instruct @value{GDBN} to completely canonicalize each
16185 pair of file names it needs to compare. This will make file-name
16186 comparisons accurate, but at a price of a significant slowdown.
16189 @item set basenames-may-differ
16190 @kindex set basenames-may-differ
16191 Set whether a source file may have multiple base names.
16193 @item show basenames-may-differ
16194 @kindex show basenames-may-differ
16195 Show whether a source file may have multiple base names.
16198 @node Separate Debug Files
16199 @section Debugging Information in Separate Files
16200 @cindex separate debugging information files
16201 @cindex debugging information in separate files
16202 @cindex @file{.debug} subdirectories
16203 @cindex debugging information directory, global
16204 @cindex global debugging information directory
16205 @cindex build ID, and separate debugging files
16206 @cindex @file{.build-id} directory
16208 @value{GDBN} allows you to put a program's debugging information in a
16209 file separate from the executable itself, in a way that allows
16210 @value{GDBN} to find and load the debugging information automatically.
16211 Since debugging information can be very large---sometimes larger
16212 than the executable code itself---some systems distribute debugging
16213 information for their executables in separate files, which users can
16214 install only when they need to debug a problem.
16216 @value{GDBN} supports two ways of specifying the separate debug info
16221 The executable contains a @dfn{debug link} that specifies the name of
16222 the separate debug info file. The separate debug file's name is
16223 usually @file{@var{executable}.debug}, where @var{executable} is the
16224 name of the corresponding executable file without leading directories
16225 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16226 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16227 checksum for the debug file, which @value{GDBN} uses to validate that
16228 the executable and the debug file came from the same build.
16231 The executable contains a @dfn{build ID}, a unique bit string that is
16232 also present in the corresponding debug info file. (This is supported
16233 only on some operating systems, notably those which use the ELF format
16234 for binary files and the @sc{gnu} Binutils.) For more details about
16235 this feature, see the description of the @option{--build-id}
16236 command-line option in @ref{Options, , Command Line Options, ld.info,
16237 The GNU Linker}. The debug info file's name is not specified
16238 explicitly by the build ID, but can be computed from the build ID, see
16242 Depending on the way the debug info file is specified, @value{GDBN}
16243 uses two different methods of looking for the debug file:
16247 For the ``debug link'' method, @value{GDBN} looks up the named file in
16248 the directory of the executable file, then in a subdirectory of that
16249 directory named @file{.debug}, and finally under the global debug
16250 directory, in a subdirectory whose name is identical to the leading
16251 directories of the executable's absolute file name.
16254 For the ``build ID'' method, @value{GDBN} looks in the
16255 @file{.build-id} subdirectory of the global debug directory for a file
16256 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16257 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16258 are the rest of the bit string. (Real build ID strings are 32 or more
16259 hex characters, not 10.)
16262 So, for example, suppose you ask @value{GDBN} to debug
16263 @file{/usr/bin/ls}, which has a debug link that specifies the
16264 file @file{ls.debug}, and a build ID whose value in hex is
16265 @code{abcdef1234}. If the global debug directory is
16266 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16267 debug information files, in the indicated order:
16271 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16273 @file{/usr/bin/ls.debug}
16275 @file{/usr/bin/.debug/ls.debug}
16277 @file{/usr/lib/debug/usr/bin/ls.debug}.
16280 You can set the global debugging info directory's name, and view the
16281 name @value{GDBN} is currently using.
16285 @kindex set debug-file-directory
16286 @item set debug-file-directory @var{directories}
16287 Set the directories which @value{GDBN} searches for separate debugging
16288 information files to @var{directory}. Multiple path components can be set
16289 concatenating them by a path separator.
16291 @kindex show debug-file-directory
16292 @item show debug-file-directory
16293 Show the directories @value{GDBN} searches for separate debugging
16298 @cindex @code{.gnu_debuglink} sections
16299 @cindex debug link sections
16300 A debug link is a special section of the executable file named
16301 @code{.gnu_debuglink}. The section must contain:
16305 A filename, with any leading directory components removed, followed by
16308 zero to three bytes of padding, as needed to reach the next four-byte
16309 boundary within the section, and
16311 a four-byte CRC checksum, stored in the same endianness used for the
16312 executable file itself. The checksum is computed on the debugging
16313 information file's full contents by the function given below, passing
16314 zero as the @var{crc} argument.
16317 Any executable file format can carry a debug link, as long as it can
16318 contain a section named @code{.gnu_debuglink} with the contents
16321 @cindex @code{.note.gnu.build-id} sections
16322 @cindex build ID sections
16323 The build ID is a special section in the executable file (and in other
16324 ELF binary files that @value{GDBN} may consider). This section is
16325 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16326 It contains unique identification for the built files---the ID remains
16327 the same across multiple builds of the same build tree. The default
16328 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16329 content for the build ID string. The same section with an identical
16330 value is present in the original built binary with symbols, in its
16331 stripped variant, and in the separate debugging information file.
16333 The debugging information file itself should be an ordinary
16334 executable, containing a full set of linker symbols, sections, and
16335 debugging information. The sections of the debugging information file
16336 should have the same names, addresses, and sizes as the original file,
16337 but they need not contain any data---much like a @code{.bss} section
16338 in an ordinary executable.
16340 The @sc{gnu} binary utilities (Binutils) package includes the
16341 @samp{objcopy} utility that can produce
16342 the separated executable / debugging information file pairs using the
16343 following commands:
16346 @kbd{objcopy --only-keep-debug foo foo.debug}
16351 These commands remove the debugging
16352 information from the executable file @file{foo} and place it in the file
16353 @file{foo.debug}. You can use the first, second or both methods to link the
16358 The debug link method needs the following additional command to also leave
16359 behind a debug link in @file{foo}:
16362 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16365 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16366 a version of the @code{strip} command such that the command @kbd{strip foo -f
16367 foo.debug} has the same functionality as the two @code{objcopy} commands and
16368 the @code{ln -s} command above, together.
16371 Build ID gets embedded into the main executable using @code{ld --build-id} or
16372 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16373 compatibility fixes for debug files separation are present in @sc{gnu} binary
16374 utilities (Binutils) package since version 2.18.
16379 @cindex CRC algorithm definition
16380 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16381 IEEE 802.3 using the polynomial:
16383 @c TexInfo requires naked braces for multi-digit exponents for Tex
16384 @c output, but this causes HTML output to barf. HTML has to be set using
16385 @c raw commands. So we end up having to specify this equation in 2
16390 <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>
16391 + <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
16397 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16398 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16402 The function is computed byte at a time, taking the least
16403 significant bit of each byte first. The initial pattern
16404 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16405 the final result is inverted to ensure trailing zeros also affect the
16408 @emph{Note:} This is the same CRC polynomial as used in handling the
16409 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16410 , @value{GDBN} Remote Serial Protocol}). However in the
16411 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16412 significant bit first, and the result is not inverted, so trailing
16413 zeros have no effect on the CRC value.
16415 To complete the description, we show below the code of the function
16416 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16417 initially supplied @code{crc} argument means that an initial call to
16418 this function passing in zero will start computing the CRC using
16421 @kindex gnu_debuglink_crc32
16424 gnu_debuglink_crc32 (unsigned long crc,
16425 unsigned char *buf, size_t len)
16427 static const unsigned long crc32_table[256] =
16429 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16430 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16431 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16432 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16433 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16434 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16435 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16436 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16437 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16438 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16439 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16440 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16441 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16442 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16443 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16444 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16445 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16446 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16447 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16448 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16449 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16450 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16451 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16452 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16453 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16454 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16455 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16456 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16457 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16458 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16459 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16460 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16461 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16462 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16463 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16464 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16465 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16466 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16467 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16468 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16469 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16470 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16471 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16472 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16473 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16474 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16475 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16476 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16477 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16478 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16479 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16482 unsigned char *end;
16484 crc = ~crc & 0xffffffff;
16485 for (end = buf + len; buf < end; ++buf)
16486 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16487 return ~crc & 0xffffffff;
16492 This computation does not apply to the ``build ID'' method.
16496 @section Index Files Speed Up @value{GDBN}
16497 @cindex index files
16498 @cindex @samp{.gdb_index} section
16500 When @value{GDBN} finds a symbol file, it scans the symbols in the
16501 file in order to construct an internal symbol table. This lets most
16502 @value{GDBN} operations work quickly---at the cost of a delay early
16503 on. For large programs, this delay can be quite lengthy, so
16504 @value{GDBN} provides a way to build an index, which speeds up
16507 The index is stored as a section in the symbol file. @value{GDBN} can
16508 write the index to a file, then you can put it into the symbol file
16509 using @command{objcopy}.
16511 To create an index file, use the @code{save gdb-index} command:
16514 @item save gdb-index @var{directory}
16515 @kindex save gdb-index
16516 Create an index file for each symbol file currently known by
16517 @value{GDBN}. Each file is named after its corresponding symbol file,
16518 with @samp{.gdb-index} appended, and is written into the given
16522 Once you have created an index file you can merge it into your symbol
16523 file, here named @file{symfile}, using @command{objcopy}:
16526 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16527 --set-section-flags .gdb_index=readonly symfile symfile
16530 There are currently some limitation on indices. They only work when
16531 for DWARF debugging information, not stabs. And, they do not
16532 currently work for programs using Ada.
16534 @node Symbol Errors
16535 @section Errors Reading Symbol Files
16537 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16538 such as symbol types it does not recognize, or known bugs in compiler
16539 output. By default, @value{GDBN} does not notify you of such problems, since
16540 they are relatively common and primarily of interest to people
16541 debugging compilers. If you are interested in seeing information
16542 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16543 only one message about each such type of problem, no matter how many
16544 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16545 to see how many times the problems occur, with the @code{set
16546 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16549 The messages currently printed, and their meanings, include:
16552 @item inner block not inside outer block in @var{symbol}
16554 The symbol information shows where symbol scopes begin and end
16555 (such as at the start of a function or a block of statements). This
16556 error indicates that an inner scope block is not fully contained
16557 in its outer scope blocks.
16559 @value{GDBN} circumvents the problem by treating the inner block as if it had
16560 the same scope as the outer block. In the error message, @var{symbol}
16561 may be shown as ``@code{(don't know)}'' if the outer block is not a
16564 @item block at @var{address} out of order
16566 The symbol information for symbol scope blocks should occur in
16567 order of increasing addresses. This error indicates that it does not
16570 @value{GDBN} does not circumvent this problem, and has trouble
16571 locating symbols in the source file whose symbols it is reading. (You
16572 can often determine what source file is affected by specifying
16573 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16576 @item bad block start address patched
16578 The symbol information for a symbol scope block has a start address
16579 smaller than the address of the preceding source line. This is known
16580 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16582 @value{GDBN} circumvents the problem by treating the symbol scope block as
16583 starting on the previous source line.
16585 @item bad string table offset in symbol @var{n}
16588 Symbol number @var{n} contains a pointer into the string table which is
16589 larger than the size of the string table.
16591 @value{GDBN} circumvents the problem by considering the symbol to have the
16592 name @code{foo}, which may cause other problems if many symbols end up
16595 @item unknown symbol type @code{0x@var{nn}}
16597 The symbol information contains new data types that @value{GDBN} does
16598 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16599 uncomprehended information, in hexadecimal.
16601 @value{GDBN} circumvents the error by ignoring this symbol information.
16602 This usually allows you to debug your program, though certain symbols
16603 are not accessible. If you encounter such a problem and feel like
16604 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16605 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16606 and examine @code{*bufp} to see the symbol.
16608 @item stub type has NULL name
16610 @value{GDBN} could not find the full definition for a struct or class.
16612 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16613 The symbol information for a C@t{++} member function is missing some
16614 information that recent versions of the compiler should have output for
16617 @item info mismatch between compiler and debugger
16619 @value{GDBN} could not parse a type specification output by the compiler.
16624 @section GDB Data Files
16626 @cindex prefix for data files
16627 @value{GDBN} will sometimes read an auxiliary data file. These files
16628 are kept in a directory known as the @dfn{data directory}.
16630 You can set the data directory's name, and view the name @value{GDBN}
16631 is currently using.
16634 @kindex set data-directory
16635 @item set data-directory @var{directory}
16636 Set the directory which @value{GDBN} searches for auxiliary data files
16637 to @var{directory}.
16639 @kindex show data-directory
16640 @item show data-directory
16641 Show the directory @value{GDBN} searches for auxiliary data files.
16644 @cindex default data directory
16645 @cindex @samp{--with-gdb-datadir}
16646 You can set the default data directory by using the configure-time
16647 @samp{--with-gdb-datadir} option. If the data directory is inside
16648 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16649 @samp{--exec-prefix}), then the default data directory will be updated
16650 automatically if the installed @value{GDBN} is moved to a new
16653 The data directory may also be specified with the
16654 @code{--data-directory} command line option.
16655 @xref{Mode Options}.
16658 @chapter Specifying a Debugging Target
16660 @cindex debugging target
16661 A @dfn{target} is the execution environment occupied by your program.
16663 Often, @value{GDBN} runs in the same host environment as your program;
16664 in that case, the debugging target is specified as a side effect when
16665 you use the @code{file} or @code{core} commands. When you need more
16666 flexibility---for example, running @value{GDBN} on a physically separate
16667 host, or controlling a standalone system over a serial port or a
16668 realtime system over a TCP/IP connection---you can use the @code{target}
16669 command to specify one of the target types configured for @value{GDBN}
16670 (@pxref{Target Commands, ,Commands for Managing Targets}).
16672 @cindex target architecture
16673 It is possible to build @value{GDBN} for several different @dfn{target
16674 architectures}. When @value{GDBN} is built like that, you can choose
16675 one of the available architectures with the @kbd{set architecture}
16679 @kindex set architecture
16680 @kindex show architecture
16681 @item set architecture @var{arch}
16682 This command sets the current target architecture to @var{arch}. The
16683 value of @var{arch} can be @code{"auto"}, in addition to one of the
16684 supported architectures.
16686 @item show architecture
16687 Show the current target architecture.
16689 @item set processor
16691 @kindex set processor
16692 @kindex show processor
16693 These are alias commands for, respectively, @code{set architecture}
16694 and @code{show architecture}.
16698 * Active Targets:: Active targets
16699 * Target Commands:: Commands for managing targets
16700 * Byte Order:: Choosing target byte order
16703 @node Active Targets
16704 @section Active Targets
16706 @cindex stacking targets
16707 @cindex active targets
16708 @cindex multiple targets
16710 There are multiple classes of targets such as: processes, executable files or
16711 recording sessions. Core files belong to the process class, making core file
16712 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16713 on multiple active targets, one in each class. This allows you to (for
16714 example) start a process and inspect its activity, while still having access to
16715 the executable file after the process finishes. Or if you start process
16716 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16717 presented a virtual layer of the recording target, while the process target
16718 remains stopped at the chronologically last point of the process execution.
16720 Use the @code{core-file} and @code{exec-file} commands to select a new core
16721 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16722 specify as a target a process that is already running, use the @code{attach}
16723 command (@pxref{Attach, ,Debugging an Already-running Process}).
16725 @node Target Commands
16726 @section Commands for Managing Targets
16729 @item target @var{type} @var{parameters}
16730 Connects the @value{GDBN} host environment to a target machine or
16731 process. A target is typically a protocol for talking to debugging
16732 facilities. You use the argument @var{type} to specify the type or
16733 protocol of the target machine.
16735 Further @var{parameters} are interpreted by the target protocol, but
16736 typically include things like device names or host names to connect
16737 with, process numbers, and baud rates.
16739 The @code{target} command does not repeat if you press @key{RET} again
16740 after executing the command.
16742 @kindex help target
16744 Displays the names of all targets available. To display targets
16745 currently selected, use either @code{info target} or @code{info files}
16746 (@pxref{Files, ,Commands to Specify Files}).
16748 @item help target @var{name}
16749 Describe a particular target, including any parameters necessary to
16752 @kindex set gnutarget
16753 @item set gnutarget @var{args}
16754 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16755 knows whether it is reading an @dfn{executable},
16756 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16757 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16758 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16761 @emph{Warning:} To specify a file format with @code{set gnutarget},
16762 you must know the actual BFD name.
16766 @xref{Files, , Commands to Specify Files}.
16768 @kindex show gnutarget
16769 @item show gnutarget
16770 Use the @code{show gnutarget} command to display what file format
16771 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16772 @value{GDBN} will determine the file format for each file automatically,
16773 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16776 @cindex common targets
16777 Here are some common targets (available, or not, depending on the GDB
16782 @item target exec @var{program}
16783 @cindex executable file target
16784 An executable file. @samp{target exec @var{program}} is the same as
16785 @samp{exec-file @var{program}}.
16787 @item target core @var{filename}
16788 @cindex core dump file target
16789 A core dump file. @samp{target core @var{filename}} is the same as
16790 @samp{core-file @var{filename}}.
16792 @item target remote @var{medium}
16793 @cindex remote target
16794 A remote system connected to @value{GDBN} via a serial line or network
16795 connection. This command tells @value{GDBN} to use its own remote
16796 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16798 For example, if you have a board connected to @file{/dev/ttya} on the
16799 machine running @value{GDBN}, you could say:
16802 target remote /dev/ttya
16805 @code{target remote} supports the @code{load} command. This is only
16806 useful if you have some other way of getting the stub to the target
16807 system, and you can put it somewhere in memory where it won't get
16808 clobbered by the download.
16810 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16811 @cindex built-in simulator target
16812 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16820 works; however, you cannot assume that a specific memory map, device
16821 drivers, or even basic I/O is available, although some simulators do
16822 provide these. For info about any processor-specific simulator details,
16823 see the appropriate section in @ref{Embedded Processors, ,Embedded
16828 Some configurations may include these targets as well:
16832 @item target nrom @var{dev}
16833 @cindex NetROM ROM emulator target
16834 NetROM ROM emulator. This target only supports downloading.
16838 Different targets are available on different configurations of @value{GDBN};
16839 your configuration may have more or fewer targets.
16841 Many remote targets require you to download the executable's code once
16842 you've successfully established a connection. You may wish to control
16843 various aspects of this process.
16848 @kindex set hash@r{, for remote monitors}
16849 @cindex hash mark while downloading
16850 This command controls whether a hash mark @samp{#} is displayed while
16851 downloading a file to the remote monitor. If on, a hash mark is
16852 displayed after each S-record is successfully downloaded to the
16856 @kindex show hash@r{, for remote monitors}
16857 Show the current status of displaying the hash mark.
16859 @item set debug monitor
16860 @kindex set debug monitor
16861 @cindex display remote monitor communications
16862 Enable or disable display of communications messages between
16863 @value{GDBN} and the remote monitor.
16865 @item show debug monitor
16866 @kindex show debug monitor
16867 Show the current status of displaying communications between
16868 @value{GDBN} and the remote monitor.
16873 @kindex load @var{filename}
16874 @item load @var{filename}
16876 Depending on what remote debugging facilities are configured into
16877 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16878 is meant to make @var{filename} (an executable) available for debugging
16879 on the remote system---by downloading, or dynamic linking, for example.
16880 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16881 the @code{add-symbol-file} command.
16883 If your @value{GDBN} does not have a @code{load} command, attempting to
16884 execute it gets the error message ``@code{You can't do that when your
16885 target is @dots{}}''
16887 The file is loaded at whatever address is specified in the executable.
16888 For some object file formats, you can specify the load address when you
16889 link the program; for other formats, like a.out, the object file format
16890 specifies a fixed address.
16891 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16893 Depending on the remote side capabilities, @value{GDBN} may be able to
16894 load programs into flash memory.
16896 @code{load} does not repeat if you press @key{RET} again after using it.
16900 @section Choosing Target Byte Order
16902 @cindex choosing target byte order
16903 @cindex target byte order
16905 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16906 offer the ability to run either big-endian or little-endian byte
16907 orders. Usually the executable or symbol will include a bit to
16908 designate the endian-ness, and you will not need to worry about
16909 which to use. However, you may still find it useful to adjust
16910 @value{GDBN}'s idea of processor endian-ness manually.
16914 @item set endian big
16915 Instruct @value{GDBN} to assume the target is big-endian.
16917 @item set endian little
16918 Instruct @value{GDBN} to assume the target is little-endian.
16920 @item set endian auto
16921 Instruct @value{GDBN} to use the byte order associated with the
16925 Display @value{GDBN}'s current idea of the target byte order.
16929 Note that these commands merely adjust interpretation of symbolic
16930 data on the host, and that they have absolutely no effect on the
16934 @node Remote Debugging
16935 @chapter Debugging Remote Programs
16936 @cindex remote debugging
16938 If you are trying to debug a program running on a machine that cannot run
16939 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16940 For example, you might use remote debugging on an operating system kernel,
16941 or on a small system which does not have a general purpose operating system
16942 powerful enough to run a full-featured debugger.
16944 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16945 to make this work with particular debugging targets. In addition,
16946 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16947 but not specific to any particular target system) which you can use if you
16948 write the remote stubs---the code that runs on the remote system to
16949 communicate with @value{GDBN}.
16951 Other remote targets may be available in your
16952 configuration of @value{GDBN}; use @code{help target} to list them.
16955 * Connecting:: Connecting to a remote target
16956 * File Transfer:: Sending files to a remote system
16957 * Server:: Using the gdbserver program
16958 * Remote Configuration:: Remote configuration
16959 * Remote Stub:: Implementing a remote stub
16963 @section Connecting to a Remote Target
16965 On the @value{GDBN} host machine, you will need an unstripped copy of
16966 your program, since @value{GDBN} needs symbol and debugging information.
16967 Start up @value{GDBN} as usual, using the name of the local copy of your
16968 program as the first argument.
16970 @cindex @code{target remote}
16971 @value{GDBN} can communicate with the target over a serial line, or
16972 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16973 each case, @value{GDBN} uses the same protocol for debugging your
16974 program; only the medium carrying the debugging packets varies. The
16975 @code{target remote} command establishes a connection to the target.
16976 Its arguments indicate which medium to use:
16980 @item target remote @var{serial-device}
16981 @cindex serial line, @code{target remote}
16982 Use @var{serial-device} to communicate with the target. For example,
16983 to use a serial line connected to the device named @file{/dev/ttyb}:
16986 target remote /dev/ttyb
16989 If you're using a serial line, you may want to give @value{GDBN} the
16990 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16991 (@pxref{Remote Configuration, set remotebaud}) before the
16992 @code{target} command.
16994 @item target remote @code{@var{host}:@var{port}}
16995 @itemx target remote @code{tcp:@var{host}:@var{port}}
16996 @cindex @acronym{TCP} port, @code{target remote}
16997 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16998 The @var{host} may be either a host name or a numeric @acronym{IP}
16999 address; @var{port} must be a decimal number. The @var{host} could be
17000 the target machine itself, if it is directly connected to the net, or
17001 it might be a terminal server which in turn has a serial line to the
17004 For example, to connect to port 2828 on a terminal server named
17008 target remote manyfarms:2828
17011 If your remote target is actually running on the same machine as your
17012 debugger session (e.g.@: a simulator for your target running on the
17013 same host), you can omit the hostname. For example, to connect to
17014 port 1234 on your local machine:
17017 target remote :1234
17021 Note that the colon is still required here.
17023 @item target remote @code{udp:@var{host}:@var{port}}
17024 @cindex @acronym{UDP} port, @code{target remote}
17025 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17026 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17029 target remote udp:manyfarms:2828
17032 When using a @acronym{UDP} connection for remote debugging, you should
17033 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17034 can silently drop packets on busy or unreliable networks, which will
17035 cause havoc with your debugging session.
17037 @item target remote | @var{command}
17038 @cindex pipe, @code{target remote} to
17039 Run @var{command} in the background and communicate with it using a
17040 pipe. The @var{command} is a shell command, to be parsed and expanded
17041 by the system's command shell, @code{/bin/sh}; it should expect remote
17042 protocol packets on its standard input, and send replies on its
17043 standard output. You could use this to run a stand-alone simulator
17044 that speaks the remote debugging protocol, to make net connections
17045 using programs like @code{ssh}, or for other similar tricks.
17047 If @var{command} closes its standard output (perhaps by exiting),
17048 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17049 program has already exited, this will have no effect.)
17053 Once the connection has been established, you can use all the usual
17054 commands to examine and change data. The remote program is already
17055 running; you can use @kbd{step} and @kbd{continue}, and you do not
17056 need to use @kbd{run}.
17058 @cindex interrupting remote programs
17059 @cindex remote programs, interrupting
17060 Whenever @value{GDBN} is waiting for the remote program, if you type the
17061 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17062 program. This may or may not succeed, depending in part on the hardware
17063 and the serial drivers the remote system uses. If you type the
17064 interrupt character once again, @value{GDBN} displays this prompt:
17067 Interrupted while waiting for the program.
17068 Give up (and stop debugging it)? (y or n)
17071 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17072 (If you decide you want to try again later, you can use @samp{target
17073 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17074 goes back to waiting.
17077 @kindex detach (remote)
17079 When you have finished debugging the remote program, you can use the
17080 @code{detach} command to release it from @value{GDBN} control.
17081 Detaching from the target normally resumes its execution, but the results
17082 will depend on your particular remote stub. After the @code{detach}
17083 command, @value{GDBN} is free to connect to another target.
17087 The @code{disconnect} command behaves like @code{detach}, except that
17088 the target is generally not resumed. It will wait for @value{GDBN}
17089 (this instance or another one) to connect and continue debugging. After
17090 the @code{disconnect} command, @value{GDBN} is again free to connect to
17093 @cindex send command to remote monitor
17094 @cindex extend @value{GDBN} for remote targets
17095 @cindex add new commands for external monitor
17097 @item monitor @var{cmd}
17098 This command allows you to send arbitrary commands directly to the
17099 remote monitor. Since @value{GDBN} doesn't care about the commands it
17100 sends like this, this command is the way to extend @value{GDBN}---you
17101 can add new commands that only the external monitor will understand
17105 @node File Transfer
17106 @section Sending files to a remote system
17107 @cindex remote target, file transfer
17108 @cindex file transfer
17109 @cindex sending files to remote systems
17111 Some remote targets offer the ability to transfer files over the same
17112 connection used to communicate with @value{GDBN}. This is convenient
17113 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17114 running @code{gdbserver} over a network interface. For other targets,
17115 e.g.@: embedded devices with only a single serial port, this may be
17116 the only way to upload or download files.
17118 Not all remote targets support these commands.
17122 @item remote put @var{hostfile} @var{targetfile}
17123 Copy file @var{hostfile} from the host system (the machine running
17124 @value{GDBN}) to @var{targetfile} on the target system.
17127 @item remote get @var{targetfile} @var{hostfile}
17128 Copy file @var{targetfile} from the target system to @var{hostfile}
17129 on the host system.
17131 @kindex remote delete
17132 @item remote delete @var{targetfile}
17133 Delete @var{targetfile} from the target system.
17138 @section Using the @code{gdbserver} Program
17141 @cindex remote connection without stubs
17142 @code{gdbserver} is a control program for Unix-like systems, which
17143 allows you to connect your program with a remote @value{GDBN} via
17144 @code{target remote}---but without linking in the usual debugging stub.
17146 @code{gdbserver} is not a complete replacement for the debugging stubs,
17147 because it requires essentially the same operating-system facilities
17148 that @value{GDBN} itself does. In fact, a system that can run
17149 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17150 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17151 because it is a much smaller program than @value{GDBN} itself. It is
17152 also easier to port than all of @value{GDBN}, so you may be able to get
17153 started more quickly on a new system by using @code{gdbserver}.
17154 Finally, if you develop code for real-time systems, you may find that
17155 the tradeoffs involved in real-time operation make it more convenient to
17156 do as much development work as possible on another system, for example
17157 by cross-compiling. You can use @code{gdbserver} to make a similar
17158 choice for debugging.
17160 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17161 or a TCP connection, using the standard @value{GDBN} remote serial
17165 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17166 Do not run @code{gdbserver} connected to any public network; a
17167 @value{GDBN} connection to @code{gdbserver} provides access to the
17168 target system with the same privileges as the user running
17172 @subsection Running @code{gdbserver}
17173 @cindex arguments, to @code{gdbserver}
17174 @cindex @code{gdbserver}, command-line arguments
17176 Run @code{gdbserver} on the target system. You need a copy of the
17177 program you want to debug, including any libraries it requires.
17178 @code{gdbserver} does not need your program's symbol table, so you can
17179 strip the program if necessary to save space. @value{GDBN} on the host
17180 system does all the symbol handling.
17182 To use the server, you must tell it how to communicate with @value{GDBN};
17183 the name of your program; and the arguments for your program. The usual
17187 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17190 @var{comm} is either a device name (to use a serial line), or a TCP
17191 hostname and portnumber, or @code{-} or @code{stdio} to use
17192 stdin/stdout of @code{gdbserver}.
17193 For example, to debug Emacs with the argument
17194 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17198 target> gdbserver /dev/com1 emacs foo.txt
17201 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17204 To use a TCP connection instead of a serial line:
17207 target> gdbserver host:2345 emacs foo.txt
17210 The only difference from the previous example is the first argument,
17211 specifying that you are communicating with the host @value{GDBN} via
17212 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17213 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17214 (Currently, the @samp{host} part is ignored.) You can choose any number
17215 you want for the port number as long as it does not conflict with any
17216 TCP ports already in use on the target system (for example, @code{23} is
17217 reserved for @code{telnet}).@footnote{If you choose a port number that
17218 conflicts with another service, @code{gdbserver} prints an error message
17219 and exits.} You must use the same port number with the host @value{GDBN}
17220 @code{target remote} command.
17222 The @code{stdio} connection is useful when starting @code{gdbserver}
17226 (gdb) target remote | ssh -T hostname gdbserver - hello
17229 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17230 and we don't want escape-character handling. Ssh does this by default when
17231 a command is provided, the flag is provided to make it explicit.
17232 You could elide it if you want to.
17234 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17235 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17236 display through a pipe connected to gdbserver.
17237 Both @code{stdout} and @code{stderr} use the same pipe.
17239 @subsubsection Attaching to a Running Program
17240 @cindex attach to a program, @code{gdbserver}
17241 @cindex @option{--attach}, @code{gdbserver} option
17243 On some targets, @code{gdbserver} can also attach to running programs.
17244 This is accomplished via the @code{--attach} argument. The syntax is:
17247 target> gdbserver --attach @var{comm} @var{pid}
17250 @var{pid} is the process ID of a currently running process. It isn't necessary
17251 to point @code{gdbserver} at a binary for the running process.
17254 You can debug processes by name instead of process ID if your target has the
17255 @code{pidof} utility:
17258 target> gdbserver --attach @var{comm} `pidof @var{program}`
17261 In case more than one copy of @var{program} is running, or @var{program}
17262 has multiple threads, most versions of @code{pidof} support the
17263 @code{-s} option to only return the first process ID.
17265 @subsubsection Multi-Process Mode for @code{gdbserver}
17266 @cindex @code{gdbserver}, multiple processes
17267 @cindex multiple processes with @code{gdbserver}
17269 When you connect to @code{gdbserver} using @code{target remote},
17270 @code{gdbserver} debugs the specified program only once. When the
17271 program exits, or you detach from it, @value{GDBN} closes the connection
17272 and @code{gdbserver} exits.
17274 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17275 enters multi-process mode. When the debugged program exits, or you
17276 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17277 though no program is running. The @code{run} and @code{attach}
17278 commands instruct @code{gdbserver} to run or attach to a new program.
17279 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17280 remote exec-file}) to select the program to run. Command line
17281 arguments are supported, except for wildcard expansion and I/O
17282 redirection (@pxref{Arguments}).
17284 @cindex @option{--multi}, @code{gdbserver} option
17285 To start @code{gdbserver} without supplying an initial command to run
17286 or process ID to attach, use the @option{--multi} command line option.
17287 Then you can connect using @kbd{target extended-remote} and start
17288 the program you want to debug.
17290 In multi-process mode @code{gdbserver} does not automatically exit unless you
17291 use the option @option{--once}. You can terminate it by using
17292 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17293 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17294 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17295 @option{--multi} option to @code{gdbserver} has no influence on that.
17297 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17299 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17301 @code{gdbserver} normally terminates after all of its debugged processes have
17302 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17303 extended-remote}, @code{gdbserver} stays running even with no processes left.
17304 @value{GDBN} normally terminates the spawned debugged process on its exit,
17305 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17306 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17307 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17308 stays running even in the @kbd{target remote} mode.
17310 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17311 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17312 completeness, at most one @value{GDBN} can be connected at a time.
17314 @cindex @option{--once}, @code{gdbserver} option
17315 By default, @code{gdbserver} keeps the listening TCP port open, so that
17316 additional connections are possible. However, if you start @code{gdbserver}
17317 with the @option{--once} option, it will stop listening for any further
17318 connection attempts after connecting to the first @value{GDBN} session. This
17319 means no further connections to @code{gdbserver} will be possible after the
17320 first one. It also means @code{gdbserver} will terminate after the first
17321 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17322 connections and even in the @kbd{target extended-remote} mode. The
17323 @option{--once} option allows reusing the same port number for connecting to
17324 multiple instances of @code{gdbserver} running on the same host, since each
17325 instance closes its port after the first connection.
17327 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17329 @cindex @option{--debug}, @code{gdbserver} option
17330 The @option{--debug} option tells @code{gdbserver} to display extra
17331 status information about the debugging process.
17332 @cindex @option{--remote-debug}, @code{gdbserver} option
17333 The @option{--remote-debug} option tells @code{gdbserver} to display
17334 remote protocol debug output. These options are intended for
17335 @code{gdbserver} development and for bug reports to the developers.
17337 @cindex @option{--wrapper}, @code{gdbserver} option
17338 The @option{--wrapper} option specifies a wrapper to launch programs
17339 for debugging. The option should be followed by the name of the
17340 wrapper, then any command-line arguments to pass to the wrapper, then
17341 @kbd{--} indicating the end of the wrapper arguments.
17343 @code{gdbserver} runs the specified wrapper program with a combined
17344 command line including the wrapper arguments, then the name of the
17345 program to debug, then any arguments to the program. The wrapper
17346 runs until it executes your program, and then @value{GDBN} gains control.
17348 You can use any program that eventually calls @code{execve} with
17349 its arguments as a wrapper. Several standard Unix utilities do
17350 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17351 with @code{exec "$@@"} will also work.
17353 For example, you can use @code{env} to pass an environment variable to
17354 the debugged program, without setting the variable in @code{gdbserver}'s
17358 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17361 @subsection Connecting to @code{gdbserver}
17363 Run @value{GDBN} on the host system.
17365 First make sure you have the necessary symbol files. Load symbols for
17366 your application using the @code{file} command before you connect. Use
17367 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17368 was compiled with the correct sysroot using @code{--with-sysroot}).
17370 The symbol file and target libraries must exactly match the executable
17371 and libraries on the target, with one exception: the files on the host
17372 system should not be stripped, even if the files on the target system
17373 are. Mismatched or missing files will lead to confusing results
17374 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17375 files may also prevent @code{gdbserver} from debugging multi-threaded
17378 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17379 For TCP connections, you must start up @code{gdbserver} prior to using
17380 the @code{target remote} command. Otherwise you may get an error whose
17381 text depends on the host system, but which usually looks something like
17382 @samp{Connection refused}. Don't use the @code{load}
17383 command in @value{GDBN} when using @code{gdbserver}, since the program is
17384 already on the target.
17386 @subsection Monitor Commands for @code{gdbserver}
17387 @cindex monitor commands, for @code{gdbserver}
17388 @anchor{Monitor Commands for gdbserver}
17390 During a @value{GDBN} session using @code{gdbserver}, you can use the
17391 @code{monitor} command to send special requests to @code{gdbserver}.
17392 Here are the available commands.
17396 List the available monitor commands.
17398 @item monitor set debug 0
17399 @itemx monitor set debug 1
17400 Disable or enable general debugging messages.
17402 @item monitor set remote-debug 0
17403 @itemx monitor set remote-debug 1
17404 Disable or enable specific debugging messages associated with the remote
17405 protocol (@pxref{Remote Protocol}).
17407 @item monitor set libthread-db-search-path [PATH]
17408 @cindex gdbserver, search path for @code{libthread_db}
17409 When this command is issued, @var{path} is a colon-separated list of
17410 directories to search for @code{libthread_db} (@pxref{Threads,,set
17411 libthread-db-search-path}). If you omit @var{path},
17412 @samp{libthread-db-search-path} will be reset to its default value.
17414 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17415 not supported in @code{gdbserver}.
17418 Tell gdbserver to exit immediately. This command should be followed by
17419 @code{disconnect} to close the debugging session. @code{gdbserver} will
17420 detach from any attached processes and kill any processes it created.
17421 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17422 of a multi-process mode debug session.
17426 @subsection Tracepoints support in @code{gdbserver}
17427 @cindex tracepoints support in @code{gdbserver}
17429 On some targets, @code{gdbserver} supports tracepoints, fast
17430 tracepoints and static tracepoints.
17432 For fast or static tracepoints to work, a special library called the
17433 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17434 This library is built and distributed as an integral part of
17435 @code{gdbserver}. In addition, support for static tracepoints
17436 requires building the in-process agent library with static tracepoints
17437 support. At present, the UST (LTTng Userspace Tracer,
17438 @url{http://lttng.org/ust}) tracing engine is supported. This support
17439 is automatically available if UST development headers are found in the
17440 standard include path when @code{gdbserver} is built, or if
17441 @code{gdbserver} was explicitly configured using @option{--with-ust}
17442 to point at such headers. You can explicitly disable the support
17443 using @option{--with-ust=no}.
17445 There are several ways to load the in-process agent in your program:
17448 @item Specifying it as dependency at link time
17450 You can link your program dynamically with the in-process agent
17451 library. On most systems, this is accomplished by adding
17452 @code{-linproctrace} to the link command.
17454 @item Using the system's preloading mechanisms
17456 You can force loading the in-process agent at startup time by using
17457 your system's support for preloading shared libraries. Many Unixes
17458 support the concept of preloading user defined libraries. In most
17459 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17460 in the environment. See also the description of @code{gdbserver}'s
17461 @option{--wrapper} command line option.
17463 @item Using @value{GDBN} to force loading the agent at run time
17465 On some systems, you can force the inferior to load a shared library,
17466 by calling a dynamic loader function in the inferior that takes care
17467 of dynamically looking up and loading a shared library. On most Unix
17468 systems, the function is @code{dlopen}. You'll use the @code{call}
17469 command for that. For example:
17472 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17475 Note that on most Unix systems, for the @code{dlopen} function to be
17476 available, the program needs to be linked with @code{-ldl}.
17479 On systems that have a userspace dynamic loader, like most Unix
17480 systems, when you connect to @code{gdbserver} using @code{target
17481 remote}, you'll find that the program is stopped at the dynamic
17482 loader's entry point, and no shared library has been loaded in the
17483 program's address space yet, including the in-process agent. In that
17484 case, before being able to use any of the fast or static tracepoints
17485 features, you need to let the loader run and load the shared
17486 libraries. The simplest way to do that is to run the program to the
17487 main procedure. E.g., if debugging a C or C@t{++} program, start
17488 @code{gdbserver} like so:
17491 $ gdbserver :9999 myprogram
17494 Start GDB and connect to @code{gdbserver} like so, and run to main:
17498 (@value{GDBP}) target remote myhost:9999
17499 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17500 (@value{GDBP}) b main
17501 (@value{GDBP}) continue
17504 The in-process tracing agent library should now be loaded into the
17505 process; you can confirm it with the @code{info sharedlibrary}
17506 command, which will list @file{libinproctrace.so} as loaded in the
17507 process. You are now ready to install fast tracepoints, list static
17508 tracepoint markers, probe static tracepoints markers, and start
17511 @node Remote Configuration
17512 @section Remote Configuration
17515 @kindex show remote
17516 This section documents the configuration options available when
17517 debugging remote programs. For the options related to the File I/O
17518 extensions of the remote protocol, see @ref{system,
17519 system-call-allowed}.
17522 @item set remoteaddresssize @var{bits}
17523 @cindex address size for remote targets
17524 @cindex bits in remote address
17525 Set the maximum size of address in a memory packet to the specified
17526 number of bits. @value{GDBN} will mask off the address bits above
17527 that number, when it passes addresses to the remote target. The
17528 default value is the number of bits in the target's address.
17530 @item show remoteaddresssize
17531 Show the current value of remote address size in bits.
17533 @item set remotebaud @var{n}
17534 @cindex baud rate for remote targets
17535 Set the baud rate for the remote serial I/O to @var{n} baud. The
17536 value is used to set the speed of the serial port used for debugging
17539 @item show remotebaud
17540 Show the current speed of the remote connection.
17542 @item set remotebreak
17543 @cindex interrupt remote programs
17544 @cindex BREAK signal instead of Ctrl-C
17545 @anchor{set remotebreak}
17546 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17547 when you type @kbd{Ctrl-c} to interrupt the program running
17548 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17549 character instead. The default is off, since most remote systems
17550 expect to see @samp{Ctrl-C} as the interrupt signal.
17552 @item show remotebreak
17553 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17554 interrupt the remote program.
17556 @item set remoteflow on
17557 @itemx set remoteflow off
17558 @kindex set remoteflow
17559 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17560 on the serial port used to communicate to the remote target.
17562 @item show remoteflow
17563 @kindex show remoteflow
17564 Show the current setting of hardware flow control.
17566 @item set remotelogbase @var{base}
17567 Set the base (a.k.a.@: radix) of logging serial protocol
17568 communications to @var{base}. Supported values of @var{base} are:
17569 @code{ascii}, @code{octal}, and @code{hex}. The default is
17572 @item show remotelogbase
17573 Show the current setting of the radix for logging remote serial
17576 @item set remotelogfile @var{file}
17577 @cindex record serial communications on file
17578 Record remote serial communications on the named @var{file}. The
17579 default is not to record at all.
17581 @item show remotelogfile.
17582 Show the current setting of the file name on which to record the
17583 serial communications.
17585 @item set remotetimeout @var{num}
17586 @cindex timeout for serial communications
17587 @cindex remote timeout
17588 Set the timeout limit to wait for the remote target to respond to
17589 @var{num} seconds. The default is 2 seconds.
17591 @item show remotetimeout
17592 Show the current number of seconds to wait for the remote target
17595 @cindex limit hardware breakpoints and watchpoints
17596 @cindex remote target, limit break- and watchpoints
17597 @anchor{set remote hardware-watchpoint-limit}
17598 @anchor{set remote hardware-breakpoint-limit}
17599 @item set remote hardware-watchpoint-limit @var{limit}
17600 @itemx set remote hardware-breakpoint-limit @var{limit}
17601 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17602 watchpoints. A limit of -1, the default, is treated as unlimited.
17604 @cindex limit hardware watchpoints length
17605 @cindex remote target, limit watchpoints length
17606 @anchor{set remote hardware-watchpoint-length-limit}
17607 @item set remote hardware-watchpoint-length-limit @var{limit}
17608 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17609 a remote hardware watchpoint. A limit of -1, the default, is treated
17612 @item show remote hardware-watchpoint-length-limit
17613 Show the current limit (in bytes) of the maximum length of
17614 a remote hardware watchpoint.
17616 @item set remote exec-file @var{filename}
17617 @itemx show remote exec-file
17618 @anchor{set remote exec-file}
17619 @cindex executable file, for remote target
17620 Select the file used for @code{run} with @code{target
17621 extended-remote}. This should be set to a filename valid on the
17622 target system. If it is not set, the target will use a default
17623 filename (e.g.@: the last program run).
17625 @item set remote interrupt-sequence
17626 @cindex interrupt remote programs
17627 @cindex select Ctrl-C, BREAK or BREAK-g
17628 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17629 @samp{BREAK-g} as the
17630 sequence to the remote target in order to interrupt the execution.
17631 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17632 is high level of serial line for some certain time.
17633 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17634 It is @code{BREAK} signal followed by character @code{g}.
17636 @item show interrupt-sequence
17637 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17638 is sent by @value{GDBN} to interrupt the remote program.
17639 @code{BREAK-g} is BREAK signal followed by @code{g} and
17640 also known as Magic SysRq g.
17642 @item set remote interrupt-on-connect
17643 @cindex send interrupt-sequence on start
17644 Specify whether interrupt-sequence is sent to remote target when
17645 @value{GDBN} connects to it. This is mostly needed when you debug
17646 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17647 which is known as Magic SysRq g in order to connect @value{GDBN}.
17649 @item show interrupt-on-connect
17650 Show whether interrupt-sequence is sent
17651 to remote target when @value{GDBN} connects to it.
17655 @item set tcp auto-retry on
17656 @cindex auto-retry, for remote TCP target
17657 Enable auto-retry for remote TCP connections. This is useful if the remote
17658 debugging agent is launched in parallel with @value{GDBN}; there is a race
17659 condition because the agent may not become ready to accept the connection
17660 before @value{GDBN} attempts to connect. When auto-retry is
17661 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17662 to establish the connection using the timeout specified by
17663 @code{set tcp connect-timeout}.
17665 @item set tcp auto-retry off
17666 Do not auto-retry failed TCP connections.
17668 @item show tcp auto-retry
17669 Show the current auto-retry setting.
17671 @item set tcp connect-timeout @var{seconds}
17672 @cindex connection timeout, for remote TCP target
17673 @cindex timeout, for remote target connection
17674 Set the timeout for establishing a TCP connection to the remote target to
17675 @var{seconds}. The timeout affects both polling to retry failed connections
17676 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17677 that are merely slow to complete, and represents an approximate cumulative
17680 @item show tcp connect-timeout
17681 Show the current connection timeout setting.
17684 @cindex remote packets, enabling and disabling
17685 The @value{GDBN} remote protocol autodetects the packets supported by
17686 your debugging stub. If you need to override the autodetection, you
17687 can use these commands to enable or disable individual packets. Each
17688 packet can be set to @samp{on} (the remote target supports this
17689 packet), @samp{off} (the remote target does not support this packet),
17690 or @samp{auto} (detect remote target support for this packet). They
17691 all default to @samp{auto}. For more information about each packet,
17692 see @ref{Remote Protocol}.
17694 During normal use, you should not have to use any of these commands.
17695 If you do, that may be a bug in your remote debugging stub, or a bug
17696 in @value{GDBN}. You may want to report the problem to the
17697 @value{GDBN} developers.
17699 For each packet @var{name}, the command to enable or disable the
17700 packet is @code{set remote @var{name}-packet}. The available settings
17703 @multitable @columnfractions 0.28 0.32 0.25
17706 @tab Related Features
17708 @item @code{fetch-register}
17710 @tab @code{info registers}
17712 @item @code{set-register}
17716 @item @code{binary-download}
17718 @tab @code{load}, @code{set}
17720 @item @code{read-aux-vector}
17721 @tab @code{qXfer:auxv:read}
17722 @tab @code{info auxv}
17724 @item @code{symbol-lookup}
17725 @tab @code{qSymbol}
17726 @tab Detecting multiple threads
17728 @item @code{attach}
17729 @tab @code{vAttach}
17732 @item @code{verbose-resume}
17734 @tab Stepping or resuming multiple threads
17740 @item @code{software-breakpoint}
17744 @item @code{hardware-breakpoint}
17748 @item @code{write-watchpoint}
17752 @item @code{read-watchpoint}
17756 @item @code{access-watchpoint}
17760 @item @code{target-features}
17761 @tab @code{qXfer:features:read}
17762 @tab @code{set architecture}
17764 @item @code{library-info}
17765 @tab @code{qXfer:libraries:read}
17766 @tab @code{info sharedlibrary}
17768 @item @code{memory-map}
17769 @tab @code{qXfer:memory-map:read}
17770 @tab @code{info mem}
17772 @item @code{read-sdata-object}
17773 @tab @code{qXfer:sdata:read}
17774 @tab @code{print $_sdata}
17776 @item @code{read-spu-object}
17777 @tab @code{qXfer:spu:read}
17778 @tab @code{info spu}
17780 @item @code{write-spu-object}
17781 @tab @code{qXfer:spu:write}
17782 @tab @code{info spu}
17784 @item @code{read-siginfo-object}
17785 @tab @code{qXfer:siginfo:read}
17786 @tab @code{print $_siginfo}
17788 @item @code{write-siginfo-object}
17789 @tab @code{qXfer:siginfo:write}
17790 @tab @code{set $_siginfo}
17792 @item @code{threads}
17793 @tab @code{qXfer:threads:read}
17794 @tab @code{info threads}
17796 @item @code{get-thread-local-@*storage-address}
17797 @tab @code{qGetTLSAddr}
17798 @tab Displaying @code{__thread} variables
17800 @item @code{get-thread-information-block-address}
17801 @tab @code{qGetTIBAddr}
17802 @tab Display MS-Windows Thread Information Block.
17804 @item @code{search-memory}
17805 @tab @code{qSearch:memory}
17808 @item @code{supported-packets}
17809 @tab @code{qSupported}
17810 @tab Remote communications parameters
17812 @item @code{pass-signals}
17813 @tab @code{QPassSignals}
17814 @tab @code{handle @var{signal}}
17816 @item @code{program-signals}
17817 @tab @code{QProgramSignals}
17818 @tab @code{handle @var{signal}}
17820 @item @code{hostio-close-packet}
17821 @tab @code{vFile:close}
17822 @tab @code{remote get}, @code{remote put}
17824 @item @code{hostio-open-packet}
17825 @tab @code{vFile:open}
17826 @tab @code{remote get}, @code{remote put}
17828 @item @code{hostio-pread-packet}
17829 @tab @code{vFile:pread}
17830 @tab @code{remote get}, @code{remote put}
17832 @item @code{hostio-pwrite-packet}
17833 @tab @code{vFile:pwrite}
17834 @tab @code{remote get}, @code{remote put}
17836 @item @code{hostio-unlink-packet}
17837 @tab @code{vFile:unlink}
17838 @tab @code{remote delete}
17840 @item @code{hostio-readlink-packet}
17841 @tab @code{vFile:readlink}
17844 @item @code{noack-packet}
17845 @tab @code{QStartNoAckMode}
17846 @tab Packet acknowledgment
17848 @item @code{osdata}
17849 @tab @code{qXfer:osdata:read}
17850 @tab @code{info os}
17852 @item @code{query-attached}
17853 @tab @code{qAttached}
17854 @tab Querying remote process attach state.
17856 @item @code{traceframe-info}
17857 @tab @code{qXfer:traceframe-info:read}
17858 @tab Traceframe info
17860 @item @code{install-in-trace}
17861 @tab @code{InstallInTrace}
17862 @tab Install tracepoint in tracing
17864 @item @code{disable-randomization}
17865 @tab @code{QDisableRandomization}
17866 @tab @code{set disable-randomization}
17868 @item @code{conditional-breakpoints-packet}
17869 @tab @code{Z0 and Z1}
17870 @tab @code{Support for target-side breakpoint condition evaluation}
17874 @section Implementing a Remote Stub
17876 @cindex debugging stub, example
17877 @cindex remote stub, example
17878 @cindex stub example, remote debugging
17879 The stub files provided with @value{GDBN} implement the target side of the
17880 communication protocol, and the @value{GDBN} side is implemented in the
17881 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17882 these subroutines to communicate, and ignore the details. (If you're
17883 implementing your own stub file, you can still ignore the details: start
17884 with one of the existing stub files. @file{sparc-stub.c} is the best
17885 organized, and therefore the easiest to read.)
17887 @cindex remote serial debugging, overview
17888 To debug a program running on another machine (the debugging
17889 @dfn{target} machine), you must first arrange for all the usual
17890 prerequisites for the program to run by itself. For example, for a C
17895 A startup routine to set up the C runtime environment; these usually
17896 have a name like @file{crt0}. The startup routine may be supplied by
17897 your hardware supplier, or you may have to write your own.
17900 A C subroutine library to support your program's
17901 subroutine calls, notably managing input and output.
17904 A way of getting your program to the other machine---for example, a
17905 download program. These are often supplied by the hardware
17906 manufacturer, but you may have to write your own from hardware
17910 The next step is to arrange for your program to use a serial port to
17911 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17912 machine). In general terms, the scheme looks like this:
17916 @value{GDBN} already understands how to use this protocol; when everything
17917 else is set up, you can simply use the @samp{target remote} command
17918 (@pxref{Targets,,Specifying a Debugging Target}).
17920 @item On the target,
17921 you must link with your program a few special-purpose subroutines that
17922 implement the @value{GDBN} remote serial protocol. The file containing these
17923 subroutines is called a @dfn{debugging stub}.
17925 On certain remote targets, you can use an auxiliary program
17926 @code{gdbserver} instead of linking a stub into your program.
17927 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17930 The debugging stub is specific to the architecture of the remote
17931 machine; for example, use @file{sparc-stub.c} to debug programs on
17934 @cindex remote serial stub list
17935 These working remote stubs are distributed with @value{GDBN}:
17940 @cindex @file{i386-stub.c}
17943 For Intel 386 and compatible architectures.
17946 @cindex @file{m68k-stub.c}
17947 @cindex Motorola 680x0
17949 For Motorola 680x0 architectures.
17952 @cindex @file{sh-stub.c}
17955 For Renesas SH architectures.
17958 @cindex @file{sparc-stub.c}
17960 For @sc{sparc} architectures.
17962 @item sparcl-stub.c
17963 @cindex @file{sparcl-stub.c}
17966 For Fujitsu @sc{sparclite} architectures.
17970 The @file{README} file in the @value{GDBN} distribution may list other
17971 recently added stubs.
17974 * Stub Contents:: What the stub can do for you
17975 * Bootstrapping:: What you must do for the stub
17976 * Debug Session:: Putting it all together
17979 @node Stub Contents
17980 @subsection What the Stub Can Do for You
17982 @cindex remote serial stub
17983 The debugging stub for your architecture supplies these three
17987 @item set_debug_traps
17988 @findex set_debug_traps
17989 @cindex remote serial stub, initialization
17990 This routine arranges for @code{handle_exception} to run when your
17991 program stops. You must call this subroutine explicitly in your
17992 program's startup code.
17994 @item handle_exception
17995 @findex handle_exception
17996 @cindex remote serial stub, main routine
17997 This is the central workhorse, but your program never calls it
17998 explicitly---the setup code arranges for @code{handle_exception} to
17999 run when a trap is triggered.
18001 @code{handle_exception} takes control when your program stops during
18002 execution (for example, on a breakpoint), and mediates communications
18003 with @value{GDBN} on the host machine. This is where the communications
18004 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18005 representative on the target machine. It begins by sending summary
18006 information on the state of your program, then continues to execute,
18007 retrieving and transmitting any information @value{GDBN} needs, until you
18008 execute a @value{GDBN} command that makes your program resume; at that point,
18009 @code{handle_exception} returns control to your own code on the target
18013 @cindex @code{breakpoint} subroutine, remote
18014 Use this auxiliary subroutine to make your program contain a
18015 breakpoint. Depending on the particular situation, this may be the only
18016 way for @value{GDBN} to get control. For instance, if your target
18017 machine has some sort of interrupt button, you won't need to call this;
18018 pressing the interrupt button transfers control to
18019 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18020 simply receiving characters on the serial port may also trigger a trap;
18021 again, in that situation, you don't need to call @code{breakpoint} from
18022 your own program---simply running @samp{target remote} from the host
18023 @value{GDBN} session gets control.
18025 Call @code{breakpoint} if none of these is true, or if you simply want
18026 to make certain your program stops at a predetermined point for the
18027 start of your debugging session.
18030 @node Bootstrapping
18031 @subsection What You Must Do for the Stub
18033 @cindex remote stub, support routines
18034 The debugging stubs that come with @value{GDBN} are set up for a particular
18035 chip architecture, but they have no information about the rest of your
18036 debugging target machine.
18038 First of all you need to tell the stub how to communicate with the
18042 @item int getDebugChar()
18043 @findex getDebugChar
18044 Write this subroutine to read a single character from the serial port.
18045 It may be identical to @code{getchar} for your target system; a
18046 different name is used to allow you to distinguish the two if you wish.
18048 @item void putDebugChar(int)
18049 @findex putDebugChar
18050 Write this subroutine to write a single character to the serial port.
18051 It may be identical to @code{putchar} for your target system; a
18052 different name is used to allow you to distinguish the two if you wish.
18055 @cindex control C, and remote debugging
18056 @cindex interrupting remote targets
18057 If you want @value{GDBN} to be able to stop your program while it is
18058 running, you need to use an interrupt-driven serial driver, and arrange
18059 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18060 character). That is the character which @value{GDBN} uses to tell the
18061 remote system to stop.
18063 Getting the debugging target to return the proper status to @value{GDBN}
18064 probably requires changes to the standard stub; one quick and dirty way
18065 is to just execute a breakpoint instruction (the ``dirty'' part is that
18066 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18068 Other routines you need to supply are:
18071 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18072 @findex exceptionHandler
18073 Write this function to install @var{exception_address} in the exception
18074 handling tables. You need to do this because the stub does not have any
18075 way of knowing what the exception handling tables on your target system
18076 are like (for example, the processor's table might be in @sc{rom},
18077 containing entries which point to a table in @sc{ram}).
18078 @var{exception_number} is the exception number which should be changed;
18079 its meaning is architecture-dependent (for example, different numbers
18080 might represent divide by zero, misaligned access, etc). When this
18081 exception occurs, control should be transferred directly to
18082 @var{exception_address}, and the processor state (stack, registers,
18083 and so on) should be just as it is when a processor exception occurs. So if
18084 you want to use a jump instruction to reach @var{exception_address}, it
18085 should be a simple jump, not a jump to subroutine.
18087 For the 386, @var{exception_address} should be installed as an interrupt
18088 gate so that interrupts are masked while the handler runs. The gate
18089 should be at privilege level 0 (the most privileged level). The
18090 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18091 help from @code{exceptionHandler}.
18093 @item void flush_i_cache()
18094 @findex flush_i_cache
18095 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18096 instruction cache, if any, on your target machine. If there is no
18097 instruction cache, this subroutine may be a no-op.
18099 On target machines that have instruction caches, @value{GDBN} requires this
18100 function to make certain that the state of your program is stable.
18104 You must also make sure this library routine is available:
18107 @item void *memset(void *, int, int)
18109 This is the standard library function @code{memset} that sets an area of
18110 memory to a known value. If you have one of the free versions of
18111 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18112 either obtain it from your hardware manufacturer, or write your own.
18115 If you do not use the GNU C compiler, you may need other standard
18116 library subroutines as well; this varies from one stub to another,
18117 but in general the stubs are likely to use any of the common library
18118 subroutines which @code{@value{NGCC}} generates as inline code.
18121 @node Debug Session
18122 @subsection Putting it All Together
18124 @cindex remote serial debugging summary
18125 In summary, when your program is ready to debug, you must follow these
18130 Make sure you have defined the supporting low-level routines
18131 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18133 @code{getDebugChar}, @code{putDebugChar},
18134 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18138 Insert these lines in your program's startup code, before the main
18139 procedure is called:
18146 On some machines, when a breakpoint trap is raised, the hardware
18147 automatically makes the PC point to the instruction after the
18148 breakpoint. If your machine doesn't do that, you may need to adjust
18149 @code{handle_exception} to arrange for it to return to the instruction
18150 after the breakpoint on this first invocation, so that your program
18151 doesn't keep hitting the initial breakpoint instead of making
18155 For the 680x0 stub only, you need to provide a variable called
18156 @code{exceptionHook}. Normally you just use:
18159 void (*exceptionHook)() = 0;
18163 but if before calling @code{set_debug_traps}, you set it to point to a
18164 function in your program, that function is called when
18165 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18166 error). The function indicated by @code{exceptionHook} is called with
18167 one parameter: an @code{int} which is the exception number.
18170 Compile and link together: your program, the @value{GDBN} debugging stub for
18171 your target architecture, and the supporting subroutines.
18174 Make sure you have a serial connection between your target machine and
18175 the @value{GDBN} host, and identify the serial port on the host.
18178 @c The "remote" target now provides a `load' command, so we should
18179 @c document that. FIXME.
18180 Download your program to your target machine (or get it there by
18181 whatever means the manufacturer provides), and start it.
18184 Start @value{GDBN} on the host, and connect to the target
18185 (@pxref{Connecting,,Connecting to a Remote Target}).
18189 @node Configurations
18190 @chapter Configuration-Specific Information
18192 While nearly all @value{GDBN} commands are available for all native and
18193 cross versions of the debugger, there are some exceptions. This chapter
18194 describes things that are only available in certain configurations.
18196 There are three major categories of configurations: native
18197 configurations, where the host and target are the same, embedded
18198 operating system configurations, which are usually the same for several
18199 different processor architectures, and bare embedded processors, which
18200 are quite different from each other.
18205 * Embedded Processors::
18212 This section describes details specific to particular native
18217 * BSD libkvm Interface:: Debugging BSD kernel memory images
18218 * SVR4 Process Information:: SVR4 process information
18219 * DJGPP Native:: Features specific to the DJGPP port
18220 * Cygwin Native:: Features specific to the Cygwin port
18221 * Hurd Native:: Features specific to @sc{gnu} Hurd
18222 * Neutrino:: Features specific to QNX Neutrino
18223 * Darwin:: Features specific to Darwin
18229 On HP-UX systems, if you refer to a function or variable name that
18230 begins with a dollar sign, @value{GDBN} searches for a user or system
18231 name first, before it searches for a convenience variable.
18234 @node BSD libkvm Interface
18235 @subsection BSD libkvm Interface
18238 @cindex kernel memory image
18239 @cindex kernel crash dump
18241 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18242 interface that provides a uniform interface for accessing kernel virtual
18243 memory images, including live systems and crash dumps. @value{GDBN}
18244 uses this interface to allow you to debug live kernels and kernel crash
18245 dumps on many native BSD configurations. This is implemented as a
18246 special @code{kvm} debugging target. For debugging a live system, load
18247 the currently running kernel into @value{GDBN} and connect to the
18251 (@value{GDBP}) @b{target kvm}
18254 For debugging crash dumps, provide the file name of the crash dump as an
18258 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18261 Once connected to the @code{kvm} target, the following commands are
18267 Set current context from the @dfn{Process Control Block} (PCB) address.
18270 Set current context from proc address. This command isn't available on
18271 modern FreeBSD systems.
18274 @node SVR4 Process Information
18275 @subsection SVR4 Process Information
18277 @cindex examine process image
18278 @cindex process info via @file{/proc}
18280 Many versions of SVR4 and compatible systems provide a facility called
18281 @samp{/proc} that can be used to examine the image of a running
18282 process using file-system subroutines. If @value{GDBN} is configured
18283 for an operating system with this facility, the command @code{info
18284 proc} is available to report information about the process running
18285 your program, or about any process running on your system. @code{info
18286 proc} works only on SVR4 systems that include the @code{procfs} code.
18287 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
18288 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
18294 @itemx info proc @var{process-id}
18295 Summarize available information about any running process. If a
18296 process ID is specified by @var{process-id}, display information about
18297 that process; otherwise display information about the program being
18298 debugged. The summary includes the debugged process ID, the command
18299 line used to invoke it, its current working directory, and its
18300 executable file's absolute file name.
18302 On some systems, @var{process-id} can be of the form
18303 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18304 within a process. If the optional @var{pid} part is missing, it means
18305 a thread from the process being debugged (the leading @samp{/} still
18306 needs to be present, or else @value{GDBN} will interpret the number as
18307 a process ID rather than a thread ID).
18309 @item info proc mappings
18310 @cindex memory address space mappings
18311 Report the memory address space ranges accessible in the program, with
18312 information on whether the process has read, write, or execute access
18313 rights to each range. On @sc{gnu}/Linux systems, each memory range
18314 includes the object file which is mapped to that range, instead of the
18315 memory access rights to that range.
18317 @item info proc stat
18318 @itemx info proc status
18319 @cindex process detailed status information
18320 These subcommands are specific to @sc{gnu}/Linux systems. They show
18321 the process-related information, including the user ID and group ID;
18322 how many threads are there in the process; its virtual memory usage;
18323 the signals that are pending, blocked, and ignored; its TTY; its
18324 consumption of system and user time; its stack size; its @samp{nice}
18325 value; etc. For more information, see the @samp{proc} man page
18326 (type @kbd{man 5 proc} from your shell prompt).
18328 @item info proc all
18329 Show all the information about the process described under all of the
18330 above @code{info proc} subcommands.
18333 @comment These sub-options of 'info proc' were not included when
18334 @comment procfs.c was re-written. Keep their descriptions around
18335 @comment against the day when someone finds the time to put them back in.
18336 @kindex info proc times
18337 @item info proc times
18338 Starting time, user CPU time, and system CPU time for your program and
18341 @kindex info proc id
18343 Report on the process IDs related to your program: its own process ID,
18344 the ID of its parent, the process group ID, and the session ID.
18347 @item set procfs-trace
18348 @kindex set procfs-trace
18349 @cindex @code{procfs} API calls
18350 This command enables and disables tracing of @code{procfs} API calls.
18352 @item show procfs-trace
18353 @kindex show procfs-trace
18354 Show the current state of @code{procfs} API call tracing.
18356 @item set procfs-file @var{file}
18357 @kindex set procfs-file
18358 Tell @value{GDBN} to write @code{procfs} API trace to the named
18359 @var{file}. @value{GDBN} appends the trace info to the previous
18360 contents of the file. The default is to display the trace on the
18363 @item show procfs-file
18364 @kindex show procfs-file
18365 Show the file to which @code{procfs} API trace is written.
18367 @item proc-trace-entry
18368 @itemx proc-trace-exit
18369 @itemx proc-untrace-entry
18370 @itemx proc-untrace-exit
18371 @kindex proc-trace-entry
18372 @kindex proc-trace-exit
18373 @kindex proc-untrace-entry
18374 @kindex proc-untrace-exit
18375 These commands enable and disable tracing of entries into and exits
18376 from the @code{syscall} interface.
18379 @kindex info pidlist
18380 @cindex process list, QNX Neutrino
18381 For QNX Neutrino only, this command displays the list of all the
18382 processes and all the threads within each process.
18385 @kindex info meminfo
18386 @cindex mapinfo list, QNX Neutrino
18387 For QNX Neutrino only, this command displays the list of all mapinfos.
18391 @subsection Features for Debugging @sc{djgpp} Programs
18392 @cindex @sc{djgpp} debugging
18393 @cindex native @sc{djgpp} debugging
18394 @cindex MS-DOS-specific commands
18397 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18398 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18399 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18400 top of real-mode DOS systems and their emulations.
18402 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18403 defines a few commands specific to the @sc{djgpp} port. This
18404 subsection describes those commands.
18409 This is a prefix of @sc{djgpp}-specific commands which print
18410 information about the target system and important OS structures.
18413 @cindex MS-DOS system info
18414 @cindex free memory information (MS-DOS)
18415 @item info dos sysinfo
18416 This command displays assorted information about the underlying
18417 platform: the CPU type and features, the OS version and flavor, the
18418 DPMI version, and the available conventional and DPMI memory.
18423 @cindex segment descriptor tables
18424 @cindex descriptor tables display
18426 @itemx info dos ldt
18427 @itemx info dos idt
18428 These 3 commands display entries from, respectively, Global, Local,
18429 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18430 tables are data structures which store a descriptor for each segment
18431 that is currently in use. The segment's selector is an index into a
18432 descriptor table; the table entry for that index holds the
18433 descriptor's base address and limit, and its attributes and access
18436 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18437 segment (used for both data and the stack), and a DOS segment (which
18438 allows access to DOS/BIOS data structures and absolute addresses in
18439 conventional memory). However, the DPMI host will usually define
18440 additional segments in order to support the DPMI environment.
18442 @cindex garbled pointers
18443 These commands allow to display entries from the descriptor tables.
18444 Without an argument, all entries from the specified table are
18445 displayed. An argument, which should be an integer expression, means
18446 display a single entry whose index is given by the argument. For
18447 example, here's a convenient way to display information about the
18448 debugged program's data segment:
18451 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18452 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18456 This comes in handy when you want to see whether a pointer is outside
18457 the data segment's limit (i.e.@: @dfn{garbled}).
18459 @cindex page tables display (MS-DOS)
18461 @itemx info dos pte
18462 These two commands display entries from, respectively, the Page
18463 Directory and the Page Tables. Page Directories and Page Tables are
18464 data structures which control how virtual memory addresses are mapped
18465 into physical addresses. A Page Table includes an entry for every
18466 page of memory that is mapped into the program's address space; there
18467 may be several Page Tables, each one holding up to 4096 entries. A
18468 Page Directory has up to 4096 entries, one each for every Page Table
18469 that is currently in use.
18471 Without an argument, @kbd{info dos pde} displays the entire Page
18472 Directory, and @kbd{info dos pte} displays all the entries in all of
18473 the Page Tables. An argument, an integer expression, given to the
18474 @kbd{info dos pde} command means display only that entry from the Page
18475 Directory table. An argument given to the @kbd{info dos pte} command
18476 means display entries from a single Page Table, the one pointed to by
18477 the specified entry in the Page Directory.
18479 @cindex direct memory access (DMA) on MS-DOS
18480 These commands are useful when your program uses @dfn{DMA} (Direct
18481 Memory Access), which needs physical addresses to program the DMA
18484 These commands are supported only with some DPMI servers.
18486 @cindex physical address from linear address
18487 @item info dos address-pte @var{addr}
18488 This command displays the Page Table entry for a specified linear
18489 address. The argument @var{addr} is a linear address which should
18490 already have the appropriate segment's base address added to it,
18491 because this command accepts addresses which may belong to @emph{any}
18492 segment. For example, here's how to display the Page Table entry for
18493 the page where a variable @code{i} is stored:
18496 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18497 @exdent @code{Page Table entry for address 0x11a00d30:}
18498 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18502 This says that @code{i} is stored at offset @code{0xd30} from the page
18503 whose physical base address is @code{0x02698000}, and shows all the
18504 attributes of that page.
18506 Note that you must cast the addresses of variables to a @code{char *},
18507 since otherwise the value of @code{__djgpp_base_address}, the base
18508 address of all variables and functions in a @sc{djgpp} program, will
18509 be added using the rules of C pointer arithmetics: if @code{i} is
18510 declared an @code{int}, @value{GDBN} will add 4 times the value of
18511 @code{__djgpp_base_address} to the address of @code{i}.
18513 Here's another example, it displays the Page Table entry for the
18517 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18518 @exdent @code{Page Table entry for address 0x29110:}
18519 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18523 (The @code{+ 3} offset is because the transfer buffer's address is the
18524 3rd member of the @code{_go32_info_block} structure.) The output
18525 clearly shows that this DPMI server maps the addresses in conventional
18526 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18527 linear (@code{0x29110}) addresses are identical.
18529 This command is supported only with some DPMI servers.
18532 @cindex DOS serial data link, remote debugging
18533 In addition to native debugging, the DJGPP port supports remote
18534 debugging via a serial data link. The following commands are specific
18535 to remote serial debugging in the DJGPP port of @value{GDBN}.
18538 @kindex set com1base
18539 @kindex set com1irq
18540 @kindex set com2base
18541 @kindex set com2irq
18542 @kindex set com3base
18543 @kindex set com3irq
18544 @kindex set com4base
18545 @kindex set com4irq
18546 @item set com1base @var{addr}
18547 This command sets the base I/O port address of the @file{COM1} serial
18550 @item set com1irq @var{irq}
18551 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18552 for the @file{COM1} serial port.
18554 There are similar commands @samp{set com2base}, @samp{set com3irq},
18555 etc.@: for setting the port address and the @code{IRQ} lines for the
18558 @kindex show com1base
18559 @kindex show com1irq
18560 @kindex show com2base
18561 @kindex show com2irq
18562 @kindex show com3base
18563 @kindex show com3irq
18564 @kindex show com4base
18565 @kindex show com4irq
18566 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18567 display the current settings of the base address and the @code{IRQ}
18568 lines used by the COM ports.
18571 @kindex info serial
18572 @cindex DOS serial port status
18573 This command prints the status of the 4 DOS serial ports. For each
18574 port, it prints whether it's active or not, its I/O base address and
18575 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18576 counts of various errors encountered so far.
18580 @node Cygwin Native
18581 @subsection Features for Debugging MS Windows PE Executables
18582 @cindex MS Windows debugging
18583 @cindex native Cygwin debugging
18584 @cindex Cygwin-specific commands
18586 @value{GDBN} supports native debugging of MS Windows programs, including
18587 DLLs with and without symbolic debugging information.
18589 @cindex Ctrl-BREAK, MS-Windows
18590 @cindex interrupt debuggee on MS-Windows
18591 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18592 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18593 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18594 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18595 sequence, which can be used to interrupt the debuggee even if it
18598 There are various additional Cygwin-specific commands, described in
18599 this section. Working with DLLs that have no debugging symbols is
18600 described in @ref{Non-debug DLL Symbols}.
18605 This is a prefix of MS Windows-specific commands which print
18606 information about the target system and important OS structures.
18608 @item info w32 selector
18609 This command displays information returned by
18610 the Win32 API @code{GetThreadSelectorEntry} function.
18611 It takes an optional argument that is evaluated to
18612 a long value to give the information about this given selector.
18613 Without argument, this command displays information
18614 about the six segment registers.
18616 @item info w32 thread-information-block
18617 This command displays thread specific information stored in the
18618 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18619 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18623 This is a Cygwin-specific alias of @code{info shared}.
18625 @kindex dll-symbols
18627 This command loads symbols from a dll similarly to
18628 add-sym command but without the need to specify a base address.
18630 @kindex set cygwin-exceptions
18631 @cindex debugging the Cygwin DLL
18632 @cindex Cygwin DLL, debugging
18633 @item set cygwin-exceptions @var{mode}
18634 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18635 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18636 @value{GDBN} will delay recognition of exceptions, and may ignore some
18637 exceptions which seem to be caused by internal Cygwin DLL
18638 ``bookkeeping''. This option is meant primarily for debugging the
18639 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18640 @value{GDBN} users with false @code{SIGSEGV} signals.
18642 @kindex show cygwin-exceptions
18643 @item show cygwin-exceptions
18644 Displays whether @value{GDBN} will break on exceptions that happen
18645 inside the Cygwin DLL itself.
18647 @kindex set new-console
18648 @item set new-console @var{mode}
18649 If @var{mode} is @code{on} the debuggee will
18650 be started in a new console on next start.
18651 If @var{mode} is @code{off}, the debuggee will
18652 be started in the same console as the debugger.
18654 @kindex show new-console
18655 @item show new-console
18656 Displays whether a new console is used
18657 when the debuggee is started.
18659 @kindex set new-group
18660 @item set new-group @var{mode}
18661 This boolean value controls whether the debuggee should
18662 start a new group or stay in the same group as the debugger.
18663 This affects the way the Windows OS handles
18666 @kindex show new-group
18667 @item show new-group
18668 Displays current value of new-group boolean.
18670 @kindex set debugevents
18671 @item set debugevents
18672 This boolean value adds debug output concerning kernel events related
18673 to the debuggee seen by the debugger. This includes events that
18674 signal thread and process creation and exit, DLL loading and
18675 unloading, console interrupts, and debugging messages produced by the
18676 Windows @code{OutputDebugString} API call.
18678 @kindex set debugexec
18679 @item set debugexec
18680 This boolean value adds debug output concerning execute events
18681 (such as resume thread) seen by the debugger.
18683 @kindex set debugexceptions
18684 @item set debugexceptions
18685 This boolean value adds debug output concerning exceptions in the
18686 debuggee seen by the debugger.
18688 @kindex set debugmemory
18689 @item set debugmemory
18690 This boolean value adds debug output concerning debuggee memory reads
18691 and writes by the debugger.
18695 This boolean values specifies whether the debuggee is called
18696 via a shell or directly (default value is on).
18700 Displays if the debuggee will be started with a shell.
18705 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18708 @node Non-debug DLL Symbols
18709 @subsubsection Support for DLLs without Debugging Symbols
18710 @cindex DLLs with no debugging symbols
18711 @cindex Minimal symbols and DLLs
18713 Very often on windows, some of the DLLs that your program relies on do
18714 not include symbolic debugging information (for example,
18715 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18716 symbols in a DLL, it relies on the minimal amount of symbolic
18717 information contained in the DLL's export table. This section
18718 describes working with such symbols, known internally to @value{GDBN} as
18719 ``minimal symbols''.
18721 Note that before the debugged program has started execution, no DLLs
18722 will have been loaded. The easiest way around this problem is simply to
18723 start the program --- either by setting a breakpoint or letting the
18724 program run once to completion. It is also possible to force
18725 @value{GDBN} to load a particular DLL before starting the executable ---
18726 see the shared library information in @ref{Files}, or the
18727 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18728 explicitly loading symbols from a DLL with no debugging information will
18729 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18730 which may adversely affect symbol lookup performance.
18732 @subsubsection DLL Name Prefixes
18734 In keeping with the naming conventions used by the Microsoft debugging
18735 tools, DLL export symbols are made available with a prefix based on the
18736 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18737 also entered into the symbol table, so @code{CreateFileA} is often
18738 sufficient. In some cases there will be name clashes within a program
18739 (particularly if the executable itself includes full debugging symbols)
18740 necessitating the use of the fully qualified name when referring to the
18741 contents of the DLL. Use single-quotes around the name to avoid the
18742 exclamation mark (``!'') being interpreted as a language operator.
18744 Note that the internal name of the DLL may be all upper-case, even
18745 though the file name of the DLL is lower-case, or vice-versa. Since
18746 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18747 some confusion. If in doubt, try the @code{info functions} and
18748 @code{info variables} commands or even @code{maint print msymbols}
18749 (@pxref{Symbols}). Here's an example:
18752 (@value{GDBP}) info function CreateFileA
18753 All functions matching regular expression "CreateFileA":
18755 Non-debugging symbols:
18756 0x77e885f4 CreateFileA
18757 0x77e885f4 KERNEL32!CreateFileA
18761 (@value{GDBP}) info function !
18762 All functions matching regular expression "!":
18764 Non-debugging symbols:
18765 0x6100114c cygwin1!__assert
18766 0x61004034 cygwin1!_dll_crt0@@0
18767 0x61004240 cygwin1!dll_crt0(per_process *)
18771 @subsubsection Working with Minimal Symbols
18773 Symbols extracted from a DLL's export table do not contain very much
18774 type information. All that @value{GDBN} can do is guess whether a symbol
18775 refers to a function or variable depending on the linker section that
18776 contains the symbol. Also note that the actual contents of the memory
18777 contained in a DLL are not available unless the program is running. This
18778 means that you cannot examine the contents of a variable or disassemble
18779 a function within a DLL without a running program.
18781 Variables are generally treated as pointers and dereferenced
18782 automatically. For this reason, it is often necessary to prefix a
18783 variable name with the address-of operator (``&'') and provide explicit
18784 type information in the command. Here's an example of the type of
18788 (@value{GDBP}) print 'cygwin1!__argv'
18793 (@value{GDBP}) x 'cygwin1!__argv'
18794 0x10021610: "\230y\""
18797 And two possible solutions:
18800 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18801 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18805 (@value{GDBP}) x/2x &'cygwin1!__argv'
18806 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18807 (@value{GDBP}) x/x 0x10021608
18808 0x10021608: 0x0022fd98
18809 (@value{GDBP}) x/s 0x0022fd98
18810 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18813 Setting a break point within a DLL is possible even before the program
18814 starts execution. However, under these circumstances, @value{GDBN} can't
18815 examine the initial instructions of the function in order to skip the
18816 function's frame set-up code. You can work around this by using ``*&''
18817 to set the breakpoint at a raw memory address:
18820 (@value{GDBP}) break *&'python22!PyOS_Readline'
18821 Breakpoint 1 at 0x1e04eff0
18824 The author of these extensions is not entirely convinced that setting a
18825 break point within a shared DLL like @file{kernel32.dll} is completely
18829 @subsection Commands Specific to @sc{gnu} Hurd Systems
18830 @cindex @sc{gnu} Hurd debugging
18832 This subsection describes @value{GDBN} commands specific to the
18833 @sc{gnu} Hurd native debugging.
18838 @kindex set signals@r{, Hurd command}
18839 @kindex set sigs@r{, Hurd command}
18840 This command toggles the state of inferior signal interception by
18841 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18842 affected by this command. @code{sigs} is a shorthand alias for
18847 @kindex show signals@r{, Hurd command}
18848 @kindex show sigs@r{, Hurd command}
18849 Show the current state of intercepting inferior's signals.
18851 @item set signal-thread
18852 @itemx set sigthread
18853 @kindex set signal-thread
18854 @kindex set sigthread
18855 This command tells @value{GDBN} which thread is the @code{libc} signal
18856 thread. That thread is run when a signal is delivered to a running
18857 process. @code{set sigthread} is the shorthand alias of @code{set
18860 @item show signal-thread
18861 @itemx show sigthread
18862 @kindex show signal-thread
18863 @kindex show sigthread
18864 These two commands show which thread will run when the inferior is
18865 delivered a signal.
18868 @kindex set stopped@r{, Hurd command}
18869 This commands tells @value{GDBN} that the inferior process is stopped,
18870 as with the @code{SIGSTOP} signal. The stopped process can be
18871 continued by delivering a signal to it.
18874 @kindex show stopped@r{, Hurd command}
18875 This command shows whether @value{GDBN} thinks the debuggee is
18878 @item set exceptions
18879 @kindex set exceptions@r{, Hurd command}
18880 Use this command to turn off trapping of exceptions in the inferior.
18881 When exception trapping is off, neither breakpoints nor
18882 single-stepping will work. To restore the default, set exception
18885 @item show exceptions
18886 @kindex show exceptions@r{, Hurd command}
18887 Show the current state of trapping exceptions in the inferior.
18889 @item set task pause
18890 @kindex set task@r{, Hurd commands}
18891 @cindex task attributes (@sc{gnu} Hurd)
18892 @cindex pause current task (@sc{gnu} Hurd)
18893 This command toggles task suspension when @value{GDBN} has control.
18894 Setting it to on takes effect immediately, and the task is suspended
18895 whenever @value{GDBN} gets control. Setting it to off will take
18896 effect the next time the inferior is continued. If this option is set
18897 to off, you can use @code{set thread default pause on} or @code{set
18898 thread pause on} (see below) to pause individual threads.
18900 @item show task pause
18901 @kindex show task@r{, Hurd commands}
18902 Show the current state of task suspension.
18904 @item set task detach-suspend-count
18905 @cindex task suspend count
18906 @cindex detach from task, @sc{gnu} Hurd
18907 This command sets the suspend count the task will be left with when
18908 @value{GDBN} detaches from it.
18910 @item show task detach-suspend-count
18911 Show the suspend count the task will be left with when detaching.
18913 @item set task exception-port
18914 @itemx set task excp
18915 @cindex task exception port, @sc{gnu} Hurd
18916 This command sets the task exception port to which @value{GDBN} will
18917 forward exceptions. The argument should be the value of the @dfn{send
18918 rights} of the task. @code{set task excp} is a shorthand alias.
18920 @item set noninvasive
18921 @cindex noninvasive task options
18922 This command switches @value{GDBN} to a mode that is the least
18923 invasive as far as interfering with the inferior is concerned. This
18924 is the same as using @code{set task pause}, @code{set exceptions}, and
18925 @code{set signals} to values opposite to the defaults.
18927 @item info send-rights
18928 @itemx info receive-rights
18929 @itemx info port-rights
18930 @itemx info port-sets
18931 @itemx info dead-names
18934 @cindex send rights, @sc{gnu} Hurd
18935 @cindex receive rights, @sc{gnu} Hurd
18936 @cindex port rights, @sc{gnu} Hurd
18937 @cindex port sets, @sc{gnu} Hurd
18938 @cindex dead names, @sc{gnu} Hurd
18939 These commands display information about, respectively, send rights,
18940 receive rights, port rights, port sets, and dead names of a task.
18941 There are also shorthand aliases: @code{info ports} for @code{info
18942 port-rights} and @code{info psets} for @code{info port-sets}.
18944 @item set thread pause
18945 @kindex set thread@r{, Hurd command}
18946 @cindex thread properties, @sc{gnu} Hurd
18947 @cindex pause current thread (@sc{gnu} Hurd)
18948 This command toggles current thread suspension when @value{GDBN} has
18949 control. Setting it to on takes effect immediately, and the current
18950 thread is suspended whenever @value{GDBN} gets control. Setting it to
18951 off will take effect the next time the inferior is continued.
18952 Normally, this command has no effect, since when @value{GDBN} has
18953 control, the whole task is suspended. However, if you used @code{set
18954 task pause off} (see above), this command comes in handy to suspend
18955 only the current thread.
18957 @item show thread pause
18958 @kindex show thread@r{, Hurd command}
18959 This command shows the state of current thread suspension.
18961 @item set thread run
18962 This command sets whether the current thread is allowed to run.
18964 @item show thread run
18965 Show whether the current thread is allowed to run.
18967 @item set thread detach-suspend-count
18968 @cindex thread suspend count, @sc{gnu} Hurd
18969 @cindex detach from thread, @sc{gnu} Hurd
18970 This command sets the suspend count @value{GDBN} will leave on a
18971 thread when detaching. This number is relative to the suspend count
18972 found by @value{GDBN} when it notices the thread; use @code{set thread
18973 takeover-suspend-count} to force it to an absolute value.
18975 @item show thread detach-suspend-count
18976 Show the suspend count @value{GDBN} will leave on the thread when
18979 @item set thread exception-port
18980 @itemx set thread excp
18981 Set the thread exception port to which to forward exceptions. This
18982 overrides the port set by @code{set task exception-port} (see above).
18983 @code{set thread excp} is the shorthand alias.
18985 @item set thread takeover-suspend-count
18986 Normally, @value{GDBN}'s thread suspend counts are relative to the
18987 value @value{GDBN} finds when it notices each thread. This command
18988 changes the suspend counts to be absolute instead.
18990 @item set thread default
18991 @itemx show thread default
18992 @cindex thread default settings, @sc{gnu} Hurd
18993 Each of the above @code{set thread} commands has a @code{set thread
18994 default} counterpart (e.g., @code{set thread default pause}, @code{set
18995 thread default exception-port}, etc.). The @code{thread default}
18996 variety of commands sets the default thread properties for all
18997 threads; you can then change the properties of individual threads with
18998 the non-default commands.
19003 @subsection QNX Neutrino
19004 @cindex QNX Neutrino
19006 @value{GDBN} provides the following commands specific to the QNX
19010 @item set debug nto-debug
19011 @kindex set debug nto-debug
19012 When set to on, enables debugging messages specific to the QNX
19015 @item show debug nto-debug
19016 @kindex show debug nto-debug
19017 Show the current state of QNX Neutrino messages.
19024 @value{GDBN} provides the following commands specific to the Darwin target:
19027 @item set debug darwin @var{num}
19028 @kindex set debug darwin
19029 When set to a non zero value, enables debugging messages specific to
19030 the Darwin support. Higher values produce more verbose output.
19032 @item show debug darwin
19033 @kindex show debug darwin
19034 Show the current state of Darwin messages.
19036 @item set debug mach-o @var{num}
19037 @kindex set debug mach-o
19038 When set to a non zero value, enables debugging messages while
19039 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19040 file format used on Darwin for object and executable files.) Higher
19041 values produce more verbose output. This is a command to diagnose
19042 problems internal to @value{GDBN} and should not be needed in normal
19045 @item show debug mach-o
19046 @kindex show debug mach-o
19047 Show the current state of Mach-O file messages.
19049 @item set mach-exceptions on
19050 @itemx set mach-exceptions off
19051 @kindex set mach-exceptions
19052 On Darwin, faults are first reported as a Mach exception and are then
19053 mapped to a Posix signal. Use this command to turn on trapping of
19054 Mach exceptions in the inferior. This might be sometimes useful to
19055 better understand the cause of a fault. The default is off.
19057 @item show mach-exceptions
19058 @kindex show mach-exceptions
19059 Show the current state of exceptions trapping.
19064 @section Embedded Operating Systems
19066 This section describes configurations involving the debugging of
19067 embedded operating systems that are available for several different
19071 * VxWorks:: Using @value{GDBN} with VxWorks
19074 @value{GDBN} includes the ability to debug programs running on
19075 various real-time operating systems.
19078 @subsection Using @value{GDBN} with VxWorks
19084 @kindex target vxworks
19085 @item target vxworks @var{machinename}
19086 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19087 is the target system's machine name or IP address.
19091 On VxWorks, @code{load} links @var{filename} dynamically on the
19092 current target system as well as adding its symbols in @value{GDBN}.
19094 @value{GDBN} enables developers to spawn and debug tasks running on networked
19095 VxWorks targets from a Unix host. Already-running tasks spawned from
19096 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19097 both the Unix host and on the VxWorks target. The program
19098 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19099 installed with the name @code{vxgdb}, to distinguish it from a
19100 @value{GDBN} for debugging programs on the host itself.)
19103 @item VxWorks-timeout @var{args}
19104 @kindex vxworks-timeout
19105 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19106 This option is set by the user, and @var{args} represents the number of
19107 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19108 your VxWorks target is a slow software simulator or is on the far side
19109 of a thin network line.
19112 The following information on connecting to VxWorks was current when
19113 this manual was produced; newer releases of VxWorks may use revised
19116 @findex INCLUDE_RDB
19117 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19118 to include the remote debugging interface routines in the VxWorks
19119 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19120 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19121 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19122 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19123 information on configuring and remaking VxWorks, see the manufacturer's
19125 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19127 Once you have included @file{rdb.a} in your VxWorks system image and set
19128 your Unix execution search path to find @value{GDBN}, you are ready to
19129 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19130 @code{vxgdb}, depending on your installation).
19132 @value{GDBN} comes up showing the prompt:
19139 * VxWorks Connection:: Connecting to VxWorks
19140 * VxWorks Download:: VxWorks download
19141 * VxWorks Attach:: Running tasks
19144 @node VxWorks Connection
19145 @subsubsection Connecting to VxWorks
19147 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19148 network. To connect to a target whose host name is ``@code{tt}'', type:
19151 (vxgdb) target vxworks tt
19155 @value{GDBN} displays messages like these:
19158 Attaching remote machine across net...
19163 @value{GDBN} then attempts to read the symbol tables of any object modules
19164 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19165 these files by searching the directories listed in the command search
19166 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19167 to find an object file, it displays a message such as:
19170 prog.o: No such file or directory.
19173 When this happens, add the appropriate directory to the search path with
19174 the @value{GDBN} command @code{path}, and execute the @code{target}
19177 @node VxWorks Download
19178 @subsubsection VxWorks Download
19180 @cindex download to VxWorks
19181 If you have connected to the VxWorks target and you want to debug an
19182 object that has not yet been loaded, you can use the @value{GDBN}
19183 @code{load} command to download a file from Unix to VxWorks
19184 incrementally. The object file given as an argument to the @code{load}
19185 command is actually opened twice: first by the VxWorks target in order
19186 to download the code, then by @value{GDBN} in order to read the symbol
19187 table. This can lead to problems if the current working directories on
19188 the two systems differ. If both systems have NFS mounted the same
19189 filesystems, you can avoid these problems by using absolute paths.
19190 Otherwise, it is simplest to set the working directory on both systems
19191 to the directory in which the object file resides, and then to reference
19192 the file by its name, without any path. For instance, a program
19193 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19194 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19195 program, type this on VxWorks:
19198 -> cd "@var{vxpath}/vw/demo/rdb"
19202 Then, in @value{GDBN}, type:
19205 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19206 (vxgdb) load prog.o
19209 @value{GDBN} displays a response similar to this:
19212 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19215 You can also use the @code{load} command to reload an object module
19216 after editing and recompiling the corresponding source file. Note that
19217 this makes @value{GDBN} delete all currently-defined breakpoints,
19218 auto-displays, and convenience variables, and to clear the value
19219 history. (This is necessary in order to preserve the integrity of
19220 debugger's data structures that reference the target system's symbol
19223 @node VxWorks Attach
19224 @subsubsection Running Tasks
19226 @cindex running VxWorks tasks
19227 You can also attach to an existing task using the @code{attach} command as
19231 (vxgdb) attach @var{task}
19235 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19236 or suspended when you attach to it. Running tasks are suspended at
19237 the time of attachment.
19239 @node Embedded Processors
19240 @section Embedded Processors
19242 This section goes into details specific to particular embedded
19245 @cindex send command to simulator
19246 Whenever a specific embedded processor has a simulator, @value{GDBN}
19247 allows to send an arbitrary command to the simulator.
19250 @item sim @var{command}
19251 @kindex sim@r{, a command}
19252 Send an arbitrary @var{command} string to the simulator. Consult the
19253 documentation for the specific simulator in use for information about
19254 acceptable commands.
19260 * M32R/D:: Renesas M32R/D
19261 * M68K:: Motorola M68K
19262 * MicroBlaze:: Xilinx MicroBlaze
19263 * MIPS Embedded:: MIPS Embedded
19264 * OpenRISC 1000:: OpenRisc 1000
19265 * PA:: HP PA Embedded
19266 * PowerPC Embedded:: PowerPC Embedded
19267 * Sparclet:: Tsqware Sparclet
19268 * Sparclite:: Fujitsu Sparclite
19269 * Z8000:: Zilog Z8000
19272 * Super-H:: Renesas Super-H
19281 @item target rdi @var{dev}
19282 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19283 use this target to communicate with both boards running the Angel
19284 monitor, or with the EmbeddedICE JTAG debug device.
19287 @item target rdp @var{dev}
19292 @value{GDBN} provides the following ARM-specific commands:
19295 @item set arm disassembler
19297 This commands selects from a list of disassembly styles. The
19298 @code{"std"} style is the standard style.
19300 @item show arm disassembler
19302 Show the current disassembly style.
19304 @item set arm apcs32
19305 @cindex ARM 32-bit mode
19306 This command toggles ARM operation mode between 32-bit and 26-bit.
19308 @item show arm apcs32
19309 Display the current usage of the ARM 32-bit mode.
19311 @item set arm fpu @var{fputype}
19312 This command sets the ARM floating-point unit (FPU) type. The
19313 argument @var{fputype} can be one of these:
19317 Determine the FPU type by querying the OS ABI.
19319 Software FPU, with mixed-endian doubles on little-endian ARM
19322 GCC-compiled FPA co-processor.
19324 Software FPU with pure-endian doubles.
19330 Show the current type of the FPU.
19333 This command forces @value{GDBN} to use the specified ABI.
19336 Show the currently used ABI.
19338 @item set arm fallback-mode (arm|thumb|auto)
19339 @value{GDBN} uses the symbol table, when available, to determine
19340 whether instructions are ARM or Thumb. This command controls
19341 @value{GDBN}'s default behavior when the symbol table is not
19342 available. The default is @samp{auto}, which causes @value{GDBN} to
19343 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19346 @item show arm fallback-mode
19347 Show the current fallback instruction mode.
19349 @item set arm force-mode (arm|thumb|auto)
19350 This command overrides use of the symbol table to determine whether
19351 instructions are ARM or Thumb. The default is @samp{auto}, which
19352 causes @value{GDBN} to use the symbol table and then the setting
19353 of @samp{set arm fallback-mode}.
19355 @item show arm force-mode
19356 Show the current forced instruction mode.
19358 @item set debug arm
19359 Toggle whether to display ARM-specific debugging messages from the ARM
19360 target support subsystem.
19362 @item show debug arm
19363 Show whether ARM-specific debugging messages are enabled.
19366 The following commands are available when an ARM target is debugged
19367 using the RDI interface:
19370 @item rdilogfile @r{[}@var{file}@r{]}
19372 @cindex ADP (Angel Debugger Protocol) logging
19373 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19374 With an argument, sets the log file to the specified @var{file}. With
19375 no argument, show the current log file name. The default log file is
19378 @item rdilogenable @r{[}@var{arg}@r{]}
19379 @kindex rdilogenable
19380 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19381 enables logging, with an argument 0 or @code{"no"} disables it. With
19382 no arguments displays the current setting. When logging is enabled,
19383 ADP packets exchanged between @value{GDBN} and the RDI target device
19384 are logged to a file.
19386 @item set rdiromatzero
19387 @kindex set rdiromatzero
19388 @cindex ROM at zero address, RDI
19389 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19390 vector catching is disabled, so that zero address can be used. If off
19391 (the default), vector catching is enabled. For this command to take
19392 effect, it needs to be invoked prior to the @code{target rdi} command.
19394 @item show rdiromatzero
19395 @kindex show rdiromatzero
19396 Show the current setting of ROM at zero address.
19398 @item set rdiheartbeat
19399 @kindex set rdiheartbeat
19400 @cindex RDI heartbeat
19401 Enable or disable RDI heartbeat packets. It is not recommended to
19402 turn on this option, since it confuses ARM and EPI JTAG interface, as
19403 well as the Angel monitor.
19405 @item show rdiheartbeat
19406 @kindex show rdiheartbeat
19407 Show the setting of RDI heartbeat packets.
19411 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19412 The @value{GDBN} ARM simulator accepts the following optional arguments.
19415 @item --swi-support=@var{type}
19416 Tell the simulator which SWI interfaces to support.
19417 @var{type} may be a comma separated list of the following values.
19418 The default value is @code{all}.
19431 @subsection Renesas M32R/D and M32R/SDI
19434 @kindex target m32r
19435 @item target m32r @var{dev}
19436 Renesas M32R/D ROM monitor.
19438 @kindex target m32rsdi
19439 @item target m32rsdi @var{dev}
19440 Renesas M32R SDI server, connected via parallel port to the board.
19443 The following @value{GDBN} commands are specific to the M32R monitor:
19446 @item set download-path @var{path}
19447 @kindex set download-path
19448 @cindex find downloadable @sc{srec} files (M32R)
19449 Set the default path for finding downloadable @sc{srec} files.
19451 @item show download-path
19452 @kindex show download-path
19453 Show the default path for downloadable @sc{srec} files.
19455 @item set board-address @var{addr}
19456 @kindex set board-address
19457 @cindex M32-EVA target board address
19458 Set the IP address for the M32R-EVA target board.
19460 @item show board-address
19461 @kindex show board-address
19462 Show the current IP address of the target board.
19464 @item set server-address @var{addr}
19465 @kindex set server-address
19466 @cindex download server address (M32R)
19467 Set the IP address for the download server, which is the @value{GDBN}'s
19470 @item show server-address
19471 @kindex show server-address
19472 Display the IP address of the download server.
19474 @item upload @r{[}@var{file}@r{]}
19475 @kindex upload@r{, M32R}
19476 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19477 upload capability. If no @var{file} argument is given, the current
19478 executable file is uploaded.
19480 @item tload @r{[}@var{file}@r{]}
19481 @kindex tload@r{, M32R}
19482 Test the @code{upload} command.
19485 The following commands are available for M32R/SDI:
19490 @cindex reset SDI connection, M32R
19491 This command resets the SDI connection.
19495 This command shows the SDI connection status.
19498 @kindex debug_chaos
19499 @cindex M32R/Chaos debugging
19500 Instructs the remote that M32R/Chaos debugging is to be used.
19502 @item use_debug_dma
19503 @kindex use_debug_dma
19504 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19507 @kindex use_mon_code
19508 Instructs the remote to use the MON_CODE method of accessing memory.
19511 @kindex use_ib_break
19512 Instructs the remote to set breakpoints by IB break.
19514 @item use_dbt_break
19515 @kindex use_dbt_break
19516 Instructs the remote to set breakpoints by DBT.
19522 The Motorola m68k configuration includes ColdFire support, and a
19523 target command for the following ROM monitor.
19527 @kindex target dbug
19528 @item target dbug @var{dev}
19529 dBUG ROM monitor for Motorola ColdFire.
19534 @subsection MicroBlaze
19535 @cindex Xilinx MicroBlaze
19536 @cindex XMD, Xilinx Microprocessor Debugger
19538 The MicroBlaze is a soft-core processor supported on various Xilinx
19539 FPGAs, such as Spartan or Virtex series. Boards with these processors
19540 usually have JTAG ports which connect to a host system running the Xilinx
19541 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19542 This host system is used to download the configuration bitstream to
19543 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19544 communicates with the target board using the JTAG interface and
19545 presents a @code{gdbserver} interface to the board. By default
19546 @code{xmd} uses port @code{1234}. (While it is possible to change
19547 this default port, it requires the use of undocumented @code{xmd}
19548 commands. Contact Xilinx support if you need to do this.)
19550 Use these GDB commands to connect to the MicroBlaze target processor.
19553 @item target remote :1234
19554 Use this command to connect to the target if you are running @value{GDBN}
19555 on the same system as @code{xmd}.
19557 @item target remote @var{xmd-host}:1234
19558 Use this command to connect to the target if it is connected to @code{xmd}
19559 running on a different system named @var{xmd-host}.
19562 Use this command to download a program to the MicroBlaze target.
19564 @item set debug microblaze @var{n}
19565 Enable MicroBlaze-specific debugging messages if non-zero.
19567 @item show debug microblaze @var{n}
19568 Show MicroBlaze-specific debugging level.
19571 @node MIPS Embedded
19572 @subsection MIPS Embedded
19574 @cindex MIPS boards
19575 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19576 MIPS board attached to a serial line. This is available when
19577 you configure @value{GDBN} with @samp{--target=mips-elf}.
19580 Use these @value{GDBN} commands to specify the connection to your target board:
19583 @item target mips @var{port}
19584 @kindex target mips @var{port}
19585 To run a program on the board, start up @code{@value{GDBP}} with the
19586 name of your program as the argument. To connect to the board, use the
19587 command @samp{target mips @var{port}}, where @var{port} is the name of
19588 the serial port connected to the board. If the program has not already
19589 been downloaded to the board, you may use the @code{load} command to
19590 download it. You can then use all the usual @value{GDBN} commands.
19592 For example, this sequence connects to the target board through a serial
19593 port, and loads and runs a program called @var{prog} through the
19597 host$ @value{GDBP} @var{prog}
19598 @value{GDBN} is free software and @dots{}
19599 (@value{GDBP}) target mips /dev/ttyb
19600 (@value{GDBP}) load @var{prog}
19604 @item target mips @var{hostname}:@var{portnumber}
19605 On some @value{GDBN} host configurations, you can specify a TCP
19606 connection (for instance, to a serial line managed by a terminal
19607 concentrator) instead of a serial port, using the syntax
19608 @samp{@var{hostname}:@var{portnumber}}.
19610 @item target pmon @var{port}
19611 @kindex target pmon @var{port}
19614 @item target ddb @var{port}
19615 @kindex target ddb @var{port}
19616 NEC's DDB variant of PMON for Vr4300.
19618 @item target lsi @var{port}
19619 @kindex target lsi @var{port}
19620 LSI variant of PMON.
19622 @kindex target r3900
19623 @item target r3900 @var{dev}
19624 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19626 @kindex target array
19627 @item target array @var{dev}
19628 Array Tech LSI33K RAID controller board.
19634 @value{GDBN} also supports these special commands for MIPS targets:
19637 @item set mipsfpu double
19638 @itemx set mipsfpu single
19639 @itemx set mipsfpu none
19640 @itemx set mipsfpu auto
19641 @itemx show mipsfpu
19642 @kindex set mipsfpu
19643 @kindex show mipsfpu
19644 @cindex MIPS remote floating point
19645 @cindex floating point, MIPS remote
19646 If your target board does not support the MIPS floating point
19647 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19648 need this, you may wish to put the command in your @value{GDBN} init
19649 file). This tells @value{GDBN} how to find the return value of
19650 functions which return floating point values. It also allows
19651 @value{GDBN} to avoid saving the floating point registers when calling
19652 functions on the board. If you are using a floating point coprocessor
19653 with only single precision floating point support, as on the @sc{r4650}
19654 processor, use the command @samp{set mipsfpu single}. The default
19655 double precision floating point coprocessor may be selected using
19656 @samp{set mipsfpu double}.
19658 In previous versions the only choices were double precision or no
19659 floating point, so @samp{set mipsfpu on} will select double precision
19660 and @samp{set mipsfpu off} will select no floating point.
19662 As usual, you can inquire about the @code{mipsfpu} variable with
19663 @samp{show mipsfpu}.
19665 @item set timeout @var{seconds}
19666 @itemx set retransmit-timeout @var{seconds}
19667 @itemx show timeout
19668 @itemx show retransmit-timeout
19669 @cindex @code{timeout}, MIPS protocol
19670 @cindex @code{retransmit-timeout}, MIPS protocol
19671 @kindex set timeout
19672 @kindex show timeout
19673 @kindex set retransmit-timeout
19674 @kindex show retransmit-timeout
19675 You can control the timeout used while waiting for a packet, in the MIPS
19676 remote protocol, with the @code{set timeout @var{seconds}} command. The
19677 default is 5 seconds. Similarly, you can control the timeout used while
19678 waiting for an acknowledgment of a packet with the @code{set
19679 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19680 You can inspect both values with @code{show timeout} and @code{show
19681 retransmit-timeout}. (These commands are @emph{only} available when
19682 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19684 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19685 is waiting for your program to stop. In that case, @value{GDBN} waits
19686 forever because it has no way of knowing how long the program is going
19687 to run before stopping.
19689 @item set syn-garbage-limit @var{num}
19690 @kindex set syn-garbage-limit@r{, MIPS remote}
19691 @cindex synchronize with remote MIPS target
19692 Limit the maximum number of characters @value{GDBN} should ignore when
19693 it tries to synchronize with the remote target. The default is 10
19694 characters. Setting the limit to -1 means there's no limit.
19696 @item show syn-garbage-limit
19697 @kindex show syn-garbage-limit@r{, MIPS remote}
19698 Show the current limit on the number of characters to ignore when
19699 trying to synchronize with the remote system.
19701 @item set monitor-prompt @var{prompt}
19702 @kindex set monitor-prompt@r{, MIPS remote}
19703 @cindex remote monitor prompt
19704 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19705 remote monitor. The default depends on the target:
19715 @item show monitor-prompt
19716 @kindex show monitor-prompt@r{, MIPS remote}
19717 Show the current strings @value{GDBN} expects as the prompt from the
19720 @item set monitor-warnings
19721 @kindex set monitor-warnings@r{, MIPS remote}
19722 Enable or disable monitor warnings about hardware breakpoints. This
19723 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19724 display warning messages whose codes are returned by the @code{lsi}
19725 PMON monitor for breakpoint commands.
19727 @item show monitor-warnings
19728 @kindex show monitor-warnings@r{, MIPS remote}
19729 Show the current setting of printing monitor warnings.
19731 @item pmon @var{command}
19732 @kindex pmon@r{, MIPS remote}
19733 @cindex send PMON command
19734 This command allows sending an arbitrary @var{command} string to the
19735 monitor. The monitor must be in debug mode for this to work.
19738 @node OpenRISC 1000
19739 @subsection OpenRISC 1000
19740 @cindex OpenRISC 1000
19742 @cindex or1k boards
19743 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19744 about platform and commands.
19748 @kindex target jtag
19749 @item target jtag jtag://@var{host}:@var{port}
19751 Connects to remote JTAG server.
19752 JTAG remote server can be either an or1ksim or JTAG server,
19753 connected via parallel port to the board.
19755 Example: @code{target jtag jtag://localhost:9999}
19758 @item or1ksim @var{command}
19759 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19760 Simulator, proprietary commands can be executed.
19762 @kindex info or1k spr
19763 @item info or1k spr
19764 Displays spr groups.
19766 @item info or1k spr @var{group}
19767 @itemx info or1k spr @var{groupno}
19768 Displays register names in selected group.
19770 @item info or1k spr @var{group} @var{register}
19771 @itemx info or1k spr @var{register}
19772 @itemx info or1k spr @var{groupno} @var{registerno}
19773 @itemx info or1k spr @var{registerno}
19774 Shows information about specified spr register.
19777 @item spr @var{group} @var{register} @var{value}
19778 @itemx spr @var{register @var{value}}
19779 @itemx spr @var{groupno} @var{registerno @var{value}}
19780 @itemx spr @var{registerno @var{value}}
19781 Writes @var{value} to specified spr register.
19784 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19785 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19786 program execution and is thus much faster. Hardware breakpoints/watchpoint
19787 triggers can be set using:
19790 Load effective address/data
19792 Store effective address/data
19794 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19799 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19800 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19802 @code{htrace} commands:
19803 @cindex OpenRISC 1000 htrace
19806 @item hwatch @var{conditional}
19807 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19808 or Data. For example:
19810 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19812 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19816 Display information about current HW trace configuration.
19818 @item htrace trigger @var{conditional}
19819 Set starting criteria for HW trace.
19821 @item htrace qualifier @var{conditional}
19822 Set acquisition qualifier for HW trace.
19824 @item htrace stop @var{conditional}
19825 Set HW trace stopping criteria.
19827 @item htrace record [@var{data}]*
19828 Selects the data to be recorded, when qualifier is met and HW trace was
19831 @item htrace enable
19832 @itemx htrace disable
19833 Enables/disables the HW trace.
19835 @item htrace rewind [@var{filename}]
19836 Clears currently recorded trace data.
19838 If filename is specified, new trace file is made and any newly collected data
19839 will be written there.
19841 @item htrace print [@var{start} [@var{len}]]
19842 Prints trace buffer, using current record configuration.
19844 @item htrace mode continuous
19845 Set continuous trace mode.
19847 @item htrace mode suspend
19848 Set suspend trace mode.
19852 @node PowerPC Embedded
19853 @subsection PowerPC Embedded
19855 @cindex DVC register
19856 @value{GDBN} supports using the DVC (Data Value Compare) register to
19857 implement in hardware simple hardware watchpoint conditions of the form:
19860 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19861 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19864 The DVC register will be automatically used when @value{GDBN} detects
19865 such pattern in a condition expression, and the created watchpoint uses one
19866 debug register (either the @code{exact-watchpoints} option is on and the
19867 variable is scalar, or the variable has a length of one byte). This feature
19868 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19871 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19872 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19873 in which case watchpoints using only one debug register are created when
19874 watching variables of scalar types.
19876 You can create an artificial array to watch an arbitrary memory
19877 region using one of the following commands (@pxref{Expressions}):
19880 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19881 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19884 PowerPC embedded processors support masked watchpoints. See the discussion
19885 about the @code{mask} argument in @ref{Set Watchpoints}.
19887 @cindex ranged breakpoint
19888 PowerPC embedded processors support hardware accelerated
19889 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19890 the inferior whenever it executes an instruction at any address within
19891 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19892 use the @code{break-range} command.
19894 @value{GDBN} provides the following PowerPC-specific commands:
19897 @kindex break-range
19898 @item break-range @var{start-location}, @var{end-location}
19899 Set a breakpoint for an address range.
19900 @var{start-location} and @var{end-location} can specify a function name,
19901 a line number, an offset of lines from the current line or from the start
19902 location, or an address of an instruction (see @ref{Specify Location},
19903 for a list of all the possible ways to specify a @var{location}.)
19904 The breakpoint will stop execution of the inferior whenever it
19905 executes an instruction at any address within the specified range,
19906 (including @var{start-location} and @var{end-location}.)
19908 @kindex set powerpc
19909 @item set powerpc soft-float
19910 @itemx show powerpc soft-float
19911 Force @value{GDBN} to use (or not use) a software floating point calling
19912 convention. By default, @value{GDBN} selects the calling convention based
19913 on the selected architecture and the provided executable file.
19915 @item set powerpc vector-abi
19916 @itemx show powerpc vector-abi
19917 Force @value{GDBN} to use the specified calling convention for vector
19918 arguments and return values. The valid options are @samp{auto};
19919 @samp{generic}, to avoid vector registers even if they are present;
19920 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19921 registers. By default, @value{GDBN} selects the calling convention
19922 based on the selected architecture and the provided executable file.
19924 @item set powerpc exact-watchpoints
19925 @itemx show powerpc exact-watchpoints
19926 Allow @value{GDBN} to use only one debug register when watching a variable
19927 of scalar type, thus assuming that the variable is accessed through the
19928 address of its first byte.
19930 @kindex target dink32
19931 @item target dink32 @var{dev}
19932 DINK32 ROM monitor.
19934 @kindex target ppcbug
19935 @item target ppcbug @var{dev}
19936 @kindex target ppcbug1
19937 @item target ppcbug1 @var{dev}
19938 PPCBUG ROM monitor for PowerPC.
19941 @item target sds @var{dev}
19942 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19945 @cindex SDS protocol
19946 The following commands specific to the SDS protocol are supported
19950 @item set sdstimeout @var{nsec}
19951 @kindex set sdstimeout
19952 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19953 default is 2 seconds.
19955 @item show sdstimeout
19956 @kindex show sdstimeout
19957 Show the current value of the SDS timeout.
19959 @item sds @var{command}
19960 @kindex sds@r{, a command}
19961 Send the specified @var{command} string to the SDS monitor.
19966 @subsection HP PA Embedded
19970 @kindex target op50n
19971 @item target op50n @var{dev}
19972 OP50N monitor, running on an OKI HPPA board.
19974 @kindex target w89k
19975 @item target w89k @var{dev}
19976 W89K monitor, running on a Winbond HPPA board.
19981 @subsection Tsqware Sparclet
19985 @value{GDBN} enables developers to debug tasks running on
19986 Sparclet targets from a Unix host.
19987 @value{GDBN} uses code that runs on
19988 both the Unix host and on the Sparclet target. The program
19989 @code{@value{GDBP}} is installed and executed on the Unix host.
19992 @item remotetimeout @var{args}
19993 @kindex remotetimeout
19994 @value{GDBN} supports the option @code{remotetimeout}.
19995 This option is set by the user, and @var{args} represents the number of
19996 seconds @value{GDBN} waits for responses.
19999 @cindex compiling, on Sparclet
20000 When compiling for debugging, include the options @samp{-g} to get debug
20001 information and @samp{-Ttext} to relocate the program to where you wish to
20002 load it on the target. You may also want to add the options @samp{-n} or
20003 @samp{-N} in order to reduce the size of the sections. Example:
20006 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20009 You can use @code{objdump} to verify that the addresses are what you intended:
20012 sparclet-aout-objdump --headers --syms prog
20015 @cindex running, on Sparclet
20017 your Unix execution search path to find @value{GDBN}, you are ready to
20018 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20019 (or @code{sparclet-aout-gdb}, depending on your installation).
20021 @value{GDBN} comes up showing the prompt:
20028 * Sparclet File:: Setting the file to debug
20029 * Sparclet Connection:: Connecting to Sparclet
20030 * Sparclet Download:: Sparclet download
20031 * Sparclet Execution:: Running and debugging
20034 @node Sparclet File
20035 @subsubsection Setting File to Debug
20037 The @value{GDBN} command @code{file} lets you choose with program to debug.
20040 (gdbslet) file prog
20044 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20045 @value{GDBN} locates
20046 the file by searching the directories listed in the command search
20048 If the file was compiled with debug information (option @samp{-g}), source
20049 files will be searched as well.
20050 @value{GDBN} locates
20051 the source files by searching the directories listed in the directory search
20052 path (@pxref{Environment, ,Your Program's Environment}).
20054 to find a file, it displays a message such as:
20057 prog: No such file or directory.
20060 When this happens, add the appropriate directories to the search paths with
20061 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20062 @code{target} command again.
20064 @node Sparclet Connection
20065 @subsubsection Connecting to Sparclet
20067 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20068 To connect to a target on serial port ``@code{ttya}'', type:
20071 (gdbslet) target sparclet /dev/ttya
20072 Remote target sparclet connected to /dev/ttya
20073 main () at ../prog.c:3
20077 @value{GDBN} displays messages like these:
20083 @node Sparclet Download
20084 @subsubsection Sparclet Download
20086 @cindex download to Sparclet
20087 Once connected to the Sparclet target,
20088 you can use the @value{GDBN}
20089 @code{load} command to download the file from the host to the target.
20090 The file name and load offset should be given as arguments to the @code{load}
20092 Since the file format is aout, the program must be loaded to the starting
20093 address. You can use @code{objdump} to find out what this value is. The load
20094 offset is an offset which is added to the VMA (virtual memory address)
20095 of each of the file's sections.
20096 For instance, if the program
20097 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20098 and bss at 0x12010170, in @value{GDBN}, type:
20101 (gdbslet) load prog 0x12010000
20102 Loading section .text, size 0xdb0 vma 0x12010000
20105 If the code is loaded at a different address then what the program was linked
20106 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20107 to tell @value{GDBN} where to map the symbol table.
20109 @node Sparclet Execution
20110 @subsubsection Running and Debugging
20112 @cindex running and debugging Sparclet programs
20113 You can now begin debugging the task using @value{GDBN}'s execution control
20114 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20115 manual for the list of commands.
20119 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20121 Starting program: prog
20122 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20123 3 char *symarg = 0;
20125 4 char *execarg = "hello!";
20130 @subsection Fujitsu Sparclite
20134 @kindex target sparclite
20135 @item target sparclite @var{dev}
20136 Fujitsu sparclite boards, used only for the purpose of loading.
20137 You must use an additional command to debug the program.
20138 For example: target remote @var{dev} using @value{GDBN} standard
20144 @subsection Zilog Z8000
20147 @cindex simulator, Z8000
20148 @cindex Zilog Z8000 simulator
20150 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20153 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20154 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20155 segmented variant). The simulator recognizes which architecture is
20156 appropriate by inspecting the object code.
20159 @item target sim @var{args}
20161 @kindex target sim@r{, with Z8000}
20162 Debug programs on a simulated CPU. If the simulator supports setup
20163 options, specify them via @var{args}.
20167 After specifying this target, you can debug programs for the simulated
20168 CPU in the same style as programs for your host computer; use the
20169 @code{file} command to load a new program image, the @code{run} command
20170 to run your program, and so on.
20172 As well as making available all the usual machine registers
20173 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20174 additional items of information as specially named registers:
20179 Counts clock-ticks in the simulator.
20182 Counts instructions run in the simulator.
20185 Execution time in 60ths of a second.
20189 You can refer to these values in @value{GDBN} expressions with the usual
20190 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20191 conditional breakpoint that suspends only after at least 5000
20192 simulated clock ticks.
20195 @subsection Atmel AVR
20198 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20199 following AVR-specific commands:
20202 @item info io_registers
20203 @kindex info io_registers@r{, AVR}
20204 @cindex I/O registers (Atmel AVR)
20205 This command displays information about the AVR I/O registers. For
20206 each register, @value{GDBN} prints its number and value.
20213 When configured for debugging CRIS, @value{GDBN} provides the
20214 following CRIS-specific commands:
20217 @item set cris-version @var{ver}
20218 @cindex CRIS version
20219 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20220 The CRIS version affects register names and sizes. This command is useful in
20221 case autodetection of the CRIS version fails.
20223 @item show cris-version
20224 Show the current CRIS version.
20226 @item set cris-dwarf2-cfi
20227 @cindex DWARF-2 CFI and CRIS
20228 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20229 Change to @samp{off} when using @code{gcc-cris} whose version is below
20232 @item show cris-dwarf2-cfi
20233 Show the current state of using DWARF-2 CFI.
20235 @item set cris-mode @var{mode}
20237 Set the current CRIS mode to @var{mode}. It should only be changed when
20238 debugging in guru mode, in which case it should be set to
20239 @samp{guru} (the default is @samp{normal}).
20241 @item show cris-mode
20242 Show the current CRIS mode.
20246 @subsection Renesas Super-H
20249 For the Renesas Super-H processor, @value{GDBN} provides these
20254 @kindex regs@r{, Super-H}
20255 Show the values of all Super-H registers.
20257 @item set sh calling-convention @var{convention}
20258 @kindex set sh calling-convention
20259 Set the calling-convention used when calling functions from @value{GDBN}.
20260 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20261 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20262 convention. If the DWARF-2 information of the called function specifies
20263 that the function follows the Renesas calling convention, the function
20264 is called using the Renesas calling convention. If the calling convention
20265 is set to @samp{renesas}, the Renesas calling convention is always used,
20266 regardless of the DWARF-2 information. This can be used to override the
20267 default of @samp{gcc} if debug information is missing, or the compiler
20268 does not emit the DWARF-2 calling convention entry for a function.
20270 @item show sh calling-convention
20271 @kindex show sh calling-convention
20272 Show the current calling convention setting.
20277 @node Architectures
20278 @section Architectures
20280 This section describes characteristics of architectures that affect
20281 all uses of @value{GDBN} with the architecture, both native and cross.
20287 * HPPA:: HP PA architecture
20288 * SPU:: Cell Broadband Engine SPU architecture
20293 @subsection x86 Architecture-specific Issues
20296 @item set struct-convention @var{mode}
20297 @kindex set struct-convention
20298 @cindex struct return convention
20299 @cindex struct/union returned in registers
20300 Set the convention used by the inferior to return @code{struct}s and
20301 @code{union}s from functions to @var{mode}. Possible values of
20302 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20303 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20304 are returned on the stack, while @code{"reg"} means that a
20305 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20306 be returned in a register.
20308 @item show struct-convention
20309 @kindex show struct-convention
20310 Show the current setting of the convention to return @code{struct}s
20317 See the following section.
20322 @cindex stack on Alpha
20323 @cindex stack on MIPS
20324 @cindex Alpha stack
20326 Alpha- and MIPS-based computers use an unusual stack frame, which
20327 sometimes requires @value{GDBN} to search backward in the object code to
20328 find the beginning of a function.
20330 @cindex response time, MIPS debugging
20331 To improve response time (especially for embedded applications, where
20332 @value{GDBN} may be restricted to a slow serial line for this search)
20333 you may want to limit the size of this search, using one of these
20337 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
20338 @item set heuristic-fence-post @var{limit}
20339 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20340 search for the beginning of a function. A value of @var{0} (the
20341 default) means there is no limit. However, except for @var{0}, the
20342 larger the limit the more bytes @code{heuristic-fence-post} must search
20343 and therefore the longer it takes to run. You should only need to use
20344 this command when debugging a stripped executable.
20346 @item show heuristic-fence-post
20347 Display the current limit.
20351 These commands are available @emph{only} when @value{GDBN} is configured
20352 for debugging programs on Alpha or MIPS processors.
20354 Several MIPS-specific commands are available when debugging MIPS
20358 @item set mips abi @var{arg}
20359 @kindex set mips abi
20360 @cindex set ABI for MIPS
20361 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
20362 values of @var{arg} are:
20366 The default ABI associated with the current binary (this is the
20376 @item show mips abi
20377 @kindex show mips abi
20378 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20381 @itemx show mipsfpu
20382 @xref{MIPS Embedded, set mipsfpu}.
20384 @item set mips mask-address @var{arg}
20385 @kindex set mips mask-address
20386 @cindex MIPS addresses, masking
20387 This command determines whether the most-significant 32 bits of 64-bit
20388 MIPS addresses are masked off. The argument @var{arg} can be
20389 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20390 setting, which lets @value{GDBN} determine the correct value.
20392 @item show mips mask-address
20393 @kindex show mips mask-address
20394 Show whether the upper 32 bits of MIPS addresses are masked off or
20397 @item set remote-mips64-transfers-32bit-regs
20398 @kindex set remote-mips64-transfers-32bit-regs
20399 This command controls compatibility with 64-bit MIPS targets that
20400 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20401 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20402 and 64 bits for other registers, set this option to @samp{on}.
20404 @item show remote-mips64-transfers-32bit-regs
20405 @kindex show remote-mips64-transfers-32bit-regs
20406 Show the current setting of compatibility with older MIPS 64 targets.
20408 @item set debug mips
20409 @kindex set debug mips
20410 This command turns on and off debugging messages for the MIPS-specific
20411 target code in @value{GDBN}.
20413 @item show debug mips
20414 @kindex show debug mips
20415 Show the current setting of MIPS debugging messages.
20421 @cindex HPPA support
20423 When @value{GDBN} is debugging the HP PA architecture, it provides the
20424 following special commands:
20427 @item set debug hppa
20428 @kindex set debug hppa
20429 This command determines whether HPPA architecture-specific debugging
20430 messages are to be displayed.
20432 @item show debug hppa
20433 Show whether HPPA debugging messages are displayed.
20435 @item maint print unwind @var{address}
20436 @kindex maint print unwind@r{, HPPA}
20437 This command displays the contents of the unwind table entry at the
20438 given @var{address}.
20444 @subsection Cell Broadband Engine SPU architecture
20445 @cindex Cell Broadband Engine
20448 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20449 it provides the following special commands:
20452 @item info spu event
20454 Display SPU event facility status. Shows current event mask
20455 and pending event status.
20457 @item info spu signal
20458 Display SPU signal notification facility status. Shows pending
20459 signal-control word and signal notification mode of both signal
20460 notification channels.
20462 @item info spu mailbox
20463 Display SPU mailbox facility status. Shows all pending entries,
20464 in order of processing, in each of the SPU Write Outbound,
20465 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20468 Display MFC DMA status. Shows all pending commands in the MFC
20469 DMA queue. For each entry, opcode, tag, class IDs, effective
20470 and local store addresses and transfer size are shown.
20472 @item info spu proxydma
20473 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20474 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20475 and local store addresses and transfer size are shown.
20479 When @value{GDBN} is debugging a combined PowerPC/SPU application
20480 on the Cell Broadband Engine, it provides in addition the following
20484 @item set spu stop-on-load @var{arg}
20486 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20487 will give control to the user when a new SPE thread enters its @code{main}
20488 function. The default is @code{off}.
20490 @item show spu stop-on-load
20492 Show whether to stop for new SPE threads.
20494 @item set spu auto-flush-cache @var{arg}
20495 Set whether to automatically flush the software-managed cache. When set to
20496 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20497 cache to be flushed whenever SPE execution stops. This provides a consistent
20498 view of PowerPC memory that is accessed via the cache. If an application
20499 does not use the software-managed cache, this option has no effect.
20501 @item show spu auto-flush-cache
20502 Show whether to automatically flush the software-managed cache.
20507 @subsection PowerPC
20508 @cindex PowerPC architecture
20510 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20511 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20512 numbers stored in the floating point registers. These values must be stored
20513 in two consecutive registers, always starting at an even register like
20514 @code{f0} or @code{f2}.
20516 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20517 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20518 @code{f2} and @code{f3} for @code{$dl1} and so on.
20520 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20521 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20524 @node Controlling GDB
20525 @chapter Controlling @value{GDBN}
20527 You can alter the way @value{GDBN} interacts with you by using the
20528 @code{set} command. For commands controlling how @value{GDBN} displays
20529 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20534 * Editing:: Command editing
20535 * Command History:: Command history
20536 * Screen Size:: Screen size
20537 * Numbers:: Numbers
20538 * ABI:: Configuring the current ABI
20539 * Auto-loading:: Automatically loading associated files
20540 * Messages/Warnings:: Optional warnings and messages
20541 * Debugging Output:: Optional messages about internal happenings
20542 * Other Misc Settings:: Other Miscellaneous Settings
20550 @value{GDBN} indicates its readiness to read a command by printing a string
20551 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20552 can change the prompt string with the @code{set prompt} command. For
20553 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20554 the prompt in one of the @value{GDBN} sessions so that you can always tell
20555 which one you are talking to.
20557 @emph{Note:} @code{set prompt} does not add a space for you after the
20558 prompt you set. This allows you to set a prompt which ends in a space
20559 or a prompt that does not.
20563 @item set prompt @var{newprompt}
20564 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20566 @kindex show prompt
20568 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20571 Versions of @value{GDBN} that ship with Python scripting enabled have
20572 prompt extensions. The commands for interacting with these extensions
20576 @kindex set extended-prompt
20577 @item set extended-prompt @var{prompt}
20578 Set an extended prompt that allows for substitutions.
20579 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20580 substitution. Any escape sequences specified as part of the prompt
20581 string are replaced with the corresponding strings each time the prompt
20587 set extended-prompt Current working directory: \w (gdb)
20590 Note that when an extended-prompt is set, it takes control of the
20591 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20593 @kindex show extended-prompt
20594 @item show extended-prompt
20595 Prints the extended prompt. Any escape sequences specified as part of
20596 the prompt string with @code{set extended-prompt}, are replaced with the
20597 corresponding strings each time the prompt is displayed.
20601 @section Command Editing
20603 @cindex command line editing
20605 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20606 @sc{gnu} library provides consistent behavior for programs which provide a
20607 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20608 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20609 substitution, and a storage and recall of command history across
20610 debugging sessions.
20612 You may control the behavior of command line editing in @value{GDBN} with the
20613 command @code{set}.
20616 @kindex set editing
20619 @itemx set editing on
20620 Enable command line editing (enabled by default).
20622 @item set editing off
20623 Disable command line editing.
20625 @kindex show editing
20627 Show whether command line editing is enabled.
20630 @ifset SYSTEM_READLINE
20631 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20633 @ifclear SYSTEM_READLINE
20634 @xref{Command Line Editing},
20636 for more details about the Readline
20637 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20638 encouraged to read that chapter.
20640 @node Command History
20641 @section Command History
20642 @cindex command history
20644 @value{GDBN} can keep track of the commands you type during your
20645 debugging sessions, so that you can be certain of precisely what
20646 happened. Use these commands to manage the @value{GDBN} command
20649 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20650 package, to provide the history facility.
20651 @ifset SYSTEM_READLINE
20652 @xref{Using History Interactively, , , history, GNU History Library},
20654 @ifclear SYSTEM_READLINE
20655 @xref{Using History Interactively},
20657 for the detailed description of the History library.
20659 To issue a command to @value{GDBN} without affecting certain aspects of
20660 the state which is seen by users, prefix it with @samp{server }
20661 (@pxref{Server Prefix}). This
20662 means that this command will not affect the command history, nor will it
20663 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20664 pressed on a line by itself.
20666 @cindex @code{server}, command prefix
20667 The server prefix does not affect the recording of values into the value
20668 history; to print a value without recording it into the value history,
20669 use the @code{output} command instead of the @code{print} command.
20671 Here is the description of @value{GDBN} commands related to command
20675 @cindex history substitution
20676 @cindex history file
20677 @kindex set history filename
20678 @cindex @env{GDBHISTFILE}, environment variable
20679 @item set history filename @var{fname}
20680 Set the name of the @value{GDBN} command history file to @var{fname}.
20681 This is the file where @value{GDBN} reads an initial command history
20682 list, and where it writes the command history from this session when it
20683 exits. You can access this list through history expansion or through
20684 the history command editing characters listed below. This file defaults
20685 to the value of the environment variable @code{GDBHISTFILE}, or to
20686 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20689 @cindex save command history
20690 @kindex set history save
20691 @item set history save
20692 @itemx set history save on
20693 Record command history in a file, whose name may be specified with the
20694 @code{set history filename} command. By default, this option is disabled.
20696 @item set history save off
20697 Stop recording command history in a file.
20699 @cindex history size
20700 @kindex set history size
20701 @cindex @env{HISTSIZE}, environment variable
20702 @item set history size @var{size}
20703 Set the number of commands which @value{GDBN} keeps in its history list.
20704 This defaults to the value of the environment variable
20705 @code{HISTSIZE}, or to 256 if this variable is not set.
20708 History expansion assigns special meaning to the character @kbd{!}.
20709 @ifset SYSTEM_READLINE
20710 @xref{Event Designators, , , history, GNU History Library},
20712 @ifclear SYSTEM_READLINE
20713 @xref{Event Designators},
20717 @cindex history expansion, turn on/off
20718 Since @kbd{!} is also the logical not operator in C, history expansion
20719 is off by default. If you decide to enable history expansion with the
20720 @code{set history expansion on} command, you may sometimes need to
20721 follow @kbd{!} (when it is used as logical not, in an expression) with
20722 a space or a tab to prevent it from being expanded. The readline
20723 history facilities do not attempt substitution on the strings
20724 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20726 The commands to control history expansion are:
20729 @item set history expansion on
20730 @itemx set history expansion
20731 @kindex set history expansion
20732 Enable history expansion. History expansion is off by default.
20734 @item set history expansion off
20735 Disable history expansion.
20738 @kindex show history
20740 @itemx show history filename
20741 @itemx show history save
20742 @itemx show history size
20743 @itemx show history expansion
20744 These commands display the state of the @value{GDBN} history parameters.
20745 @code{show history} by itself displays all four states.
20750 @kindex show commands
20751 @cindex show last commands
20752 @cindex display command history
20753 @item show commands
20754 Display the last ten commands in the command history.
20756 @item show commands @var{n}
20757 Print ten commands centered on command number @var{n}.
20759 @item show commands +
20760 Print ten commands just after the commands last printed.
20764 @section Screen Size
20765 @cindex size of screen
20766 @cindex pauses in output
20768 Certain commands to @value{GDBN} may produce large amounts of
20769 information output to the screen. To help you read all of it,
20770 @value{GDBN} pauses and asks you for input at the end of each page of
20771 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20772 to discard the remaining output. Also, the screen width setting
20773 determines when to wrap lines of output. Depending on what is being
20774 printed, @value{GDBN} tries to break the line at a readable place,
20775 rather than simply letting it overflow onto the following line.
20777 Normally @value{GDBN} knows the size of the screen from the terminal
20778 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20779 together with the value of the @code{TERM} environment variable and the
20780 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20781 you can override it with the @code{set height} and @code{set
20788 @kindex show height
20789 @item set height @var{lpp}
20791 @itemx set width @var{cpl}
20793 These @code{set} commands specify a screen height of @var{lpp} lines and
20794 a screen width of @var{cpl} characters. The associated @code{show}
20795 commands display the current settings.
20797 If you specify a height of zero lines, @value{GDBN} does not pause during
20798 output no matter how long the output is. This is useful if output is to a
20799 file or to an editor buffer.
20801 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20802 from wrapping its output.
20804 @item set pagination on
20805 @itemx set pagination off
20806 @kindex set pagination
20807 Turn the output pagination on or off; the default is on. Turning
20808 pagination off is the alternative to @code{set height 0}. Note that
20809 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20810 Options, -batch}) also automatically disables pagination.
20812 @item show pagination
20813 @kindex show pagination
20814 Show the current pagination mode.
20819 @cindex number representation
20820 @cindex entering numbers
20822 You can always enter numbers in octal, decimal, or hexadecimal in
20823 @value{GDBN} by the usual conventions: octal numbers begin with
20824 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20825 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20826 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20827 10; likewise, the default display for numbers---when no particular
20828 format is specified---is base 10. You can change the default base for
20829 both input and output with the commands described below.
20832 @kindex set input-radix
20833 @item set input-radix @var{base}
20834 Set the default base for numeric input. Supported choices
20835 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20836 specified either unambiguously or using the current input radix; for
20840 set input-radix 012
20841 set input-radix 10.
20842 set input-radix 0xa
20846 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20847 leaves the input radix unchanged, no matter what it was, since
20848 @samp{10}, being without any leading or trailing signs of its base, is
20849 interpreted in the current radix. Thus, if the current radix is 16,
20850 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20853 @kindex set output-radix
20854 @item set output-radix @var{base}
20855 Set the default base for numeric display. Supported choices
20856 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20857 specified either unambiguously or using the current input radix.
20859 @kindex show input-radix
20860 @item show input-radix
20861 Display the current default base for numeric input.
20863 @kindex show output-radix
20864 @item show output-radix
20865 Display the current default base for numeric display.
20867 @item set radix @r{[}@var{base}@r{]}
20871 These commands set and show the default base for both input and output
20872 of numbers. @code{set radix} sets the radix of input and output to
20873 the same base; without an argument, it resets the radix back to its
20874 default value of 10.
20879 @section Configuring the Current ABI
20881 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20882 application automatically. However, sometimes you need to override its
20883 conclusions. Use these commands to manage @value{GDBN}'s view of the
20890 One @value{GDBN} configuration can debug binaries for multiple operating
20891 system targets, either via remote debugging or native emulation.
20892 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20893 but you can override its conclusion using the @code{set osabi} command.
20894 One example where this is useful is in debugging of binaries which use
20895 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20896 not have the same identifying marks that the standard C library for your
20901 Show the OS ABI currently in use.
20904 With no argument, show the list of registered available OS ABI's.
20906 @item set osabi @var{abi}
20907 Set the current OS ABI to @var{abi}.
20910 @cindex float promotion
20912 Generally, the way that an argument of type @code{float} is passed to a
20913 function depends on whether the function is prototyped. For a prototyped
20914 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20915 according to the architecture's convention for @code{float}. For unprototyped
20916 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20917 @code{double} and then passed.
20919 Unfortunately, some forms of debug information do not reliably indicate whether
20920 a function is prototyped. If @value{GDBN} calls a function that is not marked
20921 as prototyped, it consults @kbd{set coerce-float-to-double}.
20924 @kindex set coerce-float-to-double
20925 @item set coerce-float-to-double
20926 @itemx set coerce-float-to-double on
20927 Arguments of type @code{float} will be promoted to @code{double} when passed
20928 to an unprototyped function. This is the default setting.
20930 @item set coerce-float-to-double off
20931 Arguments of type @code{float} will be passed directly to unprototyped
20934 @kindex show coerce-float-to-double
20935 @item show coerce-float-to-double
20936 Show the current setting of promoting @code{float} to @code{double}.
20940 @kindex show cp-abi
20941 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20942 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20943 used to build your application. @value{GDBN} only fully supports
20944 programs with a single C@t{++} ABI; if your program contains code using
20945 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20946 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20947 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20948 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20949 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20950 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20955 Show the C@t{++} ABI currently in use.
20958 With no argument, show the list of supported C@t{++} ABI's.
20960 @item set cp-abi @var{abi}
20961 @itemx set cp-abi auto
20962 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20966 @section Automatically loading associated files
20967 @cindex auto-loading
20969 @value{GDBN} sometimes reads files with commands and settings automatically,
20970 without being explicitly told so by the user. We call this feature
20971 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
20972 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
20973 results or introduce security risks (e.g., if the file comes from untrusted
20976 For these reasons, @value{GDBN} includes commands and options to let you
20977 control when to auto-load files and which files should be auto-loaded.
20980 @anchor{set auto-load off}
20981 @kindex set auto-load off
20982 @item set auto-load off
20983 Globally disable loading of all auto-loaded files.
20984 You may want to use this command with the @samp{-iex} option
20985 (@pxref{Option -init-eval-command}) such as:
20987 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
20990 Be aware that system init file (@pxref{System-wide configuration})
20991 and init files from your home directory (@pxref{Home Directory Init File})
20992 still get read (as they come from generally trusted directories).
20993 To prevent @value{GDBN} from auto-loading even those init files, use the
20994 @option{-nx} option (@pxref{Mode Options}), in addition to
20995 @code{set auto-load no}.
20997 @anchor{show auto-load}
20998 @kindex show auto-load
20999 @item show auto-load
21000 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21004 (gdb) show auto-load
21005 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21006 libthread-db: Auto-loading of inferior specific libthread_db is on.
21007 local-gdbinit: Auto-loading of .gdbinit script from current directory
21009 python-scripts: Auto-loading of Python scripts is on.
21010 safe-path: List of directories from which it is safe to auto-load files
21011 is $ddir/auto-load.
21012 scripts-directory: List of directories from which to load auto-loaded scripts
21013 is $ddir/auto-load.
21016 @anchor{info auto-load}
21017 @kindex info auto-load
21018 @item info auto-load
21019 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21023 (gdb) info auto-load
21026 Yes /home/user/gdb/gdb-gdb.gdb
21027 libthread-db: No auto-loaded libthread-db.
21028 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21032 Yes /home/user/gdb/gdb-gdb.py
21036 These are various kinds of files @value{GDBN} can automatically load:
21040 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21042 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21044 @xref{dotdebug_gdb_scripts section},
21045 controlled by @ref{set auto-load python-scripts}.
21047 @xref{Init File in the Current Directory},
21048 controlled by @ref{set auto-load local-gdbinit}.
21050 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21053 These are @value{GDBN} control commands for the auto-loading:
21055 @multitable @columnfractions .5 .5
21056 @item @xref{set auto-load off}.
21057 @tab Disable auto-loading globally.
21058 @item @xref{show auto-load}.
21059 @tab Show setting of all kinds of files.
21060 @item @xref{info auto-load}.
21061 @tab Show state of all kinds of files.
21062 @item @xref{set auto-load gdb-scripts}.
21063 @tab Control for @value{GDBN} command scripts.
21064 @item @xref{show auto-load gdb-scripts}.
21065 @tab Show setting of @value{GDBN} command scripts.
21066 @item @xref{info auto-load gdb-scripts}.
21067 @tab Show state of @value{GDBN} command scripts.
21068 @item @xref{set auto-load python-scripts}.
21069 @tab Control for @value{GDBN} Python scripts.
21070 @item @xref{show auto-load python-scripts}.
21071 @tab Show setting of @value{GDBN} Python scripts.
21072 @item @xref{info auto-load python-scripts}.
21073 @tab Show state of @value{GDBN} Python scripts.
21074 @item @xref{set auto-load scripts-directory}.
21075 @tab Control for @value{GDBN} auto-loaded scripts location.
21076 @item @xref{show auto-load scripts-directory}.
21077 @tab Show @value{GDBN} auto-loaded scripts location.
21078 @item @xref{set auto-load local-gdbinit}.
21079 @tab Control for init file in the current directory.
21080 @item @xref{show auto-load local-gdbinit}.
21081 @tab Show setting of init file in the current directory.
21082 @item @xref{info auto-load local-gdbinit}.
21083 @tab Show state of init file in the current directory.
21084 @item @xref{set auto-load libthread-db}.
21085 @tab Control for thread debugging library.
21086 @item @xref{show auto-load libthread-db}.
21087 @tab Show setting of thread debugging library.
21088 @item @xref{info auto-load libthread-db}.
21089 @tab Show state of thread debugging library.
21090 @item @xref{set auto-load safe-path}.
21091 @tab Control directories trusted for automatic loading.
21092 @item @xref{show auto-load safe-path}.
21093 @tab Show directories trusted for automatic loading.
21094 @item @xref{add-auto-load-safe-path}.
21095 @tab Add directory trusted for automatic loading.
21099 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21100 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21101 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21102 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21103 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21104 @xref{Python Auto-loading}.
21107 @node Init File in the Current Directory
21108 @subsection Automatically loading init file in the current directory
21109 @cindex auto-loading init file in the current directory
21111 By default, @value{GDBN} reads and executes the canned sequences of commands
21112 from init file (if any) in the current working directory,
21113 see @ref{Init File in the Current Directory during Startup}.
21116 @anchor{set auto-load local-gdbinit}
21117 @kindex set auto-load local-gdbinit
21118 @item set auto-load local-gdbinit [on|off]
21119 Enable or disable the auto-loading of canned sequences of commands
21120 (@pxref{Sequences}) found in init file in the current directory.
21122 @anchor{show auto-load local-gdbinit}
21123 @kindex show auto-load local-gdbinit
21124 @item show auto-load local-gdbinit
21125 Show whether auto-loading of canned sequences of commands from init file in the
21126 current directory is enabled or disabled.
21128 @anchor{info auto-load local-gdbinit}
21129 @kindex info auto-load local-gdbinit
21130 @item info auto-load local-gdbinit
21131 Print whether canned sequences of commands from init file in the
21132 current directory have been auto-loaded.
21135 @node libthread_db.so.1 file
21136 @subsection Automatically loading thread debugging library
21137 @cindex auto-loading libthread_db.so.1
21139 This feature is currently present only on @sc{gnu}/Linux native hosts.
21141 @value{GDBN} reads in some cases thread debugging library from places specific
21142 to the inferior (@pxref{set libthread-db-search-path}).
21144 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21145 without checking this @samp{set auto-load libthread-db} switch as system
21146 libraries have to be trusted in general. In all other cases of
21147 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21148 auto-load libthread-db} is enabled before trying to open such thread debugging
21152 @anchor{set auto-load libthread-db}
21153 @kindex set auto-load libthread-db
21154 @item set auto-load libthread-db [on|off]
21155 Enable or disable the auto-loading of inferior specific thread debugging library.
21157 @anchor{show auto-load libthread-db}
21158 @kindex show auto-load libthread-db
21159 @item show auto-load libthread-db
21160 Show whether auto-loading of inferior specific thread debugging library is
21161 enabled or disabled.
21163 @anchor{info auto-load libthread-db}
21164 @kindex info auto-load libthread-db
21165 @item info auto-load libthread-db
21166 Print the list of all loaded inferior specific thread debugging libraries and
21167 for each such library print list of inferior @var{pid}s using it.
21170 @node objfile-gdb.gdb file
21171 @subsection The @file{@var{objfile}-gdb.gdb} file
21172 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21174 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21175 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21176 auto-load gdb-scripts} is set to @samp{on}.
21178 For more background refer to the similar Python scripts auto-loading
21179 description (@pxref{objfile-gdb.py file}).
21182 @anchor{set auto-load gdb-scripts}
21183 @kindex set auto-load gdb-scripts
21184 @item set auto-load gdb-scripts [on|off]
21185 Enable or disable the auto-loading of canned sequences of commands scripts.
21187 @anchor{show auto-load gdb-scripts}
21188 @kindex show auto-load gdb-scripts
21189 @item show auto-load gdb-scripts
21190 Show whether auto-loading of canned sequences of commands scripts is enabled or
21193 @anchor{info auto-load gdb-scripts}
21194 @kindex info auto-load gdb-scripts
21195 @cindex print list of auto-loaded canned sequences of commands scripts
21196 @item info auto-load gdb-scripts [@var{regexp}]
21197 Print the list of all canned sequences of commands scripts that @value{GDBN}
21201 If @var{regexp} is supplied only canned sequences of commands scripts with
21202 matching names are printed.
21204 @node Auto-loading safe path
21205 @subsection Security restriction for auto-loading
21206 @cindex auto-loading safe-path
21208 As the files of inferior can come from untrusted source (such as submitted by
21209 an application user) @value{GDBN} does not always load any files automatically.
21210 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21211 directories trusted for loading files not explicitly requested by user.
21213 If the path is not set properly you will see a warning and the file will not
21218 Reading symbols from /home/user/gdb/gdb...done.
21219 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21220 declined by your `auto-load safe-path' set to "$ddir/auto-load".
21221 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21222 declined by your `auto-load safe-path' set to "$ddir/auto-load".
21225 The list of trusted directories is controlled by the following commands:
21228 @anchor{set auto-load safe-path}
21229 @kindex set auto-load safe-path
21230 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21231 Set the list of directories (and their subdirectories) trusted for automatic
21232 loading and execution of scripts. You can also enter a specific trusted file.
21233 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21234 its default value as specified during @value{GDBN} compilation.
21236 The list of directories uses path separator (@samp{:} on GNU and Unix
21237 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21238 to the @env{PATH} environment variable.
21240 @anchor{show auto-load safe-path}
21241 @kindex show auto-load safe-path
21242 @item show auto-load safe-path
21243 Show the list of directories trusted for automatic loading and execution of
21246 @anchor{add-auto-load-safe-path}
21247 @kindex add-auto-load-safe-path
21248 @item add-auto-load-safe-path
21249 Add an entry (or list of entries) the list of directories trusted for automatic
21250 loading and execution of scripts. Multiple entries may be delimited by the
21251 host platform path separator in use.
21254 This variable defaults to what @code{--with-auto-load-dir} has been configured
21255 to (@pxref{with-auto-load-dir}). @file{$ddir} substituation applies the same
21256 as for @xref{set auto-load scripts-directory}.
21257 The default @code{set
21258 auto-load safe-path} value can be also overriden by @value{GDBN} configuration
21259 option @option{--with-auto-load-safe-path}.
21261 Setting this variable to @file{/} disables this security protection,
21262 corresponding @value{GDBN} configuration option is
21263 @option{--without-auto-load-safe-path}.
21264 This variable is supposed to be set to the system directories writable by the
21265 system superuser only. Users can add their source directories in init files in
21266 their home directories (@pxref{Home Directory Init File}). See also deprecated
21267 init file in the current directory
21268 (@pxref{Init File in the Current Directory during Startup}).
21270 To force @value{GDBN} to load the files it declined to load in the previous
21271 example, you could use one of the following ways:
21274 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21275 Specify this trusted directory (or a file) as additional component of the list.
21276 You have to specify also any existing directories displayed by
21277 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21279 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21280 Specify this directory as in the previous case but just for a single
21281 @value{GDBN} session.
21283 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21284 Disable auto-loading safety for a single @value{GDBN} session.
21285 This assumes all the files you debug during this @value{GDBN} session will come
21286 from trusted sources.
21288 @item @kbd{./configure --without-auto-load-safe-path}
21289 During compilation of @value{GDBN} you may disable any auto-loading safety.
21290 This assumes all the files you will ever debug with this @value{GDBN} come from
21294 On the other hand you can also explicitly forbid automatic files loading which
21295 also suppresses any such warning messages:
21298 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21299 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21301 @item @file{~/.gdbinit}: @samp{set auto-load no}
21302 Disable auto-loading globally for the user
21303 (@pxref{Home Directory Init File}). While it is improbable, you could also
21304 use system init file instead (@pxref{System-wide configuration}).
21307 This setting applies to the file names as entered by user. If no entry matches
21308 @value{GDBN} tries as a last resort to also resolve all the file names into
21309 their canonical form (typically resolving symbolic links) and compare the
21310 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21311 own before starting the comparison so a canonical form of directories is
21312 recommended to be entered.
21314 @node Auto-loading verbose mode
21315 @subsection Displaying files tried for auto-load
21316 @cindex auto-loading verbose mode
21318 For better visibility of all the file locations where you can place scripts to
21319 be auto-loaded with inferior --- or to protect yourself against accidental
21320 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21321 all the files attempted to be loaded. Both existing and non-existing files may
21324 For example the list of directories from which it is safe to auto-load files
21325 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21326 may not be too obvious while setting it up.
21329 (gdb) set debug auto-load on
21330 (gdb) file ~/src/t/true
21331 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21332 for objfile "/tmp/true".
21333 auto-load: Updating directories of "/usr:/opt".
21334 auto-load: Using directory "/usr".
21335 auto-load: Using directory "/opt".
21336 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21337 by your `auto-load safe-path' set to "/usr:/opt".
21341 @anchor{set debug auto-load}
21342 @kindex set debug auto-load
21343 @item set debug auto-load [on|off]
21344 Set whether to print the filenames attempted to be auto-loaded.
21346 @anchor{show debug auto-load}
21347 @kindex show debug auto-load
21348 @item show debug auto-load
21349 Show whether printing of the filenames attempted to be auto-loaded is turned
21353 @node Messages/Warnings
21354 @section Optional Warnings and Messages
21356 @cindex verbose operation
21357 @cindex optional warnings
21358 By default, @value{GDBN} is silent about its inner workings. If you are
21359 running on a slow machine, you may want to use the @code{set verbose}
21360 command. This makes @value{GDBN} tell you when it does a lengthy
21361 internal operation, so you will not think it has crashed.
21363 Currently, the messages controlled by @code{set verbose} are those
21364 which announce that the symbol table for a source file is being read;
21365 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21368 @kindex set verbose
21369 @item set verbose on
21370 Enables @value{GDBN} output of certain informational messages.
21372 @item set verbose off
21373 Disables @value{GDBN} output of certain informational messages.
21375 @kindex show verbose
21377 Displays whether @code{set verbose} is on or off.
21380 By default, if @value{GDBN} encounters bugs in the symbol table of an
21381 object file, it is silent; but if you are debugging a compiler, you may
21382 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21387 @kindex set complaints
21388 @item set complaints @var{limit}
21389 Permits @value{GDBN} to output @var{limit} complaints about each type of
21390 unusual symbols before becoming silent about the problem. Set
21391 @var{limit} to zero to suppress all complaints; set it to a large number
21392 to prevent complaints from being suppressed.
21394 @kindex show complaints
21395 @item show complaints
21396 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21400 @anchor{confirmation requests}
21401 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21402 lot of stupid questions to confirm certain commands. For example, if
21403 you try to run a program which is already running:
21407 The program being debugged has been started already.
21408 Start it from the beginning? (y or n)
21411 If you are willing to unflinchingly face the consequences of your own
21412 commands, you can disable this ``feature'':
21416 @kindex set confirm
21418 @cindex confirmation
21419 @cindex stupid questions
21420 @item set confirm off
21421 Disables confirmation requests. Note that running @value{GDBN} with
21422 the @option{--batch} option (@pxref{Mode Options, -batch}) also
21423 automatically disables confirmation requests.
21425 @item set confirm on
21426 Enables confirmation requests (the default).
21428 @kindex show confirm
21430 Displays state of confirmation requests.
21434 @cindex command tracing
21435 If you need to debug user-defined commands or sourced files you may find it
21436 useful to enable @dfn{command tracing}. In this mode each command will be
21437 printed as it is executed, prefixed with one or more @samp{+} symbols, the
21438 quantity denoting the call depth of each command.
21441 @kindex set trace-commands
21442 @cindex command scripts, debugging
21443 @item set trace-commands on
21444 Enable command tracing.
21445 @item set trace-commands off
21446 Disable command tracing.
21447 @item show trace-commands
21448 Display the current state of command tracing.
21451 @node Debugging Output
21452 @section Optional Messages about Internal Happenings
21453 @cindex optional debugging messages
21455 @value{GDBN} has commands that enable optional debugging messages from
21456 various @value{GDBN} subsystems; normally these commands are of
21457 interest to @value{GDBN} maintainers, or when reporting a bug. This
21458 section documents those commands.
21461 @kindex set exec-done-display
21462 @item set exec-done-display
21463 Turns on or off the notification of asynchronous commands'
21464 completion. When on, @value{GDBN} will print a message when an
21465 asynchronous command finishes its execution. The default is off.
21466 @kindex show exec-done-display
21467 @item show exec-done-display
21468 Displays the current setting of asynchronous command completion
21471 @cindex gdbarch debugging info
21472 @cindex architecture debugging info
21473 @item set debug arch
21474 Turns on or off display of gdbarch debugging info. The default is off
21476 @item show debug arch
21477 Displays the current state of displaying gdbarch debugging info.
21478 @item set debug aix-thread
21479 @cindex AIX threads
21480 Display debugging messages about inner workings of the AIX thread
21482 @item show debug aix-thread
21483 Show the current state of AIX thread debugging info display.
21484 @item set debug check-physname
21486 Check the results of the ``physname'' computation. When reading DWARF
21487 debugging information for C@t{++}, @value{GDBN} attempts to compute
21488 each entity's name. @value{GDBN} can do this computation in two
21489 different ways, depending on exactly what information is present.
21490 When enabled, this setting causes @value{GDBN} to compute the names
21491 both ways and display any discrepancies.
21492 @item show debug check-physname
21493 Show the current state of ``physname'' checking.
21494 @item set debug dwarf2-die
21495 @cindex DWARF2 DIEs
21496 Dump DWARF2 DIEs after they are read in.
21497 The value is the number of nesting levels to print.
21498 A value of zero turns off the display.
21499 @item show debug dwarf2-die
21500 Show the current state of DWARF2 DIE debugging.
21501 @item set debug displaced
21502 @cindex displaced stepping debugging info
21503 Turns on or off display of @value{GDBN} debugging info for the
21504 displaced stepping support. The default is off.
21505 @item show debug displaced
21506 Displays the current state of displaying @value{GDBN} debugging info
21507 related to displaced stepping.
21508 @item set debug event
21509 @cindex event debugging info
21510 Turns on or off display of @value{GDBN} event debugging info. The
21512 @item show debug event
21513 Displays the current state of displaying @value{GDBN} event debugging
21515 @item set debug expression
21516 @cindex expression debugging info
21517 Turns on or off display of debugging info about @value{GDBN}
21518 expression parsing. The default is off.
21519 @item show debug expression
21520 Displays the current state of displaying debugging info about
21521 @value{GDBN} expression parsing.
21522 @item set debug frame
21523 @cindex frame debugging info
21524 Turns on or off display of @value{GDBN} frame debugging info. The
21526 @item show debug frame
21527 Displays the current state of displaying @value{GDBN} frame debugging
21529 @item set debug gnu-nat
21530 @cindex @sc{gnu}/Hurd debug messages
21531 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
21532 @item show debug gnu-nat
21533 Show the current state of @sc{gnu}/Hurd debugging messages.
21534 @item set debug infrun
21535 @cindex inferior debugging info
21536 Turns on or off display of @value{GDBN} debugging info for running the inferior.
21537 The default is off. @file{infrun.c} contains GDB's runtime state machine used
21538 for implementing operations such as single-stepping the inferior.
21539 @item show debug infrun
21540 Displays the current state of @value{GDBN} inferior debugging.
21541 @item set debug jit
21542 @cindex just-in-time compilation, debugging messages
21543 Turns on or off debugging messages from JIT debug support.
21544 @item show debug jit
21545 Displays the current state of @value{GDBN} JIT debugging.
21546 @item set debug lin-lwp
21547 @cindex @sc{gnu}/Linux LWP debug messages
21548 @cindex Linux lightweight processes
21549 Turns on or off debugging messages from the Linux LWP debug support.
21550 @item show debug lin-lwp
21551 Show the current state of Linux LWP debugging messages.
21552 @item set debug observer
21553 @cindex observer debugging info
21554 Turns on or off display of @value{GDBN} observer debugging. This
21555 includes info such as the notification of observable events.
21556 @item show debug observer
21557 Displays the current state of observer debugging.
21558 @item set debug overload
21559 @cindex C@t{++} overload debugging info
21560 Turns on or off display of @value{GDBN} C@t{++} overload debugging
21561 info. This includes info such as ranking of functions, etc. The default
21563 @item show debug overload
21564 Displays the current state of displaying @value{GDBN} C@t{++} overload
21566 @cindex expression parser, debugging info
21567 @cindex debug expression parser
21568 @item set debug parser
21569 Turns on or off the display of expression parser debugging output.
21570 Internally, this sets the @code{yydebug} variable in the expression
21571 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
21572 details. The default is off.
21573 @item show debug parser
21574 Show the current state of expression parser debugging.
21575 @cindex packets, reporting on stdout
21576 @cindex serial connections, debugging
21577 @cindex debug remote protocol
21578 @cindex remote protocol debugging
21579 @cindex display remote packets
21580 @item set debug remote
21581 Turns on or off display of reports on all packets sent back and forth across
21582 the serial line to the remote machine. The info is printed on the
21583 @value{GDBN} standard output stream. The default is off.
21584 @item show debug remote
21585 Displays the state of display of remote packets.
21586 @item set debug serial
21587 Turns on or off display of @value{GDBN} serial debugging info. The
21589 @item show debug serial
21590 Displays the current state of displaying @value{GDBN} serial debugging
21592 @item set debug solib-frv
21593 @cindex FR-V shared-library debugging
21594 Turns on or off debugging messages for FR-V shared-library code.
21595 @item show debug solib-frv
21596 Display the current state of FR-V shared-library code debugging
21598 @item set debug target
21599 @cindex target debugging info
21600 Turns on or off display of @value{GDBN} target debugging info. This info
21601 includes what is going on at the target level of GDB, as it happens. The
21602 default is 0. Set it to 1 to track events, and to 2 to also track the
21603 value of large memory transfers. Changes to this flag do not take effect
21604 until the next time you connect to a target or use the @code{run} command.
21605 @item show debug target
21606 Displays the current state of displaying @value{GDBN} target debugging
21608 @item set debug timestamp
21609 @cindex timestampping debugging info
21610 Turns on or off display of timestamps with @value{GDBN} debugging info.
21611 When enabled, seconds and microseconds are displayed before each debugging
21613 @item show debug timestamp
21614 Displays the current state of displaying timestamps with @value{GDBN}
21616 @item set debugvarobj
21617 @cindex variable object debugging info
21618 Turns on or off display of @value{GDBN} variable object debugging
21619 info. The default is off.
21620 @item show debugvarobj
21621 Displays the current state of displaying @value{GDBN} variable object
21623 @item set debug xml
21624 @cindex XML parser debugging
21625 Turns on or off debugging messages for built-in XML parsers.
21626 @item show debug xml
21627 Displays the current state of XML debugging messages.
21630 @node Other Misc Settings
21631 @section Other Miscellaneous Settings
21632 @cindex miscellaneous settings
21635 @kindex set interactive-mode
21636 @item set interactive-mode
21637 If @code{on}, forces @value{GDBN} to assume that GDB was started
21638 in a terminal. In practice, this means that @value{GDBN} should wait
21639 for the user to answer queries generated by commands entered at
21640 the command prompt. If @code{off}, forces @value{GDBN} to operate
21641 in the opposite mode, and it uses the default answers to all queries.
21642 If @code{auto} (the default), @value{GDBN} tries to determine whether
21643 its standard input is a terminal, and works in interactive-mode if it
21644 is, non-interactively otherwise.
21646 In the vast majority of cases, the debugger should be able to guess
21647 correctly which mode should be used. But this setting can be useful
21648 in certain specific cases, such as running a MinGW @value{GDBN}
21649 inside a cygwin window.
21651 @kindex show interactive-mode
21652 @item show interactive-mode
21653 Displays whether the debugger is operating in interactive mode or not.
21656 @node Extending GDB
21657 @chapter Extending @value{GDBN}
21658 @cindex extending GDB
21660 @value{GDBN} provides three mechanisms for extension. The first is based
21661 on composition of @value{GDBN} commands, the second is based on the
21662 Python scripting language, and the third is for defining new aliases of
21665 To facilitate the use of the first two extensions, @value{GDBN} is capable
21666 of evaluating the contents of a file. When doing so, @value{GDBN}
21667 can recognize which scripting language is being used by looking at
21668 the filename extension. Files with an unrecognized filename extension
21669 are always treated as a @value{GDBN} Command Files.
21670 @xref{Command Files,, Command files}.
21672 You can control how @value{GDBN} evaluates these files with the following
21676 @kindex set script-extension
21677 @kindex show script-extension
21678 @item set script-extension off
21679 All scripts are always evaluated as @value{GDBN} Command Files.
21681 @item set script-extension soft
21682 The debugger determines the scripting language based on filename
21683 extension. If this scripting language is supported, @value{GDBN}
21684 evaluates the script using that language. Otherwise, it evaluates
21685 the file as a @value{GDBN} Command File.
21687 @item set script-extension strict
21688 The debugger determines the scripting language based on filename
21689 extension, and evaluates the script using that language. If the
21690 language is not supported, then the evaluation fails.
21692 @item show script-extension
21693 Display the current value of the @code{script-extension} option.
21698 * Sequences:: Canned Sequences of Commands
21699 * Python:: Scripting @value{GDBN} using Python
21700 * Aliases:: Creating new spellings of existing commands
21704 @section Canned Sequences of Commands
21706 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
21707 Command Lists}), @value{GDBN} provides two ways to store sequences of
21708 commands for execution as a unit: user-defined commands and command
21712 * Define:: How to define your own commands
21713 * Hooks:: Hooks for user-defined commands
21714 * Command Files:: How to write scripts of commands to be stored in a file
21715 * Output:: Commands for controlled output
21719 @subsection User-defined Commands
21721 @cindex user-defined command
21722 @cindex arguments, to user-defined commands
21723 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
21724 which you assign a new name as a command. This is done with the
21725 @code{define} command. User commands may accept up to 10 arguments
21726 separated by whitespace. Arguments are accessed within the user command
21727 via @code{$arg0@dots{}$arg9}. A trivial example:
21731 print $arg0 + $arg1 + $arg2
21736 To execute the command use:
21743 This defines the command @code{adder}, which prints the sum of
21744 its three arguments. Note the arguments are text substitutions, so they may
21745 reference variables, use complex expressions, or even perform inferior
21748 @cindex argument count in user-defined commands
21749 @cindex how many arguments (user-defined commands)
21750 In addition, @code{$argc} may be used to find out how many arguments have
21751 been passed. This expands to a number in the range 0@dots{}10.
21756 print $arg0 + $arg1
21759 print $arg0 + $arg1 + $arg2
21767 @item define @var{commandname}
21768 Define a command named @var{commandname}. If there is already a command
21769 by that name, you are asked to confirm that you want to redefine it.
21770 @var{commandname} may be a bare command name consisting of letters,
21771 numbers, dashes, and underscores. It may also start with any predefined
21772 prefix command. For example, @samp{define target my-target} creates
21773 a user-defined @samp{target my-target} command.
21775 The definition of the command is made up of other @value{GDBN} command lines,
21776 which are given following the @code{define} command. The end of these
21777 commands is marked by a line containing @code{end}.
21780 @kindex end@r{ (user-defined commands)}
21781 @item document @var{commandname}
21782 Document the user-defined command @var{commandname}, so that it can be
21783 accessed by @code{help}. The command @var{commandname} must already be
21784 defined. This command reads lines of documentation just as @code{define}
21785 reads the lines of the command definition, ending with @code{end}.
21786 After the @code{document} command is finished, @code{help} on command
21787 @var{commandname} displays the documentation you have written.
21789 You may use the @code{document} command again to change the
21790 documentation of a command. Redefining the command with @code{define}
21791 does not change the documentation.
21793 @kindex dont-repeat
21794 @cindex don't repeat command
21796 Used inside a user-defined command, this tells @value{GDBN} that this
21797 command should not be repeated when the user hits @key{RET}
21798 (@pxref{Command Syntax, repeat last command}).
21800 @kindex help user-defined
21801 @item help user-defined
21802 List all user-defined commands and all python commands defined in class
21803 COMAND_USER. The first line of the documentation or docstring is
21808 @itemx show user @var{commandname}
21809 Display the @value{GDBN} commands used to define @var{commandname} (but
21810 not its documentation). If no @var{commandname} is given, display the
21811 definitions for all user-defined commands.
21812 This does not work for user-defined python commands.
21814 @cindex infinite recursion in user-defined commands
21815 @kindex show max-user-call-depth
21816 @kindex set max-user-call-depth
21817 @item show max-user-call-depth
21818 @itemx set max-user-call-depth
21819 The value of @code{max-user-call-depth} controls how many recursion
21820 levels are allowed in user-defined commands before @value{GDBN} suspects an
21821 infinite recursion and aborts the command.
21822 This does not apply to user-defined python commands.
21825 In addition to the above commands, user-defined commands frequently
21826 use control flow commands, described in @ref{Command Files}.
21828 When user-defined commands are executed, the
21829 commands of the definition are not printed. An error in any command
21830 stops execution of the user-defined command.
21832 If used interactively, commands that would ask for confirmation proceed
21833 without asking when used inside a user-defined command. Many @value{GDBN}
21834 commands that normally print messages to say what they are doing omit the
21835 messages when used in a user-defined command.
21838 @subsection User-defined Command Hooks
21839 @cindex command hooks
21840 @cindex hooks, for commands
21841 @cindex hooks, pre-command
21844 You may define @dfn{hooks}, which are a special kind of user-defined
21845 command. Whenever you run the command @samp{foo}, if the user-defined
21846 command @samp{hook-foo} exists, it is executed (with no arguments)
21847 before that command.
21849 @cindex hooks, post-command
21851 A hook may also be defined which is run after the command you executed.
21852 Whenever you run the command @samp{foo}, if the user-defined command
21853 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21854 that command. Post-execution hooks may exist simultaneously with
21855 pre-execution hooks, for the same command.
21857 It is valid for a hook to call the command which it hooks. If this
21858 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21860 @c It would be nice if hookpost could be passed a parameter indicating
21861 @c if the command it hooks executed properly or not. FIXME!
21863 @kindex stop@r{, a pseudo-command}
21864 In addition, a pseudo-command, @samp{stop} exists. Defining
21865 (@samp{hook-stop}) makes the associated commands execute every time
21866 execution stops in your program: before breakpoint commands are run,
21867 displays are printed, or the stack frame is printed.
21869 For example, to ignore @code{SIGALRM} signals while
21870 single-stepping, but treat them normally during normal execution,
21875 handle SIGALRM nopass
21879 handle SIGALRM pass
21882 define hook-continue
21883 handle SIGALRM pass
21887 As a further example, to hook at the beginning and end of the @code{echo}
21888 command, and to add extra text to the beginning and end of the message,
21896 define hookpost-echo
21900 (@value{GDBP}) echo Hello World
21901 <<<---Hello World--->>>
21906 You can define a hook for any single-word command in @value{GDBN}, but
21907 not for command aliases; you should define a hook for the basic command
21908 name, e.g.@: @code{backtrace} rather than @code{bt}.
21909 @c FIXME! So how does Joe User discover whether a command is an alias
21911 You can hook a multi-word command by adding @code{hook-} or
21912 @code{hookpost-} to the last word of the command, e.g.@:
21913 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21915 If an error occurs during the execution of your hook, execution of
21916 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21917 (before the command that you actually typed had a chance to run).
21919 If you try to define a hook which does not match any known command, you
21920 get a warning from the @code{define} command.
21922 @node Command Files
21923 @subsection Command Files
21925 @cindex command files
21926 @cindex scripting commands
21927 A command file for @value{GDBN} is a text file made of lines that are
21928 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21929 also be included. An empty line in a command file does nothing; it
21930 does not mean to repeat the last command, as it would from the
21933 You can request the execution of a command file with the @code{source}
21934 command. Note that the @code{source} command is also used to evaluate
21935 scripts that are not Command Files. The exact behavior can be configured
21936 using the @code{script-extension} setting.
21937 @xref{Extending GDB,, Extending GDB}.
21941 @cindex execute commands from a file
21942 @item source [-s] [-v] @var{filename}
21943 Execute the command file @var{filename}.
21946 The lines in a command file are generally executed sequentially,
21947 unless the order of execution is changed by one of the
21948 @emph{flow-control commands} described below. The commands are not
21949 printed as they are executed. An error in any command terminates
21950 execution of the command file and control is returned to the console.
21952 @value{GDBN} first searches for @var{filename} in the current directory.
21953 If the file is not found there, and @var{filename} does not specify a
21954 directory, then @value{GDBN} also looks for the file on the source search path
21955 (specified with the @samp{directory} command);
21956 except that @file{$cdir} is not searched because the compilation directory
21957 is not relevant to scripts.
21959 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21960 on the search path even if @var{filename} specifies a directory.
21961 The search is done by appending @var{filename} to each element of the
21962 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21963 and the search path contains @file{/home/user} then @value{GDBN} will
21964 look for the script @file{/home/user/mylib/myscript}.
21965 The search is also done if @var{filename} is an absolute path.
21966 For example, if @var{filename} is @file{/tmp/myscript} and
21967 the search path contains @file{/home/user} then @value{GDBN} will
21968 look for the script @file{/home/user/tmp/myscript}.
21969 For DOS-like systems, if @var{filename} contains a drive specification,
21970 it is stripped before concatenation. For example, if @var{filename} is
21971 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21972 will look for the script @file{c:/tmp/myscript}.
21974 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21975 each command as it is executed. The option must be given before
21976 @var{filename}, and is interpreted as part of the filename anywhere else.
21978 Commands that would ask for confirmation if used interactively proceed
21979 without asking when used in a command file. Many @value{GDBN} commands that
21980 normally print messages to say what they are doing omit the messages
21981 when called from command files.
21983 @value{GDBN} also accepts command input from standard input. In this
21984 mode, normal output goes to standard output and error output goes to
21985 standard error. Errors in a command file supplied on standard input do
21986 not terminate execution of the command file---execution continues with
21990 gdb < cmds > log 2>&1
21993 (The syntax above will vary depending on the shell used.) This example
21994 will execute commands from the file @file{cmds}. All output and errors
21995 would be directed to @file{log}.
21997 Since commands stored on command files tend to be more general than
21998 commands typed interactively, they frequently need to deal with
21999 complicated situations, such as different or unexpected values of
22000 variables and symbols, changes in how the program being debugged is
22001 built, etc. @value{GDBN} provides a set of flow-control commands to
22002 deal with these complexities. Using these commands, you can write
22003 complex scripts that loop over data structures, execute commands
22004 conditionally, etc.
22011 This command allows to include in your script conditionally executed
22012 commands. The @code{if} command takes a single argument, which is an
22013 expression to evaluate. It is followed by a series of commands that
22014 are executed only if the expression is true (its value is nonzero).
22015 There can then optionally be an @code{else} line, followed by a series
22016 of commands that are only executed if the expression was false. The
22017 end of the list is marked by a line containing @code{end}.
22021 This command allows to write loops. Its syntax is similar to
22022 @code{if}: the command takes a single argument, which is an expression
22023 to evaluate, and must be followed by the commands to execute, one per
22024 line, terminated by an @code{end}. These commands are called the
22025 @dfn{body} of the loop. The commands in the body of @code{while} are
22026 executed repeatedly as long as the expression evaluates to true.
22030 This command exits the @code{while} loop in whose body it is included.
22031 Execution of the script continues after that @code{while}s @code{end}
22034 @kindex loop_continue
22035 @item loop_continue
22036 This command skips the execution of the rest of the body of commands
22037 in the @code{while} loop in whose body it is included. Execution
22038 branches to the beginning of the @code{while} loop, where it evaluates
22039 the controlling expression.
22041 @kindex end@r{ (if/else/while commands)}
22043 Terminate the block of commands that are the body of @code{if},
22044 @code{else}, or @code{while} flow-control commands.
22049 @subsection Commands for Controlled Output
22051 During the execution of a command file or a user-defined command, normal
22052 @value{GDBN} output is suppressed; the only output that appears is what is
22053 explicitly printed by the commands in the definition. This section
22054 describes three commands useful for generating exactly the output you
22059 @item echo @var{text}
22060 @c I do not consider backslash-space a standard C escape sequence
22061 @c because it is not in ANSI.
22062 Print @var{text}. Nonprinting characters can be included in
22063 @var{text} using C escape sequences, such as @samp{\n} to print a
22064 newline. @strong{No newline is printed unless you specify one.}
22065 In addition to the standard C escape sequences, a backslash followed
22066 by a space stands for a space. This is useful for displaying a
22067 string with spaces at the beginning or the end, since leading and
22068 trailing spaces are otherwise trimmed from all arguments.
22069 To print @samp{@w{ }and foo =@w{ }}, use the command
22070 @samp{echo \@w{ }and foo = \@w{ }}.
22072 A backslash at the end of @var{text} can be used, as in C, to continue
22073 the command onto subsequent lines. For example,
22076 echo This is some text\n\
22077 which is continued\n\
22078 onto several lines.\n
22081 produces the same output as
22084 echo This is some text\n
22085 echo which is continued\n
22086 echo onto several lines.\n
22090 @item output @var{expression}
22091 Print the value of @var{expression} and nothing but that value: no
22092 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22093 value history either. @xref{Expressions, ,Expressions}, for more information
22096 @item output/@var{fmt} @var{expression}
22097 Print the value of @var{expression} in format @var{fmt}. You can use
22098 the same formats as for @code{print}. @xref{Output Formats,,Output
22099 Formats}, for more information.
22102 @item printf @var{template}, @var{expressions}@dots{}
22103 Print the values of one or more @var{expressions} under the control of
22104 the string @var{template}. To print several values, make
22105 @var{expressions} be a comma-separated list of individual expressions,
22106 which may be either numbers or pointers. Their values are printed as
22107 specified by @var{template}, exactly as a C program would do by
22108 executing the code below:
22111 printf (@var{template}, @var{expressions}@dots{});
22114 As in @code{C} @code{printf}, ordinary characters in @var{template}
22115 are printed verbatim, while @dfn{conversion specification} introduced
22116 by the @samp{%} character cause subsequent @var{expressions} to be
22117 evaluated, their values converted and formatted according to type and
22118 style information encoded in the conversion specifications, and then
22121 For example, you can print two values in hex like this:
22124 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22127 @code{printf} supports all the standard @code{C} conversion
22128 specifications, including the flags and modifiers between the @samp{%}
22129 character and the conversion letter, with the following exceptions:
22133 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22136 The modifier @samp{*} is not supported for specifying precision or
22140 The @samp{'} flag (for separation of digits into groups according to
22141 @code{LC_NUMERIC'}) is not supported.
22144 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22148 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22151 The conversion letters @samp{a} and @samp{A} are not supported.
22155 Note that the @samp{ll} type modifier is supported only if the
22156 underlying @code{C} implementation used to build @value{GDBN} supports
22157 the @code{long long int} type, and the @samp{L} type modifier is
22158 supported only if @code{long double} type is available.
22160 As in @code{C}, @code{printf} supports simple backslash-escape
22161 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22162 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22163 single character. Octal and hexadecimal escape sequences are not
22166 Additionally, @code{printf} supports conversion specifications for DFP
22167 (@dfn{Decimal Floating Point}) types using the following length modifiers
22168 together with a floating point specifier.
22173 @samp{H} for printing @code{Decimal32} types.
22176 @samp{D} for printing @code{Decimal64} types.
22179 @samp{DD} for printing @code{Decimal128} types.
22182 If the underlying @code{C} implementation used to build @value{GDBN} has
22183 support for the three length modifiers for DFP types, other modifiers
22184 such as width and precision will also be available for @value{GDBN} to use.
22186 In case there is no such @code{C} support, no additional modifiers will be
22187 available and the value will be printed in the standard way.
22189 Here's an example of printing DFP types using the above conversion letters:
22191 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22195 @item eval @var{template}, @var{expressions}@dots{}
22196 Convert the values of one or more @var{expressions} under the control of
22197 the string @var{template} to a command line, and call it.
22202 @section Scripting @value{GDBN} using Python
22203 @cindex python scripting
22204 @cindex scripting with python
22206 You can script @value{GDBN} using the @uref{http://www.python.org/,
22207 Python programming language}. This feature is available only if
22208 @value{GDBN} was configured using @option{--with-python}.
22210 @cindex python directory
22211 Python scripts used by @value{GDBN} should be installed in
22212 @file{@var{data-directory}/python}, where @var{data-directory} is
22213 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22214 This directory, known as the @dfn{python directory},
22215 is automatically added to the Python Search Path in order to allow
22216 the Python interpreter to locate all scripts installed at this location.
22218 Additionally, @value{GDBN} commands and convenience functions which
22219 are written in Python and are located in the
22220 @file{@var{data-directory}/python/gdb/command} or
22221 @file{@var{data-directory}/python/gdb/function} directories are
22222 automatically imported when @value{GDBN} starts.
22225 * Python Commands:: Accessing Python from @value{GDBN}.
22226 * Python API:: Accessing @value{GDBN} from Python.
22227 * Python Auto-loading:: Automatically loading Python code.
22228 * Python modules:: Python modules provided by @value{GDBN}.
22231 @node Python Commands
22232 @subsection Python Commands
22233 @cindex python commands
22234 @cindex commands to access python
22236 @value{GDBN} provides one command for accessing the Python interpreter,
22237 and one related setting:
22241 @item python @r{[}@var{code}@r{]}
22242 The @code{python} command can be used to evaluate Python code.
22244 If given an argument, the @code{python} command will evaluate the
22245 argument as a Python command. For example:
22248 (@value{GDBP}) python print 23
22252 If you do not provide an argument to @code{python}, it will act as a
22253 multi-line command, like @code{define}. In this case, the Python
22254 script is made up of subsequent command lines, given after the
22255 @code{python} command. This command list is terminated using a line
22256 containing @code{end}. For example:
22259 (@value{GDBP}) python
22261 End with a line saying just "end".
22267 @kindex set python print-stack
22268 @item set python print-stack
22269 By default, @value{GDBN} will print only the message component of a
22270 Python exception when an error occurs in a Python script. This can be
22271 controlled using @code{set python print-stack}: if @code{full}, then
22272 full Python stack printing is enabled; if @code{none}, then Python stack
22273 and message printing is disabled; if @code{message}, the default, only
22274 the message component of the error is printed.
22277 It is also possible to execute a Python script from the @value{GDBN}
22281 @item source @file{script-name}
22282 The script name must end with @samp{.py} and @value{GDBN} must be configured
22283 to recognize the script language based on filename extension using
22284 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22286 @item python execfile ("script-name")
22287 This method is based on the @code{execfile} Python built-in function,
22288 and thus is always available.
22292 @subsection Python API
22294 @cindex programming in python
22296 @cindex python stdout
22297 @cindex python pagination
22298 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22299 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22300 A Python program which outputs to one of these streams may have its
22301 output interrupted by the user (@pxref{Screen Size}). In this
22302 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22305 * Basic Python:: Basic Python Functions.
22306 * Exception Handling:: How Python exceptions are translated.
22307 * Values From Inferior:: Python representation of values.
22308 * Types In Python:: Python representation of types.
22309 * Pretty Printing API:: Pretty-printing values.
22310 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22311 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22312 * Inferiors In Python:: Python representation of inferiors (processes)
22313 * Events In Python:: Listening for events from @value{GDBN}.
22314 * Threads In Python:: Accessing inferior threads from Python.
22315 * Commands In Python:: Implementing new commands in Python.
22316 * Parameters In Python:: Adding new @value{GDBN} parameters.
22317 * Functions In Python:: Writing new convenience functions.
22318 * Progspaces In Python:: Program spaces.
22319 * Objfiles In Python:: Object files.
22320 * Frames In Python:: Accessing inferior stack frames from Python.
22321 * Blocks In Python:: Accessing frame blocks from Python.
22322 * Symbols In Python:: Python representation of symbols.
22323 * Symbol Tables In Python:: Python representation of symbol tables.
22324 * Lazy Strings In Python:: Python representation of lazy strings.
22325 * Breakpoints In Python:: Manipulating breakpoints using Python.
22326 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22331 @subsubsection Basic Python
22333 @cindex python functions
22334 @cindex python module
22336 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22337 methods and classes added by @value{GDBN} are placed in this module.
22338 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22339 use in all scripts evaluated by the @code{python} command.
22341 @findex gdb.PYTHONDIR
22342 @defvar gdb.PYTHONDIR
22343 A string containing the python directory (@pxref{Python}).
22346 @findex gdb.execute
22347 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
22348 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
22349 If a GDB exception happens while @var{command} runs, it is
22350 translated as described in @ref{Exception Handling,,Exception Handling}.
22352 @var{from_tty} specifies whether @value{GDBN} ought to consider this
22353 command as having originated from the user invoking it interactively.
22354 It must be a boolean value. If omitted, it defaults to @code{False}.
22356 By default, any output produced by @var{command} is sent to
22357 @value{GDBN}'s standard output. If the @var{to_string} parameter is
22358 @code{True}, then output will be collected by @code{gdb.execute} and
22359 returned as a string. The default is @code{False}, in which case the
22360 return value is @code{None}. If @var{to_string} is @code{True}, the
22361 @value{GDBN} virtual terminal will be temporarily set to unlimited width
22362 and height, and its pagination will be disabled; @pxref{Screen Size}.
22365 @findex gdb.breakpoints
22366 @defun gdb.breakpoints ()
22367 Return a sequence holding all of @value{GDBN}'s breakpoints.
22368 @xref{Breakpoints In Python}, for more information.
22371 @findex gdb.parameter
22372 @defun gdb.parameter (parameter)
22373 Return the value of a @value{GDBN} parameter. @var{parameter} is a
22374 string naming the parameter to look up; @var{parameter} may contain
22375 spaces if the parameter has a multi-part name. For example,
22376 @samp{print object} is a valid parameter name.
22378 If the named parameter does not exist, this function throws a
22379 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
22380 parameter's value is converted to a Python value of the appropriate
22381 type, and returned.
22384 @findex gdb.history
22385 @defun gdb.history (number)
22386 Return a value from @value{GDBN}'s value history (@pxref{Value
22387 History}). @var{number} indicates which history element to return.
22388 If @var{number} is negative, then @value{GDBN} will take its absolute value
22389 and count backward from the last element (i.e., the most recent element) to
22390 find the value to return. If @var{number} is zero, then @value{GDBN} will
22391 return the most recent element. If the element specified by @var{number}
22392 doesn't exist in the value history, a @code{gdb.error} exception will be
22395 If no exception is raised, the return value is always an instance of
22396 @code{gdb.Value} (@pxref{Values From Inferior}).
22399 @findex gdb.parse_and_eval
22400 @defun gdb.parse_and_eval (expression)
22401 Parse @var{expression} as an expression in the current language,
22402 evaluate it, and return the result as a @code{gdb.Value}.
22403 @var{expression} must be a string.
22405 This function can be useful when implementing a new command
22406 (@pxref{Commands In Python}), as it provides a way to parse the
22407 command's argument as an expression. It is also useful simply to
22408 compute values, for example, it is the only way to get the value of a
22409 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
22412 @findex gdb.post_event
22413 @defun gdb.post_event (event)
22414 Put @var{event}, a callable object taking no arguments, into
22415 @value{GDBN}'s internal event queue. This callable will be invoked at
22416 some later point, during @value{GDBN}'s event processing. Events
22417 posted using @code{post_event} will be run in the order in which they
22418 were posted; however, there is no way to know when they will be
22419 processed relative to other events inside @value{GDBN}.
22421 @value{GDBN} is not thread-safe. If your Python program uses multiple
22422 threads, you must be careful to only call @value{GDBN}-specific
22423 functions in the main @value{GDBN} thread. @code{post_event} ensures
22427 (@value{GDBP}) python
22431 > def __init__(self, message):
22432 > self.message = message;
22433 > def __call__(self):
22434 > gdb.write(self.message)
22436 >class MyThread1 (threading.Thread):
22438 > gdb.post_event(Writer("Hello "))
22440 >class MyThread2 (threading.Thread):
22442 > gdb.post_event(Writer("World\n"))
22444 >MyThread1().start()
22445 >MyThread2().start()
22447 (@value{GDBP}) Hello World
22452 @defun gdb.write (string @r{[}, stream{]})
22453 Print a string to @value{GDBN}'s paginated output stream. The
22454 optional @var{stream} determines the stream to print to. The default
22455 stream is @value{GDBN}'s standard output stream. Possible stream
22462 @value{GDBN}'s standard output stream.
22467 @value{GDBN}'s standard error stream.
22472 @value{GDBN}'s log stream (@pxref{Logging Output}).
22475 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
22476 call this function and will automatically direct the output to the
22481 @defun gdb.flush ()
22482 Flush the buffer of a @value{GDBN} paginated stream so that the
22483 contents are displayed immediately. @value{GDBN} will flush the
22484 contents of a stream automatically when it encounters a newline in the
22485 buffer. The optional @var{stream} determines the stream to flush. The
22486 default stream is @value{GDBN}'s standard output stream. Possible
22493 @value{GDBN}'s standard output stream.
22498 @value{GDBN}'s standard error stream.
22503 @value{GDBN}'s log stream (@pxref{Logging Output}).
22507 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
22508 call this function for the relevant stream.
22511 @findex gdb.target_charset
22512 @defun gdb.target_charset ()
22513 Return the name of the current target character set (@pxref{Character
22514 Sets}). This differs from @code{gdb.parameter('target-charset')} in
22515 that @samp{auto} is never returned.
22518 @findex gdb.target_wide_charset
22519 @defun gdb.target_wide_charset ()
22520 Return the name of the current target wide character set
22521 (@pxref{Character Sets}). This differs from
22522 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
22526 @findex gdb.solib_name
22527 @defun gdb.solib_name (address)
22528 Return the name of the shared library holding the given @var{address}
22529 as a string, or @code{None}.
22532 @findex gdb.decode_line
22533 @defun gdb.decode_line @r{[}expression@r{]}
22534 Return locations of the line specified by @var{expression}, or of the
22535 current line if no argument was given. This function returns a Python
22536 tuple containing two elements. The first element contains a string
22537 holding any unparsed section of @var{expression} (or @code{None} if
22538 the expression has been fully parsed). The second element contains
22539 either @code{None} or another tuple that contains all the locations
22540 that match the expression represented as @code{gdb.Symtab_and_line}
22541 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
22542 provided, it is decoded the way that @value{GDBN}'s inbuilt
22543 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
22546 @defun gdb.prompt_hook (current_prompt)
22547 @anchor{prompt_hook}
22549 If @var{prompt_hook} is callable, @value{GDBN} will call the method
22550 assigned to this operation before a prompt is displayed by
22553 The parameter @code{current_prompt} contains the current @value{GDBN}
22554 prompt. This method must return a Python string, or @code{None}. If
22555 a string is returned, the @value{GDBN} prompt will be set to that
22556 string. If @code{None} is returned, @value{GDBN} will continue to use
22557 the current prompt.
22559 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
22560 such as those used by readline for command input, and annotation
22561 related prompts are prohibited from being changed.
22564 @node Exception Handling
22565 @subsubsection Exception Handling
22566 @cindex python exceptions
22567 @cindex exceptions, python
22569 When executing the @code{python} command, Python exceptions
22570 uncaught within the Python code are translated to calls to
22571 @value{GDBN} error-reporting mechanism. If the command that called
22572 @code{python} does not handle the error, @value{GDBN} will
22573 terminate it and print an error message containing the Python
22574 exception name, the associated value, and the Python call stack
22575 backtrace at the point where the exception was raised. Example:
22578 (@value{GDBP}) python print foo
22579 Traceback (most recent call last):
22580 File "<string>", line 1, in <module>
22581 NameError: name 'foo' is not defined
22584 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
22585 Python code are converted to Python exceptions. The type of the
22586 Python exception depends on the error.
22590 This is the base class for most exceptions generated by @value{GDBN}.
22591 It is derived from @code{RuntimeError}, for compatibility with earlier
22592 versions of @value{GDBN}.
22594 If an error occurring in @value{GDBN} does not fit into some more
22595 specific category, then the generated exception will have this type.
22597 @item gdb.MemoryError
22598 This is a subclass of @code{gdb.error} which is thrown when an
22599 operation tried to access invalid memory in the inferior.
22601 @item KeyboardInterrupt
22602 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
22603 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
22606 In all cases, your exception handler will see the @value{GDBN} error
22607 message as its value and the Python call stack backtrace at the Python
22608 statement closest to where the @value{GDBN} error occured as the
22611 @findex gdb.GdbError
22612 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
22613 it is useful to be able to throw an exception that doesn't cause a
22614 traceback to be printed. For example, the user may have invoked the
22615 command incorrectly. Use the @code{gdb.GdbError} exception
22616 to handle this case. Example:
22620 >class HelloWorld (gdb.Command):
22621 > """Greet the whole world."""
22622 > def __init__ (self):
22623 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
22624 > def invoke (self, args, from_tty):
22625 > argv = gdb.string_to_argv (args)
22626 > if len (argv) != 0:
22627 > raise gdb.GdbError ("hello-world takes no arguments")
22628 > print "Hello, World!"
22631 (gdb) hello-world 42
22632 hello-world takes no arguments
22635 @node Values From Inferior
22636 @subsubsection Values From Inferior
22637 @cindex values from inferior, with Python
22638 @cindex python, working with values from inferior
22640 @cindex @code{gdb.Value}
22641 @value{GDBN} provides values it obtains from the inferior program in
22642 an object of type @code{gdb.Value}. @value{GDBN} uses this object
22643 for its internal bookkeeping of the inferior's values, and for
22644 fetching values when necessary.
22646 Inferior values that are simple scalars can be used directly in
22647 Python expressions that are valid for the value's data type. Here's
22648 an example for an integer or floating-point value @code{some_val}:
22655 As result of this, @code{bar} will also be a @code{gdb.Value} object
22656 whose values are of the same type as those of @code{some_val}.
22658 Inferior values that are structures or instances of some class can
22659 be accessed using the Python @dfn{dictionary syntax}. For example, if
22660 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
22661 can access its @code{foo} element with:
22664 bar = some_val['foo']
22667 Again, @code{bar} will also be a @code{gdb.Value} object.
22669 A @code{gdb.Value} that represents a function can be executed via
22670 inferior function call. Any arguments provided to the call must match
22671 the function's prototype, and must be provided in the order specified
22674 For example, @code{some_val} is a @code{gdb.Value} instance
22675 representing a function that takes two integers as arguments. To
22676 execute this function, call it like so:
22679 result = some_val (10,20)
22682 Any values returned from a function call will be stored as a
22685 The following attributes are provided:
22688 @defvar Value.address
22689 If this object is addressable, this read-only attribute holds a
22690 @code{gdb.Value} object representing the address. Otherwise,
22691 this attribute holds @code{None}.
22694 @cindex optimized out value in Python
22695 @defvar Value.is_optimized_out
22696 This read-only boolean attribute is true if the compiler optimized out
22697 this value, thus it is not available for fetching from the inferior.
22701 The type of this @code{gdb.Value}. The value of this attribute is a
22702 @code{gdb.Type} object (@pxref{Types In Python}).
22705 @defvar Value.dynamic_type
22706 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
22707 type information (@acronym{RTTI}) to determine the dynamic type of the
22708 value. If this value is of class type, it will return the class in
22709 which the value is embedded, if any. If this value is of pointer or
22710 reference to a class type, it will compute the dynamic type of the
22711 referenced object, and return a pointer or reference to that type,
22712 respectively. In all other cases, it will return the value's static
22715 Note that this feature will only work when debugging a C@t{++} program
22716 that includes @acronym{RTTI} for the object in question. Otherwise,
22717 it will just return the static type of the value as in @kbd{ptype foo}
22718 (@pxref{Symbols, ptype}).
22721 @defvar Value.is_lazy
22722 The value of this read-only boolean attribute is @code{True} if this
22723 @code{gdb.Value} has not yet been fetched from the inferior.
22724 @value{GDBN} does not fetch values until necessary, for efficiency.
22728 myval = gdb.parse_and_eval ('somevar')
22731 The value of @code{somevar} is not fetched at this time. It will be
22732 fetched when the value is needed, or when the @code{fetch_lazy}
22737 The following methods are provided:
22740 @defun Value.__init__ (@var{val})
22741 Many Python values can be converted directly to a @code{gdb.Value} via
22742 this object initializer. Specifically:
22745 @item Python boolean
22746 A Python boolean is converted to the boolean type from the current
22749 @item Python integer
22750 A Python integer is converted to the C @code{long} type for the
22751 current architecture.
22754 A Python long is converted to the C @code{long long} type for the
22755 current architecture.
22758 A Python float is converted to the C @code{double} type for the
22759 current architecture.
22761 @item Python string
22762 A Python string is converted to a target string, using the current
22765 @item @code{gdb.Value}
22766 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22768 @item @code{gdb.LazyString}
22769 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22770 Python}), then the lazy string's @code{value} method is called, and
22771 its result is used.
22775 @defun Value.cast (type)
22776 Return a new instance of @code{gdb.Value} that is the result of
22777 casting this instance to the type described by @var{type}, which must
22778 be a @code{gdb.Type} object. If the cast cannot be performed for some
22779 reason, this method throws an exception.
22782 @defun Value.dereference ()
22783 For pointer data types, this method returns a new @code{gdb.Value} object
22784 whose contents is the object pointed to by the pointer. For example, if
22785 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22792 then you can use the corresponding @code{gdb.Value} to access what
22793 @code{foo} points to like this:
22796 bar = foo.dereference ()
22799 The result @code{bar} will be a @code{gdb.Value} object holding the
22800 value pointed to by @code{foo}.
22802 A similar function @code{Value.referenced_value} exists which also
22803 returns @code{gdb.Value} objects corresonding to the values pointed to
22804 by pointer values (and additionally, values referenced by reference
22805 values). However, the behavior of @code{Value.dereference}
22806 differs from @code{Value.referenced_value} by the fact that the
22807 behavior of @code{Value.dereference} is identical to applying the C
22808 unary operator @code{*} on a given value. For example, consider a
22809 reference to a pointer @code{ptrref}, declared in your C@t{++} program
22813 typedef int *intptr;
22817 intptr &ptrref = ptr;
22820 Though @code{ptrref} is a reference value, one can apply the method
22821 @code{Value.dereference} to the @code{gdb.Value} object corresponding
22822 to it and obtain a @code{gdb.Value} which is identical to that
22823 corresponding to @code{val}. However, if you apply the method
22824 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
22825 object identical to that corresponding to @code{ptr}.
22828 py_ptrref = gdb.parse_and_eval ("ptrref")
22829 py_val = py_ptrref.dereference ()
22830 py_ptr = py_ptrref.referenced_value ()
22833 The @code{gdb.Value} object @code{py_val} is identical to that
22834 corresponding to @code{val}, and @code{py_ptr} is identical to that
22835 corresponding to @code{ptr}. In general, @code{Value.dereference} can
22836 be applied whenever the C unary operator @code{*} can be applied
22837 to the corresponding C value. For those cases where applying both
22838 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
22839 the results obtained need not be identical (as we have seen in the above
22840 example). The results are however identical when applied on
22841 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
22842 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
22845 @defun Value.referenced_value ()
22846 For pointer or reference data types, this method returns a new
22847 @code{gdb.Value} object corresponding to the value referenced by the
22848 pointer/reference value. For pointer data types,
22849 @code{Value.dereference} and @code{Value.referenced_value} produce
22850 identical results. The difference between these methods is that
22851 @code{Value.dereference} cannot get the values referenced by reference
22852 values. For example, consider a reference to an @code{int}, declared
22853 in your C@t{++} program as
22861 then applying @code{Value.dereference} to the @code{gdb.Value} object
22862 corresponding to @code{ref} will result in an error, while applying
22863 @code{Value.referenced_value} will result in a @code{gdb.Value} object
22864 identical to that corresponding to @code{val}.
22867 py_ref = gdb.parse_and_eval ("ref")
22868 er_ref = py_ref.dereference () # Results in error
22869 py_val = py_ref.referenced_value () # Returns the referenced value
22872 The @code{gdb.Value} object @code{py_val} is identical to that
22873 corresponding to @code{val}.
22876 @defun Value.dynamic_cast (type)
22877 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22878 operator were used. Consult a C@t{++} reference for details.
22881 @defun Value.reinterpret_cast (type)
22882 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22883 operator were used. Consult a C@t{++} reference for details.
22886 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22887 If this @code{gdb.Value} represents a string, then this method
22888 converts the contents to a Python string. Otherwise, this method will
22889 throw an exception.
22891 Strings are recognized in a language-specific way; whether a given
22892 @code{gdb.Value} represents a string is determined by the current
22895 For C-like languages, a value is a string if it is a pointer to or an
22896 array of characters or ints. The string is assumed to be terminated
22897 by a zero of the appropriate width. However if the optional length
22898 argument is given, the string will be converted to that given length,
22899 ignoring any embedded zeros that the string may contain.
22901 If the optional @var{encoding} argument is given, it must be a string
22902 naming the encoding of the string in the @code{gdb.Value}, such as
22903 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22904 the same encodings as the corresponding argument to Python's
22905 @code{string.decode} method, and the Python codec machinery will be used
22906 to convert the string. If @var{encoding} is not given, or if
22907 @var{encoding} is the empty string, then either the @code{target-charset}
22908 (@pxref{Character Sets}) will be used, or a language-specific encoding
22909 will be used, if the current language is able to supply one.
22911 The optional @var{errors} argument is the same as the corresponding
22912 argument to Python's @code{string.decode} method.
22914 If the optional @var{length} argument is given, the string will be
22915 fetched and converted to the given length.
22918 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22919 If this @code{gdb.Value} represents a string, then this method
22920 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22921 In Python}). Otherwise, this method will throw an exception.
22923 If the optional @var{encoding} argument is given, it must be a string
22924 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22925 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22926 @var{encoding} argument is an encoding that @value{GDBN} does
22927 recognize, @value{GDBN} will raise an error.
22929 When a lazy string is printed, the @value{GDBN} encoding machinery is
22930 used to convert the string during printing. If the optional
22931 @var{encoding} argument is not provided, or is an empty string,
22932 @value{GDBN} will automatically select the encoding most suitable for
22933 the string type. For further information on encoding in @value{GDBN}
22934 please see @ref{Character Sets}.
22936 If the optional @var{length} argument is given, the string will be
22937 fetched and encoded to the length of characters specified. If
22938 the @var{length} argument is not provided, the string will be fetched
22939 and encoded until a null of appropriate width is found.
22942 @defun Value.fetch_lazy ()
22943 If the @code{gdb.Value} object is currently a lazy value
22944 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22945 fetched from the inferior. Any errors that occur in the process
22946 will produce a Python exception.
22948 If the @code{gdb.Value} object is not a lazy value, this method
22951 This method does not return a value.
22956 @node Types In Python
22957 @subsubsection Types In Python
22958 @cindex types in Python
22959 @cindex Python, working with types
22962 @value{GDBN} represents types from the inferior using the class
22965 The following type-related functions are available in the @code{gdb}
22968 @findex gdb.lookup_type
22969 @defun gdb.lookup_type (name @r{[}, block@r{]})
22970 This function looks up a type by name. @var{name} is the name of the
22971 type to look up. It must be a string.
22973 If @var{block} is given, then @var{name} is looked up in that scope.
22974 Otherwise, it is searched for globally.
22976 Ordinarily, this function will return an instance of @code{gdb.Type}.
22977 If the named type cannot be found, it will throw an exception.
22980 If the type is a structure or class type, or an enum type, the fields
22981 of that type can be accessed using the Python @dfn{dictionary syntax}.
22982 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22983 a structure type, you can access its @code{foo} field with:
22986 bar = some_type['foo']
22989 @code{bar} will be a @code{gdb.Field} object; see below under the
22990 description of the @code{Type.fields} method for a description of the
22991 @code{gdb.Field} class.
22993 An instance of @code{Type} has the following attributes:
22997 The type code for this type. The type code will be one of the
22998 @code{TYPE_CODE_} constants defined below.
23001 @defvar Type.sizeof
23002 The size of this type, in target @code{char} units. Usually, a
23003 target's @code{char} type will be an 8-bit byte. However, on some
23004 unusual platforms, this type may have a different size.
23008 The tag name for this type. The tag name is the name after
23009 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23010 languages have this concept. If this type has no tag name, then
23011 @code{None} is returned.
23015 The following methods are provided:
23018 @defun Type.fields ()
23019 For structure and union types, this method returns the fields. Range
23020 types have two fields, the minimum and maximum values. Enum types
23021 have one field per enum constant. Function and method types have one
23022 field per parameter. The base types of C@t{++} classes are also
23023 represented as fields. If the type has no fields, or does not fit
23024 into one of these categories, an empty sequence will be returned.
23026 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23029 This attribute is not available for @code{static} fields (as in
23030 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23031 position of the field. For @code{enum} fields, the value is the
23032 enumeration member's integer representation.
23035 The name of the field, or @code{None} for anonymous fields.
23038 This is @code{True} if the field is artificial, usually meaning that
23039 it was provided by the compiler and not the user. This attribute is
23040 always provided, and is @code{False} if the field is not artificial.
23042 @item is_base_class
23043 This is @code{True} if the field represents a base class of a C@t{++}
23044 structure. This attribute is always provided, and is @code{False}
23045 if the field is not a base class of the type that is the argument of
23046 @code{fields}, or if that type was not a C@t{++} class.
23049 If the field is packed, or is a bitfield, then this will have a
23050 non-zero value, which is the size of the field in bits. Otherwise,
23051 this will be zero; in this case the field's size is given by its type.
23054 The type of the field. This is usually an instance of @code{Type},
23055 but it can be @code{None} in some situations.
23059 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23060 Return a new @code{gdb.Type} object which represents an array of this
23061 type. If one argument is given, it is the inclusive upper bound of
23062 the array; in this case the lower bound is zero. If two arguments are
23063 given, the first argument is the lower bound of the array, and the
23064 second argument is the upper bound of the array. An array's length
23065 must not be negative, but the bounds can be.
23068 @defun Type.const ()
23069 Return a new @code{gdb.Type} object which represents a
23070 @code{const}-qualified variant of this type.
23073 @defun Type.volatile ()
23074 Return a new @code{gdb.Type} object which represents a
23075 @code{volatile}-qualified variant of this type.
23078 @defun Type.unqualified ()
23079 Return a new @code{gdb.Type} object which represents an unqualified
23080 variant of this type. That is, the result is neither @code{const} nor
23084 @defun Type.range ()
23085 Return a Python @code{Tuple} object that contains two elements: the
23086 low bound of the argument type and the high bound of that type. If
23087 the type does not have a range, @value{GDBN} will raise a
23088 @code{gdb.error} exception (@pxref{Exception Handling}).
23091 @defun Type.reference ()
23092 Return a new @code{gdb.Type} object which represents a reference to this
23096 @defun Type.pointer ()
23097 Return a new @code{gdb.Type} object which represents a pointer to this
23101 @defun Type.strip_typedefs ()
23102 Return a new @code{gdb.Type} that represents the real type,
23103 after removing all layers of typedefs.
23106 @defun Type.target ()
23107 Return a new @code{gdb.Type} object which represents the target type
23110 For a pointer type, the target type is the type of the pointed-to
23111 object. For an array type (meaning C-like arrays), the target type is
23112 the type of the elements of the array. For a function or method type,
23113 the target type is the type of the return value. For a complex type,
23114 the target type is the type of the elements. For a typedef, the
23115 target type is the aliased type.
23117 If the type does not have a target, this method will throw an
23121 @defun Type.template_argument (n @r{[}, block@r{]})
23122 If this @code{gdb.Type} is an instantiation of a template, this will
23123 return a new @code{gdb.Type} which represents the type of the
23124 @var{n}th template argument.
23126 If this @code{gdb.Type} is not a template type, this will throw an
23127 exception. Ordinarily, only C@t{++} code will have template types.
23129 If @var{block} is given, then @var{name} is looked up in that scope.
23130 Otherwise, it is searched for globally.
23135 Each type has a code, which indicates what category this type falls
23136 into. The available type categories are represented by constants
23137 defined in the @code{gdb} module:
23140 @findex TYPE_CODE_PTR
23141 @findex gdb.TYPE_CODE_PTR
23142 @item gdb.TYPE_CODE_PTR
23143 The type is a pointer.
23145 @findex TYPE_CODE_ARRAY
23146 @findex gdb.TYPE_CODE_ARRAY
23147 @item gdb.TYPE_CODE_ARRAY
23148 The type is an array.
23150 @findex TYPE_CODE_STRUCT
23151 @findex gdb.TYPE_CODE_STRUCT
23152 @item gdb.TYPE_CODE_STRUCT
23153 The type is a structure.
23155 @findex TYPE_CODE_UNION
23156 @findex gdb.TYPE_CODE_UNION
23157 @item gdb.TYPE_CODE_UNION
23158 The type is a union.
23160 @findex TYPE_CODE_ENUM
23161 @findex gdb.TYPE_CODE_ENUM
23162 @item gdb.TYPE_CODE_ENUM
23163 The type is an enum.
23165 @findex TYPE_CODE_FLAGS
23166 @findex gdb.TYPE_CODE_FLAGS
23167 @item gdb.TYPE_CODE_FLAGS
23168 A bit flags type, used for things such as status registers.
23170 @findex TYPE_CODE_FUNC
23171 @findex gdb.TYPE_CODE_FUNC
23172 @item gdb.TYPE_CODE_FUNC
23173 The type is a function.
23175 @findex TYPE_CODE_INT
23176 @findex gdb.TYPE_CODE_INT
23177 @item gdb.TYPE_CODE_INT
23178 The type is an integer type.
23180 @findex TYPE_CODE_FLT
23181 @findex gdb.TYPE_CODE_FLT
23182 @item gdb.TYPE_CODE_FLT
23183 A floating point type.
23185 @findex TYPE_CODE_VOID
23186 @findex gdb.TYPE_CODE_VOID
23187 @item gdb.TYPE_CODE_VOID
23188 The special type @code{void}.
23190 @findex TYPE_CODE_SET
23191 @findex gdb.TYPE_CODE_SET
23192 @item gdb.TYPE_CODE_SET
23195 @findex TYPE_CODE_RANGE
23196 @findex gdb.TYPE_CODE_RANGE
23197 @item gdb.TYPE_CODE_RANGE
23198 A range type, that is, an integer type with bounds.
23200 @findex TYPE_CODE_STRING
23201 @findex gdb.TYPE_CODE_STRING
23202 @item gdb.TYPE_CODE_STRING
23203 A string type. Note that this is only used for certain languages with
23204 language-defined string types; C strings are not represented this way.
23206 @findex TYPE_CODE_BITSTRING
23207 @findex gdb.TYPE_CODE_BITSTRING
23208 @item gdb.TYPE_CODE_BITSTRING
23211 @findex TYPE_CODE_ERROR
23212 @findex gdb.TYPE_CODE_ERROR
23213 @item gdb.TYPE_CODE_ERROR
23214 An unknown or erroneous type.
23216 @findex TYPE_CODE_METHOD
23217 @findex gdb.TYPE_CODE_METHOD
23218 @item gdb.TYPE_CODE_METHOD
23219 A method type, as found in C@t{++} or Java.
23221 @findex TYPE_CODE_METHODPTR
23222 @findex gdb.TYPE_CODE_METHODPTR
23223 @item gdb.TYPE_CODE_METHODPTR
23224 A pointer-to-member-function.
23226 @findex TYPE_CODE_MEMBERPTR
23227 @findex gdb.TYPE_CODE_MEMBERPTR
23228 @item gdb.TYPE_CODE_MEMBERPTR
23229 A pointer-to-member.
23231 @findex TYPE_CODE_REF
23232 @findex gdb.TYPE_CODE_REF
23233 @item gdb.TYPE_CODE_REF
23236 @findex TYPE_CODE_CHAR
23237 @findex gdb.TYPE_CODE_CHAR
23238 @item gdb.TYPE_CODE_CHAR
23241 @findex TYPE_CODE_BOOL
23242 @findex gdb.TYPE_CODE_BOOL
23243 @item gdb.TYPE_CODE_BOOL
23246 @findex TYPE_CODE_COMPLEX
23247 @findex gdb.TYPE_CODE_COMPLEX
23248 @item gdb.TYPE_CODE_COMPLEX
23249 A complex float type.
23251 @findex TYPE_CODE_TYPEDEF
23252 @findex gdb.TYPE_CODE_TYPEDEF
23253 @item gdb.TYPE_CODE_TYPEDEF
23254 A typedef to some other type.
23256 @findex TYPE_CODE_NAMESPACE
23257 @findex gdb.TYPE_CODE_NAMESPACE
23258 @item gdb.TYPE_CODE_NAMESPACE
23259 A C@t{++} namespace.
23261 @findex TYPE_CODE_DECFLOAT
23262 @findex gdb.TYPE_CODE_DECFLOAT
23263 @item gdb.TYPE_CODE_DECFLOAT
23264 A decimal floating point type.
23266 @findex TYPE_CODE_INTERNAL_FUNCTION
23267 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23268 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23269 A function internal to @value{GDBN}. This is the type used to represent
23270 convenience functions.
23273 Further support for types is provided in the @code{gdb.types}
23274 Python module (@pxref{gdb.types}).
23276 @node Pretty Printing API
23277 @subsubsection Pretty Printing API
23279 An example output is provided (@pxref{Pretty Printing}).
23281 A pretty-printer is just an object that holds a value and implements a
23282 specific interface, defined here.
23284 @defun pretty_printer.children (self)
23285 @value{GDBN} will call this method on a pretty-printer to compute the
23286 children of the pretty-printer's value.
23288 This method must return an object conforming to the Python iterator
23289 protocol. Each item returned by the iterator must be a tuple holding
23290 two elements. The first element is the ``name'' of the child; the
23291 second element is the child's value. The value can be any Python
23292 object which is convertible to a @value{GDBN} value.
23294 This method is optional. If it does not exist, @value{GDBN} will act
23295 as though the value has no children.
23298 @defun pretty_printer.display_hint (self)
23299 The CLI may call this method and use its result to change the
23300 formatting of a value. The result will also be supplied to an MI
23301 consumer as a @samp{displayhint} attribute of the variable being
23304 This method is optional. If it does exist, this method must return a
23307 Some display hints are predefined by @value{GDBN}:
23311 Indicate that the object being printed is ``array-like''. The CLI
23312 uses this to respect parameters such as @code{set print elements} and
23313 @code{set print array}.
23316 Indicate that the object being printed is ``map-like'', and that the
23317 children of this value can be assumed to alternate between keys and
23321 Indicate that the object being printed is ``string-like''. If the
23322 printer's @code{to_string} method returns a Python string of some
23323 kind, then @value{GDBN} will call its internal language-specific
23324 string-printing function to format the string. For the CLI this means
23325 adding quotation marks, possibly escaping some characters, respecting
23326 @code{set print elements}, and the like.
23330 @defun pretty_printer.to_string (self)
23331 @value{GDBN} will call this method to display the string
23332 representation of the value passed to the object's constructor.
23334 When printing from the CLI, if the @code{to_string} method exists,
23335 then @value{GDBN} will prepend its result to the values returned by
23336 @code{children}. Exactly how this formatting is done is dependent on
23337 the display hint, and may change as more hints are added. Also,
23338 depending on the print settings (@pxref{Print Settings}), the CLI may
23339 print just the result of @code{to_string} in a stack trace, omitting
23340 the result of @code{children}.
23342 If this method returns a string, it is printed verbatim.
23344 Otherwise, if this method returns an instance of @code{gdb.Value},
23345 then @value{GDBN} prints this value. This may result in a call to
23346 another pretty-printer.
23348 If instead the method returns a Python value which is convertible to a
23349 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
23350 the resulting value. Again, this may result in a call to another
23351 pretty-printer. Python scalars (integers, floats, and booleans) and
23352 strings are convertible to @code{gdb.Value}; other types are not.
23354 Finally, if this method returns @code{None} then no further operations
23355 are peformed in this method and nothing is printed.
23357 If the result is not one of these types, an exception is raised.
23360 @value{GDBN} provides a function which can be used to look up the
23361 default pretty-printer for a @code{gdb.Value}:
23363 @findex gdb.default_visualizer
23364 @defun gdb.default_visualizer (value)
23365 This function takes a @code{gdb.Value} object as an argument. If a
23366 pretty-printer for this value exists, then it is returned. If no such
23367 printer exists, then this returns @code{None}.
23370 @node Selecting Pretty-Printers
23371 @subsubsection Selecting Pretty-Printers
23373 The Python list @code{gdb.pretty_printers} contains an array of
23374 functions or callable objects that have been registered via addition
23375 as a pretty-printer. Printers in this list are called @code{global}
23376 printers, they're available when debugging all inferiors.
23377 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
23378 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
23381 Each function on these lists is passed a single @code{gdb.Value}
23382 argument and should return a pretty-printer object conforming to the
23383 interface definition above (@pxref{Pretty Printing API}). If a function
23384 cannot create a pretty-printer for the value, it should return
23387 @value{GDBN} first checks the @code{pretty_printers} attribute of each
23388 @code{gdb.Objfile} in the current program space and iteratively calls
23389 each enabled lookup routine in the list for that @code{gdb.Objfile}
23390 until it receives a pretty-printer object.
23391 If no pretty-printer is found in the objfile lists, @value{GDBN} then
23392 searches the pretty-printer list of the current program space,
23393 calling each enabled function until an object is returned.
23394 After these lists have been exhausted, it tries the global
23395 @code{gdb.pretty_printers} list, again calling each enabled function until an
23396 object is returned.
23398 The order in which the objfiles are searched is not specified. For a
23399 given list, functions are always invoked from the head of the list,
23400 and iterated over sequentially until the end of the list, or a printer
23401 object is returned.
23403 For various reasons a pretty-printer may not work.
23404 For example, the underlying data structure may have changed and
23405 the pretty-printer is out of date.
23407 The consequences of a broken pretty-printer are severe enough that
23408 @value{GDBN} provides support for enabling and disabling individual
23409 printers. For example, if @code{print frame-arguments} is on,
23410 a backtrace can become highly illegible if any argument is printed
23411 with a broken printer.
23413 Pretty-printers are enabled and disabled by attaching an @code{enabled}
23414 attribute to the registered function or callable object. If this attribute
23415 is present and its value is @code{False}, the printer is disabled, otherwise
23416 the printer is enabled.
23418 @node Writing a Pretty-Printer
23419 @subsubsection Writing a Pretty-Printer
23420 @cindex writing a pretty-printer
23422 A pretty-printer consists of two parts: a lookup function to detect
23423 if the type is supported, and the printer itself.
23425 Here is an example showing how a @code{std::string} printer might be
23426 written. @xref{Pretty Printing API}, for details on the API this class
23430 class StdStringPrinter(object):
23431 "Print a std::string"
23433 def __init__(self, val):
23436 def to_string(self):
23437 return self.val['_M_dataplus']['_M_p']
23439 def display_hint(self):
23443 And here is an example showing how a lookup function for the printer
23444 example above might be written.
23447 def str_lookup_function(val):
23448 lookup_tag = val.type.tag
23449 if lookup_tag == None:
23451 regex = re.compile("^std::basic_string<char,.*>$")
23452 if regex.match(lookup_tag):
23453 return StdStringPrinter(val)
23457 The example lookup function extracts the value's type, and attempts to
23458 match it to a type that it can pretty-print. If it is a type the
23459 printer can pretty-print, it will return a printer object. If not, it
23460 returns @code{None}.
23462 We recommend that you put your core pretty-printers into a Python
23463 package. If your pretty-printers are for use with a library, we
23464 further recommend embedding a version number into the package name.
23465 This practice will enable @value{GDBN} to load multiple versions of
23466 your pretty-printers at the same time, because they will have
23469 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
23470 can be evaluated multiple times without changing its meaning. An
23471 ideal auto-load file will consist solely of @code{import}s of your
23472 printer modules, followed by a call to a register pretty-printers with
23473 the current objfile.
23475 Taken as a whole, this approach will scale nicely to multiple
23476 inferiors, each potentially using a different library version.
23477 Embedding a version number in the Python package name will ensure that
23478 @value{GDBN} is able to load both sets of printers simultaneously.
23479 Then, because the search for pretty-printers is done by objfile, and
23480 because your auto-loaded code took care to register your library's
23481 printers with a specific objfile, @value{GDBN} will find the correct
23482 printers for the specific version of the library used by each
23485 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
23486 this code might appear in @code{gdb.libstdcxx.v6}:
23489 def register_printers(objfile):
23490 objfile.pretty_printers.append(str_lookup_function)
23494 And then the corresponding contents of the auto-load file would be:
23497 import gdb.libstdcxx.v6
23498 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
23501 The previous example illustrates a basic pretty-printer.
23502 There are a few things that can be improved on.
23503 The printer doesn't have a name, making it hard to identify in a
23504 list of installed printers. The lookup function has a name, but
23505 lookup functions can have arbitrary, even identical, names.
23507 Second, the printer only handles one type, whereas a library typically has
23508 several types. One could install a lookup function for each desired type
23509 in the library, but one could also have a single lookup function recognize
23510 several types. The latter is the conventional way this is handled.
23511 If a pretty-printer can handle multiple data types, then its
23512 @dfn{subprinters} are the printers for the individual data types.
23514 The @code{gdb.printing} module provides a formal way of solving these
23515 problems (@pxref{gdb.printing}).
23516 Here is another example that handles multiple types.
23518 These are the types we are going to pretty-print:
23521 struct foo @{ int a, b; @};
23522 struct bar @{ struct foo x, y; @};
23525 Here are the printers:
23529 """Print a foo object."""
23531 def __init__(self, val):
23534 def to_string(self):
23535 return ("a=<" + str(self.val["a"]) +
23536 "> b=<" + str(self.val["b"]) + ">")
23539 """Print a bar object."""
23541 def __init__(self, val):
23544 def to_string(self):
23545 return ("x=<" + str(self.val["x"]) +
23546 "> y=<" + str(self.val["y"]) + ">")
23549 This example doesn't need a lookup function, that is handled by the
23550 @code{gdb.printing} module. Instead a function is provided to build up
23551 the object that handles the lookup.
23554 import gdb.printing
23556 def build_pretty_printer():
23557 pp = gdb.printing.RegexpCollectionPrettyPrinter(
23559 pp.add_printer('foo', '^foo$', fooPrinter)
23560 pp.add_printer('bar', '^bar$', barPrinter)
23564 And here is the autoload support:
23567 import gdb.printing
23569 gdb.printing.register_pretty_printer(
23570 gdb.current_objfile(),
23571 my_library.build_pretty_printer())
23574 Finally, when this printer is loaded into @value{GDBN}, here is the
23575 corresponding output of @samp{info pretty-printer}:
23578 (gdb) info pretty-printer
23585 @node Inferiors In Python
23586 @subsubsection Inferiors In Python
23587 @cindex inferiors in Python
23589 @findex gdb.Inferior
23590 Programs which are being run under @value{GDBN} are called inferiors
23591 (@pxref{Inferiors and Programs}). Python scripts can access
23592 information about and manipulate inferiors controlled by @value{GDBN}
23593 via objects of the @code{gdb.Inferior} class.
23595 The following inferior-related functions are available in the @code{gdb}
23598 @defun gdb.inferiors ()
23599 Return a tuple containing all inferior objects.
23602 @defun gdb.selected_inferior ()
23603 Return an object representing the current inferior.
23606 A @code{gdb.Inferior} object has the following attributes:
23609 @defvar Inferior.num
23610 ID of inferior, as assigned by GDB.
23613 @defvar Inferior.pid
23614 Process ID of the inferior, as assigned by the underlying operating
23618 @defvar Inferior.was_attached
23619 Boolean signaling whether the inferior was created using `attach', or
23620 started by @value{GDBN} itself.
23624 A @code{gdb.Inferior} object has the following methods:
23627 @defun Inferior.is_valid ()
23628 Returns @code{True} if the @code{gdb.Inferior} object is valid,
23629 @code{False} if not. A @code{gdb.Inferior} object will become invalid
23630 if the inferior no longer exists within @value{GDBN}. All other
23631 @code{gdb.Inferior} methods will throw an exception if it is invalid
23632 at the time the method is called.
23635 @defun Inferior.threads ()
23636 This method returns a tuple holding all the threads which are valid
23637 when it is called. If there are no valid threads, the method will
23638 return an empty tuple.
23641 @findex gdb.read_memory
23642 @defun Inferior.read_memory (address, length)
23643 Read @var{length} bytes of memory from the inferior, starting at
23644 @var{address}. Returns a buffer object, which behaves much like an array
23645 or a string. It can be modified and given to the @code{gdb.write_memory}
23649 @findex gdb.write_memory
23650 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
23651 Write the contents of @var{buffer} to the inferior, starting at
23652 @var{address}. The @var{buffer} parameter must be a Python object
23653 which supports the buffer protocol, i.e., a string, an array or the
23654 object returned from @code{gdb.read_memory}. If given, @var{length}
23655 determines the number of bytes from @var{buffer} to be written.
23658 @findex gdb.search_memory
23659 @defun Inferior.search_memory (address, length, pattern)
23660 Search a region of the inferior memory starting at @var{address} with
23661 the given @var{length} using the search pattern supplied in
23662 @var{pattern}. The @var{pattern} parameter must be a Python object
23663 which supports the buffer protocol, i.e., a string, an array or the
23664 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
23665 containing the address where the pattern was found, or @code{None} if
23666 the pattern could not be found.
23670 @node Events In Python
23671 @subsubsection Events In Python
23672 @cindex inferior events in Python
23674 @value{GDBN} provides a general event facility so that Python code can be
23675 notified of various state changes, particularly changes that occur in
23678 An @dfn{event} is just an object that describes some state change. The
23679 type of the object and its attributes will vary depending on the details
23680 of the change. All the existing events are described below.
23682 In order to be notified of an event, you must register an event handler
23683 with an @dfn{event registry}. An event registry is an object in the
23684 @code{gdb.events} module which dispatches particular events. A registry
23685 provides methods to register and unregister event handlers:
23688 @defun EventRegistry.connect (object)
23689 Add the given callable @var{object} to the registry. This object will be
23690 called when an event corresponding to this registry occurs.
23693 @defun EventRegistry.disconnect (object)
23694 Remove the given @var{object} from the registry. Once removed, the object
23695 will no longer receive notifications of events.
23699 Here is an example:
23702 def exit_handler (event):
23703 print "event type: exit"
23704 print "exit code: %d" % (event.exit_code)
23706 gdb.events.exited.connect (exit_handler)
23709 In the above example we connect our handler @code{exit_handler} to the
23710 registry @code{events.exited}. Once connected, @code{exit_handler} gets
23711 called when the inferior exits. The argument @dfn{event} in this example is
23712 of type @code{gdb.ExitedEvent}. As you can see in the example the
23713 @code{ExitedEvent} object has an attribute which indicates the exit code of
23716 The following is a listing of the event registries that are available and
23717 details of the events they emit:
23722 Emits @code{gdb.ThreadEvent}.
23724 Some events can be thread specific when @value{GDBN} is running in non-stop
23725 mode. When represented in Python, these events all extend
23726 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
23727 events which are emitted by this or other modules might extend this event.
23728 Examples of these events are @code{gdb.BreakpointEvent} and
23729 @code{gdb.ContinueEvent}.
23732 @defvar ThreadEvent.inferior_thread
23733 In non-stop mode this attribute will be set to the specific thread which was
23734 involved in the emitted event. Otherwise, it will be set to @code{None}.
23738 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
23740 This event indicates that the inferior has been continued after a stop. For
23741 inherited attribute refer to @code{gdb.ThreadEvent} above.
23743 @item events.exited
23744 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
23745 @code{events.ExitedEvent} has two attributes:
23747 @defvar ExitedEvent.exit_code
23748 An integer representing the exit code, if available, which the inferior
23749 has returned. (The exit code could be unavailable if, for example,
23750 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
23751 the attribute does not exist.
23753 @defvar ExitedEvent inferior
23754 A reference to the inferior which triggered the @code{exited} event.
23759 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
23761 Indicates that the inferior has stopped. All events emitted by this registry
23762 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
23763 will indicate the stopped thread when @value{GDBN} is running in non-stop
23764 mode. Refer to @code{gdb.ThreadEvent} above for more details.
23766 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
23768 This event indicates that the inferior or one of its threads has received as
23769 signal. @code{gdb.SignalEvent} has the following attributes:
23772 @defvar SignalEvent.stop_signal
23773 A string representing the signal received by the inferior. A list of possible
23774 signal values can be obtained by running the command @code{info signals} in
23775 the @value{GDBN} command prompt.
23779 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
23781 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
23782 been hit, and has the following attributes:
23785 @defvar BreakpointEvent.breakpoints
23786 A sequence containing references to all the breakpoints (type
23787 @code{gdb.Breakpoint}) that were hit.
23788 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
23790 @defvar BreakpointEvent.breakpoint
23791 A reference to the first breakpoint that was hit.
23792 This function is maintained for backward compatibility and is now deprecated
23793 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
23797 @item events.new_objfile
23798 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
23799 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
23802 @defvar NewObjFileEvent.new_objfile
23803 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
23804 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
23810 @node Threads In Python
23811 @subsubsection Threads In Python
23812 @cindex threads in python
23814 @findex gdb.InferiorThread
23815 Python scripts can access information about, and manipulate inferior threads
23816 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
23818 The following thread-related functions are available in the @code{gdb}
23821 @findex gdb.selected_thread
23822 @defun gdb.selected_thread ()
23823 This function returns the thread object for the selected thread. If there
23824 is no selected thread, this will return @code{None}.
23827 A @code{gdb.InferiorThread} object has the following attributes:
23830 @defvar InferiorThread.name
23831 The name of the thread. If the user specified a name using
23832 @code{thread name}, then this returns that name. Otherwise, if an
23833 OS-supplied name is available, then it is returned. Otherwise, this
23834 returns @code{None}.
23836 This attribute can be assigned to. The new value must be a string
23837 object, which sets the new name, or @code{None}, which removes any
23838 user-specified thread name.
23841 @defvar InferiorThread.num
23842 ID of the thread, as assigned by GDB.
23845 @defvar InferiorThread.ptid
23846 ID of the thread, as assigned by the operating system. This attribute is a
23847 tuple containing three integers. The first is the Process ID (PID); the second
23848 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23849 Either the LWPID or TID may be 0, which indicates that the operating system
23850 does not use that identifier.
23854 A @code{gdb.InferiorThread} object has the following methods:
23857 @defun InferiorThread.is_valid ()
23858 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23859 @code{False} if not. A @code{gdb.InferiorThread} object will become
23860 invalid if the thread exits, or the inferior that the thread belongs
23861 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23862 exception if it is invalid at the time the method is called.
23865 @defun InferiorThread.switch ()
23866 This changes @value{GDBN}'s currently selected thread to the one represented
23870 @defun InferiorThread.is_stopped ()
23871 Return a Boolean indicating whether the thread is stopped.
23874 @defun InferiorThread.is_running ()
23875 Return a Boolean indicating whether the thread is running.
23878 @defun InferiorThread.is_exited ()
23879 Return a Boolean indicating whether the thread is exited.
23883 @node Commands In Python
23884 @subsubsection Commands In Python
23886 @cindex commands in python
23887 @cindex python commands
23888 You can implement new @value{GDBN} CLI commands in Python. A CLI
23889 command is implemented using an instance of the @code{gdb.Command}
23890 class, most commonly using a subclass.
23892 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23893 The object initializer for @code{Command} registers the new command
23894 with @value{GDBN}. This initializer is normally invoked from the
23895 subclass' own @code{__init__} method.
23897 @var{name} is the name of the command. If @var{name} consists of
23898 multiple words, then the initial words are looked for as prefix
23899 commands. In this case, if one of the prefix commands does not exist,
23900 an exception is raised.
23902 There is no support for multi-line commands.
23904 @var{command_class} should be one of the @samp{COMMAND_} constants
23905 defined below. This argument tells @value{GDBN} how to categorize the
23906 new command in the help system.
23908 @var{completer_class} is an optional argument. If given, it should be
23909 one of the @samp{COMPLETE_} constants defined below. This argument
23910 tells @value{GDBN} how to perform completion for this command. If not
23911 given, @value{GDBN} will attempt to complete using the object's
23912 @code{complete} method (see below); if no such method is found, an
23913 error will occur when completion is attempted.
23915 @var{prefix} is an optional argument. If @code{True}, then the new
23916 command is a prefix command; sub-commands of this command may be
23919 The help text for the new command is taken from the Python
23920 documentation string for the command's class, if there is one. If no
23921 documentation string is provided, the default value ``This command is
23922 not documented.'' is used.
23925 @cindex don't repeat Python command
23926 @defun Command.dont_repeat ()
23927 By default, a @value{GDBN} command is repeated when the user enters a
23928 blank line at the command prompt. A command can suppress this
23929 behavior by invoking the @code{dont_repeat} method. This is similar
23930 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23933 @defun Command.invoke (argument, from_tty)
23934 This method is called by @value{GDBN} when this command is invoked.
23936 @var{argument} is a string. It is the argument to the command, after
23937 leading and trailing whitespace has been stripped.
23939 @var{from_tty} is a boolean argument. When true, this means that the
23940 command was entered by the user at the terminal; when false it means
23941 that the command came from elsewhere.
23943 If this method throws an exception, it is turned into a @value{GDBN}
23944 @code{error} call. Otherwise, the return value is ignored.
23946 @findex gdb.string_to_argv
23947 To break @var{argument} up into an argv-like string use
23948 @code{gdb.string_to_argv}. This function behaves identically to
23949 @value{GDBN}'s internal argument lexer @code{buildargv}.
23950 It is recommended to use this for consistency.
23951 Arguments are separated by spaces and may be quoted.
23955 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23956 ['1', '2 "3', '4 "5', "6 '7"]
23961 @cindex completion of Python commands
23962 @defun Command.complete (text, word)
23963 This method is called by @value{GDBN} when the user attempts
23964 completion on this command. All forms of completion are handled by
23965 this method, that is, the @key{TAB} and @key{M-?} key bindings
23966 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23969 The arguments @var{text} and @var{word} are both strings. @var{text}
23970 holds the complete command line up to the cursor's location.
23971 @var{word} holds the last word of the command line; this is computed
23972 using a word-breaking heuristic.
23974 The @code{complete} method can return several values:
23977 If the return value is a sequence, the contents of the sequence are
23978 used as the completions. It is up to @code{complete} to ensure that the
23979 contents actually do complete the word. A zero-length sequence is
23980 allowed, it means that there were no completions available. Only
23981 string elements of the sequence are used; other elements in the
23982 sequence are ignored.
23985 If the return value is one of the @samp{COMPLETE_} constants defined
23986 below, then the corresponding @value{GDBN}-internal completion
23987 function is invoked, and its result is used.
23990 All other results are treated as though there were no available
23995 When a new command is registered, it must be declared as a member of
23996 some general class of commands. This is used to classify top-level
23997 commands in the on-line help system; note that prefix commands are not
23998 listed under their own category but rather that of their top-level
23999 command. The available classifications are represented by constants
24000 defined in the @code{gdb} module:
24003 @findex COMMAND_NONE
24004 @findex gdb.COMMAND_NONE
24005 @item gdb.COMMAND_NONE
24006 The command does not belong to any particular class. A command in
24007 this category will not be displayed in any of the help categories.
24009 @findex COMMAND_RUNNING
24010 @findex gdb.COMMAND_RUNNING
24011 @item gdb.COMMAND_RUNNING
24012 The command is related to running the inferior. For example,
24013 @code{start}, @code{step}, and @code{continue} are in this category.
24014 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24015 commands in this category.
24017 @findex COMMAND_DATA
24018 @findex gdb.COMMAND_DATA
24019 @item gdb.COMMAND_DATA
24020 The command is related to data or variables. For example,
24021 @code{call}, @code{find}, and @code{print} are in this category. Type
24022 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24025 @findex COMMAND_STACK
24026 @findex gdb.COMMAND_STACK
24027 @item gdb.COMMAND_STACK
24028 The command has to do with manipulation of the stack. For example,
24029 @code{backtrace}, @code{frame}, and @code{return} are in this
24030 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24031 list of commands in this category.
24033 @findex COMMAND_FILES
24034 @findex gdb.COMMAND_FILES
24035 @item gdb.COMMAND_FILES
24036 This class is used for file-related commands. For example,
24037 @code{file}, @code{list} and @code{section} are in this category.
24038 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24039 commands in this category.
24041 @findex COMMAND_SUPPORT
24042 @findex gdb.COMMAND_SUPPORT
24043 @item gdb.COMMAND_SUPPORT
24044 This should be used for ``support facilities'', generally meaning
24045 things that are useful to the user when interacting with @value{GDBN},
24046 but not related to the state of the inferior. For example,
24047 @code{help}, @code{make}, and @code{shell} are in this category. Type
24048 @kbd{help support} at the @value{GDBN} prompt to see a list of
24049 commands in this category.
24051 @findex COMMAND_STATUS
24052 @findex gdb.COMMAND_STATUS
24053 @item gdb.COMMAND_STATUS
24054 The command is an @samp{info}-related command, that is, related to the
24055 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24056 and @code{show} are in this category. Type @kbd{help status} at the
24057 @value{GDBN} prompt to see a list of commands in this category.
24059 @findex COMMAND_BREAKPOINTS
24060 @findex gdb.COMMAND_BREAKPOINTS
24061 @item gdb.COMMAND_BREAKPOINTS
24062 The command has to do with breakpoints. For example, @code{break},
24063 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24064 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24067 @findex COMMAND_TRACEPOINTS
24068 @findex gdb.COMMAND_TRACEPOINTS
24069 @item gdb.COMMAND_TRACEPOINTS
24070 The command has to do with tracepoints. For example, @code{trace},
24071 @code{actions}, and @code{tfind} are in this category. Type
24072 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24073 commands in this category.
24075 @findex COMMAND_USER
24076 @findex gdb.COMMAND_USER
24077 @item gdb.COMMAND_USER
24078 The command is a general purpose command for the user, and typically
24079 does not fit in one of the other categories.
24080 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24081 a list of commands in this category, as well as the list of gdb macros
24082 (@pxref{Sequences}).
24084 @findex COMMAND_OBSCURE
24085 @findex gdb.COMMAND_OBSCURE
24086 @item gdb.COMMAND_OBSCURE
24087 The command is only used in unusual circumstances, or is not of
24088 general interest to users. For example, @code{checkpoint},
24089 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24090 obscure} at the @value{GDBN} prompt to see a list of commands in this
24093 @findex COMMAND_MAINTENANCE
24094 @findex gdb.COMMAND_MAINTENANCE
24095 @item gdb.COMMAND_MAINTENANCE
24096 The command is only useful to @value{GDBN} maintainers. The
24097 @code{maintenance} and @code{flushregs} commands are in this category.
24098 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24099 commands in this category.
24102 A new command can use a predefined completion function, either by
24103 specifying it via an argument at initialization, or by returning it
24104 from the @code{complete} method. These predefined completion
24105 constants are all defined in the @code{gdb} module:
24108 @findex COMPLETE_NONE
24109 @findex gdb.COMPLETE_NONE
24110 @item gdb.COMPLETE_NONE
24111 This constant means that no completion should be done.
24113 @findex COMPLETE_FILENAME
24114 @findex gdb.COMPLETE_FILENAME
24115 @item gdb.COMPLETE_FILENAME
24116 This constant means that filename completion should be performed.
24118 @findex COMPLETE_LOCATION
24119 @findex gdb.COMPLETE_LOCATION
24120 @item gdb.COMPLETE_LOCATION
24121 This constant means that location completion should be done.
24122 @xref{Specify Location}.
24124 @findex COMPLETE_COMMAND
24125 @findex gdb.COMPLETE_COMMAND
24126 @item gdb.COMPLETE_COMMAND
24127 This constant means that completion should examine @value{GDBN}
24130 @findex COMPLETE_SYMBOL
24131 @findex gdb.COMPLETE_SYMBOL
24132 @item gdb.COMPLETE_SYMBOL
24133 This constant means that completion should be done using symbol names
24137 The following code snippet shows how a trivial CLI command can be
24138 implemented in Python:
24141 class HelloWorld (gdb.Command):
24142 """Greet the whole world."""
24144 def __init__ (self):
24145 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24147 def invoke (self, arg, from_tty):
24148 print "Hello, World!"
24153 The last line instantiates the class, and is necessary to trigger the
24154 registration of the command with @value{GDBN}. Depending on how the
24155 Python code is read into @value{GDBN}, you may need to import the
24156 @code{gdb} module explicitly.
24158 @node Parameters In Python
24159 @subsubsection Parameters In Python
24161 @cindex parameters in python
24162 @cindex python parameters
24163 @tindex gdb.Parameter
24165 You can implement new @value{GDBN} parameters using Python. A new
24166 parameter is implemented as an instance of the @code{gdb.Parameter}
24169 Parameters are exposed to the user via the @code{set} and
24170 @code{show} commands. @xref{Help}.
24172 There are many parameters that already exist and can be set in
24173 @value{GDBN}. Two examples are: @code{set follow fork} and
24174 @code{set charset}. Setting these parameters influences certain
24175 behavior in @value{GDBN}. Similarly, you can define parameters that
24176 can be used to influence behavior in custom Python scripts and commands.
24178 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24179 The object initializer for @code{Parameter} registers the new
24180 parameter with @value{GDBN}. This initializer is normally invoked
24181 from the subclass' own @code{__init__} method.
24183 @var{name} is the name of the new parameter. If @var{name} consists
24184 of multiple words, then the initial words are looked for as prefix
24185 parameters. An example of this can be illustrated with the
24186 @code{set print} set of parameters. If @var{name} is
24187 @code{print foo}, then @code{print} will be searched as the prefix
24188 parameter. In this case the parameter can subsequently be accessed in
24189 @value{GDBN} as @code{set print foo}.
24191 If @var{name} consists of multiple words, and no prefix parameter group
24192 can be found, an exception is raised.
24194 @var{command-class} should be one of the @samp{COMMAND_} constants
24195 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24196 categorize the new parameter in the help system.
24198 @var{parameter-class} should be one of the @samp{PARAM_} constants
24199 defined below. This argument tells @value{GDBN} the type of the new
24200 parameter; this information is used for input validation and
24203 If @var{parameter-class} is @code{PARAM_ENUM}, then
24204 @var{enum-sequence} must be a sequence of strings. These strings
24205 represent the possible values for the parameter.
24207 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24208 of a fourth argument will cause an exception to be thrown.
24210 The help text for the new parameter is taken from the Python
24211 documentation string for the parameter's class, if there is one. If
24212 there is no documentation string, a default value is used.
24215 @defvar Parameter.set_doc
24216 If this attribute exists, and is a string, then its value is used as
24217 the help text for this parameter's @code{set} command. The value is
24218 examined when @code{Parameter.__init__} is invoked; subsequent changes
24222 @defvar Parameter.show_doc
24223 If this attribute exists, and is a string, then its value is used as
24224 the help text for this parameter's @code{show} command. The value is
24225 examined when @code{Parameter.__init__} is invoked; subsequent changes
24229 @defvar Parameter.value
24230 The @code{value} attribute holds the underlying value of the
24231 parameter. It can be read and assigned to just as any other
24232 attribute. @value{GDBN} does validation when assignments are made.
24235 There are two methods that should be implemented in any
24236 @code{Parameter} class. These are:
24238 @defun Parameter.get_set_string (self)
24239 @value{GDBN} will call this method when a @var{parameter}'s value has
24240 been changed via the @code{set} API (for example, @kbd{set foo off}).
24241 The @code{value} attribute has already been populated with the new
24242 value and may be used in output. This method must return a string.
24245 @defun Parameter.get_show_string (self, svalue)
24246 @value{GDBN} will call this method when a @var{parameter}'s
24247 @code{show} API has been invoked (for example, @kbd{show foo}). The
24248 argument @code{svalue} receives the string representation of the
24249 current value. This method must return a string.
24252 When a new parameter is defined, its type must be specified. The
24253 available types are represented by constants defined in the @code{gdb}
24257 @findex PARAM_BOOLEAN
24258 @findex gdb.PARAM_BOOLEAN
24259 @item gdb.PARAM_BOOLEAN
24260 The value is a plain boolean. The Python boolean values, @code{True}
24261 and @code{False} are the only valid values.
24263 @findex PARAM_AUTO_BOOLEAN
24264 @findex gdb.PARAM_AUTO_BOOLEAN
24265 @item gdb.PARAM_AUTO_BOOLEAN
24266 The value has three possible states: true, false, and @samp{auto}. In
24267 Python, true and false are represented using boolean constants, and
24268 @samp{auto} is represented using @code{None}.
24270 @findex PARAM_UINTEGER
24271 @findex gdb.PARAM_UINTEGER
24272 @item gdb.PARAM_UINTEGER
24273 The value is an unsigned integer. The value of 0 should be
24274 interpreted to mean ``unlimited''.
24276 @findex PARAM_INTEGER
24277 @findex gdb.PARAM_INTEGER
24278 @item gdb.PARAM_INTEGER
24279 The value is a signed integer. The value of 0 should be interpreted
24280 to mean ``unlimited''.
24282 @findex PARAM_STRING
24283 @findex gdb.PARAM_STRING
24284 @item gdb.PARAM_STRING
24285 The value is a string. When the user modifies the string, any escape
24286 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
24287 translated into corresponding characters and encoded into the current
24290 @findex PARAM_STRING_NOESCAPE
24291 @findex gdb.PARAM_STRING_NOESCAPE
24292 @item gdb.PARAM_STRING_NOESCAPE
24293 The value is a string. When the user modifies the string, escapes are
24294 passed through untranslated.
24296 @findex PARAM_OPTIONAL_FILENAME
24297 @findex gdb.PARAM_OPTIONAL_FILENAME
24298 @item gdb.PARAM_OPTIONAL_FILENAME
24299 The value is a either a filename (a string), or @code{None}.
24301 @findex PARAM_FILENAME
24302 @findex gdb.PARAM_FILENAME
24303 @item gdb.PARAM_FILENAME
24304 The value is a filename. This is just like
24305 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
24307 @findex PARAM_ZINTEGER
24308 @findex gdb.PARAM_ZINTEGER
24309 @item gdb.PARAM_ZINTEGER
24310 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
24311 is interpreted as itself.
24314 @findex gdb.PARAM_ENUM
24315 @item gdb.PARAM_ENUM
24316 The value is a string, which must be one of a collection string
24317 constants provided when the parameter is created.
24320 @node Functions In Python
24321 @subsubsection Writing new convenience functions
24323 @cindex writing convenience functions
24324 @cindex convenience functions in python
24325 @cindex python convenience functions
24326 @tindex gdb.Function
24328 You can implement new convenience functions (@pxref{Convenience Vars})
24329 in Python. A convenience function is an instance of a subclass of the
24330 class @code{gdb.Function}.
24332 @defun Function.__init__ (name)
24333 The initializer for @code{Function} registers the new function with
24334 @value{GDBN}. The argument @var{name} is the name of the function,
24335 a string. The function will be visible to the user as a convenience
24336 variable of type @code{internal function}, whose name is the same as
24337 the given @var{name}.
24339 The documentation for the new function is taken from the documentation
24340 string for the new class.
24343 @defun Function.invoke (@var{*args})
24344 When a convenience function is evaluated, its arguments are converted
24345 to instances of @code{gdb.Value}, and then the function's
24346 @code{invoke} method is called. Note that @value{GDBN} does not
24347 predetermine the arity of convenience functions. Instead, all
24348 available arguments are passed to @code{invoke}, following the
24349 standard Python calling convention. In particular, a convenience
24350 function can have default values for parameters without ill effect.
24352 The return value of this method is used as its value in the enclosing
24353 expression. If an ordinary Python value is returned, it is converted
24354 to a @code{gdb.Value} following the usual rules.
24357 The following code snippet shows how a trivial convenience function can
24358 be implemented in Python:
24361 class Greet (gdb.Function):
24362 """Return string to greet someone.
24363 Takes a name as argument."""
24365 def __init__ (self):
24366 super (Greet, self).__init__ ("greet")
24368 def invoke (self, name):
24369 return "Hello, %s!" % name.string ()
24374 The last line instantiates the class, and is necessary to trigger the
24375 registration of the function with @value{GDBN}. Depending on how the
24376 Python code is read into @value{GDBN}, you may need to import the
24377 @code{gdb} module explicitly.
24379 @node Progspaces In Python
24380 @subsubsection Program Spaces In Python
24382 @cindex progspaces in python
24383 @tindex gdb.Progspace
24385 A program space, or @dfn{progspace}, represents a symbolic view
24386 of an address space.
24387 It consists of all of the objfiles of the program.
24388 @xref{Objfiles In Python}.
24389 @xref{Inferiors and Programs, program spaces}, for more details
24390 about program spaces.
24392 The following progspace-related functions are available in the
24395 @findex gdb.current_progspace
24396 @defun gdb.current_progspace ()
24397 This function returns the program space of the currently selected inferior.
24398 @xref{Inferiors and Programs}.
24401 @findex gdb.progspaces
24402 @defun gdb.progspaces ()
24403 Return a sequence of all the progspaces currently known to @value{GDBN}.
24406 Each progspace is represented by an instance of the @code{gdb.Progspace}
24409 @defvar Progspace.filename
24410 The file name of the progspace as a string.
24413 @defvar Progspace.pretty_printers
24414 The @code{pretty_printers} attribute is a list of functions. It is
24415 used to look up pretty-printers. A @code{Value} is passed to each
24416 function in order; if the function returns @code{None}, then the
24417 search continues. Otherwise, the return value should be an object
24418 which is used to format the value. @xref{Pretty Printing API}, for more
24422 @node Objfiles In Python
24423 @subsubsection Objfiles In Python
24425 @cindex objfiles in python
24426 @tindex gdb.Objfile
24428 @value{GDBN} loads symbols for an inferior from various
24429 symbol-containing files (@pxref{Files}). These include the primary
24430 executable file, any shared libraries used by the inferior, and any
24431 separate debug info files (@pxref{Separate Debug Files}).
24432 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
24434 The following objfile-related functions are available in the
24437 @findex gdb.current_objfile
24438 @defun gdb.current_objfile ()
24439 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
24440 sets the ``current objfile'' to the corresponding objfile. This
24441 function returns the current objfile. If there is no current objfile,
24442 this function returns @code{None}.
24445 @findex gdb.objfiles
24446 @defun gdb.objfiles ()
24447 Return a sequence of all the objfiles current known to @value{GDBN}.
24448 @xref{Objfiles In Python}.
24451 Each objfile is represented by an instance of the @code{gdb.Objfile}
24454 @defvar Objfile.filename
24455 The file name of the objfile as a string.
24458 @defvar Objfile.pretty_printers
24459 The @code{pretty_printers} attribute is a list of functions. It is
24460 used to look up pretty-printers. A @code{Value} is passed to each
24461 function in order; if the function returns @code{None}, then the
24462 search continues. Otherwise, the return value should be an object
24463 which is used to format the value. @xref{Pretty Printing API}, for more
24467 A @code{gdb.Objfile} object has the following methods:
24469 @defun Objfile.is_valid ()
24470 Returns @code{True} if the @code{gdb.Objfile} object is valid,
24471 @code{False} if not. A @code{gdb.Objfile} object can become invalid
24472 if the object file it refers to is not loaded in @value{GDBN} any
24473 longer. All other @code{gdb.Objfile} methods will throw an exception
24474 if it is invalid at the time the method is called.
24477 @node Frames In Python
24478 @subsubsection Accessing inferior stack frames from Python.
24480 @cindex frames in python
24481 When the debugged program stops, @value{GDBN} is able to analyze its call
24482 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
24483 represents a frame in the stack. A @code{gdb.Frame} object is only valid
24484 while its corresponding frame exists in the inferior's stack. If you try
24485 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
24486 exception (@pxref{Exception Handling}).
24488 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
24492 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
24496 The following frame-related functions are available in the @code{gdb} module:
24498 @findex gdb.selected_frame
24499 @defun gdb.selected_frame ()
24500 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
24503 @findex gdb.newest_frame
24504 @defun gdb.newest_frame ()
24505 Return the newest frame object for the selected thread.
24508 @defun gdb.frame_stop_reason_string (reason)
24509 Return a string explaining the reason why @value{GDBN} stopped unwinding
24510 frames, as expressed by the given @var{reason} code (an integer, see the
24511 @code{unwind_stop_reason} method further down in this section).
24514 A @code{gdb.Frame} object has the following methods:
24517 @defun Frame.is_valid ()
24518 Returns true if the @code{gdb.Frame} object is valid, false if not.
24519 A frame object can become invalid if the frame it refers to doesn't
24520 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
24521 an exception if it is invalid at the time the method is called.
24524 @defun Frame.name ()
24525 Returns the function name of the frame, or @code{None} if it can't be
24529 @defun Frame.type ()
24530 Returns the type of the frame. The value can be one of:
24532 @item gdb.NORMAL_FRAME
24533 An ordinary stack frame.
24535 @item gdb.DUMMY_FRAME
24536 A fake stack frame that was created by @value{GDBN} when performing an
24537 inferior function call.
24539 @item gdb.INLINE_FRAME
24540 A frame representing an inlined function. The function was inlined
24541 into a @code{gdb.NORMAL_FRAME} that is older than this one.
24543 @item gdb.TAILCALL_FRAME
24544 A frame representing a tail call. @xref{Tail Call Frames}.
24546 @item gdb.SIGTRAMP_FRAME
24547 A signal trampoline frame. This is the frame created by the OS when
24548 it calls into a signal handler.
24550 @item gdb.ARCH_FRAME
24551 A fake stack frame representing a cross-architecture call.
24553 @item gdb.SENTINEL_FRAME
24554 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
24559 @defun Frame.unwind_stop_reason ()
24560 Return an integer representing the reason why it's not possible to find
24561 more frames toward the outermost frame. Use
24562 @code{gdb.frame_stop_reason_string} to convert the value returned by this
24563 function to a string. The value can be one of:
24566 @item gdb.FRAME_UNWIND_NO_REASON
24567 No particular reason (older frames should be available).
24569 @item gdb.FRAME_UNWIND_NULL_ID
24570 The previous frame's analyzer returns an invalid result.
24572 @item gdb.FRAME_UNWIND_OUTERMOST
24573 This frame is the outermost.
24575 @item gdb.FRAME_UNWIND_UNAVAILABLE
24576 Cannot unwind further, because that would require knowing the
24577 values of registers or memory that have not been collected.
24579 @item gdb.FRAME_UNWIND_INNER_ID
24580 This frame ID looks like it ought to belong to a NEXT frame,
24581 but we got it for a PREV frame. Normally, this is a sign of
24582 unwinder failure. It could also indicate stack corruption.
24584 @item gdb.FRAME_UNWIND_SAME_ID
24585 This frame has the same ID as the previous one. That means
24586 that unwinding further would almost certainly give us another
24587 frame with exactly the same ID, so break the chain. Normally,
24588 this is a sign of unwinder failure. It could also indicate
24591 @item gdb.FRAME_UNWIND_NO_SAVED_PC
24592 The frame unwinder did not find any saved PC, but we needed
24593 one to unwind further.
24595 @item gdb.FRAME_UNWIND_FIRST_ERROR
24596 Any stop reason greater or equal to this value indicates some kind
24597 of error. This special value facilitates writing code that tests
24598 for errors in unwinding in a way that will work correctly even if
24599 the list of the other values is modified in future @value{GDBN}
24600 versions. Using it, you could write:
24602 reason = gdb.selected_frame().unwind_stop_reason ()
24603 reason_str = gdb.frame_stop_reason_string (reason)
24604 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
24605 print "An error occured: %s" % reason_str
24612 Returns the frame's resume address.
24615 @defun Frame.block ()
24616 Return the frame's code block. @xref{Blocks In Python}.
24619 @defun Frame.function ()
24620 Return the symbol for the function corresponding to this frame.
24621 @xref{Symbols In Python}.
24624 @defun Frame.older ()
24625 Return the frame that called this frame.
24628 @defun Frame.newer ()
24629 Return the frame called by this frame.
24632 @defun Frame.find_sal ()
24633 Return the frame's symtab and line object.
24634 @xref{Symbol Tables In Python}.
24637 @defun Frame.read_var (variable @r{[}, block@r{]})
24638 Return the value of @var{variable} in this frame. If the optional
24639 argument @var{block} is provided, search for the variable from that
24640 block; otherwise start at the frame's current block (which is
24641 determined by the frame's current program counter). @var{variable}
24642 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
24643 @code{gdb.Block} object.
24646 @defun Frame.select ()
24647 Set this frame to be the selected frame. @xref{Stack, ,Examining the
24652 @node Blocks In Python
24653 @subsubsection Accessing frame blocks from Python.
24655 @cindex blocks in python
24658 Within each frame, @value{GDBN} maintains information on each block
24659 stored in that frame. These blocks are organized hierarchically, and
24660 are represented individually in Python as a @code{gdb.Block}.
24661 Please see @ref{Frames In Python}, for a more in-depth discussion on
24662 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
24663 detailed technical information on @value{GDBN}'s book-keeping of the
24666 A @code{gdb.Block} is iterable. The iterator returns the symbols
24667 (@pxref{Symbols In Python}) local to the block. Python programs
24668 should not assume that a specific block object will always contain a
24669 given symbol, since changes in @value{GDBN} features and
24670 infrastructure may cause symbols move across blocks in a symbol
24673 The following block-related functions are available in the @code{gdb}
24676 @findex gdb.block_for_pc
24677 @defun gdb.block_for_pc (pc)
24678 Return the @code{gdb.Block} containing the given @var{pc} value. If the
24679 block cannot be found for the @var{pc} value specified, the function
24680 will return @code{None}.
24683 A @code{gdb.Block} object has the following methods:
24686 @defun Block.is_valid ()
24687 Returns @code{True} if the @code{gdb.Block} object is valid,
24688 @code{False} if not. A block object can become invalid if the block it
24689 refers to doesn't exist anymore in the inferior. All other
24690 @code{gdb.Block} methods will throw an exception if it is invalid at
24691 the time the method is called. The block's validity is also checked
24692 during iteration over symbols of the block.
24696 A @code{gdb.Block} object has the following attributes:
24699 @defvar Block.start
24700 The start address of the block. This attribute is not writable.
24704 The end address of the block. This attribute is not writable.
24707 @defvar Block.function
24708 The name of the block represented as a @code{gdb.Symbol}. If the
24709 block is not named, then this attribute holds @code{None}. This
24710 attribute is not writable.
24713 @defvar Block.superblock
24714 The block containing this block. If this parent block does not exist,
24715 this attribute holds @code{None}. This attribute is not writable.
24718 @defvar Block.global_block
24719 The global block associated with this block. This attribute is not
24723 @defvar Block.static_block
24724 The static block associated with this block. This attribute is not
24728 @defvar Block.is_global
24729 @code{True} if the @code{gdb.Block} object is a global block,
24730 @code{False} if not. This attribute is not
24734 @defvar Block.is_static
24735 @code{True} if the @code{gdb.Block} object is a static block,
24736 @code{False} if not. This attribute is not writable.
24740 @node Symbols In Python
24741 @subsubsection Python representation of Symbols.
24743 @cindex symbols in python
24746 @value{GDBN} represents every variable, function and type as an
24747 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
24748 Similarly, Python represents these symbols in @value{GDBN} with the
24749 @code{gdb.Symbol} object.
24751 The following symbol-related functions are available in the @code{gdb}
24754 @findex gdb.lookup_symbol
24755 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
24756 This function searches for a symbol by name. The search scope can be
24757 restricted to the parameters defined in the optional domain and block
24760 @var{name} is the name of the symbol. It must be a string. The
24761 optional @var{block} argument restricts the search to symbols visible
24762 in that @var{block}. The @var{block} argument must be a
24763 @code{gdb.Block} object. If omitted, the block for the current frame
24764 is used. The optional @var{domain} argument restricts
24765 the search to the domain type. The @var{domain} argument must be a
24766 domain constant defined in the @code{gdb} module and described later
24769 The result is a tuple of two elements.
24770 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
24772 If the symbol is found, the second element is @code{True} if the symbol
24773 is a field of a method's object (e.g., @code{this} in C@t{++}),
24774 otherwise it is @code{False}.
24775 If the symbol is not found, the second element is @code{False}.
24778 @findex gdb.lookup_global_symbol
24779 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
24780 This function searches for a global symbol by name.
24781 The search scope can be restricted to by the domain argument.
24783 @var{name} is the name of the symbol. It must be a string.
24784 The optional @var{domain} argument restricts the search to the domain type.
24785 The @var{domain} argument must be a domain constant defined in the @code{gdb}
24786 module and described later in this chapter.
24788 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
24792 A @code{gdb.Symbol} object has the following attributes:
24795 @defvar Symbol.type
24796 The type of the symbol or @code{None} if no type is recorded.
24797 This attribute is represented as a @code{gdb.Type} object.
24798 @xref{Types In Python}. This attribute is not writable.
24801 @defvar Symbol.symtab
24802 The symbol table in which the symbol appears. This attribute is
24803 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
24804 Python}. This attribute is not writable.
24807 @defvar Symbol.line
24808 The line number in the source code at which the symbol was defined.
24809 This is an integer.
24812 @defvar Symbol.name
24813 The name of the symbol as a string. This attribute is not writable.
24816 @defvar Symbol.linkage_name
24817 The name of the symbol, as used by the linker (i.e., may be mangled).
24818 This attribute is not writable.
24821 @defvar Symbol.print_name
24822 The name of the symbol in a form suitable for output. This is either
24823 @code{name} or @code{linkage_name}, depending on whether the user
24824 asked @value{GDBN} to display demangled or mangled names.
24827 @defvar Symbol.addr_class
24828 The address class of the symbol. This classifies how to find the value
24829 of a symbol. Each address class is a constant defined in the
24830 @code{gdb} module and described later in this chapter.
24833 @defvar Symbol.needs_frame
24834 This is @code{True} if evaluating this symbol's value requires a frame
24835 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
24836 local variables will require a frame, but other symbols will not.
24839 @defvar Symbol.is_argument
24840 @code{True} if the symbol is an argument of a function.
24843 @defvar Symbol.is_constant
24844 @code{True} if the symbol is a constant.
24847 @defvar Symbol.is_function
24848 @code{True} if the symbol is a function or a method.
24851 @defvar Symbol.is_variable
24852 @code{True} if the symbol is a variable.
24856 A @code{gdb.Symbol} object has the following methods:
24859 @defun Symbol.is_valid ()
24860 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24861 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24862 the symbol it refers to does not exist in @value{GDBN} any longer.
24863 All other @code{gdb.Symbol} methods will throw an exception if it is
24864 invalid at the time the method is called.
24867 @defun Symbol.value (@r{[}frame@r{]})
24868 Compute the value of the symbol, as a @code{gdb.Value}. For
24869 functions, this computes the address of the function, cast to the
24870 appropriate type. If the symbol requires a frame in order to compute
24871 its value, then @var{frame} must be given. If @var{frame} is not
24872 given, or if @var{frame} is invalid, then this method will throw an
24877 The available domain categories in @code{gdb.Symbol} are represented
24878 as constants in the @code{gdb} module:
24881 @findex SYMBOL_UNDEF_DOMAIN
24882 @findex gdb.SYMBOL_UNDEF_DOMAIN
24883 @item gdb.SYMBOL_UNDEF_DOMAIN
24884 This is used when a domain has not been discovered or none of the
24885 following domains apply. This usually indicates an error either
24886 in the symbol information or in @value{GDBN}'s handling of symbols.
24887 @findex SYMBOL_VAR_DOMAIN
24888 @findex gdb.SYMBOL_VAR_DOMAIN
24889 @item gdb.SYMBOL_VAR_DOMAIN
24890 This domain contains variables, function names, typedef names and enum
24892 @findex SYMBOL_STRUCT_DOMAIN
24893 @findex gdb.SYMBOL_STRUCT_DOMAIN
24894 @item gdb.SYMBOL_STRUCT_DOMAIN
24895 This domain holds struct, union and enum type names.
24896 @findex SYMBOL_LABEL_DOMAIN
24897 @findex gdb.SYMBOL_LABEL_DOMAIN
24898 @item gdb.SYMBOL_LABEL_DOMAIN
24899 This domain contains names of labels (for gotos).
24900 @findex SYMBOL_VARIABLES_DOMAIN
24901 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24902 @item gdb.SYMBOL_VARIABLES_DOMAIN
24903 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24904 contains everything minus functions and types.
24905 @findex SYMBOL_FUNCTIONS_DOMAIN
24906 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24907 @item gdb.SYMBOL_FUNCTION_DOMAIN
24908 This domain contains all functions.
24909 @findex SYMBOL_TYPES_DOMAIN
24910 @findex gdb.SYMBOL_TYPES_DOMAIN
24911 @item gdb.SYMBOL_TYPES_DOMAIN
24912 This domain contains all types.
24915 The available address class categories in @code{gdb.Symbol} are represented
24916 as constants in the @code{gdb} module:
24919 @findex SYMBOL_LOC_UNDEF
24920 @findex gdb.SYMBOL_LOC_UNDEF
24921 @item gdb.SYMBOL_LOC_UNDEF
24922 If this is returned by address class, it indicates an error either in
24923 the symbol information or in @value{GDBN}'s handling of symbols.
24924 @findex SYMBOL_LOC_CONST
24925 @findex gdb.SYMBOL_LOC_CONST
24926 @item gdb.SYMBOL_LOC_CONST
24927 Value is constant int.
24928 @findex SYMBOL_LOC_STATIC
24929 @findex gdb.SYMBOL_LOC_STATIC
24930 @item gdb.SYMBOL_LOC_STATIC
24931 Value is at a fixed address.
24932 @findex SYMBOL_LOC_REGISTER
24933 @findex gdb.SYMBOL_LOC_REGISTER
24934 @item gdb.SYMBOL_LOC_REGISTER
24935 Value is in a register.
24936 @findex SYMBOL_LOC_ARG
24937 @findex gdb.SYMBOL_LOC_ARG
24938 @item gdb.SYMBOL_LOC_ARG
24939 Value is an argument. This value is at the offset stored within the
24940 symbol inside the frame's argument list.
24941 @findex SYMBOL_LOC_REF_ARG
24942 @findex gdb.SYMBOL_LOC_REF_ARG
24943 @item gdb.SYMBOL_LOC_REF_ARG
24944 Value address is stored in the frame's argument list. Just like
24945 @code{LOC_ARG} except that the value's address is stored at the
24946 offset, not the value itself.
24947 @findex SYMBOL_LOC_REGPARM_ADDR
24948 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24949 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24950 Value is a specified register. Just like @code{LOC_REGISTER} except
24951 the register holds the address of the argument instead of the argument
24953 @findex SYMBOL_LOC_LOCAL
24954 @findex gdb.SYMBOL_LOC_LOCAL
24955 @item gdb.SYMBOL_LOC_LOCAL
24956 Value is a local variable.
24957 @findex SYMBOL_LOC_TYPEDEF
24958 @findex gdb.SYMBOL_LOC_TYPEDEF
24959 @item gdb.SYMBOL_LOC_TYPEDEF
24960 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24962 @findex SYMBOL_LOC_BLOCK
24963 @findex gdb.SYMBOL_LOC_BLOCK
24964 @item gdb.SYMBOL_LOC_BLOCK
24966 @findex SYMBOL_LOC_CONST_BYTES
24967 @findex gdb.SYMBOL_LOC_CONST_BYTES
24968 @item gdb.SYMBOL_LOC_CONST_BYTES
24969 Value is a byte-sequence.
24970 @findex SYMBOL_LOC_UNRESOLVED
24971 @findex gdb.SYMBOL_LOC_UNRESOLVED
24972 @item gdb.SYMBOL_LOC_UNRESOLVED
24973 Value is at a fixed address, but the address of the variable has to be
24974 determined from the minimal symbol table whenever the variable is
24976 @findex SYMBOL_LOC_OPTIMIZED_OUT
24977 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24978 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24979 The value does not actually exist in the program.
24980 @findex SYMBOL_LOC_COMPUTED
24981 @findex gdb.SYMBOL_LOC_COMPUTED
24982 @item gdb.SYMBOL_LOC_COMPUTED
24983 The value's address is a computed location.
24986 @node Symbol Tables In Python
24987 @subsubsection Symbol table representation in Python.
24989 @cindex symbol tables in python
24991 @tindex gdb.Symtab_and_line
24993 Access to symbol table data maintained by @value{GDBN} on the inferior
24994 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24995 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24996 from the @code{find_sal} method in @code{gdb.Frame} object.
24997 @xref{Frames In Python}.
24999 For more information on @value{GDBN}'s symbol table management, see
25000 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25002 A @code{gdb.Symtab_and_line} object has the following attributes:
25005 @defvar Symtab_and_line.symtab
25006 The symbol table object (@code{gdb.Symtab}) for this frame.
25007 This attribute is not writable.
25010 @defvar Symtab_and_line.pc
25011 Indicates the current program counter address. This attribute is not
25015 @defvar Symtab_and_line.line
25016 Indicates the current line number for this object. This
25017 attribute is not writable.
25021 A @code{gdb.Symtab_and_line} object has the following methods:
25024 @defun Symtab_and_line.is_valid ()
25025 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25026 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25027 invalid if the Symbol table and line object it refers to does not
25028 exist in @value{GDBN} any longer. All other
25029 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25030 invalid at the time the method is called.
25034 A @code{gdb.Symtab} object has the following attributes:
25037 @defvar Symtab.filename
25038 The symbol table's source filename. This attribute is not writable.
25041 @defvar Symtab.objfile
25042 The symbol table's backing object file. @xref{Objfiles In Python}.
25043 This attribute is not writable.
25047 A @code{gdb.Symtab} object has the following methods:
25050 @defun Symtab.is_valid ()
25051 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25052 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25053 the symbol table it refers to does not exist in @value{GDBN} any
25054 longer. All other @code{gdb.Symtab} methods will throw an exception
25055 if it is invalid at the time the method is called.
25058 @defun Symtab.fullname ()
25059 Return the symbol table's source absolute file name.
25062 @defun Symtab.global_block ()
25063 Return the global block of the underlying symbol table.
25064 @xref{Blocks In Python}.
25067 @defun Symtab.static_block ()
25068 Return the static block of the underlying symbol table.
25069 @xref{Blocks In Python}.
25073 @node Breakpoints In Python
25074 @subsubsection Manipulating breakpoints using Python
25076 @cindex breakpoints in python
25077 @tindex gdb.Breakpoint
25079 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25082 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25083 Create a new breakpoint. @var{spec} is a string naming the
25084 location of the breakpoint, or an expression that defines a
25085 watchpoint. The contents can be any location recognized by the
25086 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25087 command. The optional @var{type} denotes the breakpoint to create
25088 from the types defined later in this chapter. This argument can be
25089 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25090 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25091 allows the breakpoint to become invisible to the user. The breakpoint
25092 will neither be reported when created, nor will it be listed in the
25093 output from @code{info breakpoints} (but will be listed with the
25094 @code{maint info breakpoints} command). The optional @var{wp_class}
25095 argument defines the class of watchpoint to create, if @var{type} is
25096 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25097 assumed to be a @code{gdb.WP_WRITE} class.
25100 @defun Breakpoint.stop (self)
25101 The @code{gdb.Breakpoint} class can be sub-classed and, in
25102 particular, you may choose to implement the @code{stop} method.
25103 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25104 it will be called when the inferior reaches any location of a
25105 breakpoint which instantiates that sub-class. If the method returns
25106 @code{True}, the inferior will be stopped at the location of the
25107 breakpoint, otherwise the inferior will continue.
25109 If there are multiple breakpoints at the same location with a
25110 @code{stop} method, each one will be called regardless of the
25111 return status of the previous. This ensures that all @code{stop}
25112 methods have a chance to execute at that location. In this scenario
25113 if one of the methods returns @code{True} but the others return
25114 @code{False}, the inferior will still be stopped.
25116 You should not alter the execution state of the inferior (i.e.@:, step,
25117 next, etc.), alter the current frame context (i.e.@:, change the current
25118 active frame), or alter, add or delete any breakpoint. As a general
25119 rule, you should not alter any data within @value{GDBN} or the inferior
25122 Example @code{stop} implementation:
25125 class MyBreakpoint (gdb.Breakpoint):
25127 inf_val = gdb.parse_and_eval("foo")
25134 The available watchpoint types represented by constants are defined in the
25139 @findex gdb.WP_READ
25141 Read only watchpoint.
25144 @findex gdb.WP_WRITE
25146 Write only watchpoint.
25149 @findex gdb.WP_ACCESS
25150 @item gdb.WP_ACCESS
25151 Read/Write watchpoint.
25154 @defun Breakpoint.is_valid ()
25155 Return @code{True} if this @code{Breakpoint} object is valid,
25156 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25157 if the user deletes the breakpoint. In this case, the object still
25158 exists, but the underlying breakpoint does not. In the cases of
25159 watchpoint scope, the watchpoint remains valid even if execution of the
25160 inferior leaves the scope of that watchpoint.
25163 @defun Breakpoint.delete
25164 Permanently deletes the @value{GDBN} breakpoint. This also
25165 invalidates the Python @code{Breakpoint} object. Any further access
25166 to this object's attributes or methods will raise an error.
25169 @defvar Breakpoint.enabled
25170 This attribute is @code{True} if the breakpoint is enabled, and
25171 @code{False} otherwise. This attribute is writable.
25174 @defvar Breakpoint.silent
25175 This attribute is @code{True} if the breakpoint is silent, and
25176 @code{False} otherwise. This attribute is writable.
25178 Note that a breakpoint can also be silent if it has commands and the
25179 first command is @code{silent}. This is not reported by the
25180 @code{silent} attribute.
25183 @defvar Breakpoint.thread
25184 If the breakpoint is thread-specific, this attribute holds the thread
25185 id. If the breakpoint is not thread-specific, this attribute is
25186 @code{None}. This attribute is writable.
25189 @defvar Breakpoint.task
25190 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25191 id. If the breakpoint is not task-specific (or the underlying
25192 language is not Ada), this attribute is @code{None}. This attribute
25196 @defvar Breakpoint.ignore_count
25197 This attribute holds the ignore count for the breakpoint, an integer.
25198 This attribute is writable.
25201 @defvar Breakpoint.number
25202 This attribute holds the breakpoint's number --- the identifier used by
25203 the user to manipulate the breakpoint. This attribute is not writable.
25206 @defvar Breakpoint.type
25207 This attribute holds the breakpoint's type --- the identifier used to
25208 determine the actual breakpoint type or use-case. This attribute is not
25212 @defvar Breakpoint.visible
25213 This attribute tells whether the breakpoint is visible to the user
25214 when set, or when the @samp{info breakpoints} command is run. This
25215 attribute is not writable.
25218 The available types are represented by constants defined in the @code{gdb}
25222 @findex BP_BREAKPOINT
25223 @findex gdb.BP_BREAKPOINT
25224 @item gdb.BP_BREAKPOINT
25225 Normal code breakpoint.
25227 @findex BP_WATCHPOINT
25228 @findex gdb.BP_WATCHPOINT
25229 @item gdb.BP_WATCHPOINT
25230 Watchpoint breakpoint.
25232 @findex BP_HARDWARE_WATCHPOINT
25233 @findex gdb.BP_HARDWARE_WATCHPOINT
25234 @item gdb.BP_HARDWARE_WATCHPOINT
25235 Hardware assisted watchpoint.
25237 @findex BP_READ_WATCHPOINT
25238 @findex gdb.BP_READ_WATCHPOINT
25239 @item gdb.BP_READ_WATCHPOINT
25240 Hardware assisted read watchpoint.
25242 @findex BP_ACCESS_WATCHPOINT
25243 @findex gdb.BP_ACCESS_WATCHPOINT
25244 @item gdb.BP_ACCESS_WATCHPOINT
25245 Hardware assisted access watchpoint.
25248 @defvar Breakpoint.hit_count
25249 This attribute holds the hit count for the breakpoint, an integer.
25250 This attribute is writable, but currently it can only be set to zero.
25253 @defvar Breakpoint.location
25254 This attribute holds the location of the breakpoint, as specified by
25255 the user. It is a string. If the breakpoint does not have a location
25256 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25257 attribute is not writable.
25260 @defvar Breakpoint.expression
25261 This attribute holds a breakpoint expression, as specified by
25262 the user. It is a string. If the breakpoint does not have an
25263 expression (the breakpoint is not a watchpoint) the attribute's value
25264 is @code{None}. This attribute is not writable.
25267 @defvar Breakpoint.condition
25268 This attribute holds the condition of the breakpoint, as specified by
25269 the user. It is a string. If there is no condition, this attribute's
25270 value is @code{None}. This attribute is writable.
25273 @defvar Breakpoint.commands
25274 This attribute holds the commands attached to the breakpoint. If
25275 there are commands, this attribute's value is a string holding all the
25276 commands, separated by newlines. If there are no commands, this
25277 attribute is @code{None}. This attribute is not writable.
25280 @node Finish Breakpoints in Python
25281 @subsubsection Finish Breakpoints
25283 @cindex python finish breakpoints
25284 @tindex gdb.FinishBreakpoint
25286 A finish breakpoint is a temporary breakpoint set at the return address of
25287 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
25288 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
25289 and deleted when the execution will run out of the breakpoint scope (i.e.@:
25290 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
25291 Finish breakpoints are thread specific and must be create with the right
25294 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
25295 Create a finish breakpoint at the return address of the @code{gdb.Frame}
25296 object @var{frame}. If @var{frame} is not provided, this defaults to the
25297 newest frame. The optional @var{internal} argument allows the breakpoint to
25298 become invisible to the user. @xref{Breakpoints In Python}, for further
25299 details about this argument.
25302 @defun FinishBreakpoint.out_of_scope (self)
25303 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
25304 @code{return} command, @dots{}), a function may not properly terminate, and
25305 thus never hit the finish breakpoint. When @value{GDBN} notices such a
25306 situation, the @code{out_of_scope} callback will be triggered.
25308 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
25312 class MyFinishBreakpoint (gdb.FinishBreakpoint)
25314 print "normal finish"
25317 def out_of_scope ():
25318 print "abnormal finish"
25322 @defvar FinishBreakpoint.return_value
25323 When @value{GDBN} is stopped at a finish breakpoint and the frame
25324 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
25325 attribute will contain a @code{gdb.Value} object corresponding to the return
25326 value of the function. The value will be @code{None} if the function return
25327 type is @code{void} or if the return value was not computable. This attribute
25331 @node Lazy Strings In Python
25332 @subsubsection Python representation of lazy strings.
25334 @cindex lazy strings in python
25335 @tindex gdb.LazyString
25337 A @dfn{lazy string} is a string whose contents is not retrieved or
25338 encoded until it is needed.
25340 A @code{gdb.LazyString} is represented in @value{GDBN} as an
25341 @code{address} that points to a region of memory, an @code{encoding}
25342 that will be used to encode that region of memory, and a @code{length}
25343 to delimit the region of memory that represents the string. The
25344 difference between a @code{gdb.LazyString} and a string wrapped within
25345 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
25346 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
25347 retrieved and encoded during printing, while a @code{gdb.Value}
25348 wrapping a string is immediately retrieved and encoded on creation.
25350 A @code{gdb.LazyString} object has the following functions:
25352 @defun LazyString.value ()
25353 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
25354 will point to the string in memory, but will lose all the delayed
25355 retrieval, encoding and handling that @value{GDBN} applies to a
25356 @code{gdb.LazyString}.
25359 @defvar LazyString.address
25360 This attribute holds the address of the string. This attribute is not
25364 @defvar LazyString.length
25365 This attribute holds the length of the string in characters. If the
25366 length is -1, then the string will be fetched and encoded up to the
25367 first null of appropriate width. This attribute is not writable.
25370 @defvar LazyString.encoding
25371 This attribute holds the encoding that will be applied to the string
25372 when the string is printed by @value{GDBN}. If the encoding is not
25373 set, or contains an empty string, then @value{GDBN} will select the
25374 most appropriate encoding when the string is printed. This attribute
25378 @defvar LazyString.type
25379 This attribute holds the type that is represented by the lazy string's
25380 type. For a lazy string this will always be a pointer type. To
25381 resolve this to the lazy string's character type, use the type's
25382 @code{target} method. @xref{Types In Python}. This attribute is not
25386 @node Python Auto-loading
25387 @subsection Python Auto-loading
25388 @cindex Python auto-loading
25390 When a new object file is read (for example, due to the @code{file}
25391 command, or because the inferior has loaded a shared library),
25392 @value{GDBN} will look for Python support scripts in several ways:
25393 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
25394 and @code{.debug_gdb_scripts} section
25395 (@pxref{dotdebug_gdb_scripts section}).
25397 The auto-loading feature is useful for supplying application-specific
25398 debugging commands and scripts.
25400 Auto-loading can be enabled or disabled,
25401 and the list of auto-loaded scripts can be printed.
25404 @anchor{set auto-load python-scripts}
25405 @kindex set auto-load python-scripts
25406 @item set auto-load python-scripts [on|off]
25407 Enable or disable the auto-loading of Python scripts.
25409 @anchor{show auto-load python-scripts}
25410 @kindex show auto-load python-scripts
25411 @item show auto-load python-scripts
25412 Show whether auto-loading of Python scripts is enabled or disabled.
25414 @anchor{info auto-load python-scripts}
25415 @kindex info auto-load python-scripts
25416 @cindex print list of auto-loaded Python scripts
25417 @item info auto-load python-scripts [@var{regexp}]
25418 Print the list of all Python scripts that @value{GDBN} auto-loaded.
25420 Also printed is the list of Python scripts that were mentioned in
25421 the @code{.debug_gdb_scripts} section and were not found
25422 (@pxref{dotdebug_gdb_scripts section}).
25423 This is useful because their names are not printed when @value{GDBN}
25424 tries to load them and fails. There may be many of them, and printing
25425 an error message for each one is problematic.
25427 If @var{regexp} is supplied only Python scripts with matching names are printed.
25432 (gdb) info auto-load python-scripts
25434 Yes py-section-script.py
25435 full name: /tmp/py-section-script.py
25436 No my-foo-pretty-printers.py
25440 When reading an auto-loaded file, @value{GDBN} sets the
25441 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
25442 function (@pxref{Objfiles In Python}). This can be useful for
25443 registering objfile-specific pretty-printers.
25446 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
25447 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
25448 * Which flavor to choose?::
25451 @node objfile-gdb.py file
25452 @subsubsection The @file{@var{objfile}-gdb.py} file
25453 @cindex @file{@var{objfile}-gdb.py}
25455 When a new object file is read, @value{GDBN} looks for
25456 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
25457 where @var{objfile} is the object file's real name, formed by ensuring
25458 that the file name is absolute, following all symlinks, and resolving
25459 @code{.} and @code{..} components. If this file exists and is
25460 readable, @value{GDBN} will evaluate it as a Python script.
25462 If this file does not exist, and if the parameter
25463 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
25464 then @value{GDBN} will look for @var{script-name} in all of the
25465 directories mentioned in the value of @code{debug-file-directory}.
25467 Finally, if this file does not exist, then @value{GDBN} will look for
25468 @var{script-name} file in all of the directories specified by:
25471 @anchor{set auto-load scripts-directory}
25472 @kindex set auto-load scripts-directory
25473 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25474 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25475 may be delimited by the host platform path separator in use
25476 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25478 Each entry here needs to be covered also by the security setting
25479 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25481 @anchor{with-auto-load-dir}
25482 This variable defaults to @file{$ddir/auto-load}. The default @code{set
25483 auto-load safe-path} value can be also overriden by @value{GDBN} configuration
25484 option @option{--with-auto-load-dir}.
25486 Any used string @file{$ddir} will get replaced by @var{data-directory} which is
25487 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$ddir} must be
25488 be placed as a directory component --- either alone or delimited by @file{/} or
25489 @file{\} directory separators, depending on the host platform.
25491 The list of directories uses path separator (@samp{:} on GNU and Unix
25492 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25493 to the @env{PATH} environment variable.
25495 @anchor{show auto-load scripts-directory}
25496 @kindex show auto-load scripts-directory
25497 @item show auto-load scripts-directory
25498 Show @value{GDBN} auto-loaded scripts location.
25501 @value{GDBN} does not track which files it has already auto-loaded this way.
25502 @value{GDBN} will load the associated script every time the corresponding
25503 @var{objfile} is opened.
25504 So your @file{-gdb.py} file should be careful to avoid errors if it
25505 is evaluated more than once.
25507 @node dotdebug_gdb_scripts section
25508 @subsubsection The @code{.debug_gdb_scripts} section
25509 @cindex @code{.debug_gdb_scripts} section
25511 For systems using file formats like ELF and COFF,
25512 when @value{GDBN} loads a new object file
25513 it will look for a special section named @samp{.debug_gdb_scripts}.
25514 If this section exists, its contents is a list of names of scripts to load.
25516 @value{GDBN} will look for each specified script file first in the
25517 current directory and then along the source search path
25518 (@pxref{Source Path, ,Specifying Source Directories}),
25519 except that @file{$cdir} is not searched, since the compilation
25520 directory is not relevant to scripts.
25522 Entries can be placed in section @code{.debug_gdb_scripts} with,
25523 for example, this GCC macro:
25526 /* Note: The "MS" section flags are to remove duplicates. */
25527 #define DEFINE_GDB_SCRIPT(script_name) \
25529 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25531 .asciz \"" script_name "\"\n\
25537 Then one can reference the macro in a header or source file like this:
25540 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
25543 The script name may include directories if desired.
25545 If the macro is put in a header, any application or library
25546 using this header will get a reference to the specified script.
25548 @node Which flavor to choose?
25549 @subsubsection Which flavor to choose?
25551 Given the multiple ways of auto-loading Python scripts, it might not always
25552 be clear which one to choose. This section provides some guidance.
25554 Benefits of the @file{-gdb.py} way:
25558 Can be used with file formats that don't support multiple sections.
25561 Ease of finding scripts for public libraries.
25563 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25564 in the source search path.
25565 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25566 isn't a source directory in which to find the script.
25569 Doesn't require source code additions.
25572 Benefits of the @code{.debug_gdb_scripts} way:
25576 Works with static linking.
25578 Scripts for libraries done the @file{-gdb.py} way require an objfile to
25579 trigger their loading. When an application is statically linked the only
25580 objfile available is the executable, and it is cumbersome to attach all the
25581 scripts from all the input libraries to the executable's @file{-gdb.py} script.
25584 Works with classes that are entirely inlined.
25586 Some classes can be entirely inlined, and thus there may not be an associated
25587 shared library to attach a @file{-gdb.py} script to.
25590 Scripts needn't be copied out of the source tree.
25592 In some circumstances, apps can be built out of large collections of internal
25593 libraries, and the build infrastructure necessary to install the
25594 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
25595 cumbersome. It may be easier to specify the scripts in the
25596 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25597 top of the source tree to the source search path.
25600 @node Python modules
25601 @subsection Python modules
25602 @cindex python modules
25604 @value{GDBN} comes with several modules to assist writing Python code.
25607 * gdb.printing:: Building and registering pretty-printers.
25608 * gdb.types:: Utilities for working with types.
25609 * gdb.prompt:: Utilities for prompt value substitution.
25613 @subsubsection gdb.printing
25614 @cindex gdb.printing
25616 This module provides a collection of utilities for working with
25620 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
25621 This class specifies the API that makes @samp{info pretty-printer},
25622 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
25623 Pretty-printers should generally inherit from this class.
25625 @item SubPrettyPrinter (@var{name})
25626 For printers that handle multiple types, this class specifies the
25627 corresponding API for the subprinters.
25629 @item RegexpCollectionPrettyPrinter (@var{name})
25630 Utility class for handling multiple printers, all recognized via
25631 regular expressions.
25632 @xref{Writing a Pretty-Printer}, for an example.
25634 @item FlagEnumerationPrinter (@var{name})
25635 A pretty-printer which handles printing of @code{enum} values. Unlike
25636 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
25637 work properly when there is some overlap between the enumeration
25638 constants. @var{name} is the name of the printer and also the name of
25639 the @code{enum} type to look up.
25641 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
25642 Register @var{printer} with the pretty-printer list of @var{obj}.
25643 If @var{replace} is @code{True} then any existing copy of the printer
25644 is replaced. Otherwise a @code{RuntimeError} exception is raised
25645 if a printer with the same name already exists.
25649 @subsubsection gdb.types
25652 This module provides a collection of utilities for working with
25653 @code{gdb.Types} objects.
25656 @item get_basic_type (@var{type})
25657 Return @var{type} with const and volatile qualifiers stripped,
25658 and with typedefs and C@t{++} references converted to the underlying type.
25663 typedef const int const_int;
25665 const_int& foo_ref (foo);
25666 int main () @{ return 0; @}
25673 (gdb) python import gdb.types
25674 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
25675 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
25679 @item has_field (@var{type}, @var{field})
25680 Return @code{True} if @var{type}, assumed to be a type with fields
25681 (e.g., a structure or union), has field @var{field}.
25683 @item make_enum_dict (@var{enum_type})
25684 Return a Python @code{dictionary} type produced from @var{enum_type}.
25686 @item deep_items (@var{type})
25687 Returns a Python iterator similar to the standard
25688 @code{gdb.Type.iteritems} method, except that the iterator returned
25689 by @code{deep_items} will recursively traverse anonymous struct or
25690 union fields. For example:
25704 Then in @value{GDBN}:
25706 (@value{GDBP}) python import gdb.types
25707 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
25708 (@value{GDBP}) python print struct_a.keys ()
25710 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
25711 @{['a', 'b0', 'b1']@}
25717 @subsubsection gdb.prompt
25720 This module provides a method for prompt value-substitution.
25723 @item substitute_prompt (@var{string})
25724 Return @var{string} with escape sequences substituted by values. Some
25725 escape sequences take arguments. You can specify arguments inside
25726 ``@{@}'' immediately following the escape sequence.
25728 The escape sequences you can pass to this function are:
25732 Substitute a backslash.
25734 Substitute an ESC character.
25736 Substitute the selected frame; an argument names a frame parameter.
25738 Substitute a newline.
25740 Substitute a parameter's value; the argument names the parameter.
25742 Substitute a carriage return.
25744 Substitute the selected thread; an argument names a thread parameter.
25746 Substitute the version of GDB.
25748 Substitute the current working directory.
25750 Begin a sequence of non-printing characters. These sequences are
25751 typically used with the ESC character, and are not counted in the string
25752 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
25753 blue-colored ``(gdb)'' prompt where the length is five.
25755 End a sequence of non-printing characters.
25761 substitute_prompt (``frame: \f,
25762 print arguments: \p@{print frame-arguments@}'')
25765 @exdent will return the string:
25768 "frame: main, print arguments: scalars"
25773 @section Creating new spellings of existing commands
25774 @cindex aliases for commands
25776 It is often useful to define alternate spellings of existing commands.
25777 For example, if a new @value{GDBN} command defined in Python has
25778 a long name to type, it is handy to have an abbreviated version of it
25779 that involves less typing.
25781 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25782 of the @samp{step} command even though it is otherwise an ambiguous
25783 abbreviation of other commands like @samp{set} and @samp{show}.
25785 Aliases are also used to provide shortened or more common versions
25786 of multi-word commands. For example, @value{GDBN} provides the
25787 @samp{tty} alias of the @samp{set inferior-tty} command.
25789 You can define a new alias with the @samp{alias} command.
25794 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25798 @var{ALIAS} specifies the name of the new alias.
25799 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25802 @var{COMMAND} specifies the name of an existing command
25803 that is being aliased.
25805 The @samp{-a} option specifies that the new alias is an abbreviation
25806 of the command. Abbreviations are not shown in command
25807 lists displayed by the @samp{help} command.
25809 The @samp{--} option specifies the end of options,
25810 and is useful when @var{ALIAS} begins with a dash.
25812 Here is a simple example showing how to make an abbreviation
25813 of a command so that there is less to type.
25814 Suppose you were tired of typing @samp{disas}, the current
25815 shortest unambiguous abbreviation of the @samp{disassemble} command
25816 and you wanted an even shorter version named @samp{di}.
25817 The following will accomplish this.
25820 (gdb) alias -a di = disas
25823 Note that aliases are different from user-defined commands.
25824 With a user-defined command, you also need to write documentation
25825 for it with the @samp{document} command.
25826 An alias automatically picks up the documentation of the existing command.
25828 Here is an example where we make @samp{elms} an abbreviation of
25829 @samp{elements} in the @samp{set print elements} command.
25830 This is to show that you can make an abbreviation of any part
25834 (gdb) alias -a set print elms = set print elements
25835 (gdb) alias -a show print elms = show print elements
25836 (gdb) set p elms 20
25838 Limit on string chars or array elements to print is 200.
25841 Note that if you are defining an alias of a @samp{set} command,
25842 and you want to have an alias for the corresponding @samp{show}
25843 command, then you need to define the latter separately.
25845 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25846 @var{ALIAS}, just as they are normally.
25849 (gdb) alias -a set pr elms = set p ele
25852 Finally, here is an example showing the creation of a one word
25853 alias for a more complex command.
25854 This creates alias @samp{spe} of the command @samp{set print elements}.
25857 (gdb) alias spe = set print elements
25862 @chapter Command Interpreters
25863 @cindex command interpreters
25865 @value{GDBN} supports multiple command interpreters, and some command
25866 infrastructure to allow users or user interface writers to switch
25867 between interpreters or run commands in other interpreters.
25869 @value{GDBN} currently supports two command interpreters, the console
25870 interpreter (sometimes called the command-line interpreter or @sc{cli})
25871 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25872 describes both of these interfaces in great detail.
25874 By default, @value{GDBN} will start with the console interpreter.
25875 However, the user may choose to start @value{GDBN} with another
25876 interpreter by specifying the @option{-i} or @option{--interpreter}
25877 startup options. Defined interpreters include:
25881 @cindex console interpreter
25882 The traditional console or command-line interpreter. This is the most often
25883 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25884 @value{GDBN} will use this interpreter.
25887 @cindex mi interpreter
25888 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25889 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25890 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25894 @cindex mi2 interpreter
25895 The current @sc{gdb/mi} interface.
25898 @cindex mi1 interpreter
25899 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25903 @cindex invoke another interpreter
25904 The interpreter being used by @value{GDBN} may not be dynamically
25905 switched at runtime. Although possible, this could lead to a very
25906 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
25907 enters the command "interpreter-set console" in a console view,
25908 @value{GDBN} would switch to using the console interpreter, rendering
25909 the IDE inoperable!
25911 @kindex interpreter-exec
25912 Although you may only choose a single interpreter at startup, you may execute
25913 commands in any interpreter from the current interpreter using the appropriate
25914 command. If you are running the console interpreter, simply use the
25915 @code{interpreter-exec} command:
25918 interpreter-exec mi "-data-list-register-names"
25921 @sc{gdb/mi} has a similar command, although it is only available in versions of
25922 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25925 @chapter @value{GDBN} Text User Interface
25927 @cindex Text User Interface
25930 * TUI Overview:: TUI overview
25931 * TUI Keys:: TUI key bindings
25932 * TUI Single Key Mode:: TUI single key mode
25933 * TUI Commands:: TUI-specific commands
25934 * TUI Configuration:: TUI configuration variables
25937 The @value{GDBN} Text User Interface (TUI) is a terminal
25938 interface which uses the @code{curses} library to show the source
25939 file, the assembly output, the program registers and @value{GDBN}
25940 commands in separate text windows. The TUI mode is supported only
25941 on platforms where a suitable version of the @code{curses} library
25944 The TUI mode is enabled by default when you invoke @value{GDBN} as
25945 @samp{@value{GDBP} -tui}.
25946 You can also switch in and out of TUI mode while @value{GDBN} runs by
25947 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25948 @xref{TUI Keys, ,TUI Key Bindings}.
25951 @section TUI Overview
25953 In TUI mode, @value{GDBN} can display several text windows:
25957 This window is the @value{GDBN} command window with the @value{GDBN}
25958 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25959 managed using readline.
25962 The source window shows the source file of the program. The current
25963 line and active breakpoints are displayed in this window.
25966 The assembly window shows the disassembly output of the program.
25969 This window shows the processor registers. Registers are highlighted
25970 when their values change.
25973 The source and assembly windows show the current program position
25974 by highlighting the current line and marking it with a @samp{>} marker.
25975 Breakpoints are indicated with two markers. The first marker
25976 indicates the breakpoint type:
25980 Breakpoint which was hit at least once.
25983 Breakpoint which was never hit.
25986 Hardware breakpoint which was hit at least once.
25989 Hardware breakpoint which was never hit.
25992 The second marker indicates whether the breakpoint is enabled or not:
25996 Breakpoint is enabled.
25999 Breakpoint is disabled.
26002 The source, assembly and register windows are updated when the current
26003 thread changes, when the frame changes, or when the program counter
26006 These windows are not all visible at the same time. The command
26007 window is always visible. The others can be arranged in several
26018 source and assembly,
26021 source and registers, or
26024 assembly and registers.
26027 A status line above the command window shows the following information:
26031 Indicates the current @value{GDBN} target.
26032 (@pxref{Targets, ,Specifying a Debugging Target}).
26035 Gives the current process or thread number.
26036 When no process is being debugged, this field is set to @code{No process}.
26039 Gives the current function name for the selected frame.
26040 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26041 When there is no symbol corresponding to the current program counter,
26042 the string @code{??} is displayed.
26045 Indicates the current line number for the selected frame.
26046 When the current line number is not known, the string @code{??} is displayed.
26049 Indicates the current program counter address.
26053 @section TUI Key Bindings
26054 @cindex TUI key bindings
26056 The TUI installs several key bindings in the readline keymaps
26057 @ifset SYSTEM_READLINE
26058 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26060 @ifclear SYSTEM_READLINE
26061 (@pxref{Command Line Editing}).
26063 The following key bindings are installed for both TUI mode and the
26064 @value{GDBN} standard mode.
26073 Enter or leave the TUI mode. When leaving the TUI mode,
26074 the curses window management stops and @value{GDBN} operates using
26075 its standard mode, writing on the terminal directly. When reentering
26076 the TUI mode, control is given back to the curses windows.
26077 The screen is then refreshed.
26081 Use a TUI layout with only one window. The layout will
26082 either be @samp{source} or @samp{assembly}. When the TUI mode
26083 is not active, it will switch to the TUI mode.
26085 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26089 Use a TUI layout with at least two windows. When the current
26090 layout already has two windows, the next layout with two windows is used.
26091 When a new layout is chosen, one window will always be common to the
26092 previous layout and the new one.
26094 Think of it as the Emacs @kbd{C-x 2} binding.
26098 Change the active window. The TUI associates several key bindings
26099 (like scrolling and arrow keys) with the active window. This command
26100 gives the focus to the next TUI window.
26102 Think of it as the Emacs @kbd{C-x o} binding.
26106 Switch in and out of the TUI SingleKey mode that binds single
26107 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26110 The following key bindings only work in the TUI mode:
26115 Scroll the active window one page up.
26119 Scroll the active window one page down.
26123 Scroll the active window one line up.
26127 Scroll the active window one line down.
26131 Scroll the active window one column left.
26135 Scroll the active window one column right.
26139 Refresh the screen.
26142 Because the arrow keys scroll the active window in the TUI mode, they
26143 are not available for their normal use by readline unless the command
26144 window has the focus. When another window is active, you must use
26145 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26146 and @kbd{C-f} to control the command window.
26148 @node TUI Single Key Mode
26149 @section TUI Single Key Mode
26150 @cindex TUI single key mode
26152 The TUI also provides a @dfn{SingleKey} mode, which binds several
26153 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26154 switch into this mode, where the following key bindings are used:
26157 @kindex c @r{(SingleKey TUI key)}
26161 @kindex d @r{(SingleKey TUI key)}
26165 @kindex f @r{(SingleKey TUI key)}
26169 @kindex n @r{(SingleKey TUI key)}
26173 @kindex q @r{(SingleKey TUI key)}
26175 exit the SingleKey mode.
26177 @kindex r @r{(SingleKey TUI key)}
26181 @kindex s @r{(SingleKey TUI key)}
26185 @kindex u @r{(SingleKey TUI key)}
26189 @kindex v @r{(SingleKey TUI key)}
26193 @kindex w @r{(SingleKey TUI key)}
26198 Other keys temporarily switch to the @value{GDBN} command prompt.
26199 The key that was pressed is inserted in the editing buffer so that
26200 it is possible to type most @value{GDBN} commands without interaction
26201 with the TUI SingleKey mode. Once the command is entered the TUI
26202 SingleKey mode is restored. The only way to permanently leave
26203 this mode is by typing @kbd{q} or @kbd{C-x s}.
26207 @section TUI-specific Commands
26208 @cindex TUI commands
26210 The TUI has specific commands to control the text windows.
26211 These commands are always available, even when @value{GDBN} is not in
26212 the TUI mode. When @value{GDBN} is in the standard mode, most
26213 of these commands will automatically switch to the TUI mode.
26215 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26216 terminal, or @value{GDBN} has been started with the machine interface
26217 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26218 these commands will fail with an error, because it would not be
26219 possible or desirable to enable curses window management.
26224 List and give the size of all displayed windows.
26228 Display the next layout.
26231 Display the previous layout.
26234 Display the source window only.
26237 Display the assembly window only.
26240 Display the source and assembly window.
26243 Display the register window together with the source or assembly window.
26247 Make the next window active for scrolling.
26250 Make the previous window active for scrolling.
26253 Make the source window active for scrolling.
26256 Make the assembly window active for scrolling.
26259 Make the register window active for scrolling.
26262 Make the command window active for scrolling.
26266 Refresh the screen. This is similar to typing @kbd{C-L}.
26268 @item tui reg float
26270 Show the floating point registers in the register window.
26272 @item tui reg general
26273 Show the general registers in the register window.
26276 Show the next register group. The list of register groups as well as
26277 their order is target specific. The predefined register groups are the
26278 following: @code{general}, @code{float}, @code{system}, @code{vector},
26279 @code{all}, @code{save}, @code{restore}.
26281 @item tui reg system
26282 Show the system registers in the register window.
26286 Update the source window and the current execution point.
26288 @item winheight @var{name} +@var{count}
26289 @itemx winheight @var{name} -@var{count}
26291 Change the height of the window @var{name} by @var{count}
26292 lines. Positive counts increase the height, while negative counts
26295 @item tabset @var{nchars}
26297 Set the width of tab stops to be @var{nchars} characters.
26300 @node TUI Configuration
26301 @section TUI Configuration Variables
26302 @cindex TUI configuration variables
26304 Several configuration variables control the appearance of TUI windows.
26307 @item set tui border-kind @var{kind}
26308 @kindex set tui border-kind
26309 Select the border appearance for the source, assembly and register windows.
26310 The possible values are the following:
26313 Use a space character to draw the border.
26316 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26319 Use the Alternate Character Set to draw the border. The border is
26320 drawn using character line graphics if the terminal supports them.
26323 @item set tui border-mode @var{mode}
26324 @kindex set tui border-mode
26325 @itemx set tui active-border-mode @var{mode}
26326 @kindex set tui active-border-mode
26327 Select the display attributes for the borders of the inactive windows
26328 or the active window. The @var{mode} can be one of the following:
26331 Use normal attributes to display the border.
26337 Use reverse video mode.
26340 Use half bright mode.
26342 @item half-standout
26343 Use half bright and standout mode.
26346 Use extra bright or bold mode.
26348 @item bold-standout
26349 Use extra bright or bold and standout mode.
26354 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26357 @cindex @sc{gnu} Emacs
26358 A special interface allows you to use @sc{gnu} Emacs to view (and
26359 edit) the source files for the program you are debugging with
26362 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26363 executable file you want to debug as an argument. This command starts
26364 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26365 created Emacs buffer.
26366 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26368 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26373 All ``terminal'' input and output goes through an Emacs buffer, called
26376 This applies both to @value{GDBN} commands and their output, and to the input
26377 and output done by the program you are debugging.
26379 This is useful because it means that you can copy the text of previous
26380 commands and input them again; you can even use parts of the output
26383 All the facilities of Emacs' Shell mode are available for interacting
26384 with your program. In particular, you can send signals the usual
26385 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26389 @value{GDBN} displays source code through Emacs.
26391 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26392 source file for that frame and puts an arrow (@samp{=>}) at the
26393 left margin of the current line. Emacs uses a separate buffer for
26394 source display, and splits the screen to show both your @value{GDBN} session
26397 Explicit @value{GDBN} @code{list} or search commands still produce output as
26398 usual, but you probably have no reason to use them from Emacs.
26401 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26402 a graphical mode, enabled by default, which provides further buffers
26403 that can control the execution and describe the state of your program.
26404 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26406 If you specify an absolute file name when prompted for the @kbd{M-x
26407 gdb} argument, then Emacs sets your current working directory to where
26408 your program resides. If you only specify the file name, then Emacs
26409 sets your current working directory to the directory associated
26410 with the previous buffer. In this case, @value{GDBN} may find your
26411 program by searching your environment's @code{PATH} variable, but on
26412 some operating systems it might not find the source. So, although the
26413 @value{GDBN} input and output session proceeds normally, the auxiliary
26414 buffer does not display the current source and line of execution.
26416 The initial working directory of @value{GDBN} is printed on the top
26417 line of the GUD buffer and this serves as a default for the commands
26418 that specify files for @value{GDBN} to operate on. @xref{Files,
26419 ,Commands to Specify Files}.
26421 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26422 need to call @value{GDBN} by a different name (for example, if you
26423 keep several configurations around, with different names) you can
26424 customize the Emacs variable @code{gud-gdb-command-name} to run the
26427 In the GUD buffer, you can use these special Emacs commands in
26428 addition to the standard Shell mode commands:
26432 Describe the features of Emacs' GUD Mode.
26435 Execute to another source line, like the @value{GDBN} @code{step} command; also
26436 update the display window to show the current file and location.
26439 Execute to next source line in this function, skipping all function
26440 calls, like the @value{GDBN} @code{next} command. Then update the display window
26441 to show the current file and location.
26444 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26445 display window accordingly.
26448 Execute until exit from the selected stack frame, like the @value{GDBN}
26449 @code{finish} command.
26452 Continue execution of your program, like the @value{GDBN} @code{continue}
26456 Go up the number of frames indicated by the numeric argument
26457 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26458 like the @value{GDBN} @code{up} command.
26461 Go down the number of frames indicated by the numeric argument, like the
26462 @value{GDBN} @code{down} command.
26465 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26466 tells @value{GDBN} to set a breakpoint on the source line point is on.
26468 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26469 separate frame which shows a backtrace when the GUD buffer is current.
26470 Move point to any frame in the stack and type @key{RET} to make it
26471 become the current frame and display the associated source in the
26472 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26473 selected frame become the current one. In graphical mode, the
26474 speedbar displays watch expressions.
26476 If you accidentally delete the source-display buffer, an easy way to get
26477 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26478 request a frame display; when you run under Emacs, this recreates
26479 the source buffer if necessary to show you the context of the current
26482 The source files displayed in Emacs are in ordinary Emacs buffers
26483 which are visiting the source files in the usual way. You can edit
26484 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26485 communicates with Emacs in terms of line numbers. If you add or
26486 delete lines from the text, the line numbers that @value{GDBN} knows cease
26487 to correspond properly with the code.
26489 A more detailed description of Emacs' interaction with @value{GDBN} is
26490 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26493 @c The following dropped because Epoch is nonstandard. Reactivate
26494 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
26496 @kindex Emacs Epoch environment
26500 Version 18 of @sc{gnu} Emacs has a built-in window system
26501 called the @code{epoch}
26502 environment. Users of this environment can use a new command,
26503 @code{inspect} which performs identically to @code{print} except that
26504 each value is printed in its own window.
26509 @chapter The @sc{gdb/mi} Interface
26511 @unnumberedsec Function and Purpose
26513 @cindex @sc{gdb/mi}, its purpose
26514 @sc{gdb/mi} is a line based machine oriented text interface to
26515 @value{GDBN} and is activated by specifying using the
26516 @option{--interpreter} command line option (@pxref{Mode Options}). It
26517 is specifically intended to support the development of systems which
26518 use the debugger as just one small component of a larger system.
26520 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26521 in the form of a reference manual.
26523 Note that @sc{gdb/mi} is still under construction, so some of the
26524 features described below are incomplete and subject to change
26525 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26527 @unnumberedsec Notation and Terminology
26529 @cindex notational conventions, for @sc{gdb/mi}
26530 This chapter uses the following notation:
26534 @code{|} separates two alternatives.
26537 @code{[ @var{something} ]} indicates that @var{something} is optional:
26538 it may or may not be given.
26541 @code{( @var{group} )*} means that @var{group} inside the parentheses
26542 may repeat zero or more times.
26545 @code{( @var{group} )+} means that @var{group} inside the parentheses
26546 may repeat one or more times.
26549 @code{"@var{string}"} means a literal @var{string}.
26553 @heading Dependencies
26557 * GDB/MI General Design::
26558 * GDB/MI Command Syntax::
26559 * GDB/MI Compatibility with CLI::
26560 * GDB/MI Development and Front Ends::
26561 * GDB/MI Output Records::
26562 * GDB/MI Simple Examples::
26563 * GDB/MI Command Description Format::
26564 * GDB/MI Breakpoint Commands::
26565 * GDB/MI Program Context::
26566 * GDB/MI Thread Commands::
26567 * GDB/MI Ada Tasking Commands::
26568 * GDB/MI Program Execution::
26569 * GDB/MI Stack Manipulation::
26570 * GDB/MI Variable Objects::
26571 * GDB/MI Data Manipulation::
26572 * GDB/MI Tracepoint Commands::
26573 * GDB/MI Symbol Query::
26574 * GDB/MI File Commands::
26576 * GDB/MI Kod Commands::
26577 * GDB/MI Memory Overlay Commands::
26578 * GDB/MI Signal Handling Commands::
26580 * GDB/MI Target Manipulation::
26581 * GDB/MI File Transfer Commands::
26582 * GDB/MI Miscellaneous Commands::
26585 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26586 @node GDB/MI General Design
26587 @section @sc{gdb/mi} General Design
26588 @cindex GDB/MI General Design
26590 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26591 parts---commands sent to @value{GDBN}, responses to those commands
26592 and notifications. Each command results in exactly one response,
26593 indicating either successful completion of the command, or an error.
26594 For the commands that do not resume the target, the response contains the
26595 requested information. For the commands that resume the target, the
26596 response only indicates whether the target was successfully resumed.
26597 Notifications is the mechanism for reporting changes in the state of the
26598 target, or in @value{GDBN} state, that cannot conveniently be associated with
26599 a command and reported as part of that command response.
26601 The important examples of notifications are:
26605 Exec notifications. These are used to report changes in
26606 target state---when a target is resumed, or stopped. It would not
26607 be feasible to include this information in response of resuming
26608 commands, because one resume commands can result in multiple events in
26609 different threads. Also, quite some time may pass before any event
26610 happens in the target, while a frontend needs to know whether the resuming
26611 command itself was successfully executed.
26614 Console output, and status notifications. Console output
26615 notifications are used to report output of CLI commands, as well as
26616 diagnostics for other commands. Status notifications are used to
26617 report the progress of a long-running operation. Naturally, including
26618 this information in command response would mean no output is produced
26619 until the command is finished, which is undesirable.
26622 General notifications. Commands may have various side effects on
26623 the @value{GDBN} or target state beyond their official purpose. For example,
26624 a command may change the selected thread. Although such changes can
26625 be included in command response, using notification allows for more
26626 orthogonal frontend design.
26630 There's no guarantee that whenever an MI command reports an error,
26631 @value{GDBN} or the target are in any specific state, and especially,
26632 the state is not reverted to the state before the MI command was
26633 processed. Therefore, whenever an MI command results in an error,
26634 we recommend that the frontend refreshes all the information shown in
26635 the user interface.
26639 * Context management::
26640 * Asynchronous and non-stop modes::
26644 @node Context management
26645 @subsection Context management
26647 In most cases when @value{GDBN} accesses the target, this access is
26648 done in context of a specific thread and frame (@pxref{Frames}).
26649 Often, even when accessing global data, the target requires that a thread
26650 be specified. The CLI interface maintains the selected thread and frame,
26651 and supplies them to target on each command. This is convenient,
26652 because a command line user would not want to specify that information
26653 explicitly on each command, and because user interacts with
26654 @value{GDBN} via a single terminal, so no confusion is possible as
26655 to what thread and frame are the current ones.
26657 In the case of MI, the concept of selected thread and frame is less
26658 useful. First, a frontend can easily remember this information
26659 itself. Second, a graphical frontend can have more than one window,
26660 each one used for debugging a different thread, and the frontend might
26661 want to access additional threads for internal purposes. This
26662 increases the risk that by relying on implicitly selected thread, the
26663 frontend may be operating on a wrong one. Therefore, each MI command
26664 should explicitly specify which thread and frame to operate on. To
26665 make it possible, each MI command accepts the @samp{--thread} and
26666 @samp{--frame} options, the value to each is @value{GDBN} identifier
26667 for thread and frame to operate on.
26669 Usually, each top-level window in a frontend allows the user to select
26670 a thread and a frame, and remembers the user selection for further
26671 operations. However, in some cases @value{GDBN} may suggest that the
26672 current thread be changed. For example, when stopping on a breakpoint
26673 it is reasonable to switch to the thread where breakpoint is hit. For
26674 another example, if the user issues the CLI @samp{thread} command via
26675 the frontend, it is desirable to change the frontend's selected thread to the
26676 one specified by user. @value{GDBN} communicates the suggestion to
26677 change current thread using the @samp{=thread-selected} notification.
26678 No such notification is available for the selected frame at the moment.
26680 Note that historically, MI shares the selected thread with CLI, so
26681 frontends used the @code{-thread-select} to execute commands in the
26682 right context. However, getting this to work right is cumbersome. The
26683 simplest way is for frontend to emit @code{-thread-select} command
26684 before every command. This doubles the number of commands that need
26685 to be sent. The alternative approach is to suppress @code{-thread-select}
26686 if the selected thread in @value{GDBN} is supposed to be identical to the
26687 thread the frontend wants to operate on. However, getting this
26688 optimization right can be tricky. In particular, if the frontend
26689 sends several commands to @value{GDBN}, and one of the commands changes the
26690 selected thread, then the behaviour of subsequent commands will
26691 change. So, a frontend should either wait for response from such
26692 problematic commands, or explicitly add @code{-thread-select} for
26693 all subsequent commands. No frontend is known to do this exactly
26694 right, so it is suggested to just always pass the @samp{--thread} and
26695 @samp{--frame} options.
26697 @node Asynchronous and non-stop modes
26698 @subsection Asynchronous command execution and non-stop mode
26700 On some targets, @value{GDBN} is capable of processing MI commands
26701 even while the target is running. This is called @dfn{asynchronous
26702 command execution} (@pxref{Background Execution}). The frontend may
26703 specify a preferrence for asynchronous execution using the
26704 @code{-gdb-set target-async 1} command, which should be emitted before
26705 either running the executable or attaching to the target. After the
26706 frontend has started the executable or attached to the target, it can
26707 find if asynchronous execution is enabled using the
26708 @code{-list-target-features} command.
26710 Even if @value{GDBN} can accept a command while target is running,
26711 many commands that access the target do not work when the target is
26712 running. Therefore, asynchronous command execution is most useful
26713 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26714 it is possible to examine the state of one thread, while other threads
26717 When a given thread is running, MI commands that try to access the
26718 target in the context of that thread may not work, or may work only on
26719 some targets. In particular, commands that try to operate on thread's
26720 stack will not work, on any target. Commands that read memory, or
26721 modify breakpoints, may work or not work, depending on the target. Note
26722 that even commands that operate on global state, such as @code{print},
26723 @code{set}, and breakpoint commands, still access the target in the
26724 context of a specific thread, so frontend should try to find a
26725 stopped thread and perform the operation on that thread (using the
26726 @samp{--thread} option).
26728 Which commands will work in the context of a running thread is
26729 highly target dependent. However, the two commands
26730 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26731 to find the state of a thread, will always work.
26733 @node Thread groups
26734 @subsection Thread groups
26735 @value{GDBN} may be used to debug several processes at the same time.
26736 On some platfroms, @value{GDBN} may support debugging of several
26737 hardware systems, each one having several cores with several different
26738 processes running on each core. This section describes the MI
26739 mechanism to support such debugging scenarios.
26741 The key observation is that regardless of the structure of the
26742 target, MI can have a global list of threads, because most commands that
26743 accept the @samp{--thread} option do not need to know what process that
26744 thread belongs to. Therefore, it is not necessary to introduce
26745 neither additional @samp{--process} option, nor an notion of the
26746 current process in the MI interface. The only strictly new feature
26747 that is required is the ability to find how the threads are grouped
26750 To allow the user to discover such grouping, and to support arbitrary
26751 hierarchy of machines/cores/processes, MI introduces the concept of a
26752 @dfn{thread group}. Thread group is a collection of threads and other
26753 thread groups. A thread group always has a string identifier, a type,
26754 and may have additional attributes specific to the type. A new
26755 command, @code{-list-thread-groups}, returns the list of top-level
26756 thread groups, which correspond to processes that @value{GDBN} is
26757 debugging at the moment. By passing an identifier of a thread group
26758 to the @code{-list-thread-groups} command, it is possible to obtain
26759 the members of specific thread group.
26761 To allow the user to easily discover processes, and other objects, he
26762 wishes to debug, a concept of @dfn{available thread group} is
26763 introduced. Available thread group is an thread group that
26764 @value{GDBN} is not debugging, but that can be attached to, using the
26765 @code{-target-attach} command. The list of available top-level thread
26766 groups can be obtained using @samp{-list-thread-groups --available}.
26767 In general, the content of a thread group may be only retrieved only
26768 after attaching to that thread group.
26770 Thread groups are related to inferiors (@pxref{Inferiors and
26771 Programs}). Each inferior corresponds to a thread group of a special
26772 type @samp{process}, and some additional operations are permitted on
26773 such thread groups.
26775 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26776 @node GDB/MI Command Syntax
26777 @section @sc{gdb/mi} Command Syntax
26780 * GDB/MI Input Syntax::
26781 * GDB/MI Output Syntax::
26784 @node GDB/MI Input Syntax
26785 @subsection @sc{gdb/mi} Input Syntax
26787 @cindex input syntax for @sc{gdb/mi}
26788 @cindex @sc{gdb/mi}, input syntax
26790 @item @var{command} @expansion{}
26791 @code{@var{cli-command} | @var{mi-command}}
26793 @item @var{cli-command} @expansion{}
26794 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26795 @var{cli-command} is any existing @value{GDBN} CLI command.
26797 @item @var{mi-command} @expansion{}
26798 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26799 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26801 @item @var{token} @expansion{}
26802 "any sequence of digits"
26804 @item @var{option} @expansion{}
26805 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26807 @item @var{parameter} @expansion{}
26808 @code{@var{non-blank-sequence} | @var{c-string}}
26810 @item @var{operation} @expansion{}
26811 @emph{any of the operations described in this chapter}
26813 @item @var{non-blank-sequence} @expansion{}
26814 @emph{anything, provided it doesn't contain special characters such as
26815 "-", @var{nl}, """ and of course " "}
26817 @item @var{c-string} @expansion{}
26818 @code{""" @var{seven-bit-iso-c-string-content} """}
26820 @item @var{nl} @expansion{}
26829 The CLI commands are still handled by the @sc{mi} interpreter; their
26830 output is described below.
26833 The @code{@var{token}}, when present, is passed back when the command
26837 Some @sc{mi} commands accept optional arguments as part of the parameter
26838 list. Each option is identified by a leading @samp{-} (dash) and may be
26839 followed by an optional argument parameter. Options occur first in the
26840 parameter list and can be delimited from normal parameters using
26841 @samp{--} (this is useful when some parameters begin with a dash).
26848 We want easy access to the existing CLI syntax (for debugging).
26851 We want it to be easy to spot a @sc{mi} operation.
26854 @node GDB/MI Output Syntax
26855 @subsection @sc{gdb/mi} Output Syntax
26857 @cindex output syntax of @sc{gdb/mi}
26858 @cindex @sc{gdb/mi}, output syntax
26859 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26860 followed, optionally, by a single result record. This result record
26861 is for the most recent command. The sequence of output records is
26862 terminated by @samp{(gdb)}.
26864 If an input command was prefixed with a @code{@var{token}} then the
26865 corresponding output for that command will also be prefixed by that same
26869 @item @var{output} @expansion{}
26870 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26872 @item @var{result-record} @expansion{}
26873 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26875 @item @var{out-of-band-record} @expansion{}
26876 @code{@var{async-record} | @var{stream-record}}
26878 @item @var{async-record} @expansion{}
26879 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26881 @item @var{exec-async-output} @expansion{}
26882 @code{[ @var{token} ] "*" @var{async-output}}
26884 @item @var{status-async-output} @expansion{}
26885 @code{[ @var{token} ] "+" @var{async-output}}
26887 @item @var{notify-async-output} @expansion{}
26888 @code{[ @var{token} ] "=" @var{async-output}}
26890 @item @var{async-output} @expansion{}
26891 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
26893 @item @var{result-class} @expansion{}
26894 @code{"done" | "running" | "connected" | "error" | "exit"}
26896 @item @var{async-class} @expansion{}
26897 @code{"stopped" | @var{others}} (where @var{others} will be added
26898 depending on the needs---this is still in development).
26900 @item @var{result} @expansion{}
26901 @code{ @var{variable} "=" @var{value}}
26903 @item @var{variable} @expansion{}
26904 @code{ @var{string} }
26906 @item @var{value} @expansion{}
26907 @code{ @var{const} | @var{tuple} | @var{list} }
26909 @item @var{const} @expansion{}
26910 @code{@var{c-string}}
26912 @item @var{tuple} @expansion{}
26913 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26915 @item @var{list} @expansion{}
26916 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26917 @var{result} ( "," @var{result} )* "]" }
26919 @item @var{stream-record} @expansion{}
26920 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26922 @item @var{console-stream-output} @expansion{}
26923 @code{"~" @var{c-string}}
26925 @item @var{target-stream-output} @expansion{}
26926 @code{"@@" @var{c-string}}
26928 @item @var{log-stream-output} @expansion{}
26929 @code{"&" @var{c-string}}
26931 @item @var{nl} @expansion{}
26934 @item @var{token} @expansion{}
26935 @emph{any sequence of digits}.
26943 All output sequences end in a single line containing a period.
26946 The @code{@var{token}} is from the corresponding request. Note that
26947 for all async output, while the token is allowed by the grammar and
26948 may be output by future versions of @value{GDBN} for select async
26949 output messages, it is generally omitted. Frontends should treat
26950 all async output as reporting general changes in the state of the
26951 target and there should be no need to associate async output to any
26955 @cindex status output in @sc{gdb/mi}
26956 @var{status-async-output} contains on-going status information about the
26957 progress of a slow operation. It can be discarded. All status output is
26958 prefixed by @samp{+}.
26961 @cindex async output in @sc{gdb/mi}
26962 @var{exec-async-output} contains asynchronous state change on the target
26963 (stopped, started, disappeared). All async output is prefixed by
26967 @cindex notify output in @sc{gdb/mi}
26968 @var{notify-async-output} contains supplementary information that the
26969 client should handle (e.g., a new breakpoint information). All notify
26970 output is prefixed by @samp{=}.
26973 @cindex console output in @sc{gdb/mi}
26974 @var{console-stream-output} is output that should be displayed as is in the
26975 console. It is the textual response to a CLI command. All the console
26976 output is prefixed by @samp{~}.
26979 @cindex target output in @sc{gdb/mi}
26980 @var{target-stream-output} is the output produced by the target program.
26981 All the target output is prefixed by @samp{@@}.
26984 @cindex log output in @sc{gdb/mi}
26985 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26986 instance messages that should be displayed as part of an error log. All
26987 the log output is prefixed by @samp{&}.
26990 @cindex list output in @sc{gdb/mi}
26991 New @sc{gdb/mi} commands should only output @var{lists} containing
26997 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26998 details about the various output records.
27000 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27001 @node GDB/MI Compatibility with CLI
27002 @section @sc{gdb/mi} Compatibility with CLI
27004 @cindex compatibility, @sc{gdb/mi} and CLI
27005 @cindex @sc{gdb/mi}, compatibility with CLI
27007 For the developers convenience CLI commands can be entered directly,
27008 but there may be some unexpected behaviour. For example, commands
27009 that query the user will behave as if the user replied yes, breakpoint
27010 command lists are not executed and some CLI commands, such as
27011 @code{if}, @code{when} and @code{define}, prompt for further input with
27012 @samp{>}, which is not valid MI output.
27014 This feature may be removed at some stage in the future and it is
27015 recommended that front ends use the @code{-interpreter-exec} command
27016 (@pxref{-interpreter-exec}).
27018 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27019 @node GDB/MI Development and Front Ends
27020 @section @sc{gdb/mi} Development and Front Ends
27021 @cindex @sc{gdb/mi} development
27023 The application which takes the MI output and presents the state of the
27024 program being debugged to the user is called a @dfn{front end}.
27026 Although @sc{gdb/mi} is still incomplete, it is currently being used
27027 by a variety of front ends to @value{GDBN}. This makes it difficult
27028 to introduce new functionality without breaking existing usage. This
27029 section tries to minimize the problems by describing how the protocol
27032 Some changes in MI need not break a carefully designed front end, and
27033 for these the MI version will remain unchanged. The following is a
27034 list of changes that may occur within one level, so front ends should
27035 parse MI output in a way that can handle them:
27039 New MI commands may be added.
27042 New fields may be added to the output of any MI command.
27045 The range of values for fields with specified values, e.g.,
27046 @code{in_scope} (@pxref{-var-update}) may be extended.
27048 @c The format of field's content e.g type prefix, may change so parse it
27049 @c at your own risk. Yes, in general?
27051 @c The order of fields may change? Shouldn't really matter but it might
27052 @c resolve inconsistencies.
27055 If the changes are likely to break front ends, the MI version level
27056 will be increased by one. This will allow the front end to parse the
27057 output according to the MI version. Apart from mi0, new versions of
27058 @value{GDBN} will not support old versions of MI and it will be the
27059 responsibility of the front end to work with the new one.
27061 @c Starting with mi3, add a new command -mi-version that prints the MI
27064 The best way to avoid unexpected changes in MI that might break your front
27065 end is to make your project known to @value{GDBN} developers and
27066 follow development on @email{gdb@@sourceware.org} and
27067 @email{gdb-patches@@sourceware.org}.
27068 @cindex mailing lists
27070 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27071 @node GDB/MI Output Records
27072 @section @sc{gdb/mi} Output Records
27075 * GDB/MI Result Records::
27076 * GDB/MI Stream Records::
27077 * GDB/MI Async Records::
27078 * GDB/MI Frame Information::
27079 * GDB/MI Thread Information::
27080 * GDB/MI Ada Exception Information::
27083 @node GDB/MI Result Records
27084 @subsection @sc{gdb/mi} Result Records
27086 @cindex result records in @sc{gdb/mi}
27087 @cindex @sc{gdb/mi}, result records
27088 In addition to a number of out-of-band notifications, the response to a
27089 @sc{gdb/mi} command includes one of the following result indications:
27093 @item "^done" [ "," @var{results} ]
27094 The synchronous operation was successful, @code{@var{results}} are the return
27099 This result record is equivalent to @samp{^done}. Historically, it
27100 was output instead of @samp{^done} if the command has resumed the
27101 target. This behaviour is maintained for backward compatibility, but
27102 all frontends should treat @samp{^done} and @samp{^running}
27103 identically and rely on the @samp{*running} output record to determine
27104 which threads are resumed.
27108 @value{GDBN} has connected to a remote target.
27110 @item "^error" "," @var{c-string}
27112 The operation failed. The @code{@var{c-string}} contains the corresponding
27117 @value{GDBN} has terminated.
27121 @node GDB/MI Stream Records
27122 @subsection @sc{gdb/mi} Stream Records
27124 @cindex @sc{gdb/mi}, stream records
27125 @cindex stream records in @sc{gdb/mi}
27126 @value{GDBN} internally maintains a number of output streams: the console, the
27127 target, and the log. The output intended for each of these streams is
27128 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27130 Each stream record begins with a unique @dfn{prefix character} which
27131 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27132 Syntax}). In addition to the prefix, each stream record contains a
27133 @code{@var{string-output}}. This is either raw text (with an implicit new
27134 line) or a quoted C string (which does not contain an implicit newline).
27137 @item "~" @var{string-output}
27138 The console output stream contains text that should be displayed in the
27139 CLI console window. It contains the textual responses to CLI commands.
27141 @item "@@" @var{string-output}
27142 The target output stream contains any textual output from the running
27143 target. This is only present when GDB's event loop is truly
27144 asynchronous, which is currently only the case for remote targets.
27146 @item "&" @var{string-output}
27147 The log stream contains debugging messages being produced by @value{GDBN}'s
27151 @node GDB/MI Async Records
27152 @subsection @sc{gdb/mi} Async Records
27154 @cindex async records in @sc{gdb/mi}
27155 @cindex @sc{gdb/mi}, async records
27156 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27157 additional changes that have occurred. Those changes can either be a
27158 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27159 target activity (e.g., target stopped).
27161 The following is the list of possible async records:
27165 @item *running,thread-id="@var{thread}"
27166 The target is now running. The @var{thread} field tells which
27167 specific thread is now running, and can be @samp{all} if all threads
27168 are running. The frontend should assume that no interaction with a
27169 running thread is possible after this notification is produced.
27170 The frontend should not assume that this notification is output
27171 only once for any command. @value{GDBN} may emit this notification
27172 several times, either for different threads, because it cannot resume
27173 all threads together, or even for a single thread, if the thread must
27174 be stepped though some code before letting it run freely.
27176 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27177 The target has stopped. The @var{reason} field can have one of the
27181 @item breakpoint-hit
27182 A breakpoint was reached.
27183 @item watchpoint-trigger
27184 A watchpoint was triggered.
27185 @item read-watchpoint-trigger
27186 A read watchpoint was triggered.
27187 @item access-watchpoint-trigger
27188 An access watchpoint was triggered.
27189 @item function-finished
27190 An -exec-finish or similar CLI command was accomplished.
27191 @item location-reached
27192 An -exec-until or similar CLI command was accomplished.
27193 @item watchpoint-scope
27194 A watchpoint has gone out of scope.
27195 @item end-stepping-range
27196 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27197 similar CLI command was accomplished.
27198 @item exited-signalled
27199 The inferior exited because of a signal.
27201 The inferior exited.
27202 @item exited-normally
27203 The inferior exited normally.
27204 @item signal-received
27205 A signal was received by the inferior.
27207 The inferior has stopped due to a library being loaded or unloaded.
27208 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27209 set or when a @code{catch load} or @code{catch unload} catchpoint is
27210 in use (@pxref{Set Catchpoints}).
27212 The inferior has forked. This is reported when @code{catch fork}
27213 (@pxref{Set Catchpoints}) has been used.
27215 The inferior has vforked. This is reported in when @code{catch vfork}
27216 (@pxref{Set Catchpoints}) has been used.
27217 @item syscall-entry
27218 The inferior entered a system call. This is reported when @code{catch
27219 syscall} (@pxref{Set Catchpoints}) has been used.
27220 @item syscall-entry
27221 The inferior returned from a system call. This is reported when
27222 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27224 The inferior called @code{exec}. This is reported when @code{catch exec}
27225 (@pxref{Set Catchpoints}) has been used.
27228 The @var{id} field identifies the thread that directly caused the stop
27229 -- for example by hitting a breakpoint. Depending on whether all-stop
27230 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27231 stop all threads, or only the thread that directly triggered the stop.
27232 If all threads are stopped, the @var{stopped} field will have the
27233 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27234 field will be a list of thread identifiers. Presently, this list will
27235 always include a single thread, but frontend should be prepared to see
27236 several threads in the list. The @var{core} field reports the
27237 processor core on which the stop event has happened. This field may be absent
27238 if such information is not available.
27240 @item =thread-group-added,id="@var{id}"
27241 @itemx =thread-group-removed,id="@var{id}"
27242 A thread group was either added or removed. The @var{id} field
27243 contains the @value{GDBN} identifier of the thread group. When a thread
27244 group is added, it generally might not be associated with a running
27245 process. When a thread group is removed, its id becomes invalid and
27246 cannot be used in any way.
27248 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27249 A thread group became associated with a running program,
27250 either because the program was just started or the thread group
27251 was attached to a program. The @var{id} field contains the
27252 @value{GDBN} identifier of the thread group. The @var{pid} field
27253 contains process identifier, specific to the operating system.
27255 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27256 A thread group is no longer associated with a running program,
27257 either because the program has exited, or because it was detached
27258 from. The @var{id} field contains the @value{GDBN} identifier of the
27259 thread group. @var{code} is the exit code of the inferior; it exists
27260 only when the inferior exited with some code.
27262 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27263 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27264 A thread either was created, or has exited. The @var{id} field
27265 contains the @value{GDBN} identifier of the thread. The @var{gid}
27266 field identifies the thread group this thread belongs to.
27268 @item =thread-selected,id="@var{id}"
27269 Informs that the selected thread was changed as result of the last
27270 command. This notification is not emitted as result of @code{-thread-select}
27271 command but is emitted whenever an MI command that is not documented
27272 to change the selected thread actually changes it. In particular,
27273 invoking, directly or indirectly (via user-defined command), the CLI
27274 @code{thread} command, will generate this notification.
27276 We suggest that in response to this notification, front ends
27277 highlight the selected thread and cause subsequent commands to apply to
27280 @item =library-loaded,...
27281 Reports that a new library file was loaded by the program. This
27282 notification has 4 fields---@var{id}, @var{target-name},
27283 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
27284 opaque identifier of the library. For remote debugging case,
27285 @var{target-name} and @var{host-name} fields give the name of the
27286 library file on the target, and on the host respectively. For native
27287 debugging, both those fields have the same value. The
27288 @var{symbols-loaded} field is emitted only for backward compatibility
27289 and should not be relied on to convey any useful information. The
27290 @var{thread-group} field, if present, specifies the id of the thread
27291 group in whose context the library was loaded. If the field is
27292 absent, it means the library was loaded in the context of all present
27295 @item =library-unloaded,...
27296 Reports that a library was unloaded by the program. This notification
27297 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27298 the same meaning as for the @code{=library-loaded} notification.
27299 The @var{thread-group} field, if present, specifies the id of the
27300 thread group in whose context the library was unloaded. If the field is
27301 absent, it means the library was unloaded in the context of all present
27304 @item =breakpoint-created,bkpt=@{...@}
27305 @itemx =breakpoint-modified,bkpt=@{...@}
27306 @itemx =breakpoint-deleted,bkpt=@{...@}
27307 Reports that a breakpoint was created, modified, or deleted,
27308 respectively. Only user-visible breakpoints are reported to the MI
27311 The @var{bkpt} argument is of the same form as returned by the various
27312 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
27314 Note that if a breakpoint is emitted in the result record of a
27315 command, then it will not also be emitted in an async record.
27319 @node GDB/MI Frame Information
27320 @subsection @sc{gdb/mi} Frame Information
27322 Response from many MI commands includes an information about stack
27323 frame. This information is a tuple that may have the following
27328 The level of the stack frame. The innermost frame has the level of
27329 zero. This field is always present.
27332 The name of the function corresponding to the frame. This field may
27333 be absent if @value{GDBN} is unable to determine the function name.
27336 The code address for the frame. This field is always present.
27339 The name of the source files that correspond to the frame's code
27340 address. This field may be absent.
27343 The source line corresponding to the frames' code address. This field
27347 The name of the binary file (either executable or shared library) the
27348 corresponds to the frame's code address. This field may be absent.
27352 @node GDB/MI Thread Information
27353 @subsection @sc{gdb/mi} Thread Information
27355 Whenever @value{GDBN} has to report an information about a thread, it
27356 uses a tuple with the following fields:
27360 The numeric id assigned to the thread by @value{GDBN}. This field is
27364 Target-specific string identifying the thread. This field is always present.
27367 Additional information about the thread provided by the target.
27368 It is supposed to be human-readable and not interpreted by the
27369 frontend. This field is optional.
27372 Either @samp{stopped} or @samp{running}, depending on whether the
27373 thread is presently running. This field is always present.
27376 The value of this field is an integer number of the processor core the
27377 thread was last seen on. This field is optional.
27380 @node GDB/MI Ada Exception Information
27381 @subsection @sc{gdb/mi} Ada Exception Information
27383 Whenever a @code{*stopped} record is emitted because the program
27384 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27385 @value{GDBN} provides the name of the exception that was raised via
27386 the @code{exception-name} field.
27388 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27389 @node GDB/MI Simple Examples
27390 @section Simple Examples of @sc{gdb/mi} Interaction
27391 @cindex @sc{gdb/mi}, simple examples
27393 This subsection presents several simple examples of interaction using
27394 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27395 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27396 the output received from @sc{gdb/mi}.
27398 Note the line breaks shown in the examples are here only for
27399 readability, they don't appear in the real output.
27401 @subheading Setting a Breakpoint
27403 Setting a breakpoint generates synchronous output which contains detailed
27404 information of the breakpoint.
27407 -> -break-insert main
27408 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27409 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27410 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
27414 @subheading Program Execution
27416 Program execution generates asynchronous records and MI gives the
27417 reason that execution stopped.
27423 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27424 frame=@{addr="0x08048564",func="main",
27425 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27426 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27431 <- *stopped,reason="exited-normally"
27435 @subheading Quitting @value{GDBN}
27437 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27445 Please note that @samp{^exit} is printed immediately, but it might
27446 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27447 performs necessary cleanups, including killing programs being debugged
27448 or disconnecting from debug hardware, so the frontend should wait till
27449 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27450 fails to exit in reasonable time.
27452 @subheading A Bad Command
27454 Here's what happens if you pass a non-existent command:
27458 <- ^error,msg="Undefined MI command: rubbish"
27463 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27464 @node GDB/MI Command Description Format
27465 @section @sc{gdb/mi} Command Description Format
27467 The remaining sections describe blocks of commands. Each block of
27468 commands is laid out in a fashion similar to this section.
27470 @subheading Motivation
27472 The motivation for this collection of commands.
27474 @subheading Introduction
27476 A brief introduction to this collection of commands as a whole.
27478 @subheading Commands
27480 For each command in the block, the following is described:
27482 @subsubheading Synopsis
27485 -command @var{args}@dots{}
27488 @subsubheading Result
27490 @subsubheading @value{GDBN} Command
27492 The corresponding @value{GDBN} CLI command(s), if any.
27494 @subsubheading Example
27496 Example(s) formatted for readability. Some of the described commands have
27497 not been implemented yet and these are labeled N.A.@: (not available).
27500 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27501 @node GDB/MI Breakpoint Commands
27502 @section @sc{gdb/mi} Breakpoint Commands
27504 @cindex breakpoint commands for @sc{gdb/mi}
27505 @cindex @sc{gdb/mi}, breakpoint commands
27506 This section documents @sc{gdb/mi} commands for manipulating
27509 @subheading The @code{-break-after} Command
27510 @findex -break-after
27512 @subsubheading Synopsis
27515 -break-after @var{number} @var{count}
27518 The breakpoint number @var{number} is not in effect until it has been
27519 hit @var{count} times. To see how this is reflected in the output of
27520 the @samp{-break-list} command, see the description of the
27521 @samp{-break-list} command below.
27523 @subsubheading @value{GDBN} Command
27525 The corresponding @value{GDBN} command is @samp{ignore}.
27527 @subsubheading Example
27532 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27533 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27534 fullname="/home/foo/hello.c",line="5",times="0"@}
27541 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27542 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27543 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27544 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27545 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27546 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27547 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27548 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27549 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27550 line="5",times="0",ignore="3"@}]@}
27555 @subheading The @code{-break-catch} Command
27556 @findex -break-catch
27559 @subheading The @code{-break-commands} Command
27560 @findex -break-commands
27562 @subsubheading Synopsis
27565 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27568 Specifies the CLI commands that should be executed when breakpoint
27569 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27570 are the commands. If no command is specified, any previously-set
27571 commands are cleared. @xref{Break Commands}. Typical use of this
27572 functionality is tracing a program, that is, printing of values of
27573 some variables whenever breakpoint is hit and then continuing.
27575 @subsubheading @value{GDBN} Command
27577 The corresponding @value{GDBN} command is @samp{commands}.
27579 @subsubheading Example
27584 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27585 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27586 fullname="/home/foo/hello.c",line="5",times="0"@}
27588 -break-commands 1 "print v" "continue"
27593 @subheading The @code{-break-condition} Command
27594 @findex -break-condition
27596 @subsubheading Synopsis
27599 -break-condition @var{number} @var{expr}
27602 Breakpoint @var{number} will stop the program only if the condition in
27603 @var{expr} is true. The condition becomes part of the
27604 @samp{-break-list} output (see the description of the @samp{-break-list}
27607 @subsubheading @value{GDBN} Command
27609 The corresponding @value{GDBN} command is @samp{condition}.
27611 @subsubheading Example
27615 -break-condition 1 1
27619 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27620 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27621 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27622 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27623 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27624 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27625 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27626 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27627 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27628 line="5",cond="1",times="0",ignore="3"@}]@}
27632 @subheading The @code{-break-delete} Command
27633 @findex -break-delete
27635 @subsubheading Synopsis
27638 -break-delete ( @var{breakpoint} )+
27641 Delete the breakpoint(s) whose number(s) are specified in the argument
27642 list. This is obviously reflected in the breakpoint list.
27644 @subsubheading @value{GDBN} Command
27646 The corresponding @value{GDBN} command is @samp{delete}.
27648 @subsubheading Example
27656 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27657 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27658 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27659 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27660 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27661 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27662 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27667 @subheading The @code{-break-disable} Command
27668 @findex -break-disable
27670 @subsubheading Synopsis
27673 -break-disable ( @var{breakpoint} )+
27676 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27677 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27679 @subsubheading @value{GDBN} Command
27681 The corresponding @value{GDBN} command is @samp{disable}.
27683 @subsubheading Example
27691 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27692 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27693 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27694 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27695 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27696 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27697 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27698 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27699 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27700 line="5",times="0"@}]@}
27704 @subheading The @code{-break-enable} Command
27705 @findex -break-enable
27707 @subsubheading Synopsis
27710 -break-enable ( @var{breakpoint} )+
27713 Enable (previously disabled) @var{breakpoint}(s).
27715 @subsubheading @value{GDBN} Command
27717 The corresponding @value{GDBN} command is @samp{enable}.
27719 @subsubheading Example
27727 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27728 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27729 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27730 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27731 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27732 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27733 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27734 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27735 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27736 line="5",times="0"@}]@}
27740 @subheading The @code{-break-info} Command
27741 @findex -break-info
27743 @subsubheading Synopsis
27746 -break-info @var{breakpoint}
27750 Get information about a single breakpoint.
27752 @subsubheading @value{GDBN} Command
27754 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27756 @subsubheading Example
27759 @subheading The @code{-break-insert} Command
27760 @findex -break-insert
27762 @subsubheading Synopsis
27765 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27766 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27767 [ -p @var{thread} ] [ @var{location} ]
27771 If specified, @var{location}, can be one of:
27778 @item filename:linenum
27779 @item filename:function
27783 The possible optional parameters of this command are:
27787 Insert a temporary breakpoint.
27789 Insert a hardware breakpoint.
27790 @item -c @var{condition}
27791 Make the breakpoint conditional on @var{condition}.
27792 @item -i @var{ignore-count}
27793 Initialize the @var{ignore-count}.
27795 If @var{location} cannot be parsed (for example if it
27796 refers to unknown files or functions), create a pending
27797 breakpoint. Without this flag, @value{GDBN} will report
27798 an error, and won't create a breakpoint, if @var{location}
27801 Create a disabled breakpoint.
27803 Create a tracepoint. @xref{Tracepoints}. When this parameter
27804 is used together with @samp{-h}, a fast tracepoint is created.
27807 @subsubheading Result
27809 The result is in the form:
27812 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
27813 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
27814 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
27815 times="@var{times}"@}
27819 where @var{number} is the @value{GDBN} number for this breakpoint,
27820 @var{funcname} is the name of the function where the breakpoint was
27821 inserted, @var{filename} is the name of the source file which contains
27822 this function, @var{lineno} is the source line number within that file
27823 and @var{times} the number of times that the breakpoint has been hit
27824 (always 0 for -break-insert but may be greater for -break-info or -break-list
27825 which use the same output).
27827 Note: this format is open to change.
27828 @c An out-of-band breakpoint instead of part of the result?
27830 @subsubheading @value{GDBN} Command
27832 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27833 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
27835 @subsubheading Example
27840 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27841 fullname="/home/foo/recursive2.c,line="4",times="0"@}
27843 -break-insert -t foo
27844 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27845 fullname="/home/foo/recursive2.c,line="11",times="0"@}
27848 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27849 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27850 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27851 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27852 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27853 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27854 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27855 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27856 addr="0x0001072c", func="main",file="recursive2.c",
27857 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
27858 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27859 addr="0x00010774",func="foo",file="recursive2.c",
27860 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
27862 -break-insert -r foo.*
27863 ~int foo(int, int);
27864 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27865 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
27869 @subheading The @code{-break-list} Command
27870 @findex -break-list
27872 @subsubheading Synopsis
27878 Displays the list of inserted breakpoints, showing the following fields:
27882 number of the breakpoint
27884 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27886 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27889 is the breakpoint enabled or no: @samp{y} or @samp{n}
27891 memory location at which the breakpoint is set
27893 logical location of the breakpoint, expressed by function name, file
27896 number of times the breakpoint has been hit
27899 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27900 @code{body} field is an empty list.
27902 @subsubheading @value{GDBN} Command
27904 The corresponding @value{GDBN} command is @samp{info break}.
27906 @subsubheading Example
27911 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27912 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27913 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27914 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27915 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27916 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27917 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27918 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27919 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27920 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27921 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27922 line="13",times="0"@}]@}
27926 Here's an example of the result when there are no breakpoints:
27931 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27932 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27933 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27934 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27935 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27936 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27937 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27942 @subheading The @code{-break-passcount} Command
27943 @findex -break-passcount
27945 @subsubheading Synopsis
27948 -break-passcount @var{tracepoint-number} @var{passcount}
27951 Set the passcount for tracepoint @var{tracepoint-number} to
27952 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27953 is not a tracepoint, error is emitted. This corresponds to CLI
27954 command @samp{passcount}.
27956 @subheading The @code{-break-watch} Command
27957 @findex -break-watch
27959 @subsubheading Synopsis
27962 -break-watch [ -a | -r ]
27965 Create a watchpoint. With the @samp{-a} option it will create an
27966 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27967 read from or on a write to the memory location. With the @samp{-r}
27968 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27969 trigger only when the memory location is accessed for reading. Without
27970 either of the options, the watchpoint created is a regular watchpoint,
27971 i.e., it will trigger when the memory location is accessed for writing.
27972 @xref{Set Watchpoints, , Setting Watchpoints}.
27974 Note that @samp{-break-list} will report a single list of watchpoints and
27975 breakpoints inserted.
27977 @subsubheading @value{GDBN} Command
27979 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27982 @subsubheading Example
27984 Setting a watchpoint on a variable in the @code{main} function:
27989 ^done,wpt=@{number="2",exp="x"@}
27994 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27995 value=@{old="-268439212",new="55"@},
27996 frame=@{func="main",args=[],file="recursive2.c",
27997 fullname="/home/foo/bar/recursive2.c",line="5"@}
28001 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28002 the program execution twice: first for the variable changing value, then
28003 for the watchpoint going out of scope.
28008 ^done,wpt=@{number="5",exp="C"@}
28013 *stopped,reason="watchpoint-trigger",
28014 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28015 frame=@{func="callee4",args=[],
28016 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28017 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28022 *stopped,reason="watchpoint-scope",wpnum="5",
28023 frame=@{func="callee3",args=[@{name="strarg",
28024 value="0x11940 \"A string argument.\""@}],
28025 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28026 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28030 Listing breakpoints and watchpoints, at different points in the program
28031 execution. Note that once the watchpoint goes out of scope, it is
28037 ^done,wpt=@{number="2",exp="C"@}
28040 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28041 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28042 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28043 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28044 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28045 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28046 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28047 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28048 addr="0x00010734",func="callee4",
28049 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28050 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
28051 bkpt=@{number="2",type="watchpoint",disp="keep",
28052 enabled="y",addr="",what="C",times="0"@}]@}
28057 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28058 value=@{old="-276895068",new="3"@},
28059 frame=@{func="callee4",args=[],
28060 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28061 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28064 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28065 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28066 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28067 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28068 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28069 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28070 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28071 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28072 addr="0x00010734",func="callee4",
28073 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28074 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
28075 bkpt=@{number="2",type="watchpoint",disp="keep",
28076 enabled="y",addr="",what="C",times="-5"@}]@}
28080 ^done,reason="watchpoint-scope",wpnum="2",
28081 frame=@{func="callee3",args=[@{name="strarg",
28082 value="0x11940 \"A string argument.\""@}],
28083 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28084 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28087 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28088 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28089 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28090 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28091 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28092 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28093 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28094 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28095 addr="0x00010734",func="callee4",
28096 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28097 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28102 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28103 @node GDB/MI Program Context
28104 @section @sc{gdb/mi} Program Context
28106 @subheading The @code{-exec-arguments} Command
28107 @findex -exec-arguments
28110 @subsubheading Synopsis
28113 -exec-arguments @var{args}
28116 Set the inferior program arguments, to be used in the next
28119 @subsubheading @value{GDBN} Command
28121 The corresponding @value{GDBN} command is @samp{set args}.
28123 @subsubheading Example
28127 -exec-arguments -v word
28134 @subheading The @code{-exec-show-arguments} Command
28135 @findex -exec-show-arguments
28137 @subsubheading Synopsis
28140 -exec-show-arguments
28143 Print the arguments of the program.
28145 @subsubheading @value{GDBN} Command
28147 The corresponding @value{GDBN} command is @samp{show args}.
28149 @subsubheading Example
28154 @subheading The @code{-environment-cd} Command
28155 @findex -environment-cd
28157 @subsubheading Synopsis
28160 -environment-cd @var{pathdir}
28163 Set @value{GDBN}'s working directory.
28165 @subsubheading @value{GDBN} Command
28167 The corresponding @value{GDBN} command is @samp{cd}.
28169 @subsubheading Example
28173 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28179 @subheading The @code{-environment-directory} Command
28180 @findex -environment-directory
28182 @subsubheading Synopsis
28185 -environment-directory [ -r ] [ @var{pathdir} ]+
28188 Add directories @var{pathdir} to beginning of search path for source files.
28189 If the @samp{-r} option is used, the search path is reset to the default
28190 search path. If directories @var{pathdir} are supplied in addition to the
28191 @samp{-r} option, the search path is first reset and then addition
28193 Multiple directories may be specified, separated by blanks. Specifying
28194 multiple directories in a single command
28195 results in the directories added to the beginning of the
28196 search path in the same order they were presented in the command.
28197 If blanks are needed as
28198 part of a directory name, double-quotes should be used around
28199 the name. In the command output, the path will show up separated
28200 by the system directory-separator character. The directory-separator
28201 character must not be used
28202 in any directory name.
28203 If no directories are specified, the current search path is displayed.
28205 @subsubheading @value{GDBN} Command
28207 The corresponding @value{GDBN} command is @samp{dir}.
28209 @subsubheading Example
28213 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28214 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28216 -environment-directory ""
28217 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28219 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28220 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28222 -environment-directory -r
28223 ^done,source-path="$cdir:$cwd"
28228 @subheading The @code{-environment-path} Command
28229 @findex -environment-path
28231 @subsubheading Synopsis
28234 -environment-path [ -r ] [ @var{pathdir} ]+
28237 Add directories @var{pathdir} to beginning of search path for object files.
28238 If the @samp{-r} option is used, the search path is reset to the original
28239 search path that existed at gdb start-up. If directories @var{pathdir} are
28240 supplied in addition to the
28241 @samp{-r} option, the search path is first reset and then addition
28243 Multiple directories may be specified, separated by blanks. Specifying
28244 multiple directories in a single command
28245 results in the directories added to the beginning of the
28246 search path in the same order they were presented in the command.
28247 If blanks are needed as
28248 part of a directory name, double-quotes should be used around
28249 the name. In the command output, the path will show up separated
28250 by the system directory-separator character. The directory-separator
28251 character must not be used
28252 in any directory name.
28253 If no directories are specified, the current path is displayed.
28256 @subsubheading @value{GDBN} Command
28258 The corresponding @value{GDBN} command is @samp{path}.
28260 @subsubheading Example
28265 ^done,path="/usr/bin"
28267 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28268 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28270 -environment-path -r /usr/local/bin
28271 ^done,path="/usr/local/bin:/usr/bin"
28276 @subheading The @code{-environment-pwd} Command
28277 @findex -environment-pwd
28279 @subsubheading Synopsis
28285 Show the current working directory.
28287 @subsubheading @value{GDBN} Command
28289 The corresponding @value{GDBN} command is @samp{pwd}.
28291 @subsubheading Example
28296 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28300 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28301 @node GDB/MI Thread Commands
28302 @section @sc{gdb/mi} Thread Commands
28305 @subheading The @code{-thread-info} Command
28306 @findex -thread-info
28308 @subsubheading Synopsis
28311 -thread-info [ @var{thread-id} ]
28314 Reports information about either a specific thread, if
28315 the @var{thread-id} parameter is present, or about all
28316 threads. When printing information about all threads,
28317 also reports the current thread.
28319 @subsubheading @value{GDBN} Command
28321 The @samp{info thread} command prints the same information
28324 @subsubheading Result
28326 The result is a list of threads. The following attributes are
28327 defined for a given thread:
28331 This field exists only for the current thread. It has the value @samp{*}.
28334 The identifier that @value{GDBN} uses to refer to the thread.
28337 The identifier that the target uses to refer to the thread.
28340 Extra information about the thread, in a target-specific format. This
28344 The name of the thread. If the user specified a name using the
28345 @code{thread name} command, then this name is given. Otherwise, if
28346 @value{GDBN} can extract the thread name from the target, then that
28347 name is given. If @value{GDBN} cannot find the thread name, then this
28351 The stack frame currently executing in the thread.
28354 The thread's state. The @samp{state} field may have the following
28359 The thread is stopped. Frame information is available for stopped
28363 The thread is running. There's no frame information for running
28369 If @value{GDBN} can find the CPU core on which this thread is running,
28370 then this field is the core identifier. This field is optional.
28374 @subsubheading Example
28379 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28380 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28381 args=[]@},state="running"@},
28382 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28383 frame=@{level="0",addr="0x0804891f",func="foo",
28384 args=[@{name="i",value="10"@}],
28385 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28386 state="running"@}],
28387 current-thread-id="1"
28391 @subheading The @code{-thread-list-ids} Command
28392 @findex -thread-list-ids
28394 @subsubheading Synopsis
28400 Produces a list of the currently known @value{GDBN} thread ids. At the
28401 end of the list it also prints the total number of such threads.
28403 This command is retained for historical reasons, the
28404 @code{-thread-info} command should be used instead.
28406 @subsubheading @value{GDBN} Command
28408 Part of @samp{info threads} supplies the same information.
28410 @subsubheading Example
28415 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28416 current-thread-id="1",number-of-threads="3"
28421 @subheading The @code{-thread-select} Command
28422 @findex -thread-select
28424 @subsubheading Synopsis
28427 -thread-select @var{threadnum}
28430 Make @var{threadnum} the current thread. It prints the number of the new
28431 current thread, and the topmost frame for that thread.
28433 This command is deprecated in favor of explicitly using the
28434 @samp{--thread} option to each command.
28436 @subsubheading @value{GDBN} Command
28438 The corresponding @value{GDBN} command is @samp{thread}.
28440 @subsubheading Example
28447 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28448 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28452 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28453 number-of-threads="3"
28456 ^done,new-thread-id="3",
28457 frame=@{level="0",func="vprintf",
28458 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28459 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28463 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28464 @node GDB/MI Ada Tasking Commands
28465 @section @sc{gdb/mi} Ada Tasking Commands
28467 @subheading The @code{-ada-task-info} Command
28468 @findex -ada-task-info
28470 @subsubheading Synopsis
28473 -ada-task-info [ @var{task-id} ]
28476 Reports information about either a specific Ada task, if the
28477 @var{task-id} parameter is present, or about all Ada tasks.
28479 @subsubheading @value{GDBN} Command
28481 The @samp{info tasks} command prints the same information
28482 about all Ada tasks (@pxref{Ada Tasks}).
28484 @subsubheading Result
28486 The result is a table of Ada tasks. The following columns are
28487 defined for each Ada task:
28491 This field exists only for the current thread. It has the value @samp{*}.
28494 The identifier that @value{GDBN} uses to refer to the Ada task.
28497 The identifier that the target uses to refer to the Ada task.
28500 The identifier of the thread corresponding to the Ada task.
28502 This field should always exist, as Ada tasks are always implemented
28503 on top of a thread. But if @value{GDBN} cannot find this corresponding
28504 thread for any reason, the field is omitted.
28507 This field exists only when the task was created by another task.
28508 In this case, it provides the ID of the parent task.
28511 The base priority of the task.
28514 The current state of the task. For a detailed description of the
28515 possible states, see @ref{Ada Tasks}.
28518 The name of the task.
28522 @subsubheading Example
28526 ^done,tasks=@{nr_rows="3",nr_cols="8",
28527 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28528 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28529 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28530 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28531 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28532 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28533 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28534 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28535 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28536 state="Child Termination Wait",name="main_task"@}]@}
28540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28541 @node GDB/MI Program Execution
28542 @section @sc{gdb/mi} Program Execution
28544 These are the asynchronous commands which generate the out-of-band
28545 record @samp{*stopped}. Currently @value{GDBN} only really executes
28546 asynchronously with remote targets and this interaction is mimicked in
28549 @subheading The @code{-exec-continue} Command
28550 @findex -exec-continue
28552 @subsubheading Synopsis
28555 -exec-continue [--reverse] [--all|--thread-group N]
28558 Resumes the execution of the inferior program, which will continue
28559 to execute until it reaches a debugger stop event. If the
28560 @samp{--reverse} option is specified, execution resumes in reverse until
28561 it reaches a stop event. Stop events may include
28564 breakpoints or watchpoints
28566 signals or exceptions
28568 the end of the process (or its beginning under @samp{--reverse})
28570 the end or beginning of a replay log if one is being used.
28572 In all-stop mode (@pxref{All-Stop
28573 Mode}), may resume only one thread, or all threads, depending on the
28574 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28575 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28576 ignored in all-stop mode. If the @samp{--thread-group} options is
28577 specified, then all threads in that thread group are resumed.
28579 @subsubheading @value{GDBN} Command
28581 The corresponding @value{GDBN} corresponding is @samp{continue}.
28583 @subsubheading Example
28590 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28591 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28597 @subheading The @code{-exec-finish} Command
28598 @findex -exec-finish
28600 @subsubheading Synopsis
28603 -exec-finish [--reverse]
28606 Resumes the execution of the inferior program until the current
28607 function is exited. Displays the results returned by the function.
28608 If the @samp{--reverse} option is specified, resumes the reverse
28609 execution of the inferior program until the point where current
28610 function was called.
28612 @subsubheading @value{GDBN} Command
28614 The corresponding @value{GDBN} command is @samp{finish}.
28616 @subsubheading Example
28618 Function returning @code{void}.
28625 *stopped,reason="function-finished",frame=@{func="main",args=[],
28626 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28630 Function returning other than @code{void}. The name of the internal
28631 @value{GDBN} variable storing the result is printed, together with the
28638 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28639 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28640 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28641 gdb-result-var="$1",return-value="0"
28646 @subheading The @code{-exec-interrupt} Command
28647 @findex -exec-interrupt
28649 @subsubheading Synopsis
28652 -exec-interrupt [--all|--thread-group N]
28655 Interrupts the background execution of the target. Note how the token
28656 associated with the stop message is the one for the execution command
28657 that has been interrupted. The token for the interrupt itself only
28658 appears in the @samp{^done} output. If the user is trying to
28659 interrupt a non-running program, an error message will be printed.
28661 Note that when asynchronous execution is enabled, this command is
28662 asynchronous just like other execution commands. That is, first the
28663 @samp{^done} response will be printed, and the target stop will be
28664 reported after that using the @samp{*stopped} notification.
28666 In non-stop mode, only the context thread is interrupted by default.
28667 All threads (in all inferiors) will be interrupted if the
28668 @samp{--all} option is specified. If the @samp{--thread-group}
28669 option is specified, all threads in that group will be interrupted.
28671 @subsubheading @value{GDBN} Command
28673 The corresponding @value{GDBN} command is @samp{interrupt}.
28675 @subsubheading Example
28686 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28687 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28688 fullname="/home/foo/bar/try.c",line="13"@}
28693 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28697 @subheading The @code{-exec-jump} Command
28700 @subsubheading Synopsis
28703 -exec-jump @var{location}
28706 Resumes execution of the inferior program at the location specified by
28707 parameter. @xref{Specify Location}, for a description of the
28708 different forms of @var{location}.
28710 @subsubheading @value{GDBN} Command
28712 The corresponding @value{GDBN} command is @samp{jump}.
28714 @subsubheading Example
28717 -exec-jump foo.c:10
28718 *running,thread-id="all"
28723 @subheading The @code{-exec-next} Command
28726 @subsubheading Synopsis
28729 -exec-next [--reverse]
28732 Resumes execution of the inferior program, stopping when the beginning
28733 of the next source line is reached.
28735 If the @samp{--reverse} option is specified, resumes reverse execution
28736 of the inferior program, stopping at the beginning of the previous
28737 source line. If you issue this command on the first line of a
28738 function, it will take you back to the caller of that function, to the
28739 source line where the function was called.
28742 @subsubheading @value{GDBN} Command
28744 The corresponding @value{GDBN} command is @samp{next}.
28746 @subsubheading Example
28752 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28757 @subheading The @code{-exec-next-instruction} Command
28758 @findex -exec-next-instruction
28760 @subsubheading Synopsis
28763 -exec-next-instruction [--reverse]
28766 Executes one machine instruction. If the instruction is a function
28767 call, continues until the function returns. If the program stops at an
28768 instruction in the middle of a source line, the address will be
28771 If the @samp{--reverse} option is specified, resumes reverse execution
28772 of the inferior program, stopping at the previous instruction. If the
28773 previously executed instruction was a return from another function,
28774 it will continue to execute in reverse until the call to that function
28775 (from the current stack frame) is reached.
28777 @subsubheading @value{GDBN} Command
28779 The corresponding @value{GDBN} command is @samp{nexti}.
28781 @subsubheading Example
28785 -exec-next-instruction
28789 *stopped,reason="end-stepping-range",
28790 addr="0x000100d4",line="5",file="hello.c"
28795 @subheading The @code{-exec-return} Command
28796 @findex -exec-return
28798 @subsubheading Synopsis
28804 Makes current function return immediately. Doesn't execute the inferior.
28805 Displays the new current frame.
28807 @subsubheading @value{GDBN} Command
28809 The corresponding @value{GDBN} command is @samp{return}.
28811 @subsubheading Example
28815 200-break-insert callee4
28816 200^done,bkpt=@{number="1",addr="0x00010734",
28817 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28822 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28823 frame=@{func="callee4",args=[],
28824 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28825 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28831 111^done,frame=@{level="0",func="callee3",
28832 args=[@{name="strarg",
28833 value="0x11940 \"A string argument.\""@}],
28834 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28835 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28840 @subheading The @code{-exec-run} Command
28843 @subsubheading Synopsis
28846 -exec-run [--all | --thread-group N]
28849 Starts execution of the inferior from the beginning. The inferior
28850 executes until either a breakpoint is encountered or the program
28851 exits. In the latter case the output will include an exit code, if
28852 the program has exited exceptionally.
28854 When no option is specified, the current inferior is started. If the
28855 @samp{--thread-group} option is specified, it should refer to a thread
28856 group of type @samp{process}, and that thread group will be started.
28857 If the @samp{--all} option is specified, then all inferiors will be started.
28859 @subsubheading @value{GDBN} Command
28861 The corresponding @value{GDBN} command is @samp{run}.
28863 @subsubheading Examples
28868 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28873 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28874 frame=@{func="main",args=[],file="recursive2.c",
28875 fullname="/home/foo/bar/recursive2.c",line="4"@}
28880 Program exited normally:
28888 *stopped,reason="exited-normally"
28893 Program exited exceptionally:
28901 *stopped,reason="exited",exit-code="01"
28905 Another way the program can terminate is if it receives a signal such as
28906 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28910 *stopped,reason="exited-signalled",signal-name="SIGINT",
28911 signal-meaning="Interrupt"
28915 @c @subheading -exec-signal
28918 @subheading The @code{-exec-step} Command
28921 @subsubheading Synopsis
28924 -exec-step [--reverse]
28927 Resumes execution of the inferior program, stopping when the beginning
28928 of the next source line is reached, if the next source line is not a
28929 function call. If it is, stop at the first instruction of the called
28930 function. If the @samp{--reverse} option is specified, resumes reverse
28931 execution of the inferior program, stopping at the beginning of the
28932 previously executed source line.
28934 @subsubheading @value{GDBN} Command
28936 The corresponding @value{GDBN} command is @samp{step}.
28938 @subsubheading Example
28940 Stepping into a function:
28946 *stopped,reason="end-stepping-range",
28947 frame=@{func="foo",args=[@{name="a",value="10"@},
28948 @{name="b",value="0"@}],file="recursive2.c",
28949 fullname="/home/foo/bar/recursive2.c",line="11"@}
28959 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28964 @subheading The @code{-exec-step-instruction} Command
28965 @findex -exec-step-instruction
28967 @subsubheading Synopsis
28970 -exec-step-instruction [--reverse]
28973 Resumes the inferior which executes one machine instruction. If the
28974 @samp{--reverse} option is specified, resumes reverse execution of the
28975 inferior program, stopping at the previously executed instruction.
28976 The output, once @value{GDBN} has stopped, will vary depending on
28977 whether we have stopped in the middle of a source line or not. In the
28978 former case, the address at which the program stopped will be printed
28981 @subsubheading @value{GDBN} Command
28983 The corresponding @value{GDBN} command is @samp{stepi}.
28985 @subsubheading Example
28989 -exec-step-instruction
28993 *stopped,reason="end-stepping-range",
28994 frame=@{func="foo",args=[],file="try.c",
28995 fullname="/home/foo/bar/try.c",line="10"@}
28997 -exec-step-instruction
29001 *stopped,reason="end-stepping-range",
29002 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29003 fullname="/home/foo/bar/try.c",line="10"@}
29008 @subheading The @code{-exec-until} Command
29009 @findex -exec-until
29011 @subsubheading Synopsis
29014 -exec-until [ @var{location} ]
29017 Executes the inferior until the @var{location} specified in the
29018 argument is reached. If there is no argument, the inferior executes
29019 until a source line greater than the current one is reached. The
29020 reason for stopping in this case will be @samp{location-reached}.
29022 @subsubheading @value{GDBN} Command
29024 The corresponding @value{GDBN} command is @samp{until}.
29026 @subsubheading Example
29030 -exec-until recursive2.c:6
29034 *stopped,reason="location-reached",frame=@{func="main",args=[],
29035 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29040 @subheading -file-clear
29041 Is this going away????
29044 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29045 @node GDB/MI Stack Manipulation
29046 @section @sc{gdb/mi} Stack Manipulation Commands
29049 @subheading The @code{-stack-info-frame} Command
29050 @findex -stack-info-frame
29052 @subsubheading Synopsis
29058 Get info on the selected frame.
29060 @subsubheading @value{GDBN} Command
29062 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29063 (without arguments).
29065 @subsubheading Example
29070 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29071 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29072 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29076 @subheading The @code{-stack-info-depth} Command
29077 @findex -stack-info-depth
29079 @subsubheading Synopsis
29082 -stack-info-depth [ @var{max-depth} ]
29085 Return the depth of the stack. If the integer argument @var{max-depth}
29086 is specified, do not count beyond @var{max-depth} frames.
29088 @subsubheading @value{GDBN} Command
29090 There's no equivalent @value{GDBN} command.
29092 @subsubheading Example
29094 For a stack with frame levels 0 through 11:
29101 -stack-info-depth 4
29104 -stack-info-depth 12
29107 -stack-info-depth 11
29110 -stack-info-depth 13
29115 @subheading The @code{-stack-list-arguments} Command
29116 @findex -stack-list-arguments
29118 @subsubheading Synopsis
29121 -stack-list-arguments @var{print-values}
29122 [ @var{low-frame} @var{high-frame} ]
29125 Display a list of the arguments for the frames between @var{low-frame}
29126 and @var{high-frame} (inclusive). If @var{low-frame} and
29127 @var{high-frame} are not provided, list the arguments for the whole
29128 call stack. If the two arguments are equal, show the single frame
29129 at the corresponding level. It is an error if @var{low-frame} is
29130 larger than the actual number of frames. On the other hand,
29131 @var{high-frame} may be larger than the actual number of frames, in
29132 which case only existing frames will be returned.
29134 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29135 the variables; if it is 1 or @code{--all-values}, print also their
29136 values; and if it is 2 or @code{--simple-values}, print the name,
29137 type and value for simple data types, and the name and type for arrays,
29138 structures and unions.
29140 Use of this command to obtain arguments in a single frame is
29141 deprecated in favor of the @samp{-stack-list-variables} command.
29143 @subsubheading @value{GDBN} Command
29145 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29146 @samp{gdb_get_args} command which partially overlaps with the
29147 functionality of @samp{-stack-list-arguments}.
29149 @subsubheading Example
29156 frame=@{level="0",addr="0x00010734",func="callee4",
29157 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29158 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29159 frame=@{level="1",addr="0x0001076c",func="callee3",
29160 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29161 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29162 frame=@{level="2",addr="0x0001078c",func="callee2",
29163 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29164 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29165 frame=@{level="3",addr="0x000107b4",func="callee1",
29166 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29167 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29168 frame=@{level="4",addr="0x000107e0",func="main",
29169 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29170 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29172 -stack-list-arguments 0
29175 frame=@{level="0",args=[]@},
29176 frame=@{level="1",args=[name="strarg"]@},
29177 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29178 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29179 frame=@{level="4",args=[]@}]
29181 -stack-list-arguments 1
29184 frame=@{level="0",args=[]@},
29186 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29187 frame=@{level="2",args=[
29188 @{name="intarg",value="2"@},
29189 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29190 @{frame=@{level="3",args=[
29191 @{name="intarg",value="2"@},
29192 @{name="strarg",value="0x11940 \"A string argument.\""@},
29193 @{name="fltarg",value="3.5"@}]@},
29194 frame=@{level="4",args=[]@}]
29196 -stack-list-arguments 0 2 2
29197 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29199 -stack-list-arguments 1 2 2
29200 ^done,stack-args=[frame=@{level="2",
29201 args=[@{name="intarg",value="2"@},
29202 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29206 @c @subheading -stack-list-exception-handlers
29209 @subheading The @code{-stack-list-frames} Command
29210 @findex -stack-list-frames
29212 @subsubheading Synopsis
29215 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
29218 List the frames currently on the stack. For each frame it displays the
29223 The frame number, 0 being the topmost frame, i.e., the innermost function.
29225 The @code{$pc} value for that frame.
29229 File name of the source file where the function lives.
29230 @item @var{fullname}
29231 The full file name of the source file where the function lives.
29233 Line number corresponding to the @code{$pc}.
29235 The shared library where this function is defined. This is only given
29236 if the frame's function is not known.
29239 If invoked without arguments, this command prints a backtrace for the
29240 whole stack. If given two integer arguments, it shows the frames whose
29241 levels are between the two arguments (inclusive). If the two arguments
29242 are equal, it shows the single frame at the corresponding level. It is
29243 an error if @var{low-frame} is larger than the actual number of
29244 frames. On the other hand, @var{high-frame} may be larger than the
29245 actual number of frames, in which case only existing frames will be returned.
29247 @subsubheading @value{GDBN} Command
29249 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29251 @subsubheading Example
29253 Full stack backtrace:
29259 [frame=@{level="0",addr="0x0001076c",func="foo",
29260 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29261 frame=@{level="1",addr="0x000107a4",func="foo",
29262 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29263 frame=@{level="2",addr="0x000107a4",func="foo",
29264 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29265 frame=@{level="3",addr="0x000107a4",func="foo",
29266 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29267 frame=@{level="4",addr="0x000107a4",func="foo",
29268 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29269 frame=@{level="5",addr="0x000107a4",func="foo",
29270 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29271 frame=@{level="6",addr="0x000107a4",func="foo",
29272 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29273 frame=@{level="7",addr="0x000107a4",func="foo",
29274 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29275 frame=@{level="8",addr="0x000107a4",func="foo",
29276 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29277 frame=@{level="9",addr="0x000107a4",func="foo",
29278 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29279 frame=@{level="10",addr="0x000107a4",func="foo",
29280 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29281 frame=@{level="11",addr="0x00010738",func="main",
29282 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29286 Show frames between @var{low_frame} and @var{high_frame}:
29290 -stack-list-frames 3 5
29292 [frame=@{level="3",addr="0x000107a4",func="foo",
29293 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29294 frame=@{level="4",addr="0x000107a4",func="foo",
29295 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29296 frame=@{level="5",addr="0x000107a4",func="foo",
29297 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29301 Show a single frame:
29305 -stack-list-frames 3 3
29307 [frame=@{level="3",addr="0x000107a4",func="foo",
29308 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29313 @subheading The @code{-stack-list-locals} Command
29314 @findex -stack-list-locals
29316 @subsubheading Synopsis
29319 -stack-list-locals @var{print-values}
29322 Display the local variable names for the selected frame. If
29323 @var{print-values} is 0 or @code{--no-values}, print only the names of
29324 the variables; if it is 1 or @code{--all-values}, print also their
29325 values; and if it is 2 or @code{--simple-values}, print the name,
29326 type and value for simple data types, and the name and type for arrays,
29327 structures and unions. In this last case, a frontend can immediately
29328 display the value of simple data types and create variable objects for
29329 other data types when the user wishes to explore their values in
29332 This command is deprecated in favor of the
29333 @samp{-stack-list-variables} command.
29335 @subsubheading @value{GDBN} Command
29337 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29339 @subsubheading Example
29343 -stack-list-locals 0
29344 ^done,locals=[name="A",name="B",name="C"]
29346 -stack-list-locals --all-values
29347 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29348 @{name="C",value="@{1, 2, 3@}"@}]
29349 -stack-list-locals --simple-values
29350 ^done,locals=[@{name="A",type="int",value="1"@},
29351 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29355 @subheading The @code{-stack-list-variables} Command
29356 @findex -stack-list-variables
29358 @subsubheading Synopsis
29361 -stack-list-variables @var{print-values}
29364 Display the names of local variables and function arguments for the selected frame. If
29365 @var{print-values} is 0 or @code{--no-values}, print only the names of
29366 the variables; if it is 1 or @code{--all-values}, print also their
29367 values; and if it is 2 or @code{--simple-values}, print the name,
29368 type and value for simple data types, and the name and type for arrays,
29369 structures and unions.
29371 @subsubheading Example
29375 -stack-list-variables --thread 1 --frame 0 --all-values
29376 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29381 @subheading The @code{-stack-select-frame} Command
29382 @findex -stack-select-frame
29384 @subsubheading Synopsis
29387 -stack-select-frame @var{framenum}
29390 Change the selected frame. Select a different frame @var{framenum} on
29393 This command in deprecated in favor of passing the @samp{--frame}
29394 option to every command.
29396 @subsubheading @value{GDBN} Command
29398 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29399 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29401 @subsubheading Example
29405 -stack-select-frame 2
29410 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29411 @node GDB/MI Variable Objects
29412 @section @sc{gdb/mi} Variable Objects
29416 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29418 For the implementation of a variable debugger window (locals, watched
29419 expressions, etc.), we are proposing the adaptation of the existing code
29420 used by @code{Insight}.
29422 The two main reasons for that are:
29426 It has been proven in practice (it is already on its second generation).
29429 It will shorten development time (needless to say how important it is
29433 The original interface was designed to be used by Tcl code, so it was
29434 slightly changed so it could be used through @sc{gdb/mi}. This section
29435 describes the @sc{gdb/mi} operations that will be available and gives some
29436 hints about their use.
29438 @emph{Note}: In addition to the set of operations described here, we
29439 expect the @sc{gui} implementation of a variable window to require, at
29440 least, the following operations:
29443 @item @code{-gdb-show} @code{output-radix}
29444 @item @code{-stack-list-arguments}
29445 @item @code{-stack-list-locals}
29446 @item @code{-stack-select-frame}
29451 @subheading Introduction to Variable Objects
29453 @cindex variable objects in @sc{gdb/mi}
29455 Variable objects are "object-oriented" MI interface for examining and
29456 changing values of expressions. Unlike some other MI interfaces that
29457 work with expressions, variable objects are specifically designed for
29458 simple and efficient presentation in the frontend. A variable object
29459 is identified by string name. When a variable object is created, the
29460 frontend specifies the expression for that variable object. The
29461 expression can be a simple variable, or it can be an arbitrary complex
29462 expression, and can even involve CPU registers. After creating a
29463 variable object, the frontend can invoke other variable object
29464 operations---for example to obtain or change the value of a variable
29465 object, or to change display format.
29467 Variable objects have hierarchical tree structure. Any variable object
29468 that corresponds to a composite type, such as structure in C, has
29469 a number of child variable objects, for example corresponding to each
29470 element of a structure. A child variable object can itself have
29471 children, recursively. Recursion ends when we reach
29472 leaf variable objects, which always have built-in types. Child variable
29473 objects are created only by explicit request, so if a frontend
29474 is not interested in the children of a particular variable object, no
29475 child will be created.
29477 For a leaf variable object it is possible to obtain its value as a
29478 string, or set the value from a string. String value can be also
29479 obtained for a non-leaf variable object, but it's generally a string
29480 that only indicates the type of the object, and does not list its
29481 contents. Assignment to a non-leaf variable object is not allowed.
29483 A frontend does not need to read the values of all variable objects each time
29484 the program stops. Instead, MI provides an update command that lists all
29485 variable objects whose values has changed since the last update
29486 operation. This considerably reduces the amount of data that must
29487 be transferred to the frontend. As noted above, children variable
29488 objects are created on demand, and only leaf variable objects have a
29489 real value. As result, gdb will read target memory only for leaf
29490 variables that frontend has created.
29492 The automatic update is not always desirable. For example, a frontend
29493 might want to keep a value of some expression for future reference,
29494 and never update it. For another example, fetching memory is
29495 relatively slow for embedded targets, so a frontend might want
29496 to disable automatic update for the variables that are either not
29497 visible on the screen, or ``closed''. This is possible using so
29498 called ``frozen variable objects''. Such variable objects are never
29499 implicitly updated.
29501 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29502 fixed variable object, the expression is parsed when the variable
29503 object is created, including associating identifiers to specific
29504 variables. The meaning of expression never changes. For a floating
29505 variable object the values of variables whose names appear in the
29506 expressions are re-evaluated every time in the context of the current
29507 frame. Consider this example:
29512 struct work_state state;
29519 If a fixed variable object for the @code{state} variable is created in
29520 this function, and we enter the recursive call, the variable
29521 object will report the value of @code{state} in the top-level
29522 @code{do_work} invocation. On the other hand, a floating variable
29523 object will report the value of @code{state} in the current frame.
29525 If an expression specified when creating a fixed variable object
29526 refers to a local variable, the variable object becomes bound to the
29527 thread and frame in which the variable object is created. When such
29528 variable object is updated, @value{GDBN} makes sure that the
29529 thread/frame combination the variable object is bound to still exists,
29530 and re-evaluates the variable object in context of that thread/frame.
29532 The following is the complete set of @sc{gdb/mi} operations defined to
29533 access this functionality:
29535 @multitable @columnfractions .4 .6
29536 @item @strong{Operation}
29537 @tab @strong{Description}
29539 @item @code{-enable-pretty-printing}
29540 @tab enable Python-based pretty-printing
29541 @item @code{-var-create}
29542 @tab create a variable object
29543 @item @code{-var-delete}
29544 @tab delete the variable object and/or its children
29545 @item @code{-var-set-format}
29546 @tab set the display format of this variable
29547 @item @code{-var-show-format}
29548 @tab show the display format of this variable
29549 @item @code{-var-info-num-children}
29550 @tab tells how many children this object has
29551 @item @code{-var-list-children}
29552 @tab return a list of the object's children
29553 @item @code{-var-info-type}
29554 @tab show the type of this variable object
29555 @item @code{-var-info-expression}
29556 @tab print parent-relative expression that this variable object represents
29557 @item @code{-var-info-path-expression}
29558 @tab print full expression that this variable object represents
29559 @item @code{-var-show-attributes}
29560 @tab is this variable editable? does it exist here?
29561 @item @code{-var-evaluate-expression}
29562 @tab get the value of this variable
29563 @item @code{-var-assign}
29564 @tab set the value of this variable
29565 @item @code{-var-update}
29566 @tab update the variable and its children
29567 @item @code{-var-set-frozen}
29568 @tab set frozeness attribute
29569 @item @code{-var-set-update-range}
29570 @tab set range of children to display on update
29573 In the next subsection we describe each operation in detail and suggest
29574 how it can be used.
29576 @subheading Description And Use of Operations on Variable Objects
29578 @subheading The @code{-enable-pretty-printing} Command
29579 @findex -enable-pretty-printing
29582 -enable-pretty-printing
29585 @value{GDBN} allows Python-based visualizers to affect the output of the
29586 MI variable object commands. However, because there was no way to
29587 implement this in a fully backward-compatible way, a front end must
29588 request that this functionality be enabled.
29590 Once enabled, this feature cannot be disabled.
29592 Note that if Python support has not been compiled into @value{GDBN},
29593 this command will still succeed (and do nothing).
29595 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29596 may work differently in future versions of @value{GDBN}.
29598 @subheading The @code{-var-create} Command
29599 @findex -var-create
29601 @subsubheading Synopsis
29604 -var-create @{@var{name} | "-"@}
29605 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29608 This operation creates a variable object, which allows the monitoring of
29609 a variable, the result of an expression, a memory cell or a CPU
29612 The @var{name} parameter is the string by which the object can be
29613 referenced. It must be unique. If @samp{-} is specified, the varobj
29614 system will generate a string ``varNNNNNN'' automatically. It will be
29615 unique provided that one does not specify @var{name} of that format.
29616 The command fails if a duplicate name is found.
29618 The frame under which the expression should be evaluated can be
29619 specified by @var{frame-addr}. A @samp{*} indicates that the current
29620 frame should be used. A @samp{@@} indicates that a floating variable
29621 object must be created.
29623 @var{expression} is any expression valid on the current language set (must not
29624 begin with a @samp{*}), or one of the following:
29628 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29631 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29634 @samp{$@var{regname}} --- a CPU register name
29637 @cindex dynamic varobj
29638 A varobj's contents may be provided by a Python-based pretty-printer. In this
29639 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29640 have slightly different semantics in some cases. If the
29641 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29642 will never create a dynamic varobj. This ensures backward
29643 compatibility for existing clients.
29645 @subsubheading Result
29647 This operation returns attributes of the newly-created varobj. These
29652 The name of the varobj.
29655 The number of children of the varobj. This number is not necessarily
29656 reliable for a dynamic varobj. Instead, you must examine the
29657 @samp{has_more} attribute.
29660 The varobj's scalar value. For a varobj whose type is some sort of
29661 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29662 will not be interesting.
29665 The varobj's type. This is a string representation of the type, as
29666 would be printed by the @value{GDBN} CLI. If @samp{print object}
29667 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29668 @emph{actual} (derived) type of the object is shown rather than the
29669 @emph{declared} one.
29672 If a variable object is bound to a specific thread, then this is the
29673 thread's identifier.
29676 For a dynamic varobj, this indicates whether there appear to be any
29677 children available. For a non-dynamic varobj, this will be 0.
29680 This attribute will be present and have the value @samp{1} if the
29681 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29682 then this attribute will not be present.
29685 A dynamic varobj can supply a display hint to the front end. The
29686 value comes directly from the Python pretty-printer object's
29687 @code{display_hint} method. @xref{Pretty Printing API}.
29690 Typical output will look like this:
29693 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29694 has_more="@var{has_more}"
29698 @subheading The @code{-var-delete} Command
29699 @findex -var-delete
29701 @subsubheading Synopsis
29704 -var-delete [ -c ] @var{name}
29707 Deletes a previously created variable object and all of its children.
29708 With the @samp{-c} option, just deletes the children.
29710 Returns an error if the object @var{name} is not found.
29713 @subheading The @code{-var-set-format} Command
29714 @findex -var-set-format
29716 @subsubheading Synopsis
29719 -var-set-format @var{name} @var{format-spec}
29722 Sets the output format for the value of the object @var{name} to be
29725 @anchor{-var-set-format}
29726 The syntax for the @var{format-spec} is as follows:
29729 @var{format-spec} @expansion{}
29730 @{binary | decimal | hexadecimal | octal | natural@}
29733 The natural format is the default format choosen automatically
29734 based on the variable type (like decimal for an @code{int}, hex
29735 for pointers, etc.).
29737 For a variable with children, the format is set only on the
29738 variable itself, and the children are not affected.
29740 @subheading The @code{-var-show-format} Command
29741 @findex -var-show-format
29743 @subsubheading Synopsis
29746 -var-show-format @var{name}
29749 Returns the format used to display the value of the object @var{name}.
29752 @var{format} @expansion{}
29757 @subheading The @code{-var-info-num-children} Command
29758 @findex -var-info-num-children
29760 @subsubheading Synopsis
29763 -var-info-num-children @var{name}
29766 Returns the number of children of a variable object @var{name}:
29772 Note that this number is not completely reliable for a dynamic varobj.
29773 It will return the current number of children, but more children may
29777 @subheading The @code{-var-list-children} Command
29778 @findex -var-list-children
29780 @subsubheading Synopsis
29783 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29785 @anchor{-var-list-children}
29787 Return a list of the children of the specified variable object and
29788 create variable objects for them, if they do not already exist. With
29789 a single argument or if @var{print-values} has a value of 0 or
29790 @code{--no-values}, print only the names of the variables; if
29791 @var{print-values} is 1 or @code{--all-values}, also print their
29792 values; and if it is 2 or @code{--simple-values} print the name and
29793 value for simple data types and just the name for arrays, structures
29796 @var{from} and @var{to}, if specified, indicate the range of children
29797 to report. If @var{from} or @var{to} is less than zero, the range is
29798 reset and all children will be reported. Otherwise, children starting
29799 at @var{from} (zero-based) and up to and excluding @var{to} will be
29802 If a child range is requested, it will only affect the current call to
29803 @code{-var-list-children}, but not future calls to @code{-var-update}.
29804 For this, you must instead use @code{-var-set-update-range}. The
29805 intent of this approach is to enable a front end to implement any
29806 update approach it likes; for example, scrolling a view may cause the
29807 front end to request more children with @code{-var-list-children}, and
29808 then the front end could call @code{-var-set-update-range} with a
29809 different range to ensure that future updates are restricted to just
29812 For each child the following results are returned:
29817 Name of the variable object created for this child.
29820 The expression to be shown to the user by the front end to designate this child.
29821 For example this may be the name of a structure member.
29823 For a dynamic varobj, this value cannot be used to form an
29824 expression. There is no way to do this at all with a dynamic varobj.
29826 For C/C@t{++} structures there are several pseudo children returned to
29827 designate access qualifiers. For these pseudo children @var{exp} is
29828 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29829 type and value are not present.
29831 A dynamic varobj will not report the access qualifying
29832 pseudo-children, regardless of the language. This information is not
29833 available at all with a dynamic varobj.
29836 Number of children this child has. For a dynamic varobj, this will be
29840 The type of the child. If @samp{print object}
29841 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29842 @emph{actual} (derived) type of the object is shown rather than the
29843 @emph{declared} one.
29846 If values were requested, this is the value.
29849 If this variable object is associated with a thread, this is the thread id.
29850 Otherwise this result is not present.
29853 If the variable object is frozen, this variable will be present with a value of 1.
29856 The result may have its own attributes:
29860 A dynamic varobj can supply a display hint to the front end. The
29861 value comes directly from the Python pretty-printer object's
29862 @code{display_hint} method. @xref{Pretty Printing API}.
29865 This is an integer attribute which is nonzero if there are children
29866 remaining after the end of the selected range.
29869 @subsubheading Example
29873 -var-list-children n
29874 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29875 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29877 -var-list-children --all-values n
29878 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29879 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29883 @subheading The @code{-var-info-type} Command
29884 @findex -var-info-type
29886 @subsubheading Synopsis
29889 -var-info-type @var{name}
29892 Returns the type of the specified variable @var{name}. The type is
29893 returned as a string in the same format as it is output by the
29897 type=@var{typename}
29901 @subheading The @code{-var-info-expression} Command
29902 @findex -var-info-expression
29904 @subsubheading Synopsis
29907 -var-info-expression @var{name}
29910 Returns a string that is suitable for presenting this
29911 variable object in user interface. The string is generally
29912 not valid expression in the current language, and cannot be evaluated.
29914 For example, if @code{a} is an array, and variable object
29915 @code{A} was created for @code{a}, then we'll get this output:
29918 (gdb) -var-info-expression A.1
29919 ^done,lang="C",exp="1"
29923 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29925 Note that the output of the @code{-var-list-children} command also
29926 includes those expressions, so the @code{-var-info-expression} command
29929 @subheading The @code{-var-info-path-expression} Command
29930 @findex -var-info-path-expression
29932 @subsubheading Synopsis
29935 -var-info-path-expression @var{name}
29938 Returns an expression that can be evaluated in the current
29939 context and will yield the same value that a variable object has.
29940 Compare this with the @code{-var-info-expression} command, which
29941 result can be used only for UI presentation. Typical use of
29942 the @code{-var-info-path-expression} command is creating a
29943 watchpoint from a variable object.
29945 This command is currently not valid for children of a dynamic varobj,
29946 and will give an error when invoked on one.
29948 For example, suppose @code{C} is a C@t{++} class, derived from class
29949 @code{Base}, and that the @code{Base} class has a member called
29950 @code{m_size}. Assume a variable @code{c} is has the type of
29951 @code{C} and a variable object @code{C} was created for variable
29952 @code{c}. Then, we'll get this output:
29954 (gdb) -var-info-path-expression C.Base.public.m_size
29955 ^done,path_expr=((Base)c).m_size)
29958 @subheading The @code{-var-show-attributes} Command
29959 @findex -var-show-attributes
29961 @subsubheading Synopsis
29964 -var-show-attributes @var{name}
29967 List attributes of the specified variable object @var{name}:
29970 status=@var{attr} [ ( ,@var{attr} )* ]
29974 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29976 @subheading The @code{-var-evaluate-expression} Command
29977 @findex -var-evaluate-expression
29979 @subsubheading Synopsis
29982 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29985 Evaluates the expression that is represented by the specified variable
29986 object and returns its value as a string. The format of the string
29987 can be specified with the @samp{-f} option. The possible values of
29988 this option are the same as for @code{-var-set-format}
29989 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29990 the current display format will be used. The current display format
29991 can be changed using the @code{-var-set-format} command.
29997 Note that one must invoke @code{-var-list-children} for a variable
29998 before the value of a child variable can be evaluated.
30000 @subheading The @code{-var-assign} Command
30001 @findex -var-assign
30003 @subsubheading Synopsis
30006 -var-assign @var{name} @var{expression}
30009 Assigns the value of @var{expression} to the variable object specified
30010 by @var{name}. The object must be @samp{editable}. If the variable's
30011 value is altered by the assign, the variable will show up in any
30012 subsequent @code{-var-update} list.
30014 @subsubheading Example
30022 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30026 @subheading The @code{-var-update} Command
30027 @findex -var-update
30029 @subsubheading Synopsis
30032 -var-update [@var{print-values}] @{@var{name} | "*"@}
30035 Reevaluate the expressions corresponding to the variable object
30036 @var{name} and all its direct and indirect children, and return the
30037 list of variable objects whose values have changed; @var{name} must
30038 be a root variable object. Here, ``changed'' means that the result of
30039 @code{-var-evaluate-expression} before and after the
30040 @code{-var-update} is different. If @samp{*} is used as the variable
30041 object names, all existing variable objects are updated, except
30042 for frozen ones (@pxref{-var-set-frozen}). The option
30043 @var{print-values} determines whether both names and values, or just
30044 names are printed. The possible values of this option are the same
30045 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30046 recommended to use the @samp{--all-values} option, to reduce the
30047 number of MI commands needed on each program stop.
30049 With the @samp{*} parameter, if a variable object is bound to a
30050 currently running thread, it will not be updated, without any
30053 If @code{-var-set-update-range} was previously used on a varobj, then
30054 only the selected range of children will be reported.
30056 @code{-var-update} reports all the changed varobjs in a tuple named
30059 Each item in the change list is itself a tuple holding:
30063 The name of the varobj.
30066 If values were requested for this update, then this field will be
30067 present and will hold the value of the varobj.
30070 @anchor{-var-update}
30071 This field is a string which may take one of three values:
30075 The variable object's current value is valid.
30078 The variable object does not currently hold a valid value but it may
30079 hold one in the future if its associated expression comes back into
30083 The variable object no longer holds a valid value.
30084 This can occur when the executable file being debugged has changed,
30085 either through recompilation or by using the @value{GDBN} @code{file}
30086 command. The front end should normally choose to delete these variable
30090 In the future new values may be added to this list so the front should
30091 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30094 This is only present if the varobj is still valid. If the type
30095 changed, then this will be the string @samp{true}; otherwise it will
30098 When a varobj's type changes, its children are also likely to have
30099 become incorrect. Therefore, the varobj's children are automatically
30100 deleted when this attribute is @samp{true}. Also, the varobj's update
30101 range, when set using the @code{-var-set-update-range} command, is
30105 If the varobj's type changed, then this field will be present and will
30108 @item new_num_children
30109 For a dynamic varobj, if the number of children changed, or if the
30110 type changed, this will be the new number of children.
30112 The @samp{numchild} field in other varobj responses is generally not
30113 valid for a dynamic varobj -- it will show the number of children that
30114 @value{GDBN} knows about, but because dynamic varobjs lazily
30115 instantiate their children, this will not reflect the number of
30116 children which may be available.
30118 The @samp{new_num_children} attribute only reports changes to the
30119 number of children known by @value{GDBN}. This is the only way to
30120 detect whether an update has removed children (which necessarily can
30121 only happen at the end of the update range).
30124 The display hint, if any.
30127 This is an integer value, which will be 1 if there are more children
30128 available outside the varobj's update range.
30131 This attribute will be present and have the value @samp{1} if the
30132 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30133 then this attribute will not be present.
30136 If new children were added to a dynamic varobj within the selected
30137 update range (as set by @code{-var-set-update-range}), then they will
30138 be listed in this attribute.
30141 @subsubheading Example
30148 -var-update --all-values var1
30149 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30150 type_changed="false"@}]
30154 @subheading The @code{-var-set-frozen} Command
30155 @findex -var-set-frozen
30156 @anchor{-var-set-frozen}
30158 @subsubheading Synopsis
30161 -var-set-frozen @var{name} @var{flag}
30164 Set the frozenness flag on the variable object @var{name}. The
30165 @var{flag} parameter should be either @samp{1} to make the variable
30166 frozen or @samp{0} to make it unfrozen. If a variable object is
30167 frozen, then neither itself, nor any of its children, are
30168 implicitly updated by @code{-var-update} of
30169 a parent variable or by @code{-var-update *}. Only
30170 @code{-var-update} of the variable itself will update its value and
30171 values of its children. After a variable object is unfrozen, it is
30172 implicitly updated by all subsequent @code{-var-update} operations.
30173 Unfreezing a variable does not update it, only subsequent
30174 @code{-var-update} does.
30176 @subsubheading Example
30180 -var-set-frozen V 1
30185 @subheading The @code{-var-set-update-range} command
30186 @findex -var-set-update-range
30187 @anchor{-var-set-update-range}
30189 @subsubheading Synopsis
30192 -var-set-update-range @var{name} @var{from} @var{to}
30195 Set the range of children to be returned by future invocations of
30196 @code{-var-update}.
30198 @var{from} and @var{to} indicate the range of children to report. If
30199 @var{from} or @var{to} is less than zero, the range is reset and all
30200 children will be reported. Otherwise, children starting at @var{from}
30201 (zero-based) and up to and excluding @var{to} will be reported.
30203 @subsubheading Example
30207 -var-set-update-range V 1 2
30211 @subheading The @code{-var-set-visualizer} command
30212 @findex -var-set-visualizer
30213 @anchor{-var-set-visualizer}
30215 @subsubheading Synopsis
30218 -var-set-visualizer @var{name} @var{visualizer}
30221 Set a visualizer for the variable object @var{name}.
30223 @var{visualizer} is the visualizer to use. The special value
30224 @samp{None} means to disable any visualizer in use.
30226 If not @samp{None}, @var{visualizer} must be a Python expression.
30227 This expression must evaluate to a callable object which accepts a
30228 single argument. @value{GDBN} will call this object with the value of
30229 the varobj @var{name} as an argument (this is done so that the same
30230 Python pretty-printing code can be used for both the CLI and MI).
30231 When called, this object must return an object which conforms to the
30232 pretty-printing interface (@pxref{Pretty Printing API}).
30234 The pre-defined function @code{gdb.default_visualizer} may be used to
30235 select a visualizer by following the built-in process
30236 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30237 a varobj is created, and so ordinarily is not needed.
30239 This feature is only available if Python support is enabled. The MI
30240 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
30241 can be used to check this.
30243 @subsubheading Example
30245 Resetting the visualizer:
30249 -var-set-visualizer V None
30253 Reselecting the default (type-based) visualizer:
30257 -var-set-visualizer V gdb.default_visualizer
30261 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30262 can be used to instantiate this class for a varobj:
30266 -var-set-visualizer V "lambda val: SomeClass()"
30270 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30271 @node GDB/MI Data Manipulation
30272 @section @sc{gdb/mi} Data Manipulation
30274 @cindex data manipulation, in @sc{gdb/mi}
30275 @cindex @sc{gdb/mi}, data manipulation
30276 This section describes the @sc{gdb/mi} commands that manipulate data:
30277 examine memory and registers, evaluate expressions, etc.
30279 @c REMOVED FROM THE INTERFACE.
30280 @c @subheading -data-assign
30281 @c Change the value of a program variable. Plenty of side effects.
30282 @c @subsubheading GDB Command
30284 @c @subsubheading Example
30287 @subheading The @code{-data-disassemble} Command
30288 @findex -data-disassemble
30290 @subsubheading Synopsis
30294 [ -s @var{start-addr} -e @var{end-addr} ]
30295 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30303 @item @var{start-addr}
30304 is the beginning address (or @code{$pc})
30305 @item @var{end-addr}
30307 @item @var{filename}
30308 is the name of the file to disassemble
30309 @item @var{linenum}
30310 is the line number to disassemble around
30312 is the number of disassembly lines to be produced. If it is -1,
30313 the whole function will be disassembled, in case no @var{end-addr} is
30314 specified. If @var{end-addr} is specified as a non-zero value, and
30315 @var{lines} is lower than the number of disassembly lines between
30316 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30317 displayed; if @var{lines} is higher than the number of lines between
30318 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30321 is either 0 (meaning only disassembly), 1 (meaning mixed source and
30322 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
30323 mixed source and disassembly with raw opcodes).
30326 @subsubheading Result
30328 The output for each instruction is composed of four fields:
30337 Note that whatever included in the instruction field, is not manipulated
30338 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
30340 @subsubheading @value{GDBN} Command
30342 There's no direct mapping from this command to the CLI.
30344 @subsubheading Example
30346 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30350 -data-disassemble -s $pc -e "$pc + 20" -- 0
30353 @{address="0x000107c0",func-name="main",offset="4",
30354 inst="mov 2, %o0"@},
30355 @{address="0x000107c4",func-name="main",offset="8",
30356 inst="sethi %hi(0x11800), %o2"@},
30357 @{address="0x000107c8",func-name="main",offset="12",
30358 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30359 @{address="0x000107cc",func-name="main",offset="16",
30360 inst="sethi %hi(0x11800), %o2"@},
30361 @{address="0x000107d0",func-name="main",offset="20",
30362 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30366 Disassemble the whole @code{main} function. Line 32 is part of
30370 -data-disassemble -f basics.c -l 32 -- 0
30372 @{address="0x000107bc",func-name="main",offset="0",
30373 inst="save %sp, -112, %sp"@},
30374 @{address="0x000107c0",func-name="main",offset="4",
30375 inst="mov 2, %o0"@},
30376 @{address="0x000107c4",func-name="main",offset="8",
30377 inst="sethi %hi(0x11800), %o2"@},
30379 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30380 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30384 Disassemble 3 instructions from the start of @code{main}:
30388 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30390 @{address="0x000107bc",func-name="main",offset="0",
30391 inst="save %sp, -112, %sp"@},
30392 @{address="0x000107c0",func-name="main",offset="4",
30393 inst="mov 2, %o0"@},
30394 @{address="0x000107c4",func-name="main",offset="8",
30395 inst="sethi %hi(0x11800), %o2"@}]
30399 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30403 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30405 src_and_asm_line=@{line="31",
30406 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30407 testsuite/gdb.mi/basics.c",line_asm_insn=[
30408 @{address="0x000107bc",func-name="main",offset="0",
30409 inst="save %sp, -112, %sp"@}]@},
30410 src_and_asm_line=@{line="32",
30411 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30412 testsuite/gdb.mi/basics.c",line_asm_insn=[
30413 @{address="0x000107c0",func-name="main",offset="4",
30414 inst="mov 2, %o0"@},
30415 @{address="0x000107c4",func-name="main",offset="8",
30416 inst="sethi %hi(0x11800), %o2"@}]@}]
30421 @subheading The @code{-data-evaluate-expression} Command
30422 @findex -data-evaluate-expression
30424 @subsubheading Synopsis
30427 -data-evaluate-expression @var{expr}
30430 Evaluate @var{expr} as an expression. The expression could contain an
30431 inferior function call. The function call will execute synchronously.
30432 If the expression contains spaces, it must be enclosed in double quotes.
30434 @subsubheading @value{GDBN} Command
30436 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30437 @samp{call}. In @code{gdbtk} only, there's a corresponding
30438 @samp{gdb_eval} command.
30440 @subsubheading Example
30442 In the following example, the numbers that precede the commands are the
30443 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30444 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30448 211-data-evaluate-expression A
30451 311-data-evaluate-expression &A
30452 311^done,value="0xefffeb7c"
30454 411-data-evaluate-expression A+3
30457 511-data-evaluate-expression "A + 3"
30463 @subheading The @code{-data-list-changed-registers} Command
30464 @findex -data-list-changed-registers
30466 @subsubheading Synopsis
30469 -data-list-changed-registers
30472 Display a list of the registers that have changed.
30474 @subsubheading @value{GDBN} Command
30476 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30477 has the corresponding command @samp{gdb_changed_register_list}.
30479 @subsubheading Example
30481 On a PPC MBX board:
30489 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30490 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30493 -data-list-changed-registers
30494 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30495 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30496 "24","25","26","27","28","30","31","64","65","66","67","69"]
30501 @subheading The @code{-data-list-register-names} Command
30502 @findex -data-list-register-names
30504 @subsubheading Synopsis
30507 -data-list-register-names [ ( @var{regno} )+ ]
30510 Show a list of register names for the current target. If no arguments
30511 are given, it shows a list of the names of all the registers. If
30512 integer numbers are given as arguments, it will print a list of the
30513 names of the registers corresponding to the arguments. To ensure
30514 consistency between a register name and its number, the output list may
30515 include empty register names.
30517 @subsubheading @value{GDBN} Command
30519 @value{GDBN} does not have a command which corresponds to
30520 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30521 corresponding command @samp{gdb_regnames}.
30523 @subsubheading Example
30525 For the PPC MBX board:
30528 -data-list-register-names
30529 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30530 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30531 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30532 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30533 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30534 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30535 "", "pc","ps","cr","lr","ctr","xer"]
30537 -data-list-register-names 1 2 3
30538 ^done,register-names=["r1","r2","r3"]
30542 @subheading The @code{-data-list-register-values} Command
30543 @findex -data-list-register-values
30545 @subsubheading Synopsis
30548 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
30551 Display the registers' contents. @var{fmt} is the format according to
30552 which the registers' contents are to be returned, followed by an optional
30553 list of numbers specifying the registers to display. A missing list of
30554 numbers indicates that the contents of all the registers must be returned.
30556 Allowed formats for @var{fmt} are:
30573 @subsubheading @value{GDBN} Command
30575 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30576 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30578 @subsubheading Example
30580 For a PPC MBX board (note: line breaks are for readability only, they
30581 don't appear in the actual output):
30585 -data-list-register-values r 64 65
30586 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30587 @{number="65",value="0x00029002"@}]
30589 -data-list-register-values x
30590 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30591 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30592 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30593 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30594 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30595 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30596 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30597 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30598 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30599 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30600 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30601 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30602 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30603 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30604 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30605 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30606 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30607 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30608 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30609 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30610 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30611 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30612 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30613 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30614 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30615 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30616 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30617 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30618 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30619 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30620 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30621 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30622 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30623 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30624 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30625 @{number="69",value="0x20002b03"@}]
30630 @subheading The @code{-data-read-memory} Command
30631 @findex -data-read-memory
30633 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30635 @subsubheading Synopsis
30638 -data-read-memory [ -o @var{byte-offset} ]
30639 @var{address} @var{word-format} @var{word-size}
30640 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30647 @item @var{address}
30648 An expression specifying the address of the first memory word to be
30649 read. Complex expressions containing embedded white space should be
30650 quoted using the C convention.
30652 @item @var{word-format}
30653 The format to be used to print the memory words. The notation is the
30654 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30657 @item @var{word-size}
30658 The size of each memory word in bytes.
30660 @item @var{nr-rows}
30661 The number of rows in the output table.
30663 @item @var{nr-cols}
30664 The number of columns in the output table.
30667 If present, indicates that each row should include an @sc{ascii} dump. The
30668 value of @var{aschar} is used as a padding character when a byte is not a
30669 member of the printable @sc{ascii} character set (printable @sc{ascii}
30670 characters are those whose code is between 32 and 126, inclusively).
30672 @item @var{byte-offset}
30673 An offset to add to the @var{address} before fetching memory.
30676 This command displays memory contents as a table of @var{nr-rows} by
30677 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30678 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30679 (returned as @samp{total-bytes}). Should less than the requested number
30680 of bytes be returned by the target, the missing words are identified
30681 using @samp{N/A}. The number of bytes read from the target is returned
30682 in @samp{nr-bytes} and the starting address used to read memory in
30685 The address of the next/previous row or page is available in
30686 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30689 @subsubheading @value{GDBN} Command
30691 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30692 @samp{gdb_get_mem} memory read command.
30694 @subsubheading Example
30696 Read six bytes of memory starting at @code{bytes+6} but then offset by
30697 @code{-6} bytes. Format as three rows of two columns. One byte per
30698 word. Display each word in hex.
30702 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30703 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30704 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30705 prev-page="0x0000138a",memory=[
30706 @{addr="0x00001390",data=["0x00","0x01"]@},
30707 @{addr="0x00001392",data=["0x02","0x03"]@},
30708 @{addr="0x00001394",data=["0x04","0x05"]@}]
30712 Read two bytes of memory starting at address @code{shorts + 64} and
30713 display as a single word formatted in decimal.
30717 5-data-read-memory shorts+64 d 2 1 1
30718 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30719 next-row="0x00001512",prev-row="0x0000150e",
30720 next-page="0x00001512",prev-page="0x0000150e",memory=[
30721 @{addr="0x00001510",data=["128"]@}]
30725 Read thirty two bytes of memory starting at @code{bytes+16} and format
30726 as eight rows of four columns. Include a string encoding with @samp{x}
30727 used as the non-printable character.
30731 4-data-read-memory bytes+16 x 1 8 4 x
30732 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30733 next-row="0x000013c0",prev-row="0x0000139c",
30734 next-page="0x000013c0",prev-page="0x00001380",memory=[
30735 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30736 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30737 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30738 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30739 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30740 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30741 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30742 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30746 @subheading The @code{-data-read-memory-bytes} Command
30747 @findex -data-read-memory-bytes
30749 @subsubheading Synopsis
30752 -data-read-memory-bytes [ -o @var{byte-offset} ]
30753 @var{address} @var{count}
30760 @item @var{address}
30761 An expression specifying the address of the first memory word to be
30762 read. Complex expressions containing embedded white space should be
30763 quoted using the C convention.
30766 The number of bytes to read. This should be an integer literal.
30768 @item @var{byte-offset}
30769 The offsets in bytes relative to @var{address} at which to start
30770 reading. This should be an integer literal. This option is provided
30771 so that a frontend is not required to first evaluate address and then
30772 perform address arithmetics itself.
30776 This command attempts to read all accessible memory regions in the
30777 specified range. First, all regions marked as unreadable in the memory
30778 map (if one is defined) will be skipped. @xref{Memory Region
30779 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30780 regions. For each one, if reading full region results in an errors,
30781 @value{GDBN} will try to read a subset of the region.
30783 In general, every single byte in the region may be readable or not,
30784 and the only way to read every readable byte is to try a read at
30785 every address, which is not practical. Therefore, @value{GDBN} will
30786 attempt to read all accessible bytes at either beginning or the end
30787 of the region, using a binary division scheme. This heuristic works
30788 well for reading accross a memory map boundary. Note that if a region
30789 has a readable range that is neither at the beginning or the end,
30790 @value{GDBN} will not read it.
30792 The result record (@pxref{GDB/MI Result Records}) that is output of
30793 the command includes a field named @samp{memory} whose content is a
30794 list of tuples. Each tuple represent a successfully read memory block
30795 and has the following fields:
30799 The start address of the memory block, as hexadecimal literal.
30802 The end address of the memory block, as hexadecimal literal.
30805 The offset of the memory block, as hexadecimal literal, relative to
30806 the start address passed to @code{-data-read-memory-bytes}.
30809 The contents of the memory block, in hex.
30815 @subsubheading @value{GDBN} Command
30817 The corresponding @value{GDBN} command is @samp{x}.
30819 @subsubheading Example
30823 -data-read-memory-bytes &a 10
30824 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30826 contents="01000000020000000300"@}]
30831 @subheading The @code{-data-write-memory-bytes} Command
30832 @findex -data-write-memory-bytes
30834 @subsubheading Synopsis
30837 -data-write-memory-bytes @var{address} @var{contents}
30844 @item @var{address}
30845 An expression specifying the address of the first memory word to be
30846 read. Complex expressions containing embedded white space should be
30847 quoted using the C convention.
30849 @item @var{contents}
30850 The hex-encoded bytes to write.
30854 @subsubheading @value{GDBN} Command
30856 There's no corresponding @value{GDBN} command.
30858 @subsubheading Example
30862 -data-write-memory-bytes &a "aabbccdd"
30868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30869 @node GDB/MI Tracepoint Commands
30870 @section @sc{gdb/mi} Tracepoint Commands
30872 The commands defined in this section implement MI support for
30873 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30875 @subheading The @code{-trace-find} Command
30876 @findex -trace-find
30878 @subsubheading Synopsis
30881 -trace-find @var{mode} [@var{parameters}@dots{}]
30884 Find a trace frame using criteria defined by @var{mode} and
30885 @var{parameters}. The following table lists permissible
30886 modes and their parameters. For details of operation, see @ref{tfind}.
30891 No parameters are required. Stops examining trace frames.
30894 An integer is required as parameter. Selects tracepoint frame with
30897 @item tracepoint-number
30898 An integer is required as parameter. Finds next
30899 trace frame that corresponds to tracepoint with the specified number.
30902 An address is required as parameter. Finds
30903 next trace frame that corresponds to any tracepoint at the specified
30906 @item pc-inside-range
30907 Two addresses are required as parameters. Finds next trace
30908 frame that corresponds to a tracepoint at an address inside the
30909 specified range. Both bounds are considered to be inside the range.
30911 @item pc-outside-range
30912 Two addresses are required as parameters. Finds
30913 next trace frame that corresponds to a tracepoint at an address outside
30914 the specified range. Both bounds are considered to be inside the range.
30917 Line specification is required as parameter. @xref{Specify Location}.
30918 Finds next trace frame that corresponds to a tracepoint at
30919 the specified location.
30923 If @samp{none} was passed as @var{mode}, the response does not
30924 have fields. Otherwise, the response may have the following fields:
30928 This field has either @samp{0} or @samp{1} as the value, depending
30929 on whether a matching tracepoint was found.
30932 The index of the found traceframe. This field is present iff
30933 the @samp{found} field has value of @samp{1}.
30936 The index of the found tracepoint. This field is present iff
30937 the @samp{found} field has value of @samp{1}.
30940 The information about the frame corresponding to the found trace
30941 frame. This field is present only if a trace frame was found.
30942 @xref{GDB/MI Frame Information}, for description of this field.
30946 @subsubheading @value{GDBN} Command
30948 The corresponding @value{GDBN} command is @samp{tfind}.
30950 @subheading -trace-define-variable
30951 @findex -trace-define-variable
30953 @subsubheading Synopsis
30956 -trace-define-variable @var{name} [ @var{value} ]
30959 Create trace variable @var{name} if it does not exist. If
30960 @var{value} is specified, sets the initial value of the specified
30961 trace variable to that value. Note that the @var{name} should start
30962 with the @samp{$} character.
30964 @subsubheading @value{GDBN} Command
30966 The corresponding @value{GDBN} command is @samp{tvariable}.
30968 @subheading -trace-list-variables
30969 @findex -trace-list-variables
30971 @subsubheading Synopsis
30974 -trace-list-variables
30977 Return a table of all defined trace variables. Each element of the
30978 table has the following fields:
30982 The name of the trace variable. This field is always present.
30985 The initial value. This is a 64-bit signed integer. This
30986 field is always present.
30989 The value the trace variable has at the moment. This is a 64-bit
30990 signed integer. This field is absent iff current value is
30991 not defined, for example if the trace was never run, or is
30996 @subsubheading @value{GDBN} Command
30998 The corresponding @value{GDBN} command is @samp{tvariables}.
31000 @subsubheading Example
31004 -trace-list-variables
31005 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31006 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31007 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31008 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31009 body=[variable=@{name="$trace_timestamp",initial="0"@}
31010 variable=@{name="$foo",initial="10",current="15"@}]@}
31014 @subheading -trace-save
31015 @findex -trace-save
31017 @subsubheading Synopsis
31020 -trace-save [-r ] @var{filename}
31023 Saves the collected trace data to @var{filename}. Without the
31024 @samp{-r} option, the data is downloaded from the target and saved
31025 in a local file. With the @samp{-r} option the target is asked
31026 to perform the save.
31028 @subsubheading @value{GDBN} Command
31030 The corresponding @value{GDBN} command is @samp{tsave}.
31033 @subheading -trace-start
31034 @findex -trace-start
31036 @subsubheading Synopsis
31042 Starts a tracing experiments. The result of this command does not
31045 @subsubheading @value{GDBN} Command
31047 The corresponding @value{GDBN} command is @samp{tstart}.
31049 @subheading -trace-status
31050 @findex -trace-status
31052 @subsubheading Synopsis
31058 Obtains the status of a tracing experiment. The result may include
31059 the following fields:
31064 May have a value of either @samp{0}, when no tracing operations are
31065 supported, @samp{1}, when all tracing operations are supported, or
31066 @samp{file} when examining trace file. In the latter case, examining
31067 of trace frame is possible but new tracing experiement cannot be
31068 started. This field is always present.
31071 May have a value of either @samp{0} or @samp{1} depending on whether
31072 tracing experiement is in progress on target. This field is present
31073 if @samp{supported} field is not @samp{0}.
31076 Report the reason why the tracing was stopped last time. This field
31077 may be absent iff tracing was never stopped on target yet. The
31078 value of @samp{request} means the tracing was stopped as result of
31079 the @code{-trace-stop} command. The value of @samp{overflow} means
31080 the tracing buffer is full. The value of @samp{disconnection} means
31081 tracing was automatically stopped when @value{GDBN} has disconnected.
31082 The value of @samp{passcount} means tracing was stopped when a
31083 tracepoint was passed a maximal number of times for that tracepoint.
31084 This field is present if @samp{supported} field is not @samp{0}.
31086 @item stopping-tracepoint
31087 The number of tracepoint whose passcount as exceeded. This field is
31088 present iff the @samp{stop-reason} field has the value of
31092 @itemx frames-created
31093 The @samp{frames} field is a count of the total number of trace frames
31094 in the trace buffer, while @samp{frames-created} is the total created
31095 during the run, including ones that were discarded, such as when a
31096 circular trace buffer filled up. Both fields are optional.
31100 These fields tell the current size of the tracing buffer and the
31101 remaining space. These fields are optional.
31104 The value of the circular trace buffer flag. @code{1} means that the
31105 trace buffer is circular and old trace frames will be discarded if
31106 necessary to make room, @code{0} means that the trace buffer is linear
31110 The value of the disconnected tracing flag. @code{1} means that
31111 tracing will continue after @value{GDBN} disconnects, @code{0} means
31112 that the trace run will stop.
31116 @subsubheading @value{GDBN} Command
31118 The corresponding @value{GDBN} command is @samp{tstatus}.
31120 @subheading -trace-stop
31121 @findex -trace-stop
31123 @subsubheading Synopsis
31129 Stops a tracing experiment. The result of this command has the same
31130 fields as @code{-trace-status}, except that the @samp{supported} and
31131 @samp{running} fields are not output.
31133 @subsubheading @value{GDBN} Command
31135 The corresponding @value{GDBN} command is @samp{tstop}.
31138 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31139 @node GDB/MI Symbol Query
31140 @section @sc{gdb/mi} Symbol Query Commands
31144 @subheading The @code{-symbol-info-address} Command
31145 @findex -symbol-info-address
31147 @subsubheading Synopsis
31150 -symbol-info-address @var{symbol}
31153 Describe where @var{symbol} is stored.
31155 @subsubheading @value{GDBN} Command
31157 The corresponding @value{GDBN} command is @samp{info address}.
31159 @subsubheading Example
31163 @subheading The @code{-symbol-info-file} Command
31164 @findex -symbol-info-file
31166 @subsubheading Synopsis
31172 Show the file for the symbol.
31174 @subsubheading @value{GDBN} Command
31176 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31177 @samp{gdb_find_file}.
31179 @subsubheading Example
31183 @subheading The @code{-symbol-info-function} Command
31184 @findex -symbol-info-function
31186 @subsubheading Synopsis
31189 -symbol-info-function
31192 Show which function the symbol lives in.
31194 @subsubheading @value{GDBN} Command
31196 @samp{gdb_get_function} in @code{gdbtk}.
31198 @subsubheading Example
31202 @subheading The @code{-symbol-info-line} Command
31203 @findex -symbol-info-line
31205 @subsubheading Synopsis
31211 Show the core addresses of the code for a source line.
31213 @subsubheading @value{GDBN} Command
31215 The corresponding @value{GDBN} command is @samp{info line}.
31216 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31218 @subsubheading Example
31222 @subheading The @code{-symbol-info-symbol} Command
31223 @findex -symbol-info-symbol
31225 @subsubheading Synopsis
31228 -symbol-info-symbol @var{addr}
31231 Describe what symbol is at location @var{addr}.
31233 @subsubheading @value{GDBN} Command
31235 The corresponding @value{GDBN} command is @samp{info symbol}.
31237 @subsubheading Example
31241 @subheading The @code{-symbol-list-functions} Command
31242 @findex -symbol-list-functions
31244 @subsubheading Synopsis
31247 -symbol-list-functions
31250 List the functions in the executable.
31252 @subsubheading @value{GDBN} Command
31254 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31255 @samp{gdb_search} in @code{gdbtk}.
31257 @subsubheading Example
31262 @subheading The @code{-symbol-list-lines} Command
31263 @findex -symbol-list-lines
31265 @subsubheading Synopsis
31268 -symbol-list-lines @var{filename}
31271 Print the list of lines that contain code and their associated program
31272 addresses for the given source filename. The entries are sorted in
31273 ascending PC order.
31275 @subsubheading @value{GDBN} Command
31277 There is no corresponding @value{GDBN} command.
31279 @subsubheading Example
31282 -symbol-list-lines basics.c
31283 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31289 @subheading The @code{-symbol-list-types} Command
31290 @findex -symbol-list-types
31292 @subsubheading Synopsis
31298 List all the type names.
31300 @subsubheading @value{GDBN} Command
31302 The corresponding commands are @samp{info types} in @value{GDBN},
31303 @samp{gdb_search} in @code{gdbtk}.
31305 @subsubheading Example
31309 @subheading The @code{-symbol-list-variables} Command
31310 @findex -symbol-list-variables
31312 @subsubheading Synopsis
31315 -symbol-list-variables
31318 List all the global and static variable names.
31320 @subsubheading @value{GDBN} Command
31322 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31324 @subsubheading Example
31328 @subheading The @code{-symbol-locate} Command
31329 @findex -symbol-locate
31331 @subsubheading Synopsis
31337 @subsubheading @value{GDBN} Command
31339 @samp{gdb_loc} in @code{gdbtk}.
31341 @subsubheading Example
31345 @subheading The @code{-symbol-type} Command
31346 @findex -symbol-type
31348 @subsubheading Synopsis
31351 -symbol-type @var{variable}
31354 Show type of @var{variable}.
31356 @subsubheading @value{GDBN} Command
31358 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31359 @samp{gdb_obj_variable}.
31361 @subsubheading Example
31366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31367 @node GDB/MI File Commands
31368 @section @sc{gdb/mi} File Commands
31370 This section describes the GDB/MI commands to specify executable file names
31371 and to read in and obtain symbol table information.
31373 @subheading The @code{-file-exec-and-symbols} Command
31374 @findex -file-exec-and-symbols
31376 @subsubheading Synopsis
31379 -file-exec-and-symbols @var{file}
31382 Specify the executable file to be debugged. This file is the one from
31383 which the symbol table is also read. If no file is specified, the
31384 command clears the executable and symbol information. If breakpoints
31385 are set when using this command with no arguments, @value{GDBN} will produce
31386 error messages. Otherwise, no output is produced, except a completion
31389 @subsubheading @value{GDBN} Command
31391 The corresponding @value{GDBN} command is @samp{file}.
31393 @subsubheading Example
31397 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31403 @subheading The @code{-file-exec-file} Command
31404 @findex -file-exec-file
31406 @subsubheading Synopsis
31409 -file-exec-file @var{file}
31412 Specify the executable file to be debugged. Unlike
31413 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31414 from this file. If used without argument, @value{GDBN} clears the information
31415 about the executable file. No output is produced, except a completion
31418 @subsubheading @value{GDBN} Command
31420 The corresponding @value{GDBN} command is @samp{exec-file}.
31422 @subsubheading Example
31426 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31433 @subheading The @code{-file-list-exec-sections} Command
31434 @findex -file-list-exec-sections
31436 @subsubheading Synopsis
31439 -file-list-exec-sections
31442 List the sections of the current executable file.
31444 @subsubheading @value{GDBN} Command
31446 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31447 information as this command. @code{gdbtk} has a corresponding command
31448 @samp{gdb_load_info}.
31450 @subsubheading Example
31455 @subheading The @code{-file-list-exec-source-file} Command
31456 @findex -file-list-exec-source-file
31458 @subsubheading Synopsis
31461 -file-list-exec-source-file
31464 List the line number, the current source file, and the absolute path
31465 to the current source file for the current executable. The macro
31466 information field has a value of @samp{1} or @samp{0} depending on
31467 whether or not the file includes preprocessor macro information.
31469 @subsubheading @value{GDBN} Command
31471 The @value{GDBN} equivalent is @samp{info source}
31473 @subsubheading Example
31477 123-file-list-exec-source-file
31478 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31483 @subheading The @code{-file-list-exec-source-files} Command
31484 @findex -file-list-exec-source-files
31486 @subsubheading Synopsis
31489 -file-list-exec-source-files
31492 List the source files for the current executable.
31494 It will always output the filename, but only when @value{GDBN} can find
31495 the absolute file name of a source file, will it output the fullname.
31497 @subsubheading @value{GDBN} Command
31499 The @value{GDBN} equivalent is @samp{info sources}.
31500 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31502 @subsubheading Example
31505 -file-list-exec-source-files
31507 @{file=foo.c,fullname=/home/foo.c@},
31508 @{file=/home/bar.c,fullname=/home/bar.c@},
31509 @{file=gdb_could_not_find_fullpath.c@}]
31514 @subheading The @code{-file-list-shared-libraries} Command
31515 @findex -file-list-shared-libraries
31517 @subsubheading Synopsis
31520 -file-list-shared-libraries
31523 List the shared libraries in the program.
31525 @subsubheading @value{GDBN} Command
31527 The corresponding @value{GDBN} command is @samp{info shared}.
31529 @subsubheading Example
31533 @subheading The @code{-file-list-symbol-files} Command
31534 @findex -file-list-symbol-files
31536 @subsubheading Synopsis
31539 -file-list-symbol-files
31544 @subsubheading @value{GDBN} Command
31546 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31548 @subsubheading Example
31553 @subheading The @code{-file-symbol-file} Command
31554 @findex -file-symbol-file
31556 @subsubheading Synopsis
31559 -file-symbol-file @var{file}
31562 Read symbol table info from the specified @var{file} argument. When
31563 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31564 produced, except for a completion notification.
31566 @subsubheading @value{GDBN} Command
31568 The corresponding @value{GDBN} command is @samp{symbol-file}.
31570 @subsubheading Example
31574 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31580 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31581 @node GDB/MI Memory Overlay Commands
31582 @section @sc{gdb/mi} Memory Overlay Commands
31584 The memory overlay commands are not implemented.
31586 @c @subheading -overlay-auto
31588 @c @subheading -overlay-list-mapping-state
31590 @c @subheading -overlay-list-overlays
31592 @c @subheading -overlay-map
31594 @c @subheading -overlay-off
31596 @c @subheading -overlay-on
31598 @c @subheading -overlay-unmap
31600 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31601 @node GDB/MI Signal Handling Commands
31602 @section @sc{gdb/mi} Signal Handling Commands
31604 Signal handling commands are not implemented.
31606 @c @subheading -signal-handle
31608 @c @subheading -signal-list-handle-actions
31610 @c @subheading -signal-list-signal-types
31614 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31615 @node GDB/MI Target Manipulation
31616 @section @sc{gdb/mi} Target Manipulation Commands
31619 @subheading The @code{-target-attach} Command
31620 @findex -target-attach
31622 @subsubheading Synopsis
31625 -target-attach @var{pid} | @var{gid} | @var{file}
31628 Attach to a process @var{pid} or a file @var{file} outside of
31629 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31630 group, the id previously returned by
31631 @samp{-list-thread-groups --available} must be used.
31633 @subsubheading @value{GDBN} Command
31635 The corresponding @value{GDBN} command is @samp{attach}.
31637 @subsubheading Example
31641 =thread-created,id="1"
31642 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31648 @subheading The @code{-target-compare-sections} Command
31649 @findex -target-compare-sections
31651 @subsubheading Synopsis
31654 -target-compare-sections [ @var{section} ]
31657 Compare data of section @var{section} on target to the exec file.
31658 Without the argument, all sections are compared.
31660 @subsubheading @value{GDBN} Command
31662 The @value{GDBN} equivalent is @samp{compare-sections}.
31664 @subsubheading Example
31669 @subheading The @code{-target-detach} Command
31670 @findex -target-detach
31672 @subsubheading Synopsis
31675 -target-detach [ @var{pid} | @var{gid} ]
31678 Detach from the remote target which normally resumes its execution.
31679 If either @var{pid} or @var{gid} is specified, detaches from either
31680 the specified process, or specified thread group. There's no output.
31682 @subsubheading @value{GDBN} Command
31684 The corresponding @value{GDBN} command is @samp{detach}.
31686 @subsubheading Example
31696 @subheading The @code{-target-disconnect} Command
31697 @findex -target-disconnect
31699 @subsubheading Synopsis
31705 Disconnect from the remote target. There's no output and the target is
31706 generally not resumed.
31708 @subsubheading @value{GDBN} Command
31710 The corresponding @value{GDBN} command is @samp{disconnect}.
31712 @subsubheading Example
31722 @subheading The @code{-target-download} Command
31723 @findex -target-download
31725 @subsubheading Synopsis
31731 Loads the executable onto the remote target.
31732 It prints out an update message every half second, which includes the fields:
31736 The name of the section.
31738 The size of what has been sent so far for that section.
31740 The size of the section.
31742 The total size of what was sent so far (the current and the previous sections).
31744 The size of the overall executable to download.
31748 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31749 @sc{gdb/mi} Output Syntax}).
31751 In addition, it prints the name and size of the sections, as they are
31752 downloaded. These messages include the following fields:
31756 The name of the section.
31758 The size of the section.
31760 The size of the overall executable to download.
31764 At the end, a summary is printed.
31766 @subsubheading @value{GDBN} Command
31768 The corresponding @value{GDBN} command is @samp{load}.
31770 @subsubheading Example
31772 Note: each status message appears on a single line. Here the messages
31773 have been broken down so that they can fit onto a page.
31778 +download,@{section=".text",section-size="6668",total-size="9880"@}
31779 +download,@{section=".text",section-sent="512",section-size="6668",
31780 total-sent="512",total-size="9880"@}
31781 +download,@{section=".text",section-sent="1024",section-size="6668",
31782 total-sent="1024",total-size="9880"@}
31783 +download,@{section=".text",section-sent="1536",section-size="6668",
31784 total-sent="1536",total-size="9880"@}
31785 +download,@{section=".text",section-sent="2048",section-size="6668",
31786 total-sent="2048",total-size="9880"@}
31787 +download,@{section=".text",section-sent="2560",section-size="6668",
31788 total-sent="2560",total-size="9880"@}
31789 +download,@{section=".text",section-sent="3072",section-size="6668",
31790 total-sent="3072",total-size="9880"@}
31791 +download,@{section=".text",section-sent="3584",section-size="6668",
31792 total-sent="3584",total-size="9880"@}
31793 +download,@{section=".text",section-sent="4096",section-size="6668",
31794 total-sent="4096",total-size="9880"@}
31795 +download,@{section=".text",section-sent="4608",section-size="6668",
31796 total-sent="4608",total-size="9880"@}
31797 +download,@{section=".text",section-sent="5120",section-size="6668",
31798 total-sent="5120",total-size="9880"@}
31799 +download,@{section=".text",section-sent="5632",section-size="6668",
31800 total-sent="5632",total-size="9880"@}
31801 +download,@{section=".text",section-sent="6144",section-size="6668",
31802 total-sent="6144",total-size="9880"@}
31803 +download,@{section=".text",section-sent="6656",section-size="6668",
31804 total-sent="6656",total-size="9880"@}
31805 +download,@{section=".init",section-size="28",total-size="9880"@}
31806 +download,@{section=".fini",section-size="28",total-size="9880"@}
31807 +download,@{section=".data",section-size="3156",total-size="9880"@}
31808 +download,@{section=".data",section-sent="512",section-size="3156",
31809 total-sent="7236",total-size="9880"@}
31810 +download,@{section=".data",section-sent="1024",section-size="3156",
31811 total-sent="7748",total-size="9880"@}
31812 +download,@{section=".data",section-sent="1536",section-size="3156",
31813 total-sent="8260",total-size="9880"@}
31814 +download,@{section=".data",section-sent="2048",section-size="3156",
31815 total-sent="8772",total-size="9880"@}
31816 +download,@{section=".data",section-sent="2560",section-size="3156",
31817 total-sent="9284",total-size="9880"@}
31818 +download,@{section=".data",section-sent="3072",section-size="3156",
31819 total-sent="9796",total-size="9880"@}
31820 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31827 @subheading The @code{-target-exec-status} Command
31828 @findex -target-exec-status
31830 @subsubheading Synopsis
31833 -target-exec-status
31836 Provide information on the state of the target (whether it is running or
31837 not, for instance).
31839 @subsubheading @value{GDBN} Command
31841 There's no equivalent @value{GDBN} command.
31843 @subsubheading Example
31847 @subheading The @code{-target-list-available-targets} Command
31848 @findex -target-list-available-targets
31850 @subsubheading Synopsis
31853 -target-list-available-targets
31856 List the possible targets to connect to.
31858 @subsubheading @value{GDBN} Command
31860 The corresponding @value{GDBN} command is @samp{help target}.
31862 @subsubheading Example
31866 @subheading The @code{-target-list-current-targets} Command
31867 @findex -target-list-current-targets
31869 @subsubheading Synopsis
31872 -target-list-current-targets
31875 Describe the current target.
31877 @subsubheading @value{GDBN} Command
31879 The corresponding information is printed by @samp{info file} (among
31882 @subsubheading Example
31886 @subheading The @code{-target-list-parameters} Command
31887 @findex -target-list-parameters
31889 @subsubheading Synopsis
31892 -target-list-parameters
31898 @subsubheading @value{GDBN} Command
31902 @subsubheading Example
31906 @subheading The @code{-target-select} Command
31907 @findex -target-select
31909 @subsubheading Synopsis
31912 -target-select @var{type} @var{parameters @dots{}}
31915 Connect @value{GDBN} to the remote target. This command takes two args:
31919 The type of target, for instance @samp{remote}, etc.
31920 @item @var{parameters}
31921 Device names, host names and the like. @xref{Target Commands, ,
31922 Commands for Managing Targets}, for more details.
31925 The output is a connection notification, followed by the address at
31926 which the target program is, in the following form:
31929 ^connected,addr="@var{address}",func="@var{function name}",
31930 args=[@var{arg list}]
31933 @subsubheading @value{GDBN} Command
31935 The corresponding @value{GDBN} command is @samp{target}.
31937 @subsubheading Example
31941 -target-select remote /dev/ttya
31942 ^connected,addr="0xfe00a300",func="??",args=[]
31946 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31947 @node GDB/MI File Transfer Commands
31948 @section @sc{gdb/mi} File Transfer Commands
31951 @subheading The @code{-target-file-put} Command
31952 @findex -target-file-put
31954 @subsubheading Synopsis
31957 -target-file-put @var{hostfile} @var{targetfile}
31960 Copy file @var{hostfile} from the host system (the machine running
31961 @value{GDBN}) to @var{targetfile} on the target system.
31963 @subsubheading @value{GDBN} Command
31965 The corresponding @value{GDBN} command is @samp{remote put}.
31967 @subsubheading Example
31971 -target-file-put localfile remotefile
31977 @subheading The @code{-target-file-get} Command
31978 @findex -target-file-get
31980 @subsubheading Synopsis
31983 -target-file-get @var{targetfile} @var{hostfile}
31986 Copy file @var{targetfile} from the target system to @var{hostfile}
31987 on the host system.
31989 @subsubheading @value{GDBN} Command
31991 The corresponding @value{GDBN} command is @samp{remote get}.
31993 @subsubheading Example
31997 -target-file-get remotefile localfile
32003 @subheading The @code{-target-file-delete} Command
32004 @findex -target-file-delete
32006 @subsubheading Synopsis
32009 -target-file-delete @var{targetfile}
32012 Delete @var{targetfile} from the target system.
32014 @subsubheading @value{GDBN} Command
32016 The corresponding @value{GDBN} command is @samp{remote delete}.
32018 @subsubheading Example
32022 -target-file-delete remotefile
32028 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32029 @node GDB/MI Miscellaneous Commands
32030 @section Miscellaneous @sc{gdb/mi} Commands
32032 @c @subheading -gdb-complete
32034 @subheading The @code{-gdb-exit} Command
32037 @subsubheading Synopsis
32043 Exit @value{GDBN} immediately.
32045 @subsubheading @value{GDBN} Command
32047 Approximately corresponds to @samp{quit}.
32049 @subsubheading Example
32059 @subheading The @code{-exec-abort} Command
32060 @findex -exec-abort
32062 @subsubheading Synopsis
32068 Kill the inferior running program.
32070 @subsubheading @value{GDBN} Command
32072 The corresponding @value{GDBN} command is @samp{kill}.
32074 @subsubheading Example
32079 @subheading The @code{-gdb-set} Command
32082 @subsubheading Synopsis
32088 Set an internal @value{GDBN} variable.
32089 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32091 @subsubheading @value{GDBN} Command
32093 The corresponding @value{GDBN} command is @samp{set}.
32095 @subsubheading Example
32105 @subheading The @code{-gdb-show} Command
32108 @subsubheading Synopsis
32114 Show the current value of a @value{GDBN} variable.
32116 @subsubheading @value{GDBN} Command
32118 The corresponding @value{GDBN} command is @samp{show}.
32120 @subsubheading Example
32129 @c @subheading -gdb-source
32132 @subheading The @code{-gdb-version} Command
32133 @findex -gdb-version
32135 @subsubheading Synopsis
32141 Show version information for @value{GDBN}. Used mostly in testing.
32143 @subsubheading @value{GDBN} Command
32145 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32146 default shows this information when you start an interactive session.
32148 @subsubheading Example
32150 @c This example modifies the actual output from GDB to avoid overfull
32156 ~Copyright 2000 Free Software Foundation, Inc.
32157 ~GDB is free software, covered by the GNU General Public License, and
32158 ~you are welcome to change it and/or distribute copies of it under
32159 ~ certain conditions.
32160 ~Type "show copying" to see the conditions.
32161 ~There is absolutely no warranty for GDB. Type "show warranty" for
32163 ~This GDB was configured as
32164 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32169 @subheading The @code{-list-features} Command
32170 @findex -list-features
32172 Returns a list of particular features of the MI protocol that
32173 this version of gdb implements. A feature can be a command,
32174 or a new field in an output of some command, or even an
32175 important bugfix. While a frontend can sometimes detect presence
32176 of a feature at runtime, it is easier to perform detection at debugger
32179 The command returns a list of strings, with each string naming an
32180 available feature. Each returned string is just a name, it does not
32181 have any internal structure. The list of possible feature names
32187 (gdb) -list-features
32188 ^done,result=["feature1","feature2"]
32191 The current list of features is:
32194 @item frozen-varobjs
32195 Indicates support for the @code{-var-set-frozen} command, as well
32196 as possible presense of the @code{frozen} field in the output
32197 of @code{-varobj-create}.
32198 @item pending-breakpoints
32199 Indicates support for the @option{-f} option to the @code{-break-insert}
32202 Indicates Python scripting support, Python-based
32203 pretty-printing commands, and possible presence of the
32204 @samp{display_hint} field in the output of @code{-var-list-children}
32206 Indicates support for the @code{-thread-info} command.
32207 @item data-read-memory-bytes
32208 Indicates support for the @code{-data-read-memory-bytes} and the
32209 @code{-data-write-memory-bytes} commands.
32210 @item breakpoint-notifications
32211 Indicates that changes to breakpoints and breakpoints created via the
32212 CLI will be announced via async records.
32213 @item ada-task-info
32214 Indicates support for the @code{-ada-task-info} command.
32217 @subheading The @code{-list-target-features} Command
32218 @findex -list-target-features
32220 Returns a list of particular features that are supported by the
32221 target. Those features affect the permitted MI commands, but
32222 unlike the features reported by the @code{-list-features} command, the
32223 features depend on which target GDB is using at the moment. Whenever
32224 a target can change, due to commands such as @code{-target-select},
32225 @code{-target-attach} or @code{-exec-run}, the list of target features
32226 may change, and the frontend should obtain it again.
32230 (gdb) -list-features
32231 ^done,result=["async"]
32234 The current list of features is:
32238 Indicates that the target is capable of asynchronous command
32239 execution, which means that @value{GDBN} will accept further commands
32240 while the target is running.
32243 Indicates that the target is capable of reverse execution.
32244 @xref{Reverse Execution}, for more information.
32248 @subheading The @code{-list-thread-groups} Command
32249 @findex -list-thread-groups
32251 @subheading Synopsis
32254 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32257 Lists thread groups (@pxref{Thread groups}). When a single thread
32258 group is passed as the argument, lists the children of that group.
32259 When several thread group are passed, lists information about those
32260 thread groups. Without any parameters, lists information about all
32261 top-level thread groups.
32263 Normally, thread groups that are being debugged are reported.
32264 With the @samp{--available} option, @value{GDBN} reports thread groups
32265 available on the target.
32267 The output of this command may have either a @samp{threads} result or
32268 a @samp{groups} result. The @samp{thread} result has a list of tuples
32269 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32270 Information}). The @samp{groups} result has a list of tuples as value,
32271 each tuple describing a thread group. If top-level groups are
32272 requested (that is, no parameter is passed), or when several groups
32273 are passed, the output always has a @samp{groups} result. The format
32274 of the @samp{group} result is described below.
32276 To reduce the number of roundtrips it's possible to list thread groups
32277 together with their children, by passing the @samp{--recurse} option
32278 and the recursion depth. Presently, only recursion depth of 1 is
32279 permitted. If this option is present, then every reported thread group
32280 will also include its children, either as @samp{group} or
32281 @samp{threads} field.
32283 In general, any combination of option and parameters is permitted, with
32284 the following caveats:
32288 When a single thread group is passed, the output will typically
32289 be the @samp{threads} result. Because threads may not contain
32290 anything, the @samp{recurse} option will be ignored.
32293 When the @samp{--available} option is passed, limited information may
32294 be available. In particular, the list of threads of a process might
32295 be inaccessible. Further, specifying specific thread groups might
32296 not give any performance advantage over listing all thread groups.
32297 The frontend should assume that @samp{-list-thread-groups --available}
32298 is always an expensive operation and cache the results.
32302 The @samp{groups} result is a list of tuples, where each tuple may
32303 have the following fields:
32307 Identifier of the thread group. This field is always present.
32308 The identifier is an opaque string; frontends should not try to
32309 convert it to an integer, even though it might look like one.
32312 The type of the thread group. At present, only @samp{process} is a
32316 The target-specific process identifier. This field is only present
32317 for thread groups of type @samp{process} and only if the process exists.
32320 The number of children this thread group has. This field may be
32321 absent for an available thread group.
32324 This field has a list of tuples as value, each tuple describing a
32325 thread. It may be present if the @samp{--recurse} option is
32326 specified, and it's actually possible to obtain the threads.
32329 This field is a list of integers, each identifying a core that one
32330 thread of the group is running on. This field may be absent if
32331 such information is not available.
32334 The name of the executable file that corresponds to this thread group.
32335 The field is only present for thread groups of type @samp{process},
32336 and only if there is a corresponding executable file.
32340 @subheading Example
32344 -list-thread-groups
32345 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32346 -list-thread-groups 17
32347 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32348 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32349 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32350 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32351 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32352 -list-thread-groups --available
32353 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32354 -list-thread-groups --available --recurse 1
32355 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32356 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32357 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32358 -list-thread-groups --available --recurse 1 17 18
32359 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32360 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32361 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32365 @subheading The @code{-add-inferior} Command
32366 @findex -add-inferior
32368 @subheading Synopsis
32374 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32375 inferior is not associated with any executable. Such association may
32376 be established with the @samp{-file-exec-and-symbols} command
32377 (@pxref{GDB/MI File Commands}). The command response has a single
32378 field, @samp{thread-group}, whose value is the identifier of the
32379 thread group corresponding to the new inferior.
32381 @subheading Example
32386 ^done,thread-group="i3"
32389 @subheading The @code{-interpreter-exec} Command
32390 @findex -interpreter-exec
32392 @subheading Synopsis
32395 -interpreter-exec @var{interpreter} @var{command}
32397 @anchor{-interpreter-exec}
32399 Execute the specified @var{command} in the given @var{interpreter}.
32401 @subheading @value{GDBN} Command
32403 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32405 @subheading Example
32409 -interpreter-exec console "break main"
32410 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32411 &"During symbol reading, bad structure-type format.\n"
32412 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32417 @subheading The @code{-inferior-tty-set} Command
32418 @findex -inferior-tty-set
32420 @subheading Synopsis
32423 -inferior-tty-set /dev/pts/1
32426 Set terminal for future runs of the program being debugged.
32428 @subheading @value{GDBN} Command
32430 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32432 @subheading Example
32436 -inferior-tty-set /dev/pts/1
32441 @subheading The @code{-inferior-tty-show} Command
32442 @findex -inferior-tty-show
32444 @subheading Synopsis
32450 Show terminal for future runs of program being debugged.
32452 @subheading @value{GDBN} Command
32454 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32456 @subheading Example
32460 -inferior-tty-set /dev/pts/1
32464 ^done,inferior_tty_terminal="/dev/pts/1"
32468 @subheading The @code{-enable-timings} Command
32469 @findex -enable-timings
32471 @subheading Synopsis
32474 -enable-timings [yes | no]
32477 Toggle the printing of the wallclock, user and system times for an MI
32478 command as a field in its output. This command is to help frontend
32479 developers optimize the performance of their code. No argument is
32480 equivalent to @samp{yes}.
32482 @subheading @value{GDBN} Command
32486 @subheading Example
32494 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32495 addr="0x080484ed",func="main",file="myprog.c",
32496 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
32497 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32505 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32506 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32507 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32508 fullname="/home/nickrob/myprog.c",line="73"@}
32513 @chapter @value{GDBN} Annotations
32515 This chapter describes annotations in @value{GDBN}. Annotations were
32516 designed to interface @value{GDBN} to graphical user interfaces or other
32517 similar programs which want to interact with @value{GDBN} at a
32518 relatively high level.
32520 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32524 This is Edition @value{EDITION}, @value{DATE}.
32528 * Annotations Overview:: What annotations are; the general syntax.
32529 * Server Prefix:: Issuing a command without affecting user state.
32530 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32531 * Errors:: Annotations for error messages.
32532 * Invalidation:: Some annotations describe things now invalid.
32533 * Annotations for Running::
32534 Whether the program is running, how it stopped, etc.
32535 * Source Annotations:: Annotations describing source code.
32538 @node Annotations Overview
32539 @section What is an Annotation?
32540 @cindex annotations
32542 Annotations start with a newline character, two @samp{control-z}
32543 characters, and the name of the annotation. If there is no additional
32544 information associated with this annotation, the name of the annotation
32545 is followed immediately by a newline. If there is additional
32546 information, the name of the annotation is followed by a space, the
32547 additional information, and a newline. The additional information
32548 cannot contain newline characters.
32550 Any output not beginning with a newline and two @samp{control-z}
32551 characters denotes literal output from @value{GDBN}. Currently there is
32552 no need for @value{GDBN} to output a newline followed by two
32553 @samp{control-z} characters, but if there was such a need, the
32554 annotations could be extended with an @samp{escape} annotation which
32555 means those three characters as output.
32557 The annotation @var{level}, which is specified using the
32558 @option{--annotate} command line option (@pxref{Mode Options}), controls
32559 how much information @value{GDBN} prints together with its prompt,
32560 values of expressions, source lines, and other types of output. Level 0
32561 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32562 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32563 for programs that control @value{GDBN}, and level 2 annotations have
32564 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32565 Interface, annotate, GDB's Obsolete Annotations}).
32568 @kindex set annotate
32569 @item set annotate @var{level}
32570 The @value{GDBN} command @code{set annotate} sets the level of
32571 annotations to the specified @var{level}.
32573 @item show annotate
32574 @kindex show annotate
32575 Show the current annotation level.
32578 This chapter describes level 3 annotations.
32580 A simple example of starting up @value{GDBN} with annotations is:
32583 $ @kbd{gdb --annotate=3}
32585 Copyright 2003 Free Software Foundation, Inc.
32586 GDB is free software, covered by the GNU General Public License,
32587 and you are welcome to change it and/or distribute copies of it
32588 under certain conditions.
32589 Type "show copying" to see the conditions.
32590 There is absolutely no warranty for GDB. Type "show warranty"
32592 This GDB was configured as "i386-pc-linux-gnu"
32603 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32604 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32605 denotes a @samp{control-z} character) are annotations; the rest is
32606 output from @value{GDBN}.
32608 @node Server Prefix
32609 @section The Server Prefix
32610 @cindex server prefix
32612 If you prefix a command with @samp{server } then it will not affect
32613 the command history, nor will it affect @value{GDBN}'s notion of which
32614 command to repeat if @key{RET} is pressed on a line by itself. This
32615 means that commands can be run behind a user's back by a front-end in
32616 a transparent manner.
32618 The @code{server } prefix does not affect the recording of values into
32619 the value history; to print a value without recording it into the
32620 value history, use the @code{output} command instead of the
32621 @code{print} command.
32623 Using this prefix also disables confirmation requests
32624 (@pxref{confirmation requests}).
32627 @section Annotation for @value{GDBN} Input
32629 @cindex annotations for prompts
32630 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32631 to know when to send output, when the output from a given command is
32634 Different kinds of input each have a different @dfn{input type}. Each
32635 input type has three annotations: a @code{pre-} annotation, which
32636 denotes the beginning of any prompt which is being output, a plain
32637 annotation, which denotes the end of the prompt, and then a @code{post-}
32638 annotation which denotes the end of any echo which may (or may not) be
32639 associated with the input. For example, the @code{prompt} input type
32640 features the following annotations:
32648 The input types are
32651 @findex pre-prompt annotation
32652 @findex prompt annotation
32653 @findex post-prompt annotation
32655 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32657 @findex pre-commands annotation
32658 @findex commands annotation
32659 @findex post-commands annotation
32661 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32662 command. The annotations are repeated for each command which is input.
32664 @findex pre-overload-choice annotation
32665 @findex overload-choice annotation
32666 @findex post-overload-choice annotation
32667 @item overload-choice
32668 When @value{GDBN} wants the user to select between various overloaded functions.
32670 @findex pre-query annotation
32671 @findex query annotation
32672 @findex post-query annotation
32674 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32676 @findex pre-prompt-for-continue annotation
32677 @findex prompt-for-continue annotation
32678 @findex post-prompt-for-continue annotation
32679 @item prompt-for-continue
32680 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32681 expect this to work well; instead use @code{set height 0} to disable
32682 prompting. This is because the counting of lines is buggy in the
32683 presence of annotations.
32688 @cindex annotations for errors, warnings and interrupts
32690 @findex quit annotation
32695 This annotation occurs right before @value{GDBN} responds to an interrupt.
32697 @findex error annotation
32702 This annotation occurs right before @value{GDBN} responds to an error.
32704 Quit and error annotations indicate that any annotations which @value{GDBN} was
32705 in the middle of may end abruptly. For example, if a
32706 @code{value-history-begin} annotation is followed by a @code{error}, one
32707 cannot expect to receive the matching @code{value-history-end}. One
32708 cannot expect not to receive it either, however; an error annotation
32709 does not necessarily mean that @value{GDBN} is immediately returning all the way
32712 @findex error-begin annotation
32713 A quit or error annotation may be preceded by
32719 Any output between that and the quit or error annotation is the error
32722 Warning messages are not yet annotated.
32723 @c If we want to change that, need to fix warning(), type_error(),
32724 @c range_error(), and possibly other places.
32727 @section Invalidation Notices
32729 @cindex annotations for invalidation messages
32730 The following annotations say that certain pieces of state may have
32734 @findex frames-invalid annotation
32735 @item ^Z^Zframes-invalid
32737 The frames (for example, output from the @code{backtrace} command) may
32740 @findex breakpoints-invalid annotation
32741 @item ^Z^Zbreakpoints-invalid
32743 The breakpoints may have changed. For example, the user just added or
32744 deleted a breakpoint.
32747 @node Annotations for Running
32748 @section Running the Program
32749 @cindex annotations for running programs
32751 @findex starting annotation
32752 @findex stopping annotation
32753 When the program starts executing due to a @value{GDBN} command such as
32754 @code{step} or @code{continue},
32760 is output. When the program stops,
32766 is output. Before the @code{stopped} annotation, a variety of
32767 annotations describe how the program stopped.
32770 @findex exited annotation
32771 @item ^Z^Zexited @var{exit-status}
32772 The program exited, and @var{exit-status} is the exit status (zero for
32773 successful exit, otherwise nonzero).
32775 @findex signalled annotation
32776 @findex signal-name annotation
32777 @findex signal-name-end annotation
32778 @findex signal-string annotation
32779 @findex signal-string-end annotation
32780 @item ^Z^Zsignalled
32781 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32782 annotation continues:
32788 ^Z^Zsignal-name-end
32792 ^Z^Zsignal-string-end
32797 where @var{name} is the name of the signal, such as @code{SIGILL} or
32798 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32799 as @code{Illegal Instruction} or @code{Segmentation fault}.
32800 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32801 user's benefit and have no particular format.
32803 @findex signal annotation
32805 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32806 just saying that the program received the signal, not that it was
32807 terminated with it.
32809 @findex breakpoint annotation
32810 @item ^Z^Zbreakpoint @var{number}
32811 The program hit breakpoint number @var{number}.
32813 @findex watchpoint annotation
32814 @item ^Z^Zwatchpoint @var{number}
32815 The program hit watchpoint number @var{number}.
32818 @node Source Annotations
32819 @section Displaying Source
32820 @cindex annotations for source display
32822 @findex source annotation
32823 The following annotation is used instead of displaying source code:
32826 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32829 where @var{filename} is an absolute file name indicating which source
32830 file, @var{line} is the line number within that file (where 1 is the
32831 first line in the file), @var{character} is the character position
32832 within the file (where 0 is the first character in the file) (for most
32833 debug formats this will necessarily point to the beginning of a line),
32834 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32835 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32836 @var{addr} is the address in the target program associated with the
32837 source which is being displayed. @var{addr} is in the form @samp{0x}
32838 followed by one or more lowercase hex digits (note that this does not
32839 depend on the language).
32841 @node JIT Interface
32842 @chapter JIT Compilation Interface
32843 @cindex just-in-time compilation
32844 @cindex JIT compilation interface
32846 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32847 interface. A JIT compiler is a program or library that generates native
32848 executable code at runtime and executes it, usually in order to achieve good
32849 performance while maintaining platform independence.
32851 Programs that use JIT compilation are normally difficult to debug because
32852 portions of their code are generated at runtime, instead of being loaded from
32853 object files, which is where @value{GDBN} normally finds the program's symbols
32854 and debug information. In order to debug programs that use JIT compilation,
32855 @value{GDBN} has an interface that allows the program to register in-memory
32856 symbol files with @value{GDBN} at runtime.
32858 If you are using @value{GDBN} to debug a program that uses this interface, then
32859 it should work transparently so long as you have not stripped the binary. If
32860 you are developing a JIT compiler, then the interface is documented in the rest
32861 of this chapter. At this time, the only known client of this interface is the
32864 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32865 JIT compiler communicates with @value{GDBN} by writing data into a global
32866 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32867 attaches, it reads a linked list of symbol files from the global variable to
32868 find existing code, and puts a breakpoint in the function so that it can find
32869 out about additional code.
32872 * Declarations:: Relevant C struct declarations
32873 * Registering Code:: Steps to register code
32874 * Unregistering Code:: Steps to unregister code
32875 * Custom Debug Info:: Emit debug information in a custom format
32879 @section JIT Declarations
32881 These are the relevant struct declarations that a C program should include to
32882 implement the interface:
32892 struct jit_code_entry
32894 struct jit_code_entry *next_entry;
32895 struct jit_code_entry *prev_entry;
32896 const char *symfile_addr;
32897 uint64_t symfile_size;
32900 struct jit_descriptor
32903 /* This type should be jit_actions_t, but we use uint32_t
32904 to be explicit about the bitwidth. */
32905 uint32_t action_flag;
32906 struct jit_code_entry *relevant_entry;
32907 struct jit_code_entry *first_entry;
32910 /* GDB puts a breakpoint in this function. */
32911 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32913 /* Make sure to specify the version statically, because the
32914 debugger may check the version before we can set it. */
32915 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32918 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32919 modifications to this global data properly, which can easily be done by putting
32920 a global mutex around modifications to these structures.
32922 @node Registering Code
32923 @section Registering Code
32925 To register code with @value{GDBN}, the JIT should follow this protocol:
32929 Generate an object file in memory with symbols and other desired debug
32930 information. The file must include the virtual addresses of the sections.
32933 Create a code entry for the file, which gives the start and size of the symbol
32937 Add it to the linked list in the JIT descriptor.
32940 Point the relevant_entry field of the descriptor at the entry.
32943 Set @code{action_flag} to @code{JIT_REGISTER} and call
32944 @code{__jit_debug_register_code}.
32947 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32948 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32949 new code. However, the linked list must still be maintained in order to allow
32950 @value{GDBN} to attach to a running process and still find the symbol files.
32952 @node Unregistering Code
32953 @section Unregistering Code
32955 If code is freed, then the JIT should use the following protocol:
32959 Remove the code entry corresponding to the code from the linked list.
32962 Point the @code{relevant_entry} field of the descriptor at the code entry.
32965 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32966 @code{__jit_debug_register_code}.
32969 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32970 and the JIT will leak the memory used for the associated symbol files.
32972 @node Custom Debug Info
32973 @section Custom Debug Info
32974 @cindex custom JIT debug info
32975 @cindex JIT debug info reader
32977 Generating debug information in platform-native file formats (like ELF
32978 or COFF) may be an overkill for JIT compilers; especially if all the
32979 debug info is used for is displaying a meaningful backtrace. The
32980 issue can be resolved by having the JIT writers decide on a debug info
32981 format and also provide a reader that parses the debug info generated
32982 by the JIT compiler. This section gives a brief overview on writing
32983 such a parser. More specific details can be found in the source file
32984 @file{gdb/jit-reader.in}, which is also installed as a header at
32985 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32987 The reader is implemented as a shared object (so this functionality is
32988 not available on platforms which don't allow loading shared objects at
32989 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32990 @code{jit-reader-unload} are provided, to be used to load and unload
32991 the readers from a preconfigured directory. Once loaded, the shared
32992 object is used the parse the debug information emitted by the JIT
32996 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32997 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33000 @node Using JIT Debug Info Readers
33001 @subsection Using JIT Debug Info Readers
33002 @kindex jit-reader-load
33003 @kindex jit-reader-unload
33005 Readers can be loaded and unloaded using the @code{jit-reader-load}
33006 and @code{jit-reader-unload} commands.
33009 @item jit-reader-load @var{reader-name}
33010 Load the JIT reader named @var{reader-name}. On a UNIX system, this
33011 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
33012 @var{libdir} is the system library directory, usually
33013 @file{/usr/local/lib}. Only one reader can be active at a time;
33014 trying to load a second reader when one is already loaded will result
33015 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
33016 first unloading the current one using @code{jit-reader-load} and then
33017 invoking @code{jit-reader-load}.
33019 @item jit-reader-unload
33020 Unload the currently loaded JIT reader.
33024 @node Writing JIT Debug Info Readers
33025 @subsection Writing JIT Debug Info Readers
33026 @cindex writing JIT debug info readers
33028 As mentioned, a reader is essentially a shared object conforming to a
33029 certain ABI. This ABI is described in @file{jit-reader.h}.
33031 @file{jit-reader.h} defines the structures, macros and functions
33032 required to write a reader. It is installed (along with
33033 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33034 the system include directory.
33036 Readers need to be released under a GPL compatible license. A reader
33037 can be declared as released under such a license by placing the macro
33038 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33040 The entry point for readers is the symbol @code{gdb_init_reader},
33041 which is expected to be a function with the prototype
33043 @findex gdb_init_reader
33045 extern struct gdb_reader_funcs *gdb_init_reader (void);
33048 @cindex @code{struct gdb_reader_funcs}
33050 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33051 functions. These functions are executed to read the debug info
33052 generated by the JIT compiler (@code{read}), to unwind stack frames
33053 (@code{unwind}) and to create canonical frame IDs
33054 (@code{get_Frame_id}). It also has a callback that is called when the
33055 reader is being unloaded (@code{destroy}). The struct looks like this
33058 struct gdb_reader_funcs
33060 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33061 int reader_version;
33063 /* For use by the reader. */
33066 gdb_read_debug_info *read;
33067 gdb_unwind_frame *unwind;
33068 gdb_get_frame_id *get_frame_id;
33069 gdb_destroy_reader *destroy;
33073 @cindex @code{struct gdb_symbol_callbacks}
33074 @cindex @code{struct gdb_unwind_callbacks}
33076 The callbacks are provided with another set of callbacks by
33077 @value{GDBN} to do their job. For @code{read}, these callbacks are
33078 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33079 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33080 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33081 files and new symbol tables inside those object files. @code{struct
33082 gdb_unwind_callbacks} has callbacks to read registers off the current
33083 frame and to write out the values of the registers in the previous
33084 frame. Both have a callback (@code{target_read}) to read bytes off the
33085 target's address space.
33087 @node In-Process Agent
33088 @chapter In-Process Agent
33089 @cindex debugging agent
33090 The traditional debugging model is conceptually low-speed, but works fine,
33091 because most bugs can be reproduced in debugging-mode execution. However,
33092 as multi-core or many-core processors are becoming mainstream, and
33093 multi-threaded programs become more and more popular, there should be more
33094 and more bugs that only manifest themselves at normal-mode execution, for
33095 example, thread races, because debugger's interference with the program's
33096 timing may conceal the bugs. On the other hand, in some applications,
33097 it is not feasible for the debugger to interrupt the program's execution
33098 long enough for the developer to learn anything helpful about its behavior.
33099 If the program's correctness depends on its real-time behavior, delays
33100 introduced by a debugger might cause the program to fail, even when the
33101 code itself is correct. It is useful to be able to observe the program's
33102 behavior without interrupting it.
33104 Therefore, traditional debugging model is too intrusive to reproduce
33105 some bugs. In order to reduce the interference with the program, we can
33106 reduce the number of operations performed by debugger. The
33107 @dfn{In-Process Agent}, a shared library, is running within the same
33108 process with inferior, and is able to perform some debugging operations
33109 itself. As a result, debugger is only involved when necessary, and
33110 performance of debugging can be improved accordingly. Note that
33111 interference with program can be reduced but can't be removed completely,
33112 because the in-process agent will still stop or slow down the program.
33114 The in-process agent can interpret and execute Agent Expressions
33115 (@pxref{Agent Expressions}) during performing debugging operations. The
33116 agent expressions can be used for different purposes, such as collecting
33117 data in tracepoints, and condition evaluation in breakpoints.
33119 @anchor{Control Agent}
33120 You can control whether the in-process agent is used as an aid for
33121 debugging with the following commands:
33124 @kindex set agent on
33126 Causes the in-process agent to perform some operations on behalf of the
33127 debugger. Just which operations requested by the user will be done
33128 by the in-process agent depends on the its capabilities. For example,
33129 if you request to evaluate breakpoint conditions in the in-process agent,
33130 and the in-process agent has such capability as well, then breakpoint
33131 conditions will be evaluated in the in-process agent.
33133 @kindex set agent off
33134 @item set agent off
33135 Disables execution of debugging operations by the in-process agent. All
33136 of the operations will be performed by @value{GDBN}.
33140 Display the current setting of execution of debugging operations by
33141 the in-process agent.
33145 @chapter Reporting Bugs in @value{GDBN}
33146 @cindex bugs in @value{GDBN}
33147 @cindex reporting bugs in @value{GDBN}
33149 Your bug reports play an essential role in making @value{GDBN} reliable.
33151 Reporting a bug may help you by bringing a solution to your problem, or it
33152 may not. But in any case the principal function of a bug report is to help
33153 the entire community by making the next version of @value{GDBN} work better. Bug
33154 reports are your contribution to the maintenance of @value{GDBN}.
33156 In order for a bug report to serve its purpose, you must include the
33157 information that enables us to fix the bug.
33160 * Bug Criteria:: Have you found a bug?
33161 * Bug Reporting:: How to report bugs
33165 @section Have You Found a Bug?
33166 @cindex bug criteria
33168 If you are not sure whether you have found a bug, here are some guidelines:
33171 @cindex fatal signal
33172 @cindex debugger crash
33173 @cindex crash of debugger
33175 If the debugger gets a fatal signal, for any input whatever, that is a
33176 @value{GDBN} bug. Reliable debuggers never crash.
33178 @cindex error on valid input
33180 If @value{GDBN} produces an error message for valid input, that is a
33181 bug. (Note that if you're cross debugging, the problem may also be
33182 somewhere in the connection to the target.)
33184 @cindex invalid input
33186 If @value{GDBN} does not produce an error message for invalid input,
33187 that is a bug. However, you should note that your idea of
33188 ``invalid input'' might be our idea of ``an extension'' or ``support
33189 for traditional practice''.
33192 If you are an experienced user of debugging tools, your suggestions
33193 for improvement of @value{GDBN} are welcome in any case.
33196 @node Bug Reporting
33197 @section How to Report Bugs
33198 @cindex bug reports
33199 @cindex @value{GDBN} bugs, reporting
33201 A number of companies and individuals offer support for @sc{gnu} products.
33202 If you obtained @value{GDBN} from a support organization, we recommend you
33203 contact that organization first.
33205 You can find contact information for many support companies and
33206 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33208 @c should add a web page ref...
33211 @ifset BUGURL_DEFAULT
33212 In any event, we also recommend that you submit bug reports for
33213 @value{GDBN}. The preferred method is to submit them directly using
33214 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33215 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33218 @strong{Do not send bug reports to @samp{info-gdb}, or to
33219 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33220 not want to receive bug reports. Those that do have arranged to receive
33223 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33224 serves as a repeater. The mailing list and the newsgroup carry exactly
33225 the same messages. Often people think of posting bug reports to the
33226 newsgroup instead of mailing them. This appears to work, but it has one
33227 problem which can be crucial: a newsgroup posting often lacks a mail
33228 path back to the sender. Thus, if we need to ask for more information,
33229 we may be unable to reach you. For this reason, it is better to send
33230 bug reports to the mailing list.
33232 @ifclear BUGURL_DEFAULT
33233 In any event, we also recommend that you submit bug reports for
33234 @value{GDBN} to @value{BUGURL}.
33238 The fundamental principle of reporting bugs usefully is this:
33239 @strong{report all the facts}. If you are not sure whether to state a
33240 fact or leave it out, state it!
33242 Often people omit facts because they think they know what causes the
33243 problem and assume that some details do not matter. Thus, you might
33244 assume that the name of the variable you use in an example does not matter.
33245 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33246 stray memory reference which happens to fetch from the location where that
33247 name is stored in memory; perhaps, if the name were different, the contents
33248 of that location would fool the debugger into doing the right thing despite
33249 the bug. Play it safe and give a specific, complete example. That is the
33250 easiest thing for you to do, and the most helpful.
33252 Keep in mind that the purpose of a bug report is to enable us to fix the
33253 bug. It may be that the bug has been reported previously, but neither
33254 you nor we can know that unless your bug report is complete and
33257 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33258 bell?'' Those bug reports are useless, and we urge everyone to
33259 @emph{refuse to respond to them} except to chide the sender to report
33262 To enable us to fix the bug, you should include all these things:
33266 The version of @value{GDBN}. @value{GDBN} announces it if you start
33267 with no arguments; you can also print it at any time using @code{show
33270 Without this, we will not know whether there is any point in looking for
33271 the bug in the current version of @value{GDBN}.
33274 The type of machine you are using, and the operating system name and
33278 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33279 ``@value{GCC}--2.8.1''.
33282 What compiler (and its version) was used to compile the program you are
33283 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33284 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33285 to get this information; for other compilers, see the documentation for
33289 The command arguments you gave the compiler to compile your example and
33290 observe the bug. For example, did you use @samp{-O}? To guarantee
33291 you will not omit something important, list them all. A copy of the
33292 Makefile (or the output from make) is sufficient.
33294 If we were to try to guess the arguments, we would probably guess wrong
33295 and then we might not encounter the bug.
33298 A complete input script, and all necessary source files, that will
33302 A description of what behavior you observe that you believe is
33303 incorrect. For example, ``It gets a fatal signal.''
33305 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33306 will certainly notice it. But if the bug is incorrect output, we might
33307 not notice unless it is glaringly wrong. You might as well not give us
33308 a chance to make a mistake.
33310 Even if the problem you experience is a fatal signal, you should still
33311 say so explicitly. Suppose something strange is going on, such as, your
33312 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33313 the C library on your system. (This has happened!) Your copy might
33314 crash and ours would not. If you told us to expect a crash, then when
33315 ours fails to crash, we would know that the bug was not happening for
33316 us. If you had not told us to expect a crash, then we would not be able
33317 to draw any conclusion from our observations.
33320 @cindex recording a session script
33321 To collect all this information, you can use a session recording program
33322 such as @command{script}, which is available on many Unix systems.
33323 Just run your @value{GDBN} session inside @command{script} and then
33324 include the @file{typescript} file with your bug report.
33326 Another way to record a @value{GDBN} session is to run @value{GDBN}
33327 inside Emacs and then save the entire buffer to a file.
33330 If you wish to suggest changes to the @value{GDBN} source, send us context
33331 diffs. If you even discuss something in the @value{GDBN} source, refer to
33332 it by context, not by line number.
33334 The line numbers in our development sources will not match those in your
33335 sources. Your line numbers would convey no useful information to us.
33339 Here are some things that are not necessary:
33343 A description of the envelope of the bug.
33345 Often people who encounter a bug spend a lot of time investigating
33346 which changes to the input file will make the bug go away and which
33347 changes will not affect it.
33349 This is often time consuming and not very useful, because the way we
33350 will find the bug is by running a single example under the debugger
33351 with breakpoints, not by pure deduction from a series of examples.
33352 We recommend that you save your time for something else.
33354 Of course, if you can find a simpler example to report @emph{instead}
33355 of the original one, that is a convenience for us. Errors in the
33356 output will be easier to spot, running under the debugger will take
33357 less time, and so on.
33359 However, simplification is not vital; if you do not want to do this,
33360 report the bug anyway and send us the entire test case you used.
33363 A patch for the bug.
33365 A patch for the bug does help us if it is a good one. But do not omit
33366 the necessary information, such as the test case, on the assumption that
33367 a patch is all we need. We might see problems with your patch and decide
33368 to fix the problem another way, or we might not understand it at all.
33370 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33371 construct an example that will make the program follow a certain path
33372 through the code. If you do not send us the example, we will not be able
33373 to construct one, so we will not be able to verify that the bug is fixed.
33375 And if we cannot understand what bug you are trying to fix, or why your
33376 patch should be an improvement, we will not install it. A test case will
33377 help us to understand.
33380 A guess about what the bug is or what it depends on.
33382 Such guesses are usually wrong. Even we cannot guess right about such
33383 things without first using the debugger to find the facts.
33386 @c The readline documentation is distributed with the readline code
33387 @c and consists of the two following files:
33390 @c Use -I with makeinfo to point to the appropriate directory,
33391 @c environment var TEXINPUTS with TeX.
33392 @ifclear SYSTEM_READLINE
33393 @include rluser.texi
33394 @include hsuser.texi
33398 @appendix In Memoriam
33400 The @value{GDBN} project mourns the loss of the following long-time
33405 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33406 to Free Software in general. Outside of @value{GDBN}, he was known in
33407 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33409 @item Michael Snyder
33410 Michael was one of the Global Maintainers of the @value{GDBN} project,
33411 with contributions recorded as early as 1996, until 2011. In addition
33412 to his day to day participation, he was a large driving force behind
33413 adding Reverse Debugging to @value{GDBN}.
33416 Beyond their technical contributions to the project, they were also
33417 enjoyable members of the Free Software Community. We will miss them.
33419 @node Formatting Documentation
33420 @appendix Formatting Documentation
33422 @cindex @value{GDBN} reference card
33423 @cindex reference card
33424 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33425 for printing with PostScript or Ghostscript, in the @file{gdb}
33426 subdirectory of the main source directory@footnote{In
33427 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33428 release.}. If you can use PostScript or Ghostscript with your printer,
33429 you can print the reference card immediately with @file{refcard.ps}.
33431 The release also includes the source for the reference card. You
33432 can format it, using @TeX{}, by typing:
33438 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33439 mode on US ``letter'' size paper;
33440 that is, on a sheet 11 inches wide by 8.5 inches
33441 high. You will need to specify this form of printing as an option to
33442 your @sc{dvi} output program.
33444 @cindex documentation
33446 All the documentation for @value{GDBN} comes as part of the machine-readable
33447 distribution. The documentation is written in Texinfo format, which is
33448 a documentation system that uses a single source file to produce both
33449 on-line information and a printed manual. You can use one of the Info
33450 formatting commands to create the on-line version of the documentation
33451 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33453 @value{GDBN} includes an already formatted copy of the on-line Info
33454 version of this manual in the @file{gdb} subdirectory. The main Info
33455 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33456 subordinate files matching @samp{gdb.info*} in the same directory. If
33457 necessary, you can print out these files, or read them with any editor;
33458 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33459 Emacs or the standalone @code{info} program, available as part of the
33460 @sc{gnu} Texinfo distribution.
33462 If you want to format these Info files yourself, you need one of the
33463 Info formatting programs, such as @code{texinfo-format-buffer} or
33466 If you have @code{makeinfo} installed, and are in the top level
33467 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33468 version @value{GDBVN}), you can make the Info file by typing:
33475 If you want to typeset and print copies of this manual, you need @TeX{},
33476 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33477 Texinfo definitions file.
33479 @TeX{} is a typesetting program; it does not print files directly, but
33480 produces output files called @sc{dvi} files. To print a typeset
33481 document, you need a program to print @sc{dvi} files. If your system
33482 has @TeX{} installed, chances are it has such a program. The precise
33483 command to use depends on your system; @kbd{lpr -d} is common; another
33484 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33485 require a file name without any extension or a @samp{.dvi} extension.
33487 @TeX{} also requires a macro definitions file called
33488 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33489 written in Texinfo format. On its own, @TeX{} cannot either read or
33490 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33491 and is located in the @file{gdb-@var{version-number}/texinfo}
33494 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33495 typeset and print this manual. First switch to the @file{gdb}
33496 subdirectory of the main source directory (for example, to
33497 @file{gdb-@value{GDBVN}/gdb}) and type:
33503 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33505 @node Installing GDB
33506 @appendix Installing @value{GDBN}
33507 @cindex installation
33510 * Requirements:: Requirements for building @value{GDBN}
33511 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33512 * Separate Objdir:: Compiling @value{GDBN} in another directory
33513 * Config Names:: Specifying names for hosts and targets
33514 * Configure Options:: Summary of options for configure
33515 * System-wide configuration:: Having a system-wide init file
33519 @section Requirements for Building @value{GDBN}
33520 @cindex building @value{GDBN}, requirements for
33522 Building @value{GDBN} requires various tools and packages to be available.
33523 Other packages will be used only if they are found.
33525 @heading Tools/Packages Necessary for Building @value{GDBN}
33527 @item ISO C90 compiler
33528 @value{GDBN} is written in ISO C90. It should be buildable with any
33529 working C90 compiler, e.g.@: GCC.
33533 @heading Tools/Packages Optional for Building @value{GDBN}
33537 @value{GDBN} can use the Expat XML parsing library. This library may be
33538 included with your operating system distribution; if it is not, you
33539 can get the latest version from @url{http://expat.sourceforge.net}.
33540 The @file{configure} script will search for this library in several
33541 standard locations; if it is installed in an unusual path, you can
33542 use the @option{--with-libexpat-prefix} option to specify its location.
33548 Remote protocol memory maps (@pxref{Memory Map Format})
33550 Target descriptions (@pxref{Target Descriptions})
33552 Remote shared library lists (@xref{Library List Format},
33553 or alternatively @pxref{Library List Format for SVR4 Targets})
33555 MS-Windows shared libraries (@pxref{Shared Libraries})
33557 Traceframe info (@pxref{Traceframe Info Format})
33561 @cindex compressed debug sections
33562 @value{GDBN} will use the @samp{zlib} library, if available, to read
33563 compressed debug sections. Some linkers, such as GNU gold, are capable
33564 of producing binaries with compressed debug sections. If @value{GDBN}
33565 is compiled with @samp{zlib}, it will be able to read the debug
33566 information in such binaries.
33568 The @samp{zlib} library is likely included with your operating system
33569 distribution; if it is not, you can get the latest version from
33570 @url{http://zlib.net}.
33573 @value{GDBN}'s features related to character sets (@pxref{Character
33574 Sets}) require a functioning @code{iconv} implementation. If you are
33575 on a GNU system, then this is provided by the GNU C Library. Some
33576 other systems also provide a working @code{iconv}.
33578 If @value{GDBN} is using the @code{iconv} program which is installed
33579 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33580 This is done with @option{--with-iconv-bin} which specifies the
33581 directory that contains the @code{iconv} program.
33583 On systems without @code{iconv}, you can install GNU Libiconv. If you
33584 have previously installed Libiconv, you can use the
33585 @option{--with-libiconv-prefix} option to configure.
33587 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33588 arrange to build Libiconv if a directory named @file{libiconv} appears
33589 in the top-most source directory. If Libiconv is built this way, and
33590 if the operating system does not provide a suitable @code{iconv}
33591 implementation, then the just-built library will automatically be used
33592 by @value{GDBN}. One easy way to set this up is to download GNU
33593 Libiconv, unpack it, and then rename the directory holding the
33594 Libiconv source code to @samp{libiconv}.
33597 @node Running Configure
33598 @section Invoking the @value{GDBN} @file{configure} Script
33599 @cindex configuring @value{GDBN}
33600 @value{GDBN} comes with a @file{configure} script that automates the process
33601 of preparing @value{GDBN} for installation; you can then use @code{make} to
33602 build the @code{gdb} program.
33604 @c irrelevant in info file; it's as current as the code it lives with.
33605 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33606 look at the @file{README} file in the sources; we may have improved the
33607 installation procedures since publishing this manual.}
33610 The @value{GDBN} distribution includes all the source code you need for
33611 @value{GDBN} in a single directory, whose name is usually composed by
33612 appending the version number to @samp{gdb}.
33614 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33615 @file{gdb-@value{GDBVN}} directory. That directory contains:
33618 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33619 script for configuring @value{GDBN} and all its supporting libraries
33621 @item gdb-@value{GDBVN}/gdb
33622 the source specific to @value{GDBN} itself
33624 @item gdb-@value{GDBVN}/bfd
33625 source for the Binary File Descriptor library
33627 @item gdb-@value{GDBVN}/include
33628 @sc{gnu} include files
33630 @item gdb-@value{GDBVN}/libiberty
33631 source for the @samp{-liberty} free software library
33633 @item gdb-@value{GDBVN}/opcodes
33634 source for the library of opcode tables and disassemblers
33636 @item gdb-@value{GDBVN}/readline
33637 source for the @sc{gnu} command-line interface
33639 @item gdb-@value{GDBVN}/glob
33640 source for the @sc{gnu} filename pattern-matching subroutine
33642 @item gdb-@value{GDBVN}/mmalloc
33643 source for the @sc{gnu} memory-mapped malloc package
33646 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33647 from the @file{gdb-@var{version-number}} source directory, which in
33648 this example is the @file{gdb-@value{GDBVN}} directory.
33650 First switch to the @file{gdb-@var{version-number}} source directory
33651 if you are not already in it; then run @file{configure}. Pass the
33652 identifier for the platform on which @value{GDBN} will run as an
33658 cd gdb-@value{GDBVN}
33659 ./configure @var{host}
33664 where @var{host} is an identifier such as @samp{sun4} or
33665 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33666 (You can often leave off @var{host}; @file{configure} tries to guess the
33667 correct value by examining your system.)
33669 Running @samp{configure @var{host}} and then running @code{make} builds the
33670 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33671 libraries, then @code{gdb} itself. The configured source files, and the
33672 binaries, are left in the corresponding source directories.
33675 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33676 system does not recognize this automatically when you run a different
33677 shell, you may need to run @code{sh} on it explicitly:
33680 sh configure @var{host}
33683 If you run @file{configure} from a directory that contains source
33684 directories for multiple libraries or programs, such as the
33685 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33687 creates configuration files for every directory level underneath (unless
33688 you tell it not to, with the @samp{--norecursion} option).
33690 You should run the @file{configure} script from the top directory in the
33691 source tree, the @file{gdb-@var{version-number}} directory. If you run
33692 @file{configure} from one of the subdirectories, you will configure only
33693 that subdirectory. That is usually not what you want. In particular,
33694 if you run the first @file{configure} from the @file{gdb} subdirectory
33695 of the @file{gdb-@var{version-number}} directory, you will omit the
33696 configuration of @file{bfd}, @file{readline}, and other sibling
33697 directories of the @file{gdb} subdirectory. This leads to build errors
33698 about missing include files such as @file{bfd/bfd.h}.
33700 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33701 However, you should make sure that the shell on your path (named by
33702 the @samp{SHELL} environment variable) is publicly readable. Remember
33703 that @value{GDBN} uses the shell to start your program---some systems refuse to
33704 let @value{GDBN} debug child processes whose programs are not readable.
33706 @node Separate Objdir
33707 @section Compiling @value{GDBN} in Another Directory
33709 If you want to run @value{GDBN} versions for several host or target machines,
33710 you need a different @code{gdb} compiled for each combination of
33711 host and target. @file{configure} is designed to make this easy by
33712 allowing you to generate each configuration in a separate subdirectory,
33713 rather than in the source directory. If your @code{make} program
33714 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33715 @code{make} in each of these directories builds the @code{gdb}
33716 program specified there.
33718 To build @code{gdb} in a separate directory, run @file{configure}
33719 with the @samp{--srcdir} option to specify where to find the source.
33720 (You also need to specify a path to find @file{configure}
33721 itself from your working directory. If the path to @file{configure}
33722 would be the same as the argument to @samp{--srcdir}, you can leave out
33723 the @samp{--srcdir} option; it is assumed.)
33725 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33726 separate directory for a Sun 4 like this:
33730 cd gdb-@value{GDBVN}
33733 ../gdb-@value{GDBVN}/configure sun4
33738 When @file{configure} builds a configuration using a remote source
33739 directory, it creates a tree for the binaries with the same structure
33740 (and using the same names) as the tree under the source directory. In
33741 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33742 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33743 @file{gdb-sun4/gdb}.
33745 Make sure that your path to the @file{configure} script has just one
33746 instance of @file{gdb} in it. If your path to @file{configure} looks
33747 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33748 one subdirectory of @value{GDBN}, not the whole package. This leads to
33749 build errors about missing include files such as @file{bfd/bfd.h}.
33751 One popular reason to build several @value{GDBN} configurations in separate
33752 directories is to configure @value{GDBN} for cross-compiling (where
33753 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33754 programs that run on another machine---the @dfn{target}).
33755 You specify a cross-debugging target by
33756 giving the @samp{--target=@var{target}} option to @file{configure}.
33758 When you run @code{make} to build a program or library, you must run
33759 it in a configured directory---whatever directory you were in when you
33760 called @file{configure} (or one of its subdirectories).
33762 The @code{Makefile} that @file{configure} generates in each source
33763 directory also runs recursively. If you type @code{make} in a source
33764 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33765 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33766 will build all the required libraries, and then build GDB.
33768 When you have multiple hosts or targets configured in separate
33769 directories, you can run @code{make} on them in parallel (for example,
33770 if they are NFS-mounted on each of the hosts); they will not interfere
33774 @section Specifying Names for Hosts and Targets
33776 The specifications used for hosts and targets in the @file{configure}
33777 script are based on a three-part naming scheme, but some short predefined
33778 aliases are also supported. The full naming scheme encodes three pieces
33779 of information in the following pattern:
33782 @var{architecture}-@var{vendor}-@var{os}
33785 For example, you can use the alias @code{sun4} as a @var{host} argument,
33786 or as the value for @var{target} in a @code{--target=@var{target}}
33787 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33789 The @file{configure} script accompanying @value{GDBN} does not provide
33790 any query facility to list all supported host and target names or
33791 aliases. @file{configure} calls the Bourne shell script
33792 @code{config.sub} to map abbreviations to full names; you can read the
33793 script, if you wish, or you can use it to test your guesses on
33794 abbreviations---for example:
33797 % sh config.sub i386-linux
33799 % sh config.sub alpha-linux
33800 alpha-unknown-linux-gnu
33801 % sh config.sub hp9k700
33803 % sh config.sub sun4
33804 sparc-sun-sunos4.1.1
33805 % sh config.sub sun3
33806 m68k-sun-sunos4.1.1
33807 % sh config.sub i986v
33808 Invalid configuration `i986v': machine `i986v' not recognized
33812 @code{config.sub} is also distributed in the @value{GDBN} source
33813 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33815 @node Configure Options
33816 @section @file{configure} Options
33818 Here is a summary of the @file{configure} options and arguments that
33819 are most often useful for building @value{GDBN}. @file{configure} also has
33820 several other options not listed here. @inforef{What Configure
33821 Does,,configure.info}, for a full explanation of @file{configure}.
33824 configure @r{[}--help@r{]}
33825 @r{[}--prefix=@var{dir}@r{]}
33826 @r{[}--exec-prefix=@var{dir}@r{]}
33827 @r{[}--srcdir=@var{dirname}@r{]}
33828 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33829 @r{[}--target=@var{target}@r{]}
33834 You may introduce options with a single @samp{-} rather than
33835 @samp{--} if you prefer; but you may abbreviate option names if you use
33840 Display a quick summary of how to invoke @file{configure}.
33842 @item --prefix=@var{dir}
33843 Configure the source to install programs and files under directory
33846 @item --exec-prefix=@var{dir}
33847 Configure the source to install programs under directory
33850 @c avoid splitting the warning from the explanation:
33852 @item --srcdir=@var{dirname}
33853 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33854 @code{make} that implements the @code{VPATH} feature.}@*
33855 Use this option to make configurations in directories separate from the
33856 @value{GDBN} source directories. Among other things, you can use this to
33857 build (or maintain) several configurations simultaneously, in separate
33858 directories. @file{configure} writes configuration-specific files in
33859 the current directory, but arranges for them to use the source in the
33860 directory @var{dirname}. @file{configure} creates directories under
33861 the working directory in parallel to the source directories below
33864 @item --norecursion
33865 Configure only the directory level where @file{configure} is executed; do not
33866 propagate configuration to subdirectories.
33868 @item --target=@var{target}
33869 Configure @value{GDBN} for cross-debugging programs running on the specified
33870 @var{target}. Without this option, @value{GDBN} is configured to debug
33871 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33873 There is no convenient way to generate a list of all available targets.
33875 @item @var{host} @dots{}
33876 Configure @value{GDBN} to run on the specified @var{host}.
33878 There is no convenient way to generate a list of all available hosts.
33881 There are many other options available as well, but they are generally
33882 needed for special purposes only.
33884 @node System-wide configuration
33885 @section System-wide configuration and settings
33886 @cindex system-wide init file
33888 @value{GDBN} can be configured to have a system-wide init file;
33889 this file will be read and executed at startup (@pxref{Startup, , What
33890 @value{GDBN} does during startup}).
33892 Here is the corresponding configure option:
33895 @item --with-system-gdbinit=@var{file}
33896 Specify that the default location of the system-wide init file is
33900 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33901 it may be subject to relocation. Two possible cases:
33905 If the default location of this init file contains @file{$prefix},
33906 it will be subject to relocation. Suppose that the configure options
33907 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33908 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33909 init file is looked for as @file{$install/etc/gdbinit} instead of
33910 @file{$prefix/etc/gdbinit}.
33913 By contrast, if the default location does not contain the prefix,
33914 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33915 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33916 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33917 wherever @value{GDBN} is installed.
33920 @node Maintenance Commands
33921 @appendix Maintenance Commands
33922 @cindex maintenance commands
33923 @cindex internal commands
33925 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33926 includes a number of commands intended for @value{GDBN} developers,
33927 that are not documented elsewhere in this manual. These commands are
33928 provided here for reference. (For commands that turn on debugging
33929 messages, see @ref{Debugging Output}.)
33932 @kindex maint agent
33933 @kindex maint agent-eval
33934 @item maint agent @var{expression}
33935 @itemx maint agent-eval @var{expression}
33936 Translate the given @var{expression} into remote agent bytecodes.
33937 This command is useful for debugging the Agent Expression mechanism
33938 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33939 expression useful for data collection, such as by tracepoints, while
33940 @samp{maint agent-eval} produces an expression that evaluates directly
33941 to a result. For instance, a collection expression for @code{globa +
33942 globb} will include bytecodes to record four bytes of memory at each
33943 of the addresses of @code{globa} and @code{globb}, while discarding
33944 the result of the addition, while an evaluation expression will do the
33945 addition and return the sum.
33947 @kindex maint info breakpoints
33948 @item @anchor{maint info breakpoints}maint info breakpoints
33949 Using the same format as @samp{info breakpoints}, display both the
33950 breakpoints you've set explicitly, and those @value{GDBN} is using for
33951 internal purposes. Internal breakpoints are shown with negative
33952 breakpoint numbers. The type column identifies what kind of breakpoint
33957 Normal, explicitly set breakpoint.
33960 Normal, explicitly set watchpoint.
33963 Internal breakpoint, used to handle correctly stepping through
33964 @code{longjmp} calls.
33966 @item longjmp resume
33967 Internal breakpoint at the target of a @code{longjmp}.
33970 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33973 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33976 Shared library events.
33980 @kindex set displaced-stepping
33981 @kindex show displaced-stepping
33982 @cindex displaced stepping support
33983 @cindex out-of-line single-stepping
33984 @item set displaced-stepping
33985 @itemx show displaced-stepping
33986 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33987 if the target supports it. Displaced stepping is a way to single-step
33988 over breakpoints without removing them from the inferior, by executing
33989 an out-of-line copy of the instruction that was originally at the
33990 breakpoint location. It is also known as out-of-line single-stepping.
33993 @item set displaced-stepping on
33994 If the target architecture supports it, @value{GDBN} will use
33995 displaced stepping to step over breakpoints.
33997 @item set displaced-stepping off
33998 @value{GDBN} will not use displaced stepping to step over breakpoints,
33999 even if such is supported by the target architecture.
34001 @cindex non-stop mode, and @samp{set displaced-stepping}
34002 @item set displaced-stepping auto
34003 This is the default mode. @value{GDBN} will use displaced stepping
34004 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34005 architecture supports displaced stepping.
34008 @kindex maint check-symtabs
34009 @item maint check-symtabs
34010 Check the consistency of psymtabs and symtabs.
34012 @kindex maint cplus first_component
34013 @item maint cplus first_component @var{name}
34014 Print the first C@t{++} class/namespace component of @var{name}.
34016 @kindex maint cplus namespace
34017 @item maint cplus namespace
34018 Print the list of possible C@t{++} namespaces.
34020 @kindex maint demangle
34021 @item maint demangle @var{name}
34022 Demangle a C@t{++} or Objective-C mangled @var{name}.
34024 @kindex maint deprecate
34025 @kindex maint undeprecate
34026 @cindex deprecated commands
34027 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34028 @itemx maint undeprecate @var{command}
34029 Deprecate or undeprecate the named @var{command}. Deprecated commands
34030 cause @value{GDBN} to issue a warning when you use them. The optional
34031 argument @var{replacement} says which newer command should be used in
34032 favor of the deprecated one; if it is given, @value{GDBN} will mention
34033 the replacement as part of the warning.
34035 @kindex maint dump-me
34036 @item maint dump-me
34037 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34038 Cause a fatal signal in the debugger and force it to dump its core.
34039 This is supported only on systems which support aborting a program
34040 with the @code{SIGQUIT} signal.
34042 @kindex maint internal-error
34043 @kindex maint internal-warning
34044 @item maint internal-error @r{[}@var{message-text}@r{]}
34045 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34046 Cause @value{GDBN} to call the internal function @code{internal_error}
34047 or @code{internal_warning} and hence behave as though an internal error
34048 or internal warning has been detected. In addition to reporting the
34049 internal problem, these functions give the user the opportunity to
34050 either quit @value{GDBN} or create a core file of the current
34051 @value{GDBN} session.
34053 These commands take an optional parameter @var{message-text} that is
34054 used as the text of the error or warning message.
34056 Here's an example of using @code{internal-error}:
34059 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34060 @dots{}/maint.c:121: internal-error: testing, 1, 2
34061 A problem internal to GDB has been detected. Further
34062 debugging may prove unreliable.
34063 Quit this debugging session? (y or n) @kbd{n}
34064 Create a core file? (y or n) @kbd{n}
34068 @cindex @value{GDBN} internal error
34069 @cindex internal errors, control of @value{GDBN} behavior
34071 @kindex maint set internal-error
34072 @kindex maint show internal-error
34073 @kindex maint set internal-warning
34074 @kindex maint show internal-warning
34075 @item maint set internal-error @var{action} [ask|yes|no]
34076 @itemx maint show internal-error @var{action}
34077 @itemx maint set internal-warning @var{action} [ask|yes|no]
34078 @itemx maint show internal-warning @var{action}
34079 When @value{GDBN} reports an internal problem (error or warning) it
34080 gives the user the opportunity to both quit @value{GDBN} and create a
34081 core file of the current @value{GDBN} session. These commands let you
34082 override the default behaviour for each particular @var{action},
34083 described in the table below.
34087 You can specify that @value{GDBN} should always (yes) or never (no)
34088 quit. The default is to ask the user what to do.
34091 You can specify that @value{GDBN} should always (yes) or never (no)
34092 create a core file. The default is to ask the user what to do.
34095 @kindex maint packet
34096 @item maint packet @var{text}
34097 If @value{GDBN} is talking to an inferior via the serial protocol,
34098 then this command sends the string @var{text} to the inferior, and
34099 displays the response packet. @value{GDBN} supplies the initial
34100 @samp{$} character, the terminating @samp{#} character, and the
34103 @kindex maint print architecture
34104 @item maint print architecture @r{[}@var{file}@r{]}
34105 Print the entire architecture configuration. The optional argument
34106 @var{file} names the file where the output goes.
34108 @kindex maint print c-tdesc
34109 @item maint print c-tdesc
34110 Print the current target description (@pxref{Target Descriptions}) as
34111 a C source file. The created source file can be used in @value{GDBN}
34112 when an XML parser is not available to parse the description.
34114 @kindex maint print dummy-frames
34115 @item maint print dummy-frames
34116 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34119 (@value{GDBP}) @kbd{b add}
34121 (@value{GDBP}) @kbd{print add(2,3)}
34122 Breakpoint 2, add (a=2, b=3) at @dots{}
34124 The program being debugged stopped while in a function called from GDB.
34126 (@value{GDBP}) @kbd{maint print dummy-frames}
34127 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
34128 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
34129 call_lo=0x01014000 call_hi=0x01014001
34133 Takes an optional file parameter.
34135 @kindex maint print registers
34136 @kindex maint print raw-registers
34137 @kindex maint print cooked-registers
34138 @kindex maint print register-groups
34139 @kindex maint print remote-registers
34140 @item maint print registers @r{[}@var{file}@r{]}
34141 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34142 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34143 @itemx maint print register-groups @r{[}@var{file}@r{]}
34144 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34145 Print @value{GDBN}'s internal register data structures.
34147 The command @code{maint print raw-registers} includes the contents of
34148 the raw register cache; the command @code{maint print
34149 cooked-registers} includes the (cooked) value of all registers,
34150 including registers which aren't available on the target nor visible
34151 to user; the command @code{maint print register-groups} includes the
34152 groups that each register is a member of; and the command @code{maint
34153 print remote-registers} includes the remote target's register numbers
34154 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
34155 @value{GDBN} Internals}.
34157 These commands take an optional parameter, a file name to which to
34158 write the information.
34160 @kindex maint print reggroups
34161 @item maint print reggroups @r{[}@var{file}@r{]}
34162 Print @value{GDBN}'s internal register group data structures. The
34163 optional argument @var{file} tells to what file to write the
34166 The register groups info looks like this:
34169 (@value{GDBP}) @kbd{maint print reggroups}
34182 This command forces @value{GDBN} to flush its internal register cache.
34184 @kindex maint print objfiles
34185 @cindex info for known object files
34186 @item maint print objfiles
34187 Print a dump of all known object files. For each object file, this
34188 command prints its name, address in memory, and all of its psymtabs
34191 @kindex maint print section-scripts
34192 @cindex info for known .debug_gdb_scripts-loaded scripts
34193 @item maint print section-scripts [@var{regexp}]
34194 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34195 If @var{regexp} is specified, only print scripts loaded by object files
34196 matching @var{regexp}.
34197 For each script, this command prints its name as specified in the objfile,
34198 and the full path if known.
34199 @xref{dotdebug_gdb_scripts section}.
34201 @kindex maint print statistics
34202 @cindex bcache statistics
34203 @item maint print statistics
34204 This command prints, for each object file in the program, various data
34205 about that object file followed by the byte cache (@dfn{bcache})
34206 statistics for the object file. The objfile data includes the number
34207 of minimal, partial, full, and stabs symbols, the number of types
34208 defined by the objfile, the number of as yet unexpanded psym tables,
34209 the number of line tables and string tables, and the amount of memory
34210 used by the various tables. The bcache statistics include the counts,
34211 sizes, and counts of duplicates of all and unique objects, max,
34212 average, and median entry size, total memory used and its overhead and
34213 savings, and various measures of the hash table size and chain
34216 @kindex maint print target-stack
34217 @cindex target stack description
34218 @item maint print target-stack
34219 A @dfn{target} is an interface between the debugger and a particular
34220 kind of file or process. Targets can be stacked in @dfn{strata},
34221 so that more than one target can potentially respond to a request.
34222 In particular, memory accesses will walk down the stack of targets
34223 until they find a target that is interested in handling that particular
34226 This command prints a short description of each layer that was pushed on
34227 the @dfn{target stack}, starting from the top layer down to the bottom one.
34229 @kindex maint print type
34230 @cindex type chain of a data type
34231 @item maint print type @var{expr}
34232 Print the type chain for a type specified by @var{expr}. The argument
34233 can be either a type name or a symbol. If it is a symbol, the type of
34234 that symbol is described. The type chain produced by this command is
34235 a recursive definition of the data type as stored in @value{GDBN}'s
34236 data structures, including its flags and contained types.
34238 @kindex maint set dwarf2 always-disassemble
34239 @kindex maint show dwarf2 always-disassemble
34240 @item maint set dwarf2 always-disassemble
34241 @item maint show dwarf2 always-disassemble
34242 Control the behavior of @code{info address} when using DWARF debugging
34245 The default is @code{off}, which means that @value{GDBN} should try to
34246 describe a variable's location in an easily readable format. When
34247 @code{on}, @value{GDBN} will instead display the DWARF location
34248 expression in an assembly-like format. Note that some locations are
34249 too complex for @value{GDBN} to describe simply; in this case you will
34250 always see the disassembly form.
34252 Here is an example of the resulting disassembly:
34255 (gdb) info addr argc
34256 Symbol "argc" is a complex DWARF expression:
34260 For more information on these expressions, see
34261 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34263 @kindex maint set dwarf2 max-cache-age
34264 @kindex maint show dwarf2 max-cache-age
34265 @item maint set dwarf2 max-cache-age
34266 @itemx maint show dwarf2 max-cache-age
34267 Control the DWARF 2 compilation unit cache.
34269 @cindex DWARF 2 compilation units cache
34270 In object files with inter-compilation-unit references, such as those
34271 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34272 reader needs to frequently refer to previously read compilation units.
34273 This setting controls how long a compilation unit will remain in the
34274 cache if it is not referenced. A higher limit means that cached
34275 compilation units will be stored in memory longer, and more total
34276 memory will be used. Setting it to zero disables caching, which will
34277 slow down @value{GDBN} startup, but reduce memory consumption.
34279 @kindex maint set profile
34280 @kindex maint show profile
34281 @cindex profiling GDB
34282 @item maint set profile
34283 @itemx maint show profile
34284 Control profiling of @value{GDBN}.
34286 Profiling will be disabled until you use the @samp{maint set profile}
34287 command to enable it. When you enable profiling, the system will begin
34288 collecting timing and execution count data; when you disable profiling or
34289 exit @value{GDBN}, the results will be written to a log file. Remember that
34290 if you use profiling, @value{GDBN} will overwrite the profiling log file
34291 (often called @file{gmon.out}). If you have a record of important profiling
34292 data in a @file{gmon.out} file, be sure to move it to a safe location.
34294 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34295 compiled with the @samp{-pg} compiler option.
34297 @kindex maint set show-debug-regs
34298 @kindex maint show show-debug-regs
34299 @cindex hardware debug registers
34300 @item maint set show-debug-regs
34301 @itemx maint show show-debug-regs
34302 Control whether to show variables that mirror the hardware debug
34303 registers. Use @code{ON} to enable, @code{OFF} to disable. If
34304 enabled, the debug registers values are shown when @value{GDBN} inserts or
34305 removes a hardware breakpoint or watchpoint, and when the inferior
34306 triggers a hardware-assisted breakpoint or watchpoint.
34308 @kindex maint set show-all-tib
34309 @kindex maint show show-all-tib
34310 @item maint set show-all-tib
34311 @itemx maint show show-all-tib
34312 Control whether to show all non zero areas within a 1k block starting
34313 at thread local base, when using the @samp{info w32 thread-information-block}
34316 @kindex maint space
34317 @cindex memory used by commands
34319 Control whether to display memory usage for each command. If set to a
34320 nonzero value, @value{GDBN} will display how much memory each command
34321 took, following the command's own output. This can also be requested
34322 by invoking @value{GDBN} with the @option{--statistics} command-line
34323 switch (@pxref{Mode Options}).
34326 @cindex time of command execution
34328 Control whether to display the execution time of @value{GDBN} for each command.
34329 If set to a nonzero value, @value{GDBN} will display how much time it
34330 took to execute each command, following the command's own output.
34331 Both CPU time and wallclock time are printed.
34332 Printing both is useful when trying to determine whether the cost is
34333 CPU or, e.g., disk/network, latency.
34334 Note that the CPU time printed is for @value{GDBN} only, it does not include
34335 the execution time of the inferior because there's no mechanism currently
34336 to compute how much time was spent by @value{GDBN} and how much time was
34337 spent by the program been debugged.
34338 This can also be requested by invoking @value{GDBN} with the
34339 @option{--statistics} command-line switch (@pxref{Mode Options}).
34341 @kindex maint translate-address
34342 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34343 Find the symbol stored at the location specified by the address
34344 @var{addr} and an optional section name @var{section}. If found,
34345 @value{GDBN} prints the name of the closest symbol and an offset from
34346 the symbol's location to the specified address. This is similar to
34347 the @code{info address} command (@pxref{Symbols}), except that this
34348 command also allows to find symbols in other sections.
34350 If section was not specified, the section in which the symbol was found
34351 is also printed. For dynamically linked executables, the name of
34352 executable or shared library containing the symbol is printed as well.
34356 The following command is useful for non-interactive invocations of
34357 @value{GDBN}, such as in the test suite.
34360 @item set watchdog @var{nsec}
34361 @kindex set watchdog
34362 @cindex watchdog timer
34363 @cindex timeout for commands
34364 Set the maximum number of seconds @value{GDBN} will wait for the
34365 target operation to finish. If this time expires, @value{GDBN}
34366 reports and error and the command is aborted.
34368 @item show watchdog
34369 Show the current setting of the target wait timeout.
34372 @node Remote Protocol
34373 @appendix @value{GDBN} Remote Serial Protocol
34378 * Stop Reply Packets::
34379 * General Query Packets::
34380 * Architecture-Specific Protocol Details::
34381 * Tracepoint Packets::
34382 * Host I/O Packets::
34384 * Notification Packets::
34385 * Remote Non-Stop::
34386 * Packet Acknowledgment::
34388 * File-I/O Remote Protocol Extension::
34389 * Library List Format::
34390 * Library List Format for SVR4 Targets::
34391 * Memory Map Format::
34392 * Thread List Format::
34393 * Traceframe Info Format::
34399 There may be occasions when you need to know something about the
34400 protocol---for example, if there is only one serial port to your target
34401 machine, you might want your program to do something special if it
34402 recognizes a packet meant for @value{GDBN}.
34404 In the examples below, @samp{->} and @samp{<-} are used to indicate
34405 transmitted and received data, respectively.
34407 @cindex protocol, @value{GDBN} remote serial
34408 @cindex serial protocol, @value{GDBN} remote
34409 @cindex remote serial protocol
34410 All @value{GDBN} commands and responses (other than acknowledgments
34411 and notifications, see @ref{Notification Packets}) are sent as a
34412 @var{packet}. A @var{packet} is introduced with the character
34413 @samp{$}, the actual @var{packet-data}, and the terminating character
34414 @samp{#} followed by a two-digit @var{checksum}:
34417 @code{$}@var{packet-data}@code{#}@var{checksum}
34421 @cindex checksum, for @value{GDBN} remote
34423 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34424 characters between the leading @samp{$} and the trailing @samp{#} (an
34425 eight bit unsigned checksum).
34427 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34428 specification also included an optional two-digit @var{sequence-id}:
34431 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34434 @cindex sequence-id, for @value{GDBN} remote
34436 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34437 has never output @var{sequence-id}s. Stubs that handle packets added
34438 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34440 When either the host or the target machine receives a packet, the first
34441 response expected is an acknowledgment: either @samp{+} (to indicate
34442 the package was received correctly) or @samp{-} (to request
34446 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34451 The @samp{+}/@samp{-} acknowledgments can be disabled
34452 once a connection is established.
34453 @xref{Packet Acknowledgment}, for details.
34455 The host (@value{GDBN}) sends @var{command}s, and the target (the
34456 debugging stub incorporated in your program) sends a @var{response}. In
34457 the case of step and continue @var{command}s, the response is only sent
34458 when the operation has completed, and the target has again stopped all
34459 threads in all attached processes. This is the default all-stop mode
34460 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34461 execution mode; see @ref{Remote Non-Stop}, for details.
34463 @var{packet-data} consists of a sequence of characters with the
34464 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34467 @cindex remote protocol, field separator
34468 Fields within the packet should be separated using @samp{,} @samp{;} or
34469 @samp{:}. Except where otherwise noted all numbers are represented in
34470 @sc{hex} with leading zeros suppressed.
34472 Implementors should note that prior to @value{GDBN} 5.0, the character
34473 @samp{:} could not appear as the third character in a packet (as it
34474 would potentially conflict with the @var{sequence-id}).
34476 @cindex remote protocol, binary data
34477 @anchor{Binary Data}
34478 Binary data in most packets is encoded either as two hexadecimal
34479 digits per byte of binary data. This allowed the traditional remote
34480 protocol to work over connections which were only seven-bit clean.
34481 Some packets designed more recently assume an eight-bit clean
34482 connection, and use a more efficient encoding to send and receive
34485 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34486 as an escape character. Any escaped byte is transmitted as the escape
34487 character followed by the original character XORed with @code{0x20}.
34488 For example, the byte @code{0x7d} would be transmitted as the two
34489 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34490 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34491 @samp{@}}) must always be escaped. Responses sent by the stub
34492 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34493 is not interpreted as the start of a run-length encoded sequence
34496 Response @var{data} can be run-length encoded to save space.
34497 Run-length encoding replaces runs of identical characters with one
34498 instance of the repeated character, followed by a @samp{*} and a
34499 repeat count. The repeat count is itself sent encoded, to avoid
34500 binary characters in @var{data}: a value of @var{n} is sent as
34501 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34502 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34503 code 32) for a repeat count of 3. (This is because run-length
34504 encoding starts to win for counts 3 or more.) Thus, for example,
34505 @samp{0* } is a run-length encoding of ``0000'': the space character
34506 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34509 The printable characters @samp{#} and @samp{$} or with a numeric value
34510 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34511 seven repeats (@samp{$}) can be expanded using a repeat count of only
34512 five (@samp{"}). For example, @samp{00000000} can be encoded as
34515 The error response returned for some packets includes a two character
34516 error number. That number is not well defined.
34518 @cindex empty response, for unsupported packets
34519 For any @var{command} not supported by the stub, an empty response
34520 (@samp{$#00}) should be returned. That way it is possible to extend the
34521 protocol. A newer @value{GDBN} can tell if a packet is supported based
34524 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34525 commands for register access, and the @samp{m} and @samp{M} commands
34526 for memory access. Stubs that only control single-threaded targets
34527 can implement run control with the @samp{c} (continue), and @samp{s}
34528 (step) commands. Stubs that support multi-threading targets should
34529 support the @samp{vCont} command. All other commands are optional.
34534 The following table provides a complete list of all currently defined
34535 @var{command}s and their corresponding response @var{data}.
34536 @xref{File-I/O Remote Protocol Extension}, for details about the File
34537 I/O extension of the remote protocol.
34539 Each packet's description has a template showing the packet's overall
34540 syntax, followed by an explanation of the packet's meaning. We
34541 include spaces in some of the templates for clarity; these are not
34542 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34543 separate its components. For example, a template like @samp{foo
34544 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34545 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34546 @var{baz}. @value{GDBN} does not transmit a space character between the
34547 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34550 @cindex @var{thread-id}, in remote protocol
34551 @anchor{thread-id syntax}
34552 Several packets and replies include a @var{thread-id} field to identify
34553 a thread. Normally these are positive numbers with a target-specific
34554 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34555 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34558 In addition, the remote protocol supports a multiprocess feature in
34559 which the @var{thread-id} syntax is extended to optionally include both
34560 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34561 The @var{pid} (process) and @var{tid} (thread) components each have the
34562 format described above: a positive number with target-specific
34563 interpretation formatted as a big-endian hex string, literal @samp{-1}
34564 to indicate all processes or threads (respectively), or @samp{0} to
34565 indicate an arbitrary process or thread. Specifying just a process, as
34566 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34567 error to specify all processes but a specific thread, such as
34568 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34569 for those packets and replies explicitly documented to include a process
34570 ID, rather than a @var{thread-id}.
34572 The multiprocess @var{thread-id} syntax extensions are only used if both
34573 @value{GDBN} and the stub report support for the @samp{multiprocess}
34574 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34577 Note that all packet forms beginning with an upper- or lower-case
34578 letter, other than those described here, are reserved for future use.
34580 Here are the packet descriptions.
34585 @cindex @samp{!} packet
34586 @anchor{extended mode}
34587 Enable extended mode. In extended mode, the remote server is made
34588 persistent. The @samp{R} packet is used to restart the program being
34594 The remote target both supports and has enabled extended mode.
34598 @cindex @samp{?} packet
34599 Indicate the reason the target halted. The reply is the same as for
34600 step and continue. This packet has a special interpretation when the
34601 target is in non-stop mode; see @ref{Remote Non-Stop}.
34604 @xref{Stop Reply Packets}, for the reply specifications.
34606 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34607 @cindex @samp{A} packet
34608 Initialized @code{argv[]} array passed into program. @var{arglen}
34609 specifies the number of bytes in the hex encoded byte stream
34610 @var{arg}. See @code{gdbserver} for more details.
34615 The arguments were set.
34621 @cindex @samp{b} packet
34622 (Don't use this packet; its behavior is not well-defined.)
34623 Change the serial line speed to @var{baud}.
34625 JTC: @emph{When does the transport layer state change? When it's
34626 received, or after the ACK is transmitted. In either case, there are
34627 problems if the command or the acknowledgment packet is dropped.}
34629 Stan: @emph{If people really wanted to add something like this, and get
34630 it working for the first time, they ought to modify ser-unix.c to send
34631 some kind of out-of-band message to a specially-setup stub and have the
34632 switch happen "in between" packets, so that from remote protocol's point
34633 of view, nothing actually happened.}
34635 @item B @var{addr},@var{mode}
34636 @cindex @samp{B} packet
34637 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34638 breakpoint at @var{addr}.
34640 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34641 (@pxref{insert breakpoint or watchpoint packet}).
34643 @cindex @samp{bc} packet
34646 Backward continue. Execute the target system in reverse. No parameter.
34647 @xref{Reverse Execution}, for more information.
34650 @xref{Stop Reply Packets}, for the reply specifications.
34652 @cindex @samp{bs} packet
34655 Backward single step. Execute one instruction in reverse. No parameter.
34656 @xref{Reverse Execution}, for more information.
34659 @xref{Stop Reply Packets}, for the reply specifications.
34661 @item c @r{[}@var{addr}@r{]}
34662 @cindex @samp{c} packet
34663 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
34664 resume at current address.
34666 This packet is deprecated for multi-threading support. @xref{vCont
34670 @xref{Stop Reply Packets}, for the reply specifications.
34672 @item C @var{sig}@r{[};@var{addr}@r{]}
34673 @cindex @samp{C} packet
34674 Continue with signal @var{sig} (hex signal number). If
34675 @samp{;@var{addr}} is omitted, resume at same address.
34677 This packet is deprecated for multi-threading support. @xref{vCont
34681 @xref{Stop Reply Packets}, for the reply specifications.
34684 @cindex @samp{d} packet
34687 Don't use this packet; instead, define a general set packet
34688 (@pxref{General Query Packets}).
34692 @cindex @samp{D} packet
34693 The first form of the packet is used to detach @value{GDBN} from the
34694 remote system. It is sent to the remote target
34695 before @value{GDBN} disconnects via the @code{detach} command.
34697 The second form, including a process ID, is used when multiprocess
34698 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34699 detach only a specific process. The @var{pid} is specified as a
34700 big-endian hex string.
34710 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34711 @cindex @samp{F} packet
34712 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34713 This is part of the File-I/O protocol extension. @xref{File-I/O
34714 Remote Protocol Extension}, for the specification.
34717 @anchor{read registers packet}
34718 @cindex @samp{g} packet
34719 Read general registers.
34723 @item @var{XX@dots{}}
34724 Each byte of register data is described by two hex digits. The bytes
34725 with the register are transmitted in target byte order. The size of
34726 each register and their position within the @samp{g} packet are
34727 determined by the @value{GDBN} internal gdbarch functions
34728 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34729 specification of several standard @samp{g} packets is specified below.
34731 When reading registers from a trace frame (@pxref{Analyze Collected
34732 Data,,Using the Collected Data}), the stub may also return a string of
34733 literal @samp{x}'s in place of the register data digits, to indicate
34734 that the corresponding register has not been collected, thus its value
34735 is unavailable. For example, for an architecture with 4 registers of
34736 4 bytes each, the following reply indicates to @value{GDBN} that
34737 registers 0 and 2 have not been collected, while registers 1 and 3
34738 have been collected, and both have zero value:
34742 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34749 @item G @var{XX@dots{}}
34750 @cindex @samp{G} packet
34751 Write general registers. @xref{read registers packet}, for a
34752 description of the @var{XX@dots{}} data.
34762 @item H @var{op} @var{thread-id}
34763 @cindex @samp{H} packet
34764 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34765 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
34766 it should be @samp{c} for step and continue operations (note that this
34767 is deprecated, supporting the @samp{vCont} command is a better
34768 option), @samp{g} for other operations. The thread designator
34769 @var{thread-id} has the format and interpretation described in
34770 @ref{thread-id syntax}.
34781 @c 'H': How restrictive (or permissive) is the thread model. If a
34782 @c thread is selected and stopped, are other threads allowed
34783 @c to continue to execute? As I mentioned above, I think the
34784 @c semantics of each command when a thread is selected must be
34785 @c described. For example:
34787 @c 'g': If the stub supports threads and a specific thread is
34788 @c selected, returns the register block from that thread;
34789 @c otherwise returns current registers.
34791 @c 'G' If the stub supports threads and a specific thread is
34792 @c selected, sets the registers of the register block of
34793 @c that thread; otherwise sets current registers.
34795 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34796 @anchor{cycle step packet}
34797 @cindex @samp{i} packet
34798 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34799 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34800 step starting at that address.
34803 @cindex @samp{I} packet
34804 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34808 @cindex @samp{k} packet
34811 FIXME: @emph{There is no description of how to operate when a specific
34812 thread context has been selected (i.e.@: does 'k' kill only that
34815 @item m @var{addr},@var{length}
34816 @cindex @samp{m} packet
34817 Read @var{length} bytes of memory starting at address @var{addr}.
34818 Note that @var{addr} may not be aligned to any particular boundary.
34820 The stub need not use any particular size or alignment when gathering
34821 data from memory for the response; even if @var{addr} is word-aligned
34822 and @var{length} is a multiple of the word size, the stub is free to
34823 use byte accesses, or not. For this reason, this packet may not be
34824 suitable for accessing memory-mapped I/O devices.
34825 @cindex alignment of remote memory accesses
34826 @cindex size of remote memory accesses
34827 @cindex memory, alignment and size of remote accesses
34831 @item @var{XX@dots{}}
34832 Memory contents; each byte is transmitted as a two-digit hexadecimal
34833 number. The reply may contain fewer bytes than requested if the
34834 server was able to read only part of the region of memory.
34839 @item M @var{addr},@var{length}:@var{XX@dots{}}
34840 @cindex @samp{M} packet
34841 Write @var{length} bytes of memory starting at address @var{addr}.
34842 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
34843 hexadecimal number.
34850 for an error (this includes the case where only part of the data was
34855 @cindex @samp{p} packet
34856 Read the value of register @var{n}; @var{n} is in hex.
34857 @xref{read registers packet}, for a description of how the returned
34858 register value is encoded.
34862 @item @var{XX@dots{}}
34863 the register's value
34867 Indicating an unrecognized @var{query}.
34870 @item P @var{n@dots{}}=@var{r@dots{}}
34871 @anchor{write register packet}
34872 @cindex @samp{P} packet
34873 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34874 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34875 digits for each byte in the register (target byte order).
34885 @item q @var{name} @var{params}@dots{}
34886 @itemx Q @var{name} @var{params}@dots{}
34887 @cindex @samp{q} packet
34888 @cindex @samp{Q} packet
34889 General query (@samp{q}) and set (@samp{Q}). These packets are
34890 described fully in @ref{General Query Packets}.
34893 @cindex @samp{r} packet
34894 Reset the entire system.
34896 Don't use this packet; use the @samp{R} packet instead.
34899 @cindex @samp{R} packet
34900 Restart the program being debugged. @var{XX}, while needed, is ignored.
34901 This packet is only available in extended mode (@pxref{extended mode}).
34903 The @samp{R} packet has no reply.
34905 @item s @r{[}@var{addr}@r{]}
34906 @cindex @samp{s} packet
34907 Single step. @var{addr} is the address at which to resume. If
34908 @var{addr} is omitted, resume at same address.
34910 This packet is deprecated for multi-threading support. @xref{vCont
34914 @xref{Stop Reply Packets}, for the reply specifications.
34916 @item S @var{sig}@r{[};@var{addr}@r{]}
34917 @anchor{step with signal packet}
34918 @cindex @samp{S} packet
34919 Step with signal. This is analogous to the @samp{C} packet, but
34920 requests a single-step, rather than a normal resumption of execution.
34922 This packet is deprecated for multi-threading support. @xref{vCont
34926 @xref{Stop Reply Packets}, for the reply specifications.
34928 @item t @var{addr}:@var{PP},@var{MM}
34929 @cindex @samp{t} packet
34930 Search backwards starting at address @var{addr} for a match with pattern
34931 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
34932 @var{addr} must be at least 3 digits.
34934 @item T @var{thread-id}
34935 @cindex @samp{T} packet
34936 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34941 thread is still alive
34947 Packets starting with @samp{v} are identified by a multi-letter name,
34948 up to the first @samp{;} or @samp{?} (or the end of the packet).
34950 @item vAttach;@var{pid}
34951 @cindex @samp{vAttach} packet
34952 Attach to a new process with the specified process ID @var{pid}.
34953 The process ID is a
34954 hexadecimal integer identifying the process. In all-stop mode, all
34955 threads in the attached process are stopped; in non-stop mode, it may be
34956 attached without being stopped if that is supported by the target.
34958 @c In non-stop mode, on a successful vAttach, the stub should set the
34959 @c current thread to a thread of the newly-attached process. After
34960 @c attaching, GDB queries for the attached process's thread ID with qC.
34961 @c Also note that, from a user perspective, whether or not the
34962 @c target is stopped on attach in non-stop mode depends on whether you
34963 @c use the foreground or background version of the attach command, not
34964 @c on what vAttach does; GDB does the right thing with respect to either
34965 @c stopping or restarting threads.
34967 This packet is only available in extended mode (@pxref{extended mode}).
34973 @item @r{Any stop packet}
34974 for success in all-stop mode (@pxref{Stop Reply Packets})
34976 for success in non-stop mode (@pxref{Remote Non-Stop})
34979 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34980 @cindex @samp{vCont} packet
34981 @anchor{vCont packet}
34982 Resume the inferior, specifying different actions for each thread.
34983 If an action is specified with no @var{thread-id}, then it is applied to any
34984 threads that don't have a specific action specified; if no default action is
34985 specified then other threads should remain stopped in all-stop mode and
34986 in their current state in non-stop mode.
34987 Specifying multiple
34988 default actions is an error; specifying no actions is also an error.
34989 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34991 Currently supported actions are:
34997 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35001 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35006 The optional argument @var{addr} normally associated with the
35007 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35008 not supported in @samp{vCont}.
35010 The @samp{t} action is only relevant in non-stop mode
35011 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35012 A stop reply should be generated for any affected thread not already stopped.
35013 When a thread is stopped by means of a @samp{t} action,
35014 the corresponding stop reply should indicate that the thread has stopped with
35015 signal @samp{0}, regardless of whether the target uses some other signal
35016 as an implementation detail.
35018 The stub must support @samp{vCont} if it reports support for
35019 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35020 this case @samp{vCont} actions can be specified to apply to all threads
35021 in a process by using the @samp{p@var{pid}.-1} form of the
35025 @xref{Stop Reply Packets}, for the reply specifications.
35028 @cindex @samp{vCont?} packet
35029 Request a list of actions supported by the @samp{vCont} packet.
35033 @item vCont@r{[};@var{action}@dots{}@r{]}
35034 The @samp{vCont} packet is supported. Each @var{action} is a supported
35035 command in the @samp{vCont} packet.
35037 The @samp{vCont} packet is not supported.
35040 @item vFile:@var{operation}:@var{parameter}@dots{}
35041 @cindex @samp{vFile} packet
35042 Perform a file operation on the target system. For details,
35043 see @ref{Host I/O Packets}.
35045 @item vFlashErase:@var{addr},@var{length}
35046 @cindex @samp{vFlashErase} packet
35047 Direct the stub to erase @var{length} bytes of flash starting at
35048 @var{addr}. The region may enclose any number of flash blocks, but
35049 its start and end must fall on block boundaries, as indicated by the
35050 flash block size appearing in the memory map (@pxref{Memory Map
35051 Format}). @value{GDBN} groups flash memory programming operations
35052 together, and sends a @samp{vFlashDone} request after each group; the
35053 stub is allowed to delay erase operation until the @samp{vFlashDone}
35054 packet is received.
35064 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35065 @cindex @samp{vFlashWrite} packet
35066 Direct the stub to write data to flash address @var{addr}. The data
35067 is passed in binary form using the same encoding as for the @samp{X}
35068 packet (@pxref{Binary Data}). The memory ranges specified by
35069 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35070 not overlap, and must appear in order of increasing addresses
35071 (although @samp{vFlashErase} packets for higher addresses may already
35072 have been received; the ordering is guaranteed only between
35073 @samp{vFlashWrite} packets). If a packet writes to an address that was
35074 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35075 target-specific method, the results are unpredictable.
35083 for vFlashWrite addressing non-flash memory
35089 @cindex @samp{vFlashDone} packet
35090 Indicate to the stub that flash programming operation is finished.
35091 The stub is permitted to delay or batch the effects of a group of
35092 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35093 @samp{vFlashDone} packet is received. The contents of the affected
35094 regions of flash memory are unpredictable until the @samp{vFlashDone}
35095 request is completed.
35097 @item vKill;@var{pid}
35098 @cindex @samp{vKill} packet
35099 Kill the process with the specified process ID. @var{pid} is a
35100 hexadecimal integer identifying the process. This packet is used in
35101 preference to @samp{k} when multiprocess protocol extensions are
35102 supported; see @ref{multiprocess extensions}.
35112 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35113 @cindex @samp{vRun} packet
35114 Run the program @var{filename}, passing it each @var{argument} on its
35115 command line. The file and arguments are hex-encoded strings. If
35116 @var{filename} is an empty string, the stub may use a default program
35117 (e.g.@: the last program run). The program is created in the stopped
35120 @c FIXME: What about non-stop mode?
35122 This packet is only available in extended mode (@pxref{extended mode}).
35128 @item @r{Any stop packet}
35129 for success (@pxref{Stop Reply Packets})
35133 @anchor{vStopped packet}
35134 @cindex @samp{vStopped} packet
35136 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
35137 reply and prompt for the stub to report another one.
35141 @item @r{Any stop packet}
35142 if there is another unreported stop event (@pxref{Stop Reply Packets})
35144 if there are no unreported stop events
35147 @item X @var{addr},@var{length}:@var{XX@dots{}}
35149 @cindex @samp{X} packet
35150 Write data to memory, where the data is transmitted in binary.
35151 @var{addr} is address, @var{length} is number of bytes,
35152 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35162 @item z @var{type},@var{addr},@var{kind}
35163 @itemx Z @var{type},@var{addr},@var{kind}
35164 @anchor{insert breakpoint or watchpoint packet}
35165 @cindex @samp{z} packet
35166 @cindex @samp{Z} packets
35167 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35168 watchpoint starting at address @var{address} of kind @var{kind}.
35170 Each breakpoint and watchpoint packet @var{type} is documented
35173 @emph{Implementation notes: A remote target shall return an empty string
35174 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35175 remote target shall support either both or neither of a given
35176 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35177 avoid potential problems with duplicate packets, the operations should
35178 be implemented in an idempotent way.}
35180 @item z0,@var{addr},@var{kind}
35181 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35182 @cindex @samp{z0} packet
35183 @cindex @samp{Z0} packet
35184 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35185 @var{addr} of type @var{kind}.
35187 A memory breakpoint is implemented by replacing the instruction at
35188 @var{addr} with a software breakpoint or trap instruction. The
35189 @var{kind} is target-specific and typically indicates the size of
35190 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35191 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35192 architectures have additional meanings for @var{kind};
35193 @var{cond_list} is an optional list of conditional expressions in bytecode
35194 form that should be evaluated on the target's side. These are the
35195 conditions that should be taken into consideration when deciding if
35196 the breakpoint trigger should be reported back to @var{GDBN}.
35198 The @var{cond_list} parameter is comprised of a series of expressions,
35199 concatenated without separators. Each expression has the following form:
35203 @item X @var{len},@var{expr}
35204 @var{len} is the length of the bytecode expression and @var{expr} is the
35205 actual conditional expression in bytecode form.
35209 see @ref{Architecture-Specific Protocol Details}.
35211 @emph{Implementation note: It is possible for a target to copy or move
35212 code that contains memory breakpoints (e.g., when implementing
35213 overlays). The behavior of this packet, in the presence of such a
35214 target, is not defined.}
35226 @item z1,@var{addr},@var{kind}
35227 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35228 @cindex @samp{z1} packet
35229 @cindex @samp{Z1} packet
35230 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35231 address @var{addr}.
35233 A hardware breakpoint is implemented using a mechanism that is not
35234 dependant on being able to modify the target's memory. @var{kind}
35235 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35237 @emph{Implementation note: A hardware breakpoint is not affected by code
35250 @item z2,@var{addr},@var{kind}
35251 @itemx Z2,@var{addr},@var{kind}
35252 @cindex @samp{z2} packet
35253 @cindex @samp{Z2} packet
35254 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35255 @var{kind} is interpreted as the number of bytes to watch.
35267 @item z3,@var{addr},@var{kind}
35268 @itemx Z3,@var{addr},@var{kind}
35269 @cindex @samp{z3} packet
35270 @cindex @samp{Z3} packet
35271 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35272 @var{kind} is interpreted as the number of bytes to watch.
35284 @item z4,@var{addr},@var{kind}
35285 @itemx Z4,@var{addr},@var{kind}
35286 @cindex @samp{z4} packet
35287 @cindex @samp{Z4} packet
35288 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35289 @var{kind} is interpreted as the number of bytes to watch.
35303 @node Stop Reply Packets
35304 @section Stop Reply Packets
35305 @cindex stop reply packets
35307 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35308 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35309 receive any of the below as a reply. Except for @samp{?}
35310 and @samp{vStopped}, that reply is only returned
35311 when the target halts. In the below the exact meaning of @dfn{signal
35312 number} is defined by the header @file{include/gdb/signals.h} in the
35313 @value{GDBN} source code.
35315 As in the description of request packets, we include spaces in the
35316 reply templates for clarity; these are not part of the reply packet's
35317 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35323 The program received signal number @var{AA} (a two-digit hexadecimal
35324 number). This is equivalent to a @samp{T} response with no
35325 @var{n}:@var{r} pairs.
35327 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35328 @cindex @samp{T} packet reply
35329 The program received signal number @var{AA} (a two-digit hexadecimal
35330 number). This is equivalent to an @samp{S} response, except that the
35331 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35332 and other information directly in the stop reply packet, reducing
35333 round-trip latency. Single-step and breakpoint traps are reported
35334 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35338 If @var{n} is a hexadecimal number, it is a register number, and the
35339 corresponding @var{r} gives that register's value. @var{r} is a
35340 series of bytes in target byte order, with each byte given by a
35341 two-digit hex number.
35344 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35345 the stopped thread, as specified in @ref{thread-id syntax}.
35348 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35349 the core on which the stop event was detected.
35352 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35353 specific event that stopped the target. The currently defined stop
35354 reasons are listed below. @var{aa} should be @samp{05}, the trap
35355 signal. At most one stop reason should be present.
35358 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35359 and go on to the next; this allows us to extend the protocol in the
35363 The currently defined stop reasons are:
35369 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35372 @cindex shared library events, remote reply
35374 The packet indicates that the loaded libraries have changed.
35375 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35376 list of loaded libraries. @var{r} is ignored.
35378 @cindex replay log events, remote reply
35380 The packet indicates that the target cannot continue replaying
35381 logged execution events, because it has reached the end (or the
35382 beginning when executing backward) of the log. The value of @var{r}
35383 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35384 for more information.
35388 @itemx W @var{AA} ; process:@var{pid}
35389 The process exited, and @var{AA} is the exit status. This is only
35390 applicable to certain targets.
35392 The second form of the response, including the process ID of the exited
35393 process, can be used only when @value{GDBN} has reported support for
35394 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35395 The @var{pid} is formatted as a big-endian hex string.
35398 @itemx X @var{AA} ; process:@var{pid}
35399 The process terminated with signal @var{AA}.
35401 The second form of the response, including the process ID of the
35402 terminated process, can be used only when @value{GDBN} has reported
35403 support for multiprocess protocol extensions; see @ref{multiprocess
35404 extensions}. The @var{pid} is formatted as a big-endian hex string.
35406 @item O @var{XX}@dots{}
35407 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35408 written as the program's console output. This can happen at any time
35409 while the program is running and the debugger should continue to wait
35410 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35412 @item F @var{call-id},@var{parameter}@dots{}
35413 @var{call-id} is the identifier which says which host system call should
35414 be called. This is just the name of the function. Translation into the
35415 correct system call is only applicable as it's defined in @value{GDBN}.
35416 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35419 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35420 this very system call.
35422 The target replies with this packet when it expects @value{GDBN} to
35423 call a host system call on behalf of the target. @value{GDBN} replies
35424 with an appropriate @samp{F} packet and keeps up waiting for the next
35425 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35426 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35427 Protocol Extension}, for more details.
35431 @node General Query Packets
35432 @section General Query Packets
35433 @cindex remote query requests
35435 Packets starting with @samp{q} are @dfn{general query packets};
35436 packets starting with @samp{Q} are @dfn{general set packets}. General
35437 query and set packets are a semi-unified form for retrieving and
35438 sending information to and from the stub.
35440 The initial letter of a query or set packet is followed by a name
35441 indicating what sort of thing the packet applies to. For example,
35442 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35443 definitions with the stub. These packet names follow some
35448 The name must not contain commas, colons or semicolons.
35450 Most @value{GDBN} query and set packets have a leading upper case
35453 The names of custom vendor packets should use a company prefix, in
35454 lower case, followed by a period. For example, packets designed at
35455 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35456 foos) or @samp{Qacme.bar} (for setting bars).
35459 The name of a query or set packet should be separated from any
35460 parameters by a @samp{:}; the parameters themselves should be
35461 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35462 full packet name, and check for a separator or the end of the packet,
35463 in case two packet names share a common prefix. New packets should not begin
35464 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35465 packets predate these conventions, and have arguments without any terminator
35466 for the packet name; we suspect they are in widespread use in places that
35467 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35468 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35471 Like the descriptions of the other packets, each description here
35472 has a template showing the packet's overall syntax, followed by an
35473 explanation of the packet's meaning. We include spaces in some of the
35474 templates for clarity; these are not part of the packet's syntax. No
35475 @value{GDBN} packet uses spaces to separate its components.
35477 Here are the currently defined query and set packets:
35483 Turn on or off the agent as a helper to perform some debugging operations
35484 delegated from @value{GDBN} (@pxref{Control Agent}).
35486 @item QAllow:@var{op}:@var{val}@dots{}
35487 @cindex @samp{QAllow} packet
35488 Specify which operations @value{GDBN} expects to request of the
35489 target, as a semicolon-separated list of operation name and value
35490 pairs. Possible values for @var{op} include @samp{WriteReg},
35491 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35492 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35493 indicating that @value{GDBN} will not request the operation, or 1,
35494 indicating that it may. (The target can then use this to set up its
35495 own internals optimally, for instance if the debugger never expects to
35496 insert breakpoints, it may not need to install its own trap handler.)
35499 @cindex current thread, remote request
35500 @cindex @samp{qC} packet
35501 Return the current thread ID.
35505 @item QC @var{thread-id}
35506 Where @var{thread-id} is a thread ID as documented in
35507 @ref{thread-id syntax}.
35508 @item @r{(anything else)}
35509 Any other reply implies the old thread ID.
35512 @item qCRC:@var{addr},@var{length}
35513 @cindex CRC of memory block, remote request
35514 @cindex @samp{qCRC} packet
35515 Compute the CRC checksum of a block of memory using CRC-32 defined in
35516 IEEE 802.3. The CRC is computed byte at a time, taking the most
35517 significant bit of each byte first. The initial pattern code
35518 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35520 @emph{Note:} This is the same CRC used in validating separate debug
35521 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35522 Files}). However the algorithm is slightly different. When validating
35523 separate debug files, the CRC is computed taking the @emph{least}
35524 significant bit of each byte first, and the final result is inverted to
35525 detect trailing zeros.
35530 An error (such as memory fault)
35531 @item C @var{crc32}
35532 The specified memory region's checksum is @var{crc32}.
35535 @item QDisableRandomization:@var{value}
35536 @cindex disable address space randomization, remote request
35537 @cindex @samp{QDisableRandomization} packet
35538 Some target operating systems will randomize the virtual address space
35539 of the inferior process as a security feature, but provide a feature
35540 to disable such randomization, e.g.@: to allow for a more deterministic
35541 debugging experience. On such systems, this packet with a @var{value}
35542 of 1 directs the target to disable address space randomization for
35543 processes subsequently started via @samp{vRun} packets, while a packet
35544 with a @var{value} of 0 tells the target to enable address space
35547 This packet is only available in extended mode (@pxref{extended mode}).
35552 The request succeeded.
35555 An error occurred. @var{nn} are hex digits.
35558 An empty reply indicates that @samp{QDisableRandomization} is not supported
35562 This packet is not probed by default; the remote stub must request it,
35563 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35564 This should only be done on targets that actually support disabling
35565 address space randomization.
35568 @itemx qsThreadInfo
35569 @cindex list active threads, remote request
35570 @cindex @samp{qfThreadInfo} packet
35571 @cindex @samp{qsThreadInfo} packet
35572 Obtain a list of all active thread IDs from the target (OS). Since there
35573 may be too many active threads to fit into one reply packet, this query
35574 works iteratively: it may require more than one query/reply sequence to
35575 obtain the entire list of threads. The first query of the sequence will
35576 be the @samp{qfThreadInfo} query; subsequent queries in the
35577 sequence will be the @samp{qsThreadInfo} query.
35579 NOTE: This packet replaces the @samp{qL} query (see below).
35583 @item m @var{thread-id}
35585 @item m @var{thread-id},@var{thread-id}@dots{}
35586 a comma-separated list of thread IDs
35588 (lower case letter @samp{L}) denotes end of list.
35591 In response to each query, the target will reply with a list of one or
35592 more thread IDs, separated by commas.
35593 @value{GDBN} will respond to each reply with a request for more thread
35594 ids (using the @samp{qs} form of the query), until the target responds
35595 with @samp{l} (lower-case ell, for @dfn{last}).
35596 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35599 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35600 @cindex get thread-local storage address, remote request
35601 @cindex @samp{qGetTLSAddr} packet
35602 Fetch the address associated with thread local storage specified
35603 by @var{thread-id}, @var{offset}, and @var{lm}.
35605 @var{thread-id} is the thread ID associated with the
35606 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35608 @var{offset} is the (big endian, hex encoded) offset associated with the
35609 thread local variable. (This offset is obtained from the debug
35610 information associated with the variable.)
35612 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35613 load module associated with the thread local storage. For example,
35614 a @sc{gnu}/Linux system will pass the link map address of the shared
35615 object associated with the thread local storage under consideration.
35616 Other operating environments may choose to represent the load module
35617 differently, so the precise meaning of this parameter will vary.
35621 @item @var{XX}@dots{}
35622 Hex encoded (big endian) bytes representing the address of the thread
35623 local storage requested.
35626 An error occurred. @var{nn} are hex digits.
35629 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35632 @item qGetTIBAddr:@var{thread-id}
35633 @cindex get thread information block address
35634 @cindex @samp{qGetTIBAddr} packet
35635 Fetch address of the Windows OS specific Thread Information Block.
35637 @var{thread-id} is the thread ID associated with the thread.
35641 @item @var{XX}@dots{}
35642 Hex encoded (big endian) bytes representing the linear address of the
35643 thread information block.
35646 An error occured. This means that either the thread was not found, or the
35647 address could not be retrieved.
35650 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35653 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35654 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35655 digit) is one to indicate the first query and zero to indicate a
35656 subsequent query; @var{threadcount} (two hex digits) is the maximum
35657 number of threads the response packet can contain; and @var{nextthread}
35658 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35659 returned in the response as @var{argthread}.
35661 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35665 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35666 Where: @var{count} (two hex digits) is the number of threads being
35667 returned; @var{done} (one hex digit) is zero to indicate more threads
35668 and one indicates no further threads; @var{argthreadid} (eight hex
35669 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35670 is a sequence of thread IDs from the target. @var{threadid} (eight hex
35671 digits). See @code{remote.c:parse_threadlist_response()}.
35675 @cindex section offsets, remote request
35676 @cindex @samp{qOffsets} packet
35677 Get section offsets that the target used when relocating the downloaded
35682 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35683 Relocate the @code{Text} section by @var{xxx} from its original address.
35684 Relocate the @code{Data} section by @var{yyy} from its original address.
35685 If the object file format provides segment information (e.g.@: @sc{elf}
35686 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35687 segments by the supplied offsets.
35689 @emph{Note: while a @code{Bss} offset may be included in the response,
35690 @value{GDBN} ignores this and instead applies the @code{Data} offset
35691 to the @code{Bss} section.}
35693 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35694 Relocate the first segment of the object file, which conventionally
35695 contains program code, to a starting address of @var{xxx}. If
35696 @samp{DataSeg} is specified, relocate the second segment, which
35697 conventionally contains modifiable data, to a starting address of
35698 @var{yyy}. @value{GDBN} will report an error if the object file
35699 does not contain segment information, or does not contain at least
35700 as many segments as mentioned in the reply. Extra segments are
35701 kept at fixed offsets relative to the last relocated segment.
35704 @item qP @var{mode} @var{thread-id}
35705 @cindex thread information, remote request
35706 @cindex @samp{qP} packet
35707 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35708 encoded 32 bit mode; @var{thread-id} is a thread ID
35709 (@pxref{thread-id syntax}).
35711 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35714 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35718 @cindex non-stop mode, remote request
35719 @cindex @samp{QNonStop} packet
35721 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35722 @xref{Remote Non-Stop}, for more information.
35727 The request succeeded.
35730 An error occurred. @var{nn} are hex digits.
35733 An empty reply indicates that @samp{QNonStop} is not supported by
35737 This packet is not probed by default; the remote stub must request it,
35738 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35739 Use of this packet is controlled by the @code{set non-stop} command;
35740 @pxref{Non-Stop Mode}.
35742 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35743 @cindex pass signals to inferior, remote request
35744 @cindex @samp{QPassSignals} packet
35745 @anchor{QPassSignals}
35746 Each listed @var{signal} should be passed directly to the inferior process.
35747 Signals are numbered identically to continue packets and stop replies
35748 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35749 strictly greater than the previous item. These signals do not need to stop
35750 the inferior, or be reported to @value{GDBN}. All other signals should be
35751 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35752 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35753 new list. This packet improves performance when using @samp{handle
35754 @var{signal} nostop noprint pass}.
35759 The request succeeded.
35762 An error occurred. @var{nn} are hex digits.
35765 An empty reply indicates that @samp{QPassSignals} is not supported by
35769 Use of this packet is controlled by the @code{set remote pass-signals}
35770 command (@pxref{Remote Configuration, set remote pass-signals}).
35771 This packet is not probed by default; the remote stub must request it,
35772 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35774 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35775 @cindex signals the inferior may see, remote request
35776 @cindex @samp{QProgramSignals} packet
35777 @anchor{QProgramSignals}
35778 Each listed @var{signal} may be delivered to the inferior process.
35779 Others should be silently discarded.
35781 In some cases, the remote stub may need to decide whether to deliver a
35782 signal to the program or not without @value{GDBN} involvement. One
35783 example of that is while detaching --- the program's threads may have
35784 stopped for signals that haven't yet had a chance of being reported to
35785 @value{GDBN}, and so the remote stub can use the signal list specified
35786 by this packet to know whether to deliver or ignore those pending
35789 This does not influence whether to deliver a signal as requested by a
35790 resumption packet (@pxref{vCont packet}).
35792 Signals are numbered identically to continue packets and stop replies
35793 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35794 strictly greater than the previous item. Multiple
35795 @samp{QProgramSignals} packets do not combine; any earlier
35796 @samp{QProgramSignals} list is completely replaced by the new list.
35801 The request succeeded.
35804 An error occurred. @var{nn} are hex digits.
35807 An empty reply indicates that @samp{QProgramSignals} is not supported
35811 Use of this packet is controlled by the @code{set remote program-signals}
35812 command (@pxref{Remote Configuration, set remote program-signals}).
35813 This packet is not probed by default; the remote stub must request it,
35814 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35816 @item qRcmd,@var{command}
35817 @cindex execute remote command, remote request
35818 @cindex @samp{qRcmd} packet
35819 @var{command} (hex encoded) is passed to the local interpreter for
35820 execution. Invalid commands should be reported using the output
35821 string. Before the final result packet, the target may also respond
35822 with a number of intermediate @samp{O@var{output}} console output
35823 packets. @emph{Implementors should note that providing access to a
35824 stubs's interpreter may have security implications}.
35829 A command response with no output.
35831 A command response with the hex encoded output string @var{OUTPUT}.
35833 Indicate a badly formed request.
35835 An empty reply indicates that @samp{qRcmd} is not recognized.
35838 (Note that the @code{qRcmd} packet's name is separated from the
35839 command by a @samp{,}, not a @samp{:}, contrary to the naming
35840 conventions above. Please don't use this packet as a model for new
35843 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35844 @cindex searching memory, in remote debugging
35845 @cindex @samp{qSearch:memory} packet
35846 @anchor{qSearch memory}
35847 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35848 @var{address} and @var{length} are encoded in hex.
35849 @var{search-pattern} is a sequence of bytes, hex encoded.
35854 The pattern was not found.
35856 The pattern was found at @var{address}.
35858 A badly formed request or an error was encountered while searching memory.
35860 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35863 @item QStartNoAckMode
35864 @cindex @samp{QStartNoAckMode} packet
35865 @anchor{QStartNoAckMode}
35866 Request that the remote stub disable the normal @samp{+}/@samp{-}
35867 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35872 The stub has switched to no-acknowledgment mode.
35873 @value{GDBN} acknowledges this reponse,
35874 but neither the stub nor @value{GDBN} shall send or expect further
35875 @samp{+}/@samp{-} acknowledgments in the current connection.
35877 An empty reply indicates that the stub does not support no-acknowledgment mode.
35880 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35881 @cindex supported packets, remote query
35882 @cindex features of the remote protocol
35883 @cindex @samp{qSupported} packet
35884 @anchor{qSupported}
35885 Tell the remote stub about features supported by @value{GDBN}, and
35886 query the stub for features it supports. This packet allows
35887 @value{GDBN} and the remote stub to take advantage of each others'
35888 features. @samp{qSupported} also consolidates multiple feature probes
35889 at startup, to improve @value{GDBN} performance---a single larger
35890 packet performs better than multiple smaller probe packets on
35891 high-latency links. Some features may enable behavior which must not
35892 be on by default, e.g.@: because it would confuse older clients or
35893 stubs. Other features may describe packets which could be
35894 automatically probed for, but are not. These features must be
35895 reported before @value{GDBN} will use them. This ``default
35896 unsupported'' behavior is not appropriate for all packets, but it
35897 helps to keep the initial connection time under control with new
35898 versions of @value{GDBN} which support increasing numbers of packets.
35902 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35903 The stub supports or does not support each returned @var{stubfeature},
35904 depending on the form of each @var{stubfeature} (see below for the
35907 An empty reply indicates that @samp{qSupported} is not recognized,
35908 or that no features needed to be reported to @value{GDBN}.
35911 The allowed forms for each feature (either a @var{gdbfeature} in the
35912 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35916 @item @var{name}=@var{value}
35917 The remote protocol feature @var{name} is supported, and associated
35918 with the specified @var{value}. The format of @var{value} depends
35919 on the feature, but it must not include a semicolon.
35921 The remote protocol feature @var{name} is supported, and does not
35922 need an associated value.
35924 The remote protocol feature @var{name} is not supported.
35926 The remote protocol feature @var{name} may be supported, and
35927 @value{GDBN} should auto-detect support in some other way when it is
35928 needed. This form will not be used for @var{gdbfeature} notifications,
35929 but may be used for @var{stubfeature} responses.
35932 Whenever the stub receives a @samp{qSupported} request, the
35933 supplied set of @value{GDBN} features should override any previous
35934 request. This allows @value{GDBN} to put the stub in a known
35935 state, even if the stub had previously been communicating with
35936 a different version of @value{GDBN}.
35938 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35943 This feature indicates whether @value{GDBN} supports multiprocess
35944 extensions to the remote protocol. @value{GDBN} does not use such
35945 extensions unless the stub also reports that it supports them by
35946 including @samp{multiprocess+} in its @samp{qSupported} reply.
35947 @xref{multiprocess extensions}, for details.
35950 This feature indicates that @value{GDBN} supports the XML target
35951 description. If the stub sees @samp{xmlRegisters=} with target
35952 specific strings separated by a comma, it will report register
35956 This feature indicates whether @value{GDBN} supports the
35957 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35958 instruction reply packet}).
35961 Stubs should ignore any unknown values for
35962 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35963 packet supports receiving packets of unlimited length (earlier
35964 versions of @value{GDBN} may reject overly long responses). Additional values
35965 for @var{gdbfeature} may be defined in the future to let the stub take
35966 advantage of new features in @value{GDBN}, e.g.@: incompatible
35967 improvements in the remote protocol---the @samp{multiprocess} feature is
35968 an example of such a feature. The stub's reply should be independent
35969 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35970 describes all the features it supports, and then the stub replies with
35971 all the features it supports.
35973 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35974 responses, as long as each response uses one of the standard forms.
35976 Some features are flags. A stub which supports a flag feature
35977 should respond with a @samp{+} form response. Other features
35978 require values, and the stub should respond with an @samp{=}
35981 Each feature has a default value, which @value{GDBN} will use if
35982 @samp{qSupported} is not available or if the feature is not mentioned
35983 in the @samp{qSupported} response. The default values are fixed; a
35984 stub is free to omit any feature responses that match the defaults.
35986 Not all features can be probed, but for those which can, the probing
35987 mechanism is useful: in some cases, a stub's internal
35988 architecture may not allow the protocol layer to know some information
35989 about the underlying target in advance. This is especially common in
35990 stubs which may be configured for multiple targets.
35992 These are the currently defined stub features and their properties:
35994 @multitable @columnfractions 0.35 0.2 0.12 0.2
35995 @c NOTE: The first row should be @headitem, but we do not yet require
35996 @c a new enough version of Texinfo (4.7) to use @headitem.
35998 @tab Value Required
36002 @item @samp{PacketSize}
36007 @item @samp{qXfer:auxv:read}
36012 @item @samp{qXfer:features:read}
36017 @item @samp{qXfer:libraries:read}
36022 @item @samp{qXfer:memory-map:read}
36027 @item @samp{qXfer:sdata:read}
36032 @item @samp{qXfer:spu:read}
36037 @item @samp{qXfer:spu:write}
36042 @item @samp{qXfer:siginfo:read}
36047 @item @samp{qXfer:siginfo:write}
36052 @item @samp{qXfer:threads:read}
36057 @item @samp{qXfer:traceframe-info:read}
36062 @item @samp{qXfer:uib:read}
36067 @item @samp{qXfer:fdpic:read}
36072 @item @samp{QNonStop}
36077 @item @samp{QPassSignals}
36082 @item @samp{QStartNoAckMode}
36087 @item @samp{multiprocess}
36092 @item @samp{ConditionalBreakpoints}
36097 @item @samp{ConditionalTracepoints}
36102 @item @samp{ReverseContinue}
36107 @item @samp{ReverseStep}
36112 @item @samp{TracepointSource}
36117 @item @samp{QAgent}
36122 @item @samp{QAllow}
36127 @item @samp{QDisableRandomization}
36132 @item @samp{EnableDisableTracepoints}
36137 @item @samp{tracenz}
36144 These are the currently defined stub features, in more detail:
36147 @cindex packet size, remote protocol
36148 @item PacketSize=@var{bytes}
36149 The remote stub can accept packets up to at least @var{bytes} in
36150 length. @value{GDBN} will send packets up to this size for bulk
36151 transfers, and will never send larger packets. This is a limit on the
36152 data characters in the packet, including the frame and checksum.
36153 There is no trailing NUL byte in a remote protocol packet; if the stub
36154 stores packets in a NUL-terminated format, it should allow an extra
36155 byte in its buffer for the NUL. If this stub feature is not supported,
36156 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36158 @item qXfer:auxv:read
36159 The remote stub understands the @samp{qXfer:auxv:read} packet
36160 (@pxref{qXfer auxiliary vector read}).
36162 @item qXfer:features:read
36163 The remote stub understands the @samp{qXfer:features:read} packet
36164 (@pxref{qXfer target description read}).
36166 @item qXfer:libraries:read
36167 The remote stub understands the @samp{qXfer:libraries:read} packet
36168 (@pxref{qXfer library list read}).
36170 @item qXfer:libraries-svr4:read
36171 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36172 (@pxref{qXfer svr4 library list read}).
36174 @item qXfer:memory-map:read
36175 The remote stub understands the @samp{qXfer:memory-map:read} packet
36176 (@pxref{qXfer memory map read}).
36178 @item qXfer:sdata:read
36179 The remote stub understands the @samp{qXfer:sdata:read} packet
36180 (@pxref{qXfer sdata read}).
36182 @item qXfer:spu:read
36183 The remote stub understands the @samp{qXfer:spu:read} packet
36184 (@pxref{qXfer spu read}).
36186 @item qXfer:spu:write
36187 The remote stub understands the @samp{qXfer:spu:write} packet
36188 (@pxref{qXfer spu write}).
36190 @item qXfer:siginfo:read
36191 The remote stub understands the @samp{qXfer:siginfo:read} packet
36192 (@pxref{qXfer siginfo read}).
36194 @item qXfer:siginfo:write
36195 The remote stub understands the @samp{qXfer:siginfo:write} packet
36196 (@pxref{qXfer siginfo write}).
36198 @item qXfer:threads:read
36199 The remote stub understands the @samp{qXfer:threads:read} packet
36200 (@pxref{qXfer threads read}).
36202 @item qXfer:traceframe-info:read
36203 The remote stub understands the @samp{qXfer:traceframe-info:read}
36204 packet (@pxref{qXfer traceframe info read}).
36206 @item qXfer:uib:read
36207 The remote stub understands the @samp{qXfer:uib:read}
36208 packet (@pxref{qXfer unwind info block}).
36210 @item qXfer:fdpic:read
36211 The remote stub understands the @samp{qXfer:fdpic:read}
36212 packet (@pxref{qXfer fdpic loadmap read}).
36215 The remote stub understands the @samp{QNonStop} packet
36216 (@pxref{QNonStop}).
36219 The remote stub understands the @samp{QPassSignals} packet
36220 (@pxref{QPassSignals}).
36222 @item QStartNoAckMode
36223 The remote stub understands the @samp{QStartNoAckMode} packet and
36224 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36227 @anchor{multiprocess extensions}
36228 @cindex multiprocess extensions, in remote protocol
36229 The remote stub understands the multiprocess extensions to the remote
36230 protocol syntax. The multiprocess extensions affect the syntax of
36231 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36232 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36233 replies. Note that reporting this feature indicates support for the
36234 syntactic extensions only, not that the stub necessarily supports
36235 debugging of more than one process at a time. The stub must not use
36236 multiprocess extensions in packet replies unless @value{GDBN} has also
36237 indicated it supports them in its @samp{qSupported} request.
36239 @item qXfer:osdata:read
36240 The remote stub understands the @samp{qXfer:osdata:read} packet
36241 ((@pxref{qXfer osdata read}).
36243 @item ConditionalBreakpoints
36244 The target accepts and implements evaluation of conditional expressions
36245 defined for breakpoints. The target will only report breakpoint triggers
36246 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36248 @item ConditionalTracepoints
36249 The remote stub accepts and implements conditional expressions defined
36250 for tracepoints (@pxref{Tracepoint Conditions}).
36252 @item ReverseContinue
36253 The remote stub accepts and implements the reverse continue packet
36257 The remote stub accepts and implements the reverse step packet
36260 @item TracepointSource
36261 The remote stub understands the @samp{QTDPsrc} packet that supplies
36262 the source form of tracepoint definitions.
36265 The remote stub understands the @samp{QAgent} packet.
36268 The remote stub understands the @samp{QAllow} packet.
36270 @item QDisableRandomization
36271 The remote stub understands the @samp{QDisableRandomization} packet.
36273 @item StaticTracepoint
36274 @cindex static tracepoints, in remote protocol
36275 The remote stub supports static tracepoints.
36277 @item InstallInTrace
36278 @anchor{install tracepoint in tracing}
36279 The remote stub supports installing tracepoint in tracing.
36281 @item EnableDisableTracepoints
36282 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36283 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36284 to be enabled and disabled while a trace experiment is running.
36287 @cindex string tracing, in remote protocol
36288 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36289 See @ref{Bytecode Descriptions} for details about the bytecode.
36294 @cindex symbol lookup, remote request
36295 @cindex @samp{qSymbol} packet
36296 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36297 requests. Accept requests from the target for the values of symbols.
36302 The target does not need to look up any (more) symbols.
36303 @item qSymbol:@var{sym_name}
36304 The target requests the value of symbol @var{sym_name} (hex encoded).
36305 @value{GDBN} may provide the value by using the
36306 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36310 @item qSymbol:@var{sym_value}:@var{sym_name}
36311 Set the value of @var{sym_name} to @var{sym_value}.
36313 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36314 target has previously requested.
36316 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36317 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36323 The target does not need to look up any (more) symbols.
36324 @item qSymbol:@var{sym_name}
36325 The target requests the value of a new symbol @var{sym_name} (hex
36326 encoded). @value{GDBN} will continue to supply the values of symbols
36327 (if available), until the target ceases to request them.
36332 @item QTDisconnected
36339 @itemx qTMinFTPILen
36341 @xref{Tracepoint Packets}.
36343 @item qThreadExtraInfo,@var{thread-id}
36344 @cindex thread attributes info, remote request
36345 @cindex @samp{qThreadExtraInfo} packet
36346 Obtain a printable string description of a thread's attributes from
36347 the target OS. @var{thread-id} is a thread ID;
36348 see @ref{thread-id syntax}. This
36349 string may contain anything that the target OS thinks is interesting
36350 for @value{GDBN} to tell the user about the thread. The string is
36351 displayed in @value{GDBN}'s @code{info threads} display. Some
36352 examples of possible thread extra info strings are @samp{Runnable}, or
36353 @samp{Blocked on Mutex}.
36357 @item @var{XX}@dots{}
36358 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36359 comprising the printable string containing the extra information about
36360 the thread's attributes.
36363 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36364 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36365 conventions above. Please don't use this packet as a model for new
36384 @xref{Tracepoint Packets}.
36386 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36387 @cindex read special object, remote request
36388 @cindex @samp{qXfer} packet
36389 @anchor{qXfer read}
36390 Read uninterpreted bytes from the target's special data area
36391 identified by the keyword @var{object}. Request @var{length} bytes
36392 starting at @var{offset} bytes into the data. The content and
36393 encoding of @var{annex} is specific to @var{object}; it can supply
36394 additional details about what data to access.
36396 Here are the specific requests of this form defined so far. All
36397 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36398 formats, listed below.
36401 @item qXfer:auxv:read::@var{offset},@var{length}
36402 @anchor{qXfer auxiliary vector read}
36403 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36404 auxiliary vector}. Note @var{annex} must be empty.
36406 This packet is not probed by default; the remote stub must request it,
36407 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36409 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36410 @anchor{qXfer target description read}
36411 Access the @dfn{target description}. @xref{Target Descriptions}. The
36412 annex specifies which XML document to access. The main description is
36413 always loaded from the @samp{target.xml} annex.
36415 This packet is not probed by default; the remote stub must request it,
36416 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36418 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36419 @anchor{qXfer library list read}
36420 Access the target's list of loaded libraries. @xref{Library List Format}.
36421 The annex part of the generic @samp{qXfer} packet must be empty
36422 (@pxref{qXfer read}).
36424 Targets which maintain a list of libraries in the program's memory do
36425 not need to implement this packet; it is designed for platforms where
36426 the operating system manages the list of loaded libraries.
36428 This packet is not probed by default; the remote stub must request it,
36429 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36431 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36432 @anchor{qXfer svr4 library list read}
36433 Access the target's list of loaded libraries when the target is an SVR4
36434 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36435 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36437 This packet is optional for better performance on SVR4 targets.
36438 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36440 This packet is not probed by default; the remote stub must request it,
36441 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36443 @item qXfer:memory-map:read::@var{offset},@var{length}
36444 @anchor{qXfer memory map read}
36445 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36446 annex part of the generic @samp{qXfer} packet must be empty
36447 (@pxref{qXfer read}).
36449 This packet is not probed by default; the remote stub must request it,
36450 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36452 @item qXfer:sdata:read::@var{offset},@var{length}
36453 @anchor{qXfer sdata read}
36455 Read contents of the extra collected static tracepoint marker
36456 information. The annex part of the generic @samp{qXfer} packet must
36457 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36460 This packet is not probed by default; the remote stub must request it,
36461 by supplying an appropriate @samp{qSupported} response
36462 (@pxref{qSupported}).
36464 @item qXfer:siginfo:read::@var{offset},@var{length}
36465 @anchor{qXfer siginfo read}
36466 Read contents of the extra signal information on the target
36467 system. The annex part of the generic @samp{qXfer} packet must be
36468 empty (@pxref{qXfer read}).
36470 This packet is not probed by default; the remote stub must request it,
36471 by supplying an appropriate @samp{qSupported} response
36472 (@pxref{qSupported}).
36474 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36475 @anchor{qXfer spu read}
36476 Read contents of an @code{spufs} file on the target system. The
36477 annex specifies which file to read; it must be of the form
36478 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36479 in the target process, and @var{name} identifes the @code{spufs} file
36480 in that context to be accessed.
36482 This packet is not probed by default; the remote stub must request it,
36483 by supplying an appropriate @samp{qSupported} response
36484 (@pxref{qSupported}).
36486 @item qXfer:threads:read::@var{offset},@var{length}
36487 @anchor{qXfer threads read}
36488 Access the list of threads on target. @xref{Thread List Format}. The
36489 annex part of the generic @samp{qXfer} packet must be empty
36490 (@pxref{qXfer read}).
36492 This packet is not probed by default; the remote stub must request it,
36493 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36495 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36496 @anchor{qXfer traceframe info read}
36498 Return a description of the current traceframe's contents.
36499 @xref{Traceframe Info Format}. The annex part of the generic
36500 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36502 This packet is not probed by default; the remote stub must request it,
36503 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36505 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36506 @anchor{qXfer unwind info block}
36508 Return the unwind information block for @var{pc}. This packet is used
36509 on OpenVMS/ia64 to ask the kernel unwind information.
36511 This packet is not probed by default.
36513 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36514 @anchor{qXfer fdpic loadmap read}
36515 Read contents of @code{loadmap}s on the target system. The
36516 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36517 executable @code{loadmap} or interpreter @code{loadmap} to read.
36519 This packet is not probed by default; the remote stub must request it,
36520 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36522 @item qXfer:osdata:read::@var{offset},@var{length}
36523 @anchor{qXfer osdata read}
36524 Access the target's @dfn{operating system information}.
36525 @xref{Operating System Information}.
36532 Data @var{data} (@pxref{Binary Data}) has been read from the
36533 target. There may be more data at a higher address (although
36534 it is permitted to return @samp{m} even for the last valid
36535 block of data, as long as at least one byte of data was read).
36536 @var{data} may have fewer bytes than the @var{length} in the
36540 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36541 There is no more data to be read. @var{data} may have fewer bytes
36542 than the @var{length} in the request.
36545 The @var{offset} in the request is at the end of the data.
36546 There is no more data to be read.
36549 The request was malformed, or @var{annex} was invalid.
36552 The offset was invalid, or there was an error encountered reading the data.
36553 @var{nn} is a hex-encoded @code{errno} value.
36556 An empty reply indicates the @var{object} string was not recognized by
36557 the stub, or that the object does not support reading.
36560 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36561 @cindex write data into object, remote request
36562 @anchor{qXfer write}
36563 Write uninterpreted bytes into the target's special data area
36564 identified by the keyword @var{object}, starting at @var{offset} bytes
36565 into the data. @var{data}@dots{} is the binary-encoded data
36566 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
36567 is specific to @var{object}; it can supply additional details about what data
36570 Here are the specific requests of this form defined so far. All
36571 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36572 formats, listed below.
36575 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36576 @anchor{qXfer siginfo write}
36577 Write @var{data} to the extra signal information on the target system.
36578 The annex part of the generic @samp{qXfer} packet must be
36579 empty (@pxref{qXfer write}).
36581 This packet is not probed by default; the remote stub must request it,
36582 by supplying an appropriate @samp{qSupported} response
36583 (@pxref{qSupported}).
36585 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36586 @anchor{qXfer spu write}
36587 Write @var{data} to an @code{spufs} file on the target system. The
36588 annex specifies which file to write; it must be of the form
36589 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36590 in the target process, and @var{name} identifes the @code{spufs} file
36591 in that context to be accessed.
36593 This packet is not probed by default; the remote stub must request it,
36594 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36600 @var{nn} (hex encoded) is the number of bytes written.
36601 This may be fewer bytes than supplied in the request.
36604 The request was malformed, or @var{annex} was invalid.
36607 The offset was invalid, or there was an error encountered writing the data.
36608 @var{nn} is a hex-encoded @code{errno} value.
36611 An empty reply indicates the @var{object} string was not
36612 recognized by the stub, or that the object does not support writing.
36615 @item qXfer:@var{object}:@var{operation}:@dots{}
36616 Requests of this form may be added in the future. When a stub does
36617 not recognize the @var{object} keyword, or its support for
36618 @var{object} does not recognize the @var{operation} keyword, the stub
36619 must respond with an empty packet.
36621 @item qAttached:@var{pid}
36622 @cindex query attached, remote request
36623 @cindex @samp{qAttached} packet
36624 Return an indication of whether the remote server attached to an
36625 existing process or created a new process. When the multiprocess
36626 protocol extensions are supported (@pxref{multiprocess extensions}),
36627 @var{pid} is an integer in hexadecimal format identifying the target
36628 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36629 the query packet will be simplified as @samp{qAttached}.
36631 This query is used, for example, to know whether the remote process
36632 should be detached or killed when a @value{GDBN} session is ended with
36633 the @code{quit} command.
36638 The remote server attached to an existing process.
36640 The remote server created a new process.
36642 A badly formed request or an error was encountered.
36647 @node Architecture-Specific Protocol Details
36648 @section Architecture-Specific Protocol Details
36650 This section describes how the remote protocol is applied to specific
36651 target architectures. Also see @ref{Standard Target Features}, for
36652 details of XML target descriptions for each architecture.
36656 @subsubsection Breakpoint Kinds
36658 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36663 16-bit Thumb mode breakpoint.
36666 32-bit Thumb mode (Thumb-2) breakpoint.
36669 32-bit ARM mode breakpoint.
36675 @subsubsection Register Packet Format
36677 The following @code{g}/@code{G} packets have previously been defined.
36678 In the below, some thirty-two bit registers are transferred as
36679 sixty-four bits. Those registers should be zero/sign extended (which?)
36680 to fill the space allocated. Register bytes are transferred in target
36681 byte order. The two nibbles within a register byte are transferred
36682 most-significant - least-significant.
36688 All registers are transferred as thirty-two bit quantities in the order:
36689 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36690 registers; fsr; fir; fp.
36694 All registers are transferred as sixty-four bit quantities (including
36695 thirty-two bit registers such as @code{sr}). The ordering is the same
36700 @node Tracepoint Packets
36701 @section Tracepoint Packets
36702 @cindex tracepoint packets
36703 @cindex packets, tracepoint
36705 Here we describe the packets @value{GDBN} uses to implement
36706 tracepoints (@pxref{Tracepoints}).
36710 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36711 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36712 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36713 the tracepoint is disabled. @var{step} is the tracepoint's step
36714 count, and @var{pass} is its pass count. If an @samp{F} is present,
36715 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36716 the number of bytes that the target should copy elsewhere to make room
36717 for the tracepoint. If an @samp{X} is present, it introduces a
36718 tracepoint condition, which consists of a hexadecimal length, followed
36719 by a comma and hex-encoded bytes, in a manner similar to action
36720 encodings as described below. If the trailing @samp{-} is present,
36721 further @samp{QTDP} packets will follow to specify this tracepoint's
36727 The packet was understood and carried out.
36729 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36731 The packet was not recognized.
36734 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36735 Define actions to be taken when a tracepoint is hit. @var{n} and
36736 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36737 this tracepoint. This packet may only be sent immediately after
36738 another @samp{QTDP} packet that ended with a @samp{-}. If the
36739 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36740 specifying more actions for this tracepoint.
36742 In the series of action packets for a given tracepoint, at most one
36743 can have an @samp{S} before its first @var{action}. If such a packet
36744 is sent, it and the following packets define ``while-stepping''
36745 actions. Any prior packets define ordinary actions --- that is, those
36746 taken when the tracepoint is first hit. If no action packet has an
36747 @samp{S}, then all the packets in the series specify ordinary
36748 tracepoint actions.
36750 The @samp{@var{action}@dots{}} portion of the packet is a series of
36751 actions, concatenated without separators. Each action has one of the
36757 Collect the registers whose bits are set in @var{mask}. @var{mask} is
36758 a hexadecimal number whose @var{i}'th bit is set if register number
36759 @var{i} should be collected. (The least significant bit is numbered
36760 zero.) Note that @var{mask} may be any number of digits long; it may
36761 not fit in a 32-bit word.
36763 @item M @var{basereg},@var{offset},@var{len}
36764 Collect @var{len} bytes of memory starting at the address in register
36765 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36766 @samp{-1}, then the range has a fixed address: @var{offset} is the
36767 address of the lowest byte to collect. The @var{basereg},
36768 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36769 values (the @samp{-1} value for @var{basereg} is a special case).
36771 @item X @var{len},@var{expr}
36772 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36773 it directs. @var{expr} is an agent expression, as described in
36774 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36775 two-digit hex number in the packet; @var{len} is the number of bytes
36776 in the expression (and thus one-half the number of hex digits in the
36781 Any number of actions may be packed together in a single @samp{QTDP}
36782 packet, as long as the packet does not exceed the maximum packet
36783 length (400 bytes, for many stubs). There may be only one @samp{R}
36784 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36785 actions. Any registers referred to by @samp{M} and @samp{X} actions
36786 must be collected by a preceding @samp{R} action. (The
36787 ``while-stepping'' actions are treated as if they were attached to a
36788 separate tracepoint, as far as these restrictions are concerned.)
36793 The packet was understood and carried out.
36795 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36797 The packet was not recognized.
36800 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36801 @cindex @samp{QTDPsrc} packet
36802 Specify a source string of tracepoint @var{n} at address @var{addr}.
36803 This is useful to get accurate reproduction of the tracepoints
36804 originally downloaded at the beginning of the trace run. @var{type}
36805 is the name of the tracepoint part, such as @samp{cond} for the
36806 tracepoint's conditional expression (see below for a list of types), while
36807 @var{bytes} is the string, encoded in hexadecimal.
36809 @var{start} is the offset of the @var{bytes} within the overall source
36810 string, while @var{slen} is the total length of the source string.
36811 This is intended for handling source strings that are longer than will
36812 fit in a single packet.
36813 @c Add detailed example when this info is moved into a dedicated
36814 @c tracepoint descriptions section.
36816 The available string types are @samp{at} for the location,
36817 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36818 @value{GDBN} sends a separate packet for each command in the action
36819 list, in the same order in which the commands are stored in the list.
36821 The target does not need to do anything with source strings except
36822 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36825 Although this packet is optional, and @value{GDBN} will only send it
36826 if the target replies with @samp{TracepointSource} @xref{General
36827 Query Packets}, it makes both disconnected tracing and trace files
36828 much easier to use. Otherwise the user must be careful that the
36829 tracepoints in effect while looking at trace frames are identical to
36830 the ones in effect during the trace run; even a small discrepancy
36831 could cause @samp{tdump} not to work, or a particular trace frame not
36834 @item QTDV:@var{n}:@var{value}
36835 @cindex define trace state variable, remote request
36836 @cindex @samp{QTDV} packet
36837 Create a new trace state variable, number @var{n}, with an initial
36838 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36839 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36840 the option of not using this packet for initial values of zero; the
36841 target should simply create the trace state variables as they are
36842 mentioned in expressions.
36844 @item QTFrame:@var{n}
36845 Select the @var{n}'th tracepoint frame from the buffer, and use the
36846 register and memory contents recorded there to answer subsequent
36847 request packets from @value{GDBN}.
36849 A successful reply from the stub indicates that the stub has found the
36850 requested frame. The response is a series of parts, concatenated
36851 without separators, describing the frame we selected. Each part has
36852 one of the following forms:
36856 The selected frame is number @var{n} in the trace frame buffer;
36857 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36858 was no frame matching the criteria in the request packet.
36861 The selected trace frame records a hit of tracepoint number @var{t};
36862 @var{t} is a hexadecimal number.
36866 @item QTFrame:pc:@var{addr}
36867 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36868 currently selected frame whose PC is @var{addr};
36869 @var{addr} is a hexadecimal number.
36871 @item QTFrame:tdp:@var{t}
36872 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36873 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36874 is a hexadecimal number.
36876 @item QTFrame:range:@var{start}:@var{end}
36877 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36878 currently selected frame whose PC is between @var{start} (inclusive)
36879 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36882 @item QTFrame:outside:@var{start}:@var{end}
36883 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36884 frame @emph{outside} the given range of addresses (exclusive).
36887 This packet requests the minimum length of instruction at which a fast
36888 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36889 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36890 it depends on the target system being able to create trampolines in
36891 the first 64K of memory, which might or might not be possible for that
36892 system. So the reply to this packet will be 4 if it is able to
36899 The minimum instruction length is currently unknown.
36901 The minimum instruction length is @var{length}, where @var{length} is greater
36902 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
36903 that a fast tracepoint may be placed on any instruction regardless of size.
36905 An error has occurred.
36907 An empty reply indicates that the request is not supported by the stub.
36911 Begin the tracepoint experiment. Begin collecting data from
36912 tracepoint hits in the trace frame buffer. This packet supports the
36913 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36914 instruction reply packet}).
36917 End the tracepoint experiment. Stop collecting trace frames.
36919 @item QTEnable:@var{n}:@var{addr}
36921 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36922 experiment. If the tracepoint was previously disabled, then collection
36923 of data from it will resume.
36925 @item QTDisable:@var{n}:@var{addr}
36927 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36928 experiment. No more data will be collected from the tracepoint unless
36929 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36932 Clear the table of tracepoints, and empty the trace frame buffer.
36934 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36935 Establish the given ranges of memory as ``transparent''. The stub
36936 will answer requests for these ranges from memory's current contents,
36937 if they were not collected as part of the tracepoint hit.
36939 @value{GDBN} uses this to mark read-only regions of memory, like those
36940 containing program code. Since these areas never change, they should
36941 still have the same contents they did when the tracepoint was hit, so
36942 there's no reason for the stub to refuse to provide their contents.
36944 @item QTDisconnected:@var{value}
36945 Set the choice to what to do with the tracing run when @value{GDBN}
36946 disconnects from the target. A @var{value} of 1 directs the target to
36947 continue the tracing run, while 0 tells the target to stop tracing if
36948 @value{GDBN} is no longer in the picture.
36951 Ask the stub if there is a trace experiment running right now.
36953 The reply has the form:
36957 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36958 @var{running} is a single digit @code{1} if the trace is presently
36959 running, or @code{0} if not. It is followed by semicolon-separated
36960 optional fields that an agent may use to report additional status.
36964 If the trace is not running, the agent may report any of several
36965 explanations as one of the optional fields:
36970 No trace has been run yet.
36972 @item tstop[:@var{text}]:0
36973 The trace was stopped by a user-originated stop command. The optional
36974 @var{text} field is a user-supplied string supplied as part of the
36975 stop command (for instance, an explanation of why the trace was
36976 stopped manually). It is hex-encoded.
36979 The trace stopped because the trace buffer filled up.
36981 @item tdisconnected:0
36982 The trace stopped because @value{GDBN} disconnected from the target.
36984 @item tpasscount:@var{tpnum}
36985 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36987 @item terror:@var{text}:@var{tpnum}
36988 The trace stopped because tracepoint @var{tpnum} had an error. The
36989 string @var{text} is available to describe the nature of the error
36990 (for instance, a divide by zero in the condition expression).
36991 @var{text} is hex encoded.
36994 The trace stopped for some other reason.
36998 Additional optional fields supply statistical and other information.
36999 Although not required, they are extremely useful for users monitoring
37000 the progress of a trace run. If a trace has stopped, and these
37001 numbers are reported, they must reflect the state of the just-stopped
37006 @item tframes:@var{n}
37007 The number of trace frames in the buffer.
37009 @item tcreated:@var{n}
37010 The total number of trace frames created during the run. This may
37011 be larger than the trace frame count, if the buffer is circular.
37013 @item tsize:@var{n}
37014 The total size of the trace buffer, in bytes.
37016 @item tfree:@var{n}
37017 The number of bytes still unused in the buffer.
37019 @item circular:@var{n}
37020 The value of the circular trace buffer flag. @code{1} means that the
37021 trace buffer is circular and old trace frames will be discarded if
37022 necessary to make room, @code{0} means that the trace buffer is linear
37025 @item disconn:@var{n}
37026 The value of the disconnected tracing flag. @code{1} means that
37027 tracing will continue after @value{GDBN} disconnects, @code{0} means
37028 that the trace run will stop.
37032 @item qTP:@var{tp}:@var{addr}
37033 @cindex tracepoint status, remote request
37034 @cindex @samp{qTP} packet
37035 Ask the stub for the current state of tracepoint number @var{tp} at
37036 address @var{addr}.
37040 @item V@var{hits}:@var{usage}
37041 The tracepoint has been hit @var{hits} times so far during the trace
37042 run, and accounts for @var{usage} in the trace buffer. Note that
37043 @code{while-stepping} steps are not counted as separate hits, but the
37044 steps' space consumption is added into the usage number.
37048 @item qTV:@var{var}
37049 @cindex trace state variable value, remote request
37050 @cindex @samp{qTV} packet
37051 Ask the stub for the value of the trace state variable number @var{var}.
37056 The value of the variable is @var{value}. This will be the current
37057 value of the variable if the user is examining a running target, or a
37058 saved value if the variable was collected in the trace frame that the
37059 user is looking at. Note that multiple requests may result in
37060 different reply values, such as when requesting values while the
37061 program is running.
37064 The value of the variable is unknown. This would occur, for example,
37065 if the user is examining a trace frame in which the requested variable
37071 These packets request data about tracepoints that are being used by
37072 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37073 of data, and multiple @code{qTsP} to get additional pieces. Replies
37074 to these packets generally take the form of the @code{QTDP} packets
37075 that define tracepoints. (FIXME add detailed syntax)
37079 These packets request data about trace state variables that are on the
37080 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37081 and multiple @code{qTsV} to get additional variables. Replies to
37082 these packets follow the syntax of the @code{QTDV} packets that define
37083 trace state variables.
37087 These packets request data about static tracepoint markers that exist
37088 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37089 first piece of data, and multiple @code{qTsSTM} to get additional
37090 pieces. Replies to these packets take the following form:
37094 @item m @var{address}:@var{id}:@var{extra}
37096 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37097 a comma-separated list of markers
37099 (lower case letter @samp{L}) denotes end of list.
37101 An error occurred. @var{nn} are hex digits.
37103 An empty reply indicates that the request is not supported by the
37107 @var{address} is encoded in hex.
37108 @var{id} and @var{extra} are strings encoded in hex.
37110 In response to each query, the target will reply with a list of one or
37111 more markers, separated by commas. @value{GDBN} will respond to each
37112 reply with a request for more markers (using the @samp{qs} form of the
37113 query), until the target responds with @samp{l} (lower-case ell, for
37116 @item qTSTMat:@var{address}
37117 This packets requests data about static tracepoint markers in the
37118 target program at @var{address}. Replies to this packet follow the
37119 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37120 tracepoint markers.
37122 @item QTSave:@var{filename}
37123 This packet directs the target to save trace data to the file name
37124 @var{filename} in the target's filesystem. @var{filename} is encoded
37125 as a hex string; the interpretation of the file name (relative vs
37126 absolute, wild cards, etc) is up to the target.
37128 @item qTBuffer:@var{offset},@var{len}
37129 Return up to @var{len} bytes of the current contents of trace buffer,
37130 starting at @var{offset}. The trace buffer is treated as if it were
37131 a contiguous collection of traceframes, as per the trace file format.
37132 The reply consists as many hex-encoded bytes as the target can deliver
37133 in a packet; it is not an error to return fewer than were asked for.
37134 A reply consisting of just @code{l} indicates that no bytes are
37137 @item QTBuffer:circular:@var{value}
37138 This packet directs the target to use a circular trace buffer if
37139 @var{value} is 1, or a linear buffer if the value is 0.
37141 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37142 This packet adds optional textual notes to the trace run. Allowable
37143 types include @code{user}, @code{notes}, and @code{tstop}, the
37144 @var{text} fields are arbitrary strings, hex-encoded.
37148 @subsection Relocate instruction reply packet
37149 When installing fast tracepoints in memory, the target may need to
37150 relocate the instruction currently at the tracepoint address to a
37151 different address in memory. For most instructions, a simple copy is
37152 enough, but, for example, call instructions that implicitly push the
37153 return address on the stack, and relative branches or other
37154 PC-relative instructions require offset adjustment, so that the effect
37155 of executing the instruction at a different address is the same as if
37156 it had executed in the original location.
37158 In response to several of the tracepoint packets, the target may also
37159 respond with a number of intermediate @samp{qRelocInsn} request
37160 packets before the final result packet, to have @value{GDBN} handle
37161 this relocation operation. If a packet supports this mechanism, its
37162 documentation will explicitly say so. See for example the above
37163 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37164 format of the request is:
37167 @item qRelocInsn:@var{from};@var{to}
37169 This requests @value{GDBN} to copy instruction at address @var{from}
37170 to address @var{to}, possibly adjusted so that executing the
37171 instruction at @var{to} has the same effect as executing it at
37172 @var{from}. @value{GDBN} writes the adjusted instruction to target
37173 memory starting at @var{to}.
37178 @item qRelocInsn:@var{adjusted_size}
37179 Informs the stub the relocation is complete. @var{adjusted_size} is
37180 the length in bytes of resulting relocated instruction sequence.
37182 A badly formed request was detected, or an error was encountered while
37183 relocating the instruction.
37186 @node Host I/O Packets
37187 @section Host I/O Packets
37188 @cindex Host I/O, remote protocol
37189 @cindex file transfer, remote protocol
37191 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37192 operations on the far side of a remote link. For example, Host I/O is
37193 used to upload and download files to a remote target with its own
37194 filesystem. Host I/O uses the same constant values and data structure
37195 layout as the target-initiated File-I/O protocol. However, the
37196 Host I/O packets are structured differently. The target-initiated
37197 protocol relies on target memory to store parameters and buffers.
37198 Host I/O requests are initiated by @value{GDBN}, and the
37199 target's memory is not involved. @xref{File-I/O Remote Protocol
37200 Extension}, for more details on the target-initiated protocol.
37202 The Host I/O request packets all encode a single operation along with
37203 its arguments. They have this format:
37207 @item vFile:@var{operation}: @var{parameter}@dots{}
37208 @var{operation} is the name of the particular request; the target
37209 should compare the entire packet name up to the second colon when checking
37210 for a supported operation. The format of @var{parameter} depends on
37211 the operation. Numbers are always passed in hexadecimal. Negative
37212 numbers have an explicit minus sign (i.e.@: two's complement is not
37213 used). Strings (e.g.@: filenames) are encoded as a series of
37214 hexadecimal bytes. The last argument to a system call may be a
37215 buffer of escaped binary data (@pxref{Binary Data}).
37219 The valid responses to Host I/O packets are:
37223 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37224 @var{result} is the integer value returned by this operation, usually
37225 non-negative for success and -1 for errors. If an error has occured,
37226 @var{errno} will be included in the result. @var{errno} will have a
37227 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37228 operations which return data, @var{attachment} supplies the data as a
37229 binary buffer. Binary buffers in response packets are escaped in the
37230 normal way (@pxref{Binary Data}). See the individual packet
37231 documentation for the interpretation of @var{result} and
37235 An empty response indicates that this operation is not recognized.
37239 These are the supported Host I/O operations:
37242 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
37243 Open a file at @var{pathname} and return a file descriptor for it, or
37244 return -1 if an error occurs. @var{pathname} is a string,
37245 @var{flags} is an integer indicating a mask of open flags
37246 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37247 of mode bits to use if the file is created (@pxref{mode_t Values}).
37248 @xref{open}, for details of the open flags and mode values.
37250 @item vFile:close: @var{fd}
37251 Close the open file corresponding to @var{fd} and return 0, or
37252 -1 if an error occurs.
37254 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37255 Read data from the open file corresponding to @var{fd}. Up to
37256 @var{count} bytes will be read from the file, starting at @var{offset}
37257 relative to the start of the file. The target may read fewer bytes;
37258 common reasons include packet size limits and an end-of-file
37259 condition. The number of bytes read is returned. Zero should only be
37260 returned for a successful read at the end of the file, or if
37261 @var{count} was zero.
37263 The data read should be returned as a binary attachment on success.
37264 If zero bytes were read, the response should include an empty binary
37265 attachment (i.e.@: a trailing semicolon). The return value is the
37266 number of target bytes read; the binary attachment may be longer if
37267 some characters were escaped.
37269 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37270 Write @var{data} (a binary buffer) to the open file corresponding
37271 to @var{fd}. Start the write at @var{offset} from the start of the
37272 file. Unlike many @code{write} system calls, there is no
37273 separate @var{count} argument; the length of @var{data} in the
37274 packet is used. @samp{vFile:write} returns the number of bytes written,
37275 which may be shorter than the length of @var{data}, or -1 if an
37278 @item vFile:unlink: @var{pathname}
37279 Delete the file at @var{pathname} on the target. Return 0,
37280 or -1 if an error occurs. @var{pathname} is a string.
37282 @item vFile:readlink: @var{filename}
37283 Read value of symbolic link @var{filename} on the target. Return
37284 the number of bytes read, or -1 if an error occurs.
37286 The data read should be returned as a binary attachment on success.
37287 If zero bytes were read, the response should include an empty binary
37288 attachment (i.e.@: a trailing semicolon). The return value is the
37289 number of target bytes read; the binary attachment may be longer if
37290 some characters were escaped.
37295 @section Interrupts
37296 @cindex interrupts (remote protocol)
37298 When a program on the remote target is running, @value{GDBN} may
37299 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37300 a @code{BREAK} followed by @code{g},
37301 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37303 The precise meaning of @code{BREAK} is defined by the transport
37304 mechanism and may, in fact, be undefined. @value{GDBN} does not
37305 currently define a @code{BREAK} mechanism for any of the network
37306 interfaces except for TCP, in which case @value{GDBN} sends the
37307 @code{telnet} BREAK sequence.
37309 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37310 transport mechanisms. It is represented by sending the single byte
37311 @code{0x03} without any of the usual packet overhead described in
37312 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37313 transmitted as part of a packet, it is considered to be packet data
37314 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37315 (@pxref{X packet}), used for binary downloads, may include an unescaped
37316 @code{0x03} as part of its packet.
37318 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37319 When Linux kernel receives this sequence from serial port,
37320 it stops execution and connects to gdb.
37322 Stubs are not required to recognize these interrupt mechanisms and the
37323 precise meaning associated with receipt of the interrupt is
37324 implementation defined. If the target supports debugging of multiple
37325 threads and/or processes, it should attempt to interrupt all
37326 currently-executing threads and processes.
37327 If the stub is successful at interrupting the
37328 running program, it should send one of the stop
37329 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37330 of successfully stopping the program in all-stop mode, and a stop reply
37331 for each stopped thread in non-stop mode.
37332 Interrupts received while the
37333 program is stopped are discarded.
37335 @node Notification Packets
37336 @section Notification Packets
37337 @cindex notification packets
37338 @cindex packets, notification
37340 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37341 packets that require no acknowledgment. Both the GDB and the stub
37342 may send notifications (although the only notifications defined at
37343 present are sent by the stub). Notifications carry information
37344 without incurring the round-trip latency of an acknowledgment, and so
37345 are useful for low-impact communications where occasional packet loss
37348 A notification packet has the form @samp{% @var{data} #
37349 @var{checksum}}, where @var{data} is the content of the notification,
37350 and @var{checksum} is a checksum of @var{data}, computed and formatted
37351 as for ordinary @value{GDBN} packets. A notification's @var{data}
37352 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37353 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37354 to acknowledge the notification's receipt or to report its corruption.
37356 Every notification's @var{data} begins with a name, which contains no
37357 colon characters, followed by a colon character.
37359 Recipients should silently ignore corrupted notifications and
37360 notifications they do not understand. Recipients should restart
37361 timeout periods on receipt of a well-formed notification, whether or
37362 not they understand it.
37364 Senders should only send the notifications described here when this
37365 protocol description specifies that they are permitted. In the
37366 future, we may extend the protocol to permit existing notifications in
37367 new contexts; this rule helps older senders avoid confusing newer
37370 (Older versions of @value{GDBN} ignore bytes received until they see
37371 the @samp{$} byte that begins an ordinary packet, so new stubs may
37372 transmit notifications without fear of confusing older clients. There
37373 are no notifications defined for @value{GDBN} to send at the moment, but we
37374 assume that most older stubs would ignore them, as well.)
37376 The following notification packets from the stub to @value{GDBN} are
37380 @item Stop: @var{reply}
37381 Report an asynchronous stop event in non-stop mode.
37382 The @var{reply} has the form of a stop reply, as
37383 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37384 for information on how these notifications are acknowledged by
37388 @node Remote Non-Stop
37389 @section Remote Protocol Support for Non-Stop Mode
37391 @value{GDBN}'s remote protocol supports non-stop debugging of
37392 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37393 supports non-stop mode, it should report that to @value{GDBN} by including
37394 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37396 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37397 establishing a new connection with the stub. Entering non-stop mode
37398 does not alter the state of any currently-running threads, but targets
37399 must stop all threads in any already-attached processes when entering
37400 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37401 probe the target state after a mode change.
37403 In non-stop mode, when an attached process encounters an event that
37404 would otherwise be reported with a stop reply, it uses the
37405 asynchronous notification mechanism (@pxref{Notification Packets}) to
37406 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37407 in all processes are stopped when a stop reply is sent, in non-stop
37408 mode only the thread reporting the stop event is stopped. That is,
37409 when reporting a @samp{S} or @samp{T} response to indicate completion
37410 of a step operation, hitting a breakpoint, or a fault, only the
37411 affected thread is stopped; any other still-running threads continue
37412 to run. When reporting a @samp{W} or @samp{X} response, all running
37413 threads belonging to other attached processes continue to run.
37415 Only one stop reply notification at a time may be pending; if
37416 additional stop events occur before @value{GDBN} has acknowledged the
37417 previous notification, they must be queued by the stub for later
37418 synchronous transmission in response to @samp{vStopped} packets from
37419 @value{GDBN}. Because the notification mechanism is unreliable,
37420 the stub is permitted to resend a stop reply notification
37421 if it believes @value{GDBN} may not have received it. @value{GDBN}
37422 ignores additional stop reply notifications received before it has
37423 finished processing a previous notification and the stub has completed
37424 sending any queued stop events.
37426 Otherwise, @value{GDBN} must be prepared to receive a stop reply
37427 notification at any time. Specifically, they may appear when
37428 @value{GDBN} is not otherwise reading input from the stub, or when
37429 @value{GDBN} is expecting to read a normal synchronous response or a
37430 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37431 Notification packets are distinct from any other communication from
37432 the stub so there is no ambiguity.
37434 After receiving a stop reply notification, @value{GDBN} shall
37435 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
37436 as a regular, synchronous request to the stub. Such acknowledgment
37437 is not required to happen immediately, as @value{GDBN} is permitted to
37438 send other, unrelated packets to the stub first, which the stub should
37441 Upon receiving a @samp{vStopped} packet, if the stub has other queued
37442 stop events to report to @value{GDBN}, it shall respond by sending a
37443 normal stop reply response. @value{GDBN} shall then send another
37444 @samp{vStopped} packet to solicit further responses; again, it is
37445 permitted to send other, unrelated packets as well which the stub
37446 should process normally.
37448 If the stub receives a @samp{vStopped} packet and there are no
37449 additional stop events to report, the stub shall return an @samp{OK}
37450 response. At this point, if further stop events occur, the stub shall
37451 send a new stop reply notification, @value{GDBN} shall accept the
37452 notification, and the process shall be repeated.
37454 In non-stop mode, the target shall respond to the @samp{?} packet as
37455 follows. First, any incomplete stop reply notification/@samp{vStopped}
37456 sequence in progress is abandoned. The target must begin a new
37457 sequence reporting stop events for all stopped threads, whether or not
37458 it has previously reported those events to @value{GDBN}. The first
37459 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37460 subsequent stop replies are sent as responses to @samp{vStopped} packets
37461 using the mechanism described above. The target must not send
37462 asynchronous stop reply notifications until the sequence is complete.
37463 If all threads are running when the target receives the @samp{?} packet,
37464 or if the target is not attached to any process, it shall respond
37467 @node Packet Acknowledgment
37468 @section Packet Acknowledgment
37470 @cindex acknowledgment, for @value{GDBN} remote
37471 @cindex packet acknowledgment, for @value{GDBN} remote
37472 By default, when either the host or the target machine receives a packet,
37473 the first response expected is an acknowledgment: either @samp{+} (to indicate
37474 the package was received correctly) or @samp{-} (to request retransmission).
37475 This mechanism allows the @value{GDBN} remote protocol to operate over
37476 unreliable transport mechanisms, such as a serial line.
37478 In cases where the transport mechanism is itself reliable (such as a pipe or
37479 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37480 It may be desirable to disable them in that case to reduce communication
37481 overhead, or for other reasons. This can be accomplished by means of the
37482 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37484 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37485 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37486 and response format still includes the normal checksum, as described in
37487 @ref{Overview}, but the checksum may be ignored by the receiver.
37489 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37490 no-acknowledgment mode, it should report that to @value{GDBN}
37491 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37492 @pxref{qSupported}.
37493 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37494 disabled via the @code{set remote noack-packet off} command
37495 (@pxref{Remote Configuration}),
37496 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37497 Only then may the stub actually turn off packet acknowledgments.
37498 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37499 response, which can be safely ignored by the stub.
37501 Note that @code{set remote noack-packet} command only affects negotiation
37502 between @value{GDBN} and the stub when subsequent connections are made;
37503 it does not affect the protocol acknowledgment state for any current
37505 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37506 new connection is established,
37507 there is also no protocol request to re-enable the acknowledgments
37508 for the current connection, once disabled.
37513 Example sequence of a target being re-started. Notice how the restart
37514 does not get any direct output:
37519 @emph{target restarts}
37522 <- @code{T001:1234123412341234}
37526 Example sequence of a target being stepped by a single instruction:
37529 -> @code{G1445@dots{}}
37534 <- @code{T001:1234123412341234}
37538 <- @code{1455@dots{}}
37542 @node File-I/O Remote Protocol Extension
37543 @section File-I/O Remote Protocol Extension
37544 @cindex File-I/O remote protocol extension
37547 * File-I/O Overview::
37548 * Protocol Basics::
37549 * The F Request Packet::
37550 * The F Reply Packet::
37551 * The Ctrl-C Message::
37553 * List of Supported Calls::
37554 * Protocol-specific Representation of Datatypes::
37556 * File-I/O Examples::
37559 @node File-I/O Overview
37560 @subsection File-I/O Overview
37561 @cindex file-i/o overview
37563 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37564 target to use the host's file system and console I/O to perform various
37565 system calls. System calls on the target system are translated into a
37566 remote protocol packet to the host system, which then performs the needed
37567 actions and returns a response packet to the target system.
37568 This simulates file system operations even on targets that lack file systems.
37570 The protocol is defined to be independent of both the host and target systems.
37571 It uses its own internal representation of datatypes and values. Both
37572 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37573 translating the system-dependent value representations into the internal
37574 protocol representations when data is transmitted.
37576 The communication is synchronous. A system call is possible only when
37577 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37578 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37579 the target is stopped to allow deterministic access to the target's
37580 memory. Therefore File-I/O is not interruptible by target signals. On
37581 the other hand, it is possible to interrupt File-I/O by a user interrupt
37582 (@samp{Ctrl-C}) within @value{GDBN}.
37584 The target's request to perform a host system call does not finish
37585 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37586 after finishing the system call, the target returns to continuing the
37587 previous activity (continue, step). No additional continue or step
37588 request from @value{GDBN} is required.
37591 (@value{GDBP}) continue
37592 <- target requests 'system call X'
37593 target is stopped, @value{GDBN} executes system call
37594 -> @value{GDBN} returns result
37595 ... target continues, @value{GDBN} returns to wait for the target
37596 <- target hits breakpoint and sends a Txx packet
37599 The protocol only supports I/O on the console and to regular files on
37600 the host file system. Character or block special devices, pipes,
37601 named pipes, sockets or any other communication method on the host
37602 system are not supported by this protocol.
37604 File I/O is not supported in non-stop mode.
37606 @node Protocol Basics
37607 @subsection Protocol Basics
37608 @cindex protocol basics, file-i/o
37610 The File-I/O protocol uses the @code{F} packet as the request as well
37611 as reply packet. Since a File-I/O system call can only occur when
37612 @value{GDBN} is waiting for a response from the continuing or stepping target,
37613 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37614 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37615 This @code{F} packet contains all information needed to allow @value{GDBN}
37616 to call the appropriate host system call:
37620 A unique identifier for the requested system call.
37623 All parameters to the system call. Pointers are given as addresses
37624 in the target memory address space. Pointers to strings are given as
37625 pointer/length pair. Numerical values are given as they are.
37626 Numerical control flags are given in a protocol-specific representation.
37630 At this point, @value{GDBN} has to perform the following actions.
37634 If the parameters include pointer values to data needed as input to a
37635 system call, @value{GDBN} requests this data from the target with a
37636 standard @code{m} packet request. This additional communication has to be
37637 expected by the target implementation and is handled as any other @code{m}
37641 @value{GDBN} translates all value from protocol representation to host
37642 representation as needed. Datatypes are coerced into the host types.
37645 @value{GDBN} calls the system call.
37648 It then coerces datatypes back to protocol representation.
37651 If the system call is expected to return data in buffer space specified
37652 by pointer parameters to the call, the data is transmitted to the
37653 target using a @code{M} or @code{X} packet. This packet has to be expected
37654 by the target implementation and is handled as any other @code{M} or @code{X}
37659 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37660 necessary information for the target to continue. This at least contains
37667 @code{errno}, if has been changed by the system call.
37674 After having done the needed type and value coercion, the target continues
37675 the latest continue or step action.
37677 @node The F Request Packet
37678 @subsection The @code{F} Request Packet
37679 @cindex file-i/o request packet
37680 @cindex @code{F} request packet
37682 The @code{F} request packet has the following format:
37685 @item F@var{call-id},@var{parameter@dots{}}
37687 @var{call-id} is the identifier to indicate the host system call to be called.
37688 This is just the name of the function.
37690 @var{parameter@dots{}} are the parameters to the system call.
37691 Parameters are hexadecimal integer values, either the actual values in case
37692 of scalar datatypes, pointers to target buffer space in case of compound
37693 datatypes and unspecified memory areas, or pointer/length pairs in case
37694 of string parameters. These are appended to the @var{call-id} as a
37695 comma-delimited list. All values are transmitted in ASCII
37696 string representation, pointer/length pairs separated by a slash.
37702 @node The F Reply Packet
37703 @subsection The @code{F} Reply Packet
37704 @cindex file-i/o reply packet
37705 @cindex @code{F} reply packet
37707 The @code{F} reply packet has the following format:
37711 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37713 @var{retcode} is the return code of the system call as hexadecimal value.
37715 @var{errno} is the @code{errno} set by the call, in protocol-specific
37717 This parameter can be omitted if the call was successful.
37719 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37720 case, @var{errno} must be sent as well, even if the call was successful.
37721 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37728 or, if the call was interrupted before the host call has been performed:
37735 assuming 4 is the protocol-specific representation of @code{EINTR}.
37740 @node The Ctrl-C Message
37741 @subsection The @samp{Ctrl-C} Message
37742 @cindex ctrl-c message, in file-i/o protocol
37744 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37745 reply packet (@pxref{The F Reply Packet}),
37746 the target should behave as if it had
37747 gotten a break message. The meaning for the target is ``system call
37748 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37749 (as with a break message) and return to @value{GDBN} with a @code{T02}
37752 It's important for the target to know in which
37753 state the system call was interrupted. There are two possible cases:
37757 The system call hasn't been performed on the host yet.
37760 The system call on the host has been finished.
37764 These two states can be distinguished by the target by the value of the
37765 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37766 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37767 on POSIX systems. In any other case, the target may presume that the
37768 system call has been finished --- successfully or not --- and should behave
37769 as if the break message arrived right after the system call.
37771 @value{GDBN} must behave reliably. If the system call has not been called
37772 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37773 @code{errno} in the packet. If the system call on the host has been finished
37774 before the user requests a break, the full action must be finished by
37775 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37776 The @code{F} packet may only be sent when either nothing has happened
37777 or the full action has been completed.
37780 @subsection Console I/O
37781 @cindex console i/o as part of file-i/o
37783 By default and if not explicitly closed by the target system, the file
37784 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37785 on the @value{GDBN} console is handled as any other file output operation
37786 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37787 by @value{GDBN} so that after the target read request from file descriptor
37788 0 all following typing is buffered until either one of the following
37793 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37795 system call is treated as finished.
37798 The user presses @key{RET}. This is treated as end of input with a trailing
37802 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37803 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37807 If the user has typed more characters than fit in the buffer given to
37808 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37809 either another @code{read(0, @dots{})} is requested by the target, or debugging
37810 is stopped at the user's request.
37813 @node List of Supported Calls
37814 @subsection List of Supported Calls
37815 @cindex list of supported file-i/o calls
37832 @unnumberedsubsubsec open
37833 @cindex open, file-i/o system call
37838 int open(const char *pathname, int flags);
37839 int open(const char *pathname, int flags, mode_t mode);
37843 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37846 @var{flags} is the bitwise @code{OR} of the following values:
37850 If the file does not exist it will be created. The host
37851 rules apply as far as file ownership and time stamps
37855 When used with @code{O_CREAT}, if the file already exists it is
37856 an error and open() fails.
37859 If the file already exists and the open mode allows
37860 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37861 truncated to zero length.
37864 The file is opened in append mode.
37867 The file is opened for reading only.
37870 The file is opened for writing only.
37873 The file is opened for reading and writing.
37877 Other bits are silently ignored.
37881 @var{mode} is the bitwise @code{OR} of the following values:
37885 User has read permission.
37888 User has write permission.
37891 Group has read permission.
37894 Group has write permission.
37897 Others have read permission.
37900 Others have write permission.
37904 Other bits are silently ignored.
37907 @item Return value:
37908 @code{open} returns the new file descriptor or -1 if an error
37915 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37918 @var{pathname} refers to a directory.
37921 The requested access is not allowed.
37924 @var{pathname} was too long.
37927 A directory component in @var{pathname} does not exist.
37930 @var{pathname} refers to a device, pipe, named pipe or socket.
37933 @var{pathname} refers to a file on a read-only filesystem and
37934 write access was requested.
37937 @var{pathname} is an invalid pointer value.
37940 No space on device to create the file.
37943 The process already has the maximum number of files open.
37946 The limit on the total number of files open on the system
37950 The call was interrupted by the user.
37956 @unnumberedsubsubsec close
37957 @cindex close, file-i/o system call
37966 @samp{Fclose,@var{fd}}
37968 @item Return value:
37969 @code{close} returns zero on success, or -1 if an error occurred.
37975 @var{fd} isn't a valid open file descriptor.
37978 The call was interrupted by the user.
37984 @unnumberedsubsubsec read
37985 @cindex read, file-i/o system call
37990 int read(int fd, void *buf, unsigned int count);
37994 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37996 @item Return value:
37997 On success, the number of bytes read is returned.
37998 Zero indicates end of file. If count is zero, read
37999 returns zero as well. On error, -1 is returned.
38005 @var{fd} is not a valid file descriptor or is not open for
38009 @var{bufptr} is an invalid pointer value.
38012 The call was interrupted by the user.
38018 @unnumberedsubsubsec write
38019 @cindex write, file-i/o system call
38024 int write(int fd, const void *buf, unsigned int count);
38028 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38030 @item Return value:
38031 On success, the number of bytes written are returned.
38032 Zero indicates nothing was written. On error, -1
38039 @var{fd} is not a valid file descriptor or is not open for
38043 @var{bufptr} is an invalid pointer value.
38046 An attempt was made to write a file that exceeds the
38047 host-specific maximum file size allowed.
38050 No space on device to write the data.
38053 The call was interrupted by the user.
38059 @unnumberedsubsubsec lseek
38060 @cindex lseek, file-i/o system call
38065 long lseek (int fd, long offset, int flag);
38069 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38071 @var{flag} is one of:
38075 The offset is set to @var{offset} bytes.
38078 The offset is set to its current location plus @var{offset}
38082 The offset is set to the size of the file plus @var{offset}
38086 @item Return value:
38087 On success, the resulting unsigned offset in bytes from
38088 the beginning of the file is returned. Otherwise, a
38089 value of -1 is returned.
38095 @var{fd} is not a valid open file descriptor.
38098 @var{fd} is associated with the @value{GDBN} console.
38101 @var{flag} is not a proper value.
38104 The call was interrupted by the user.
38110 @unnumberedsubsubsec rename
38111 @cindex rename, file-i/o system call
38116 int rename(const char *oldpath, const char *newpath);
38120 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38122 @item Return value:
38123 On success, zero is returned. On error, -1 is returned.
38129 @var{newpath} is an existing directory, but @var{oldpath} is not a
38133 @var{newpath} is a non-empty directory.
38136 @var{oldpath} or @var{newpath} is a directory that is in use by some
38140 An attempt was made to make a directory a subdirectory
38144 A component used as a directory in @var{oldpath} or new
38145 path is not a directory. Or @var{oldpath} is a directory
38146 and @var{newpath} exists but is not a directory.
38149 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38152 No access to the file or the path of the file.
38156 @var{oldpath} or @var{newpath} was too long.
38159 A directory component in @var{oldpath} or @var{newpath} does not exist.
38162 The file is on a read-only filesystem.
38165 The device containing the file has no room for the new
38169 The call was interrupted by the user.
38175 @unnumberedsubsubsec unlink
38176 @cindex unlink, file-i/o system call
38181 int unlink(const char *pathname);
38185 @samp{Funlink,@var{pathnameptr}/@var{len}}
38187 @item Return value:
38188 On success, zero is returned. On error, -1 is returned.
38194 No access to the file or the path of the file.
38197 The system does not allow unlinking of directories.
38200 The file @var{pathname} cannot be unlinked because it's
38201 being used by another process.
38204 @var{pathnameptr} is an invalid pointer value.
38207 @var{pathname} was too long.
38210 A directory component in @var{pathname} does not exist.
38213 A component of the path is not a directory.
38216 The file is on a read-only filesystem.
38219 The call was interrupted by the user.
38225 @unnumberedsubsubsec stat/fstat
38226 @cindex fstat, file-i/o system call
38227 @cindex stat, file-i/o system call
38232 int stat(const char *pathname, struct stat *buf);
38233 int fstat(int fd, struct stat *buf);
38237 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38238 @samp{Ffstat,@var{fd},@var{bufptr}}
38240 @item Return value:
38241 On success, zero is returned. On error, -1 is returned.
38247 @var{fd} is not a valid open file.
38250 A directory component in @var{pathname} does not exist or the
38251 path is an empty string.
38254 A component of the path is not a directory.
38257 @var{pathnameptr} is an invalid pointer value.
38260 No access to the file or the path of the file.
38263 @var{pathname} was too long.
38266 The call was interrupted by the user.
38272 @unnumberedsubsubsec gettimeofday
38273 @cindex gettimeofday, file-i/o system call
38278 int gettimeofday(struct timeval *tv, void *tz);
38282 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38284 @item Return value:
38285 On success, 0 is returned, -1 otherwise.
38291 @var{tz} is a non-NULL pointer.
38294 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38300 @unnumberedsubsubsec isatty
38301 @cindex isatty, file-i/o system call
38306 int isatty(int fd);
38310 @samp{Fisatty,@var{fd}}
38312 @item Return value:
38313 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38319 The call was interrupted by the user.
38324 Note that the @code{isatty} call is treated as a special case: it returns
38325 1 to the target if the file descriptor is attached
38326 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38327 would require implementing @code{ioctl} and would be more complex than
38332 @unnumberedsubsubsec system
38333 @cindex system, file-i/o system call
38338 int system(const char *command);
38342 @samp{Fsystem,@var{commandptr}/@var{len}}
38344 @item Return value:
38345 If @var{len} is zero, the return value indicates whether a shell is
38346 available. A zero return value indicates a shell is not available.
38347 For non-zero @var{len}, the value returned is -1 on error and the
38348 return status of the command otherwise. Only the exit status of the
38349 command is returned, which is extracted from the host's @code{system}
38350 return value by calling @code{WEXITSTATUS(retval)}. In case
38351 @file{/bin/sh} could not be executed, 127 is returned.
38357 The call was interrupted by the user.
38362 @value{GDBN} takes over the full task of calling the necessary host calls
38363 to perform the @code{system} call. The return value of @code{system} on
38364 the host is simplified before it's returned
38365 to the target. Any termination signal information from the child process
38366 is discarded, and the return value consists
38367 entirely of the exit status of the called command.
38369 Due to security concerns, the @code{system} call is by default refused
38370 by @value{GDBN}. The user has to allow this call explicitly with the
38371 @code{set remote system-call-allowed 1} command.
38374 @item set remote system-call-allowed
38375 @kindex set remote system-call-allowed
38376 Control whether to allow the @code{system} calls in the File I/O
38377 protocol for the remote target. The default is zero (disabled).
38379 @item show remote system-call-allowed
38380 @kindex show remote system-call-allowed
38381 Show whether the @code{system} calls are allowed in the File I/O
38385 @node Protocol-specific Representation of Datatypes
38386 @subsection Protocol-specific Representation of Datatypes
38387 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38390 * Integral Datatypes::
38392 * Memory Transfer::
38397 @node Integral Datatypes
38398 @unnumberedsubsubsec Integral Datatypes
38399 @cindex integral datatypes, in file-i/o protocol
38401 The integral datatypes used in the system calls are @code{int},
38402 @code{unsigned int}, @code{long}, @code{unsigned long},
38403 @code{mode_t}, and @code{time_t}.
38405 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38406 implemented as 32 bit values in this protocol.
38408 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38410 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38411 in @file{limits.h}) to allow range checking on host and target.
38413 @code{time_t} datatypes are defined as seconds since the Epoch.
38415 All integral datatypes transferred as part of a memory read or write of a
38416 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38419 @node Pointer Values
38420 @unnumberedsubsubsec Pointer Values
38421 @cindex pointer values, in file-i/o protocol
38423 Pointers to target data are transmitted as they are. An exception
38424 is made for pointers to buffers for which the length isn't
38425 transmitted as part of the function call, namely strings. Strings
38426 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38433 which is a pointer to data of length 18 bytes at position 0x1aaf.
38434 The length is defined as the full string length in bytes, including
38435 the trailing null byte. For example, the string @code{"hello world"}
38436 at address 0x123456 is transmitted as
38442 @node Memory Transfer
38443 @unnumberedsubsubsec Memory Transfer
38444 @cindex memory transfer, in file-i/o protocol
38446 Structured data which is transferred using a memory read or write (for
38447 example, a @code{struct stat}) is expected to be in a protocol-specific format
38448 with all scalar multibyte datatypes being big endian. Translation to
38449 this representation needs to be done both by the target before the @code{F}
38450 packet is sent, and by @value{GDBN} before
38451 it transfers memory to the target. Transferred pointers to structured
38452 data should point to the already-coerced data at any time.
38456 @unnumberedsubsubsec struct stat
38457 @cindex struct stat, in file-i/o protocol
38459 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38460 is defined as follows:
38464 unsigned int st_dev; /* device */
38465 unsigned int st_ino; /* inode */
38466 mode_t st_mode; /* protection */
38467 unsigned int st_nlink; /* number of hard links */
38468 unsigned int st_uid; /* user ID of owner */
38469 unsigned int st_gid; /* group ID of owner */
38470 unsigned int st_rdev; /* device type (if inode device) */
38471 unsigned long st_size; /* total size, in bytes */
38472 unsigned long st_blksize; /* blocksize for filesystem I/O */
38473 unsigned long st_blocks; /* number of blocks allocated */
38474 time_t st_atime; /* time of last access */
38475 time_t st_mtime; /* time of last modification */
38476 time_t st_ctime; /* time of last change */
38480 The integral datatypes conform to the definitions given in the
38481 appropriate section (see @ref{Integral Datatypes}, for details) so this
38482 structure is of size 64 bytes.
38484 The values of several fields have a restricted meaning and/or
38490 A value of 0 represents a file, 1 the console.
38493 No valid meaning for the target. Transmitted unchanged.
38496 Valid mode bits are described in @ref{Constants}. Any other
38497 bits have currently no meaning for the target.
38502 No valid meaning for the target. Transmitted unchanged.
38507 These values have a host and file system dependent
38508 accuracy. Especially on Windows hosts, the file system may not
38509 support exact timing values.
38512 The target gets a @code{struct stat} of the above representation and is
38513 responsible for coercing it to the target representation before
38516 Note that due to size differences between the host, target, and protocol
38517 representations of @code{struct stat} members, these members could eventually
38518 get truncated on the target.
38520 @node struct timeval
38521 @unnumberedsubsubsec struct timeval
38522 @cindex struct timeval, in file-i/o protocol
38524 The buffer of type @code{struct timeval} used by the File-I/O protocol
38525 is defined as follows:
38529 time_t tv_sec; /* second */
38530 long tv_usec; /* microsecond */
38534 The integral datatypes conform to the definitions given in the
38535 appropriate section (see @ref{Integral Datatypes}, for details) so this
38536 structure is of size 8 bytes.
38539 @subsection Constants
38540 @cindex constants, in file-i/o protocol
38542 The following values are used for the constants inside of the
38543 protocol. @value{GDBN} and target are responsible for translating these
38544 values before and after the call as needed.
38555 @unnumberedsubsubsec Open Flags
38556 @cindex open flags, in file-i/o protocol
38558 All values are given in hexadecimal representation.
38570 @node mode_t Values
38571 @unnumberedsubsubsec mode_t Values
38572 @cindex mode_t values, in file-i/o protocol
38574 All values are given in octal representation.
38591 @unnumberedsubsubsec Errno Values
38592 @cindex errno values, in file-i/o protocol
38594 All values are given in decimal representation.
38619 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38620 any error value not in the list of supported error numbers.
38623 @unnumberedsubsubsec Lseek Flags
38624 @cindex lseek flags, in file-i/o protocol
38633 @unnumberedsubsubsec Limits
38634 @cindex limits, in file-i/o protocol
38636 All values are given in decimal representation.
38639 INT_MIN -2147483648
38641 UINT_MAX 4294967295
38642 LONG_MIN -9223372036854775808
38643 LONG_MAX 9223372036854775807
38644 ULONG_MAX 18446744073709551615
38647 @node File-I/O Examples
38648 @subsection File-I/O Examples
38649 @cindex file-i/o examples
38651 Example sequence of a write call, file descriptor 3, buffer is at target
38652 address 0x1234, 6 bytes should be written:
38655 <- @code{Fwrite,3,1234,6}
38656 @emph{request memory read from target}
38659 @emph{return "6 bytes written"}
38663 Example sequence of a read call, file descriptor 3, buffer is at target
38664 address 0x1234, 6 bytes should be read:
38667 <- @code{Fread,3,1234,6}
38668 @emph{request memory write to target}
38669 -> @code{X1234,6:XXXXXX}
38670 @emph{return "6 bytes read"}
38674 Example sequence of a read call, call fails on the host due to invalid
38675 file descriptor (@code{EBADF}):
38678 <- @code{Fread,3,1234,6}
38682 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38686 <- @code{Fread,3,1234,6}
38691 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38695 <- @code{Fread,3,1234,6}
38696 -> @code{X1234,6:XXXXXX}
38700 @node Library List Format
38701 @section Library List Format
38702 @cindex library list format, remote protocol
38704 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38705 same process as your application to manage libraries. In this case,
38706 @value{GDBN} can use the loader's symbol table and normal memory
38707 operations to maintain a list of shared libraries. On other
38708 platforms, the operating system manages loaded libraries.
38709 @value{GDBN} can not retrieve the list of currently loaded libraries
38710 through memory operations, so it uses the @samp{qXfer:libraries:read}
38711 packet (@pxref{qXfer library list read}) instead. The remote stub
38712 queries the target's operating system and reports which libraries
38715 The @samp{qXfer:libraries:read} packet returns an XML document which
38716 lists loaded libraries and their offsets. Each library has an
38717 associated name and one or more segment or section base addresses,
38718 which report where the library was loaded in memory.
38720 For the common case of libraries that are fully linked binaries, the
38721 library should have a list of segments. If the target supports
38722 dynamic linking of a relocatable object file, its library XML element
38723 should instead include a list of allocated sections. The segment or
38724 section bases are start addresses, not relocation offsets; they do not
38725 depend on the library's link-time base addresses.
38727 @value{GDBN} must be linked with the Expat library to support XML
38728 library lists. @xref{Expat}.
38730 A simple memory map, with one loaded library relocated by a single
38731 offset, looks like this:
38735 <library name="/lib/libc.so.6">
38736 <segment address="0x10000000"/>
38741 Another simple memory map, with one loaded library with three
38742 allocated sections (.text, .data, .bss), looks like this:
38746 <library name="sharedlib.o">
38747 <section address="0x10000000"/>
38748 <section address="0x20000000"/>
38749 <section address="0x30000000"/>
38754 The format of a library list is described by this DTD:
38757 <!-- library-list: Root element with versioning -->
38758 <!ELEMENT library-list (library)*>
38759 <!ATTLIST library-list version CDATA #FIXED "1.0">
38760 <!ELEMENT library (segment*, section*)>
38761 <!ATTLIST library name CDATA #REQUIRED>
38762 <!ELEMENT segment EMPTY>
38763 <!ATTLIST segment address CDATA #REQUIRED>
38764 <!ELEMENT section EMPTY>
38765 <!ATTLIST section address CDATA #REQUIRED>
38768 In addition, segments and section descriptors cannot be mixed within a
38769 single library element, and you must supply at least one segment or
38770 section for each library.
38772 @node Library List Format for SVR4 Targets
38773 @section Library List Format for SVR4 Targets
38774 @cindex library list format, remote protocol
38776 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38777 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38778 shared libraries. Still a special library list provided by this packet is
38779 more efficient for the @value{GDBN} remote protocol.
38781 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38782 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38783 target, the following parameters are reported:
38787 @code{name}, the absolute file name from the @code{l_name} field of
38788 @code{struct link_map}.
38790 @code{lm} with address of @code{struct link_map} used for TLS
38791 (Thread Local Storage) access.
38793 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38794 @code{struct link_map}. For prelinked libraries this is not an absolute
38795 memory address. It is a displacement of absolute memory address against
38796 address the file was prelinked to during the library load.
38798 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38801 Additionally the single @code{main-lm} attribute specifies address of
38802 @code{struct link_map} used for the main executable. This parameter is used
38803 for TLS access and its presence is optional.
38805 @value{GDBN} must be linked with the Expat library to support XML
38806 SVR4 library lists. @xref{Expat}.
38808 A simple memory map, with two loaded libraries (which do not use prelink),
38812 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38813 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38815 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38817 </library-list-svr>
38820 The format of an SVR4 library list is described by this DTD:
38823 <!-- library-list-svr4: Root element with versioning -->
38824 <!ELEMENT library-list-svr4 (library)*>
38825 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38826 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38827 <!ELEMENT library EMPTY>
38828 <!ATTLIST library name CDATA #REQUIRED>
38829 <!ATTLIST library lm CDATA #REQUIRED>
38830 <!ATTLIST library l_addr CDATA #REQUIRED>
38831 <!ATTLIST library l_ld CDATA #REQUIRED>
38834 @node Memory Map Format
38835 @section Memory Map Format
38836 @cindex memory map format
38838 To be able to write into flash memory, @value{GDBN} needs to obtain a
38839 memory map from the target. This section describes the format of the
38842 The memory map is obtained using the @samp{qXfer:memory-map:read}
38843 (@pxref{qXfer memory map read}) packet and is an XML document that
38844 lists memory regions.
38846 @value{GDBN} must be linked with the Expat library to support XML
38847 memory maps. @xref{Expat}.
38849 The top-level structure of the document is shown below:
38852 <?xml version="1.0"?>
38853 <!DOCTYPE memory-map
38854 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38855 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38861 Each region can be either:
38866 A region of RAM starting at @var{addr} and extending for @var{length}
38870 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38875 A region of read-only memory:
38878 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38883 A region of flash memory, with erasure blocks @var{blocksize}
38887 <memory type="flash" start="@var{addr}" length="@var{length}">
38888 <property name="blocksize">@var{blocksize}</property>
38894 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38895 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38896 packets to write to addresses in such ranges.
38898 The formal DTD for memory map format is given below:
38901 <!-- ................................................... -->
38902 <!-- Memory Map XML DTD ................................ -->
38903 <!-- File: memory-map.dtd .............................. -->
38904 <!-- .................................... .............. -->
38905 <!-- memory-map.dtd -->
38906 <!-- memory-map: Root element with versioning -->
38907 <!ELEMENT memory-map (memory | property)>
38908 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38909 <!ELEMENT memory (property)>
38910 <!-- memory: Specifies a memory region,
38911 and its type, or device. -->
38912 <!ATTLIST memory type CDATA #REQUIRED
38913 start CDATA #REQUIRED
38914 length CDATA #REQUIRED
38915 device CDATA #IMPLIED>
38916 <!-- property: Generic attribute tag -->
38917 <!ELEMENT property (#PCDATA | property)*>
38918 <!ATTLIST property name CDATA #REQUIRED>
38921 @node Thread List Format
38922 @section Thread List Format
38923 @cindex thread list format
38925 To efficiently update the list of threads and their attributes,
38926 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38927 (@pxref{qXfer threads read}) and obtains the XML document with
38928 the following structure:
38931 <?xml version="1.0"?>
38933 <thread id="id" core="0">
38934 ... description ...
38939 Each @samp{thread} element must have the @samp{id} attribute that
38940 identifies the thread (@pxref{thread-id syntax}). The
38941 @samp{core} attribute, if present, specifies which processor core
38942 the thread was last executing on. The content of the of @samp{thread}
38943 element is interpreted as human-readable auxilliary information.
38945 @node Traceframe Info Format
38946 @section Traceframe Info Format
38947 @cindex traceframe info format
38949 To be able to know which objects in the inferior can be examined when
38950 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38951 memory ranges, registers and trace state variables that have been
38952 collected in a traceframe.
38954 This list is obtained using the @samp{qXfer:traceframe-info:read}
38955 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38957 @value{GDBN} must be linked with the Expat library to support XML
38958 traceframe info discovery. @xref{Expat}.
38960 The top-level structure of the document is shown below:
38963 <?xml version="1.0"?>
38964 <!DOCTYPE traceframe-info
38965 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38966 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38972 Each traceframe block can be either:
38977 A region of collected memory starting at @var{addr} and extending for
38978 @var{length} bytes from there:
38981 <memory start="@var{addr}" length="@var{length}"/>
38986 The formal DTD for the traceframe info format is given below:
38989 <!ELEMENT traceframe-info (memory)* >
38990 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38992 <!ELEMENT memory EMPTY>
38993 <!ATTLIST memory start CDATA #REQUIRED
38994 length CDATA #REQUIRED>
38997 @include agentexpr.texi
38999 @node Target Descriptions
39000 @appendix Target Descriptions
39001 @cindex target descriptions
39003 One of the challenges of using @value{GDBN} to debug embedded systems
39004 is that there are so many minor variants of each processor
39005 architecture in use. It is common practice for vendors to start with
39006 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
39007 and then make changes to adapt it to a particular market niche. Some
39008 architectures have hundreds of variants, available from dozens of
39009 vendors. This leads to a number of problems:
39013 With so many different customized processors, it is difficult for
39014 the @value{GDBN} maintainers to keep up with the changes.
39016 Since individual variants may have short lifetimes or limited
39017 audiences, it may not be worthwhile to carry information about every
39018 variant in the @value{GDBN} source tree.
39020 When @value{GDBN} does support the architecture of the embedded system
39021 at hand, the task of finding the correct architecture name to give the
39022 @command{set architecture} command can be error-prone.
39025 To address these problems, the @value{GDBN} remote protocol allows a
39026 target system to not only identify itself to @value{GDBN}, but to
39027 actually describe its own features. This lets @value{GDBN} support
39028 processor variants it has never seen before --- to the extent that the
39029 descriptions are accurate, and that @value{GDBN} understands them.
39031 @value{GDBN} must be linked with the Expat library to support XML
39032 target descriptions. @xref{Expat}.
39035 * Retrieving Descriptions:: How descriptions are fetched from a target.
39036 * Target Description Format:: The contents of a target description.
39037 * Predefined Target Types:: Standard types available for target
39039 * Standard Target Features:: Features @value{GDBN} knows about.
39042 @node Retrieving Descriptions
39043 @section Retrieving Descriptions
39045 Target descriptions can be read from the target automatically, or
39046 specified by the user manually. The default behavior is to read the
39047 description from the target. @value{GDBN} retrieves it via the remote
39048 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39049 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39050 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39051 XML document, of the form described in @ref{Target Description
39054 Alternatively, you can specify a file to read for the target description.
39055 If a file is set, the target will not be queried. The commands to
39056 specify a file are:
39059 @cindex set tdesc filename
39060 @item set tdesc filename @var{path}
39061 Read the target description from @var{path}.
39063 @cindex unset tdesc filename
39064 @item unset tdesc filename
39065 Do not read the XML target description from a file. @value{GDBN}
39066 will use the description supplied by the current target.
39068 @cindex show tdesc filename
39069 @item show tdesc filename
39070 Show the filename to read for a target description, if any.
39074 @node Target Description Format
39075 @section Target Description Format
39076 @cindex target descriptions, XML format
39078 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39079 document which complies with the Document Type Definition provided in
39080 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39081 means you can use generally available tools like @command{xmllint} to
39082 check that your feature descriptions are well-formed and valid.
39083 However, to help people unfamiliar with XML write descriptions for
39084 their targets, we also describe the grammar here.
39086 Target descriptions can identify the architecture of the remote target
39087 and (for some architectures) provide information about custom register
39088 sets. They can also identify the OS ABI of the remote target.
39089 @value{GDBN} can use this information to autoconfigure for your
39090 target, or to warn you if you connect to an unsupported target.
39092 Here is a simple target description:
39095 <target version="1.0">
39096 <architecture>i386:x86-64</architecture>
39101 This minimal description only says that the target uses
39102 the x86-64 architecture.
39104 A target description has the following overall form, with [ ] marking
39105 optional elements and @dots{} marking repeatable elements. The elements
39106 are explained further below.
39109 <?xml version="1.0"?>
39110 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39111 <target version="1.0">
39112 @r{[}@var{architecture}@r{]}
39113 @r{[}@var{osabi}@r{]}
39114 @r{[}@var{compatible}@r{]}
39115 @r{[}@var{feature}@dots{}@r{]}
39120 The description is generally insensitive to whitespace and line
39121 breaks, under the usual common-sense rules. The XML version
39122 declaration and document type declaration can generally be omitted
39123 (@value{GDBN} does not require them), but specifying them may be
39124 useful for XML validation tools. The @samp{version} attribute for
39125 @samp{<target>} may also be omitted, but we recommend
39126 including it; if future versions of @value{GDBN} use an incompatible
39127 revision of @file{gdb-target.dtd}, they will detect and report
39128 the version mismatch.
39130 @subsection Inclusion
39131 @cindex target descriptions, inclusion
39134 @cindex <xi:include>
39137 It can sometimes be valuable to split a target description up into
39138 several different annexes, either for organizational purposes, or to
39139 share files between different possible target descriptions. You can
39140 divide a description into multiple files by replacing any element of
39141 the target description with an inclusion directive of the form:
39144 <xi:include href="@var{document}"/>
39148 When @value{GDBN} encounters an element of this form, it will retrieve
39149 the named XML @var{document}, and replace the inclusion directive with
39150 the contents of that document. If the current description was read
39151 using @samp{qXfer}, then so will be the included document;
39152 @var{document} will be interpreted as the name of an annex. If the
39153 current description was read from a file, @value{GDBN} will look for
39154 @var{document} as a file in the same directory where it found the
39155 original description.
39157 @subsection Architecture
39158 @cindex <architecture>
39160 An @samp{<architecture>} element has this form:
39163 <architecture>@var{arch}</architecture>
39166 @var{arch} is one of the architectures from the set accepted by
39167 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39170 @cindex @code{<osabi>}
39172 This optional field was introduced in @value{GDBN} version 7.0.
39173 Previous versions of @value{GDBN} ignore it.
39175 An @samp{<osabi>} element has this form:
39178 <osabi>@var{abi-name}</osabi>
39181 @var{abi-name} is an OS ABI name from the same selection accepted by
39182 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39184 @subsection Compatible Architecture
39185 @cindex @code{<compatible>}
39187 This optional field was introduced in @value{GDBN} version 7.0.
39188 Previous versions of @value{GDBN} ignore it.
39190 A @samp{<compatible>} element has this form:
39193 <compatible>@var{arch}</compatible>
39196 @var{arch} is one of the architectures from the set accepted by
39197 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39199 A @samp{<compatible>} element is used to specify that the target
39200 is able to run binaries in some other than the main target architecture
39201 given by the @samp{<architecture>} element. For example, on the
39202 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39203 or @code{powerpc:common64}, but the system is able to run binaries
39204 in the @code{spu} architecture as well. The way to describe this
39205 capability with @samp{<compatible>} is as follows:
39208 <architecture>powerpc:common</architecture>
39209 <compatible>spu</compatible>
39212 @subsection Features
39215 Each @samp{<feature>} describes some logical portion of the target
39216 system. Features are currently used to describe available CPU
39217 registers and the types of their contents. A @samp{<feature>} element
39221 <feature name="@var{name}">
39222 @r{[}@var{type}@dots{}@r{]}
39228 Each feature's name should be unique within the description. The name
39229 of a feature does not matter unless @value{GDBN} has some special
39230 knowledge of the contents of that feature; if it does, the feature
39231 should have its standard name. @xref{Standard Target Features}.
39235 Any register's value is a collection of bits which @value{GDBN} must
39236 interpret. The default interpretation is a two's complement integer,
39237 but other types can be requested by name in the register description.
39238 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39239 Target Types}), and the description can define additional composite types.
39241 Each type element must have an @samp{id} attribute, which gives
39242 a unique (within the containing @samp{<feature>}) name to the type.
39243 Types must be defined before they are used.
39246 Some targets offer vector registers, which can be treated as arrays
39247 of scalar elements. These types are written as @samp{<vector>} elements,
39248 specifying the array element type, @var{type}, and the number of elements,
39252 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39256 If a register's value is usefully viewed in multiple ways, define it
39257 with a union type containing the useful representations. The
39258 @samp{<union>} element contains one or more @samp{<field>} elements,
39259 each of which has a @var{name} and a @var{type}:
39262 <union id="@var{id}">
39263 <field name="@var{name}" type="@var{type}"/>
39269 If a register's value is composed from several separate values, define
39270 it with a structure type. There are two forms of the @samp{<struct>}
39271 element; a @samp{<struct>} element must either contain only bitfields
39272 or contain no bitfields. If the structure contains only bitfields,
39273 its total size in bytes must be specified, each bitfield must have an
39274 explicit start and end, and bitfields are automatically assigned an
39275 integer type. The field's @var{start} should be less than or
39276 equal to its @var{end}, and zero represents the least significant bit.
39279 <struct id="@var{id}" size="@var{size}">
39280 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39285 If the structure contains no bitfields, then each field has an
39286 explicit type, and no implicit padding is added.
39289 <struct id="@var{id}">
39290 <field name="@var{name}" type="@var{type}"/>
39296 If a register's value is a series of single-bit flags, define it with
39297 a flags type. The @samp{<flags>} element has an explicit @var{size}
39298 and contains one or more @samp{<field>} elements. Each field has a
39299 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39303 <flags id="@var{id}" size="@var{size}">
39304 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39309 @subsection Registers
39312 Each register is represented as an element with this form:
39315 <reg name="@var{name}"
39316 bitsize="@var{size}"
39317 @r{[}regnum="@var{num}"@r{]}
39318 @r{[}save-restore="@var{save-restore}"@r{]}
39319 @r{[}type="@var{type}"@r{]}
39320 @r{[}group="@var{group}"@r{]}/>
39324 The components are as follows:
39329 The register's name; it must be unique within the target description.
39332 The register's size, in bits.
39335 The register's number. If omitted, a register's number is one greater
39336 than that of the previous register (either in the current feature or in
39337 a preceding feature); the first register in the target description
39338 defaults to zero. This register number is used to read or write
39339 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39340 packets, and registers appear in the @code{g} and @code{G} packets
39341 in order of increasing register number.
39344 Whether the register should be preserved across inferior function
39345 calls; this must be either @code{yes} or @code{no}. The default is
39346 @code{yes}, which is appropriate for most registers except for
39347 some system control registers; this is not related to the target's
39351 The type of the register. @var{type} may be a predefined type, a type
39352 defined in the current feature, or one of the special types @code{int}
39353 and @code{float}. @code{int} is an integer type of the correct size
39354 for @var{bitsize}, and @code{float} is a floating point type (in the
39355 architecture's normal floating point format) of the correct size for
39356 @var{bitsize}. The default is @code{int}.
39359 The register group to which this register belongs. @var{group} must
39360 be either @code{general}, @code{float}, or @code{vector}. If no
39361 @var{group} is specified, @value{GDBN} will not display the register
39362 in @code{info registers}.
39366 @node Predefined Target Types
39367 @section Predefined Target Types
39368 @cindex target descriptions, predefined types
39370 Type definitions in the self-description can build up composite types
39371 from basic building blocks, but can not define fundamental types. Instead,
39372 standard identifiers are provided by @value{GDBN} for the fundamental
39373 types. The currently supported types are:
39382 Signed integer types holding the specified number of bits.
39389 Unsigned integer types holding the specified number of bits.
39393 Pointers to unspecified code and data. The program counter and
39394 any dedicated return address register may be marked as code
39395 pointers; printing a code pointer converts it into a symbolic
39396 address. The stack pointer and any dedicated address registers
39397 may be marked as data pointers.
39400 Single precision IEEE floating point.
39403 Double precision IEEE floating point.
39406 The 12-byte extended precision format used by ARM FPA registers.
39409 The 10-byte extended precision format used by x87 registers.
39412 32bit @sc{eflags} register used by x86.
39415 32bit @sc{mxcsr} register used by x86.
39419 @node Standard Target Features
39420 @section Standard Target Features
39421 @cindex target descriptions, standard features
39423 A target description must contain either no registers or all the
39424 target's registers. If the description contains no registers, then
39425 @value{GDBN} will assume a default register layout, selected based on
39426 the architecture. If the description contains any registers, the
39427 default layout will not be used; the standard registers must be
39428 described in the target description, in such a way that @value{GDBN}
39429 can recognize them.
39431 This is accomplished by giving specific names to feature elements
39432 which contain standard registers. @value{GDBN} will look for features
39433 with those names and verify that they contain the expected registers;
39434 if any known feature is missing required registers, or if any required
39435 feature is missing, @value{GDBN} will reject the target
39436 description. You can add additional registers to any of the
39437 standard features --- @value{GDBN} will display them just as if
39438 they were added to an unrecognized feature.
39440 This section lists the known features and their expected contents.
39441 Sample XML documents for these features are included in the
39442 @value{GDBN} source tree, in the directory @file{gdb/features}.
39444 Names recognized by @value{GDBN} should include the name of the
39445 company or organization which selected the name, and the overall
39446 architecture to which the feature applies; so e.g.@: the feature
39447 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39449 The names of registers are not case sensitive for the purpose
39450 of recognizing standard features, but @value{GDBN} will only display
39451 registers using the capitalization used in the description.
39458 * PowerPC Features::
39464 @subsection ARM Features
39465 @cindex target descriptions, ARM features
39467 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39469 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39470 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39472 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39473 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39474 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39477 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39478 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39480 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39481 it should contain at least registers @samp{wR0} through @samp{wR15} and
39482 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39483 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39485 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39486 should contain at least registers @samp{d0} through @samp{d15}. If
39487 they are present, @samp{d16} through @samp{d31} should also be included.
39488 @value{GDBN} will synthesize the single-precision registers from
39489 halves of the double-precision registers.
39491 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39492 need to contain registers; it instructs @value{GDBN} to display the
39493 VFP double-precision registers as vectors and to synthesize the
39494 quad-precision registers from pairs of double-precision registers.
39495 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39496 be present and include 32 double-precision registers.
39498 @node i386 Features
39499 @subsection i386 Features
39500 @cindex target descriptions, i386 features
39502 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39503 targets. It should describe the following registers:
39507 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39509 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39511 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39512 @samp{fs}, @samp{gs}
39514 @samp{st0} through @samp{st7}
39516 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39517 @samp{foseg}, @samp{fooff} and @samp{fop}
39520 The register sets may be different, depending on the target.
39522 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39523 describe registers:
39527 @samp{xmm0} through @samp{xmm7} for i386
39529 @samp{xmm0} through @samp{xmm15} for amd64
39534 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39535 @samp{org.gnu.gdb.i386.sse} feature. It should
39536 describe the upper 128 bits of @sc{ymm} registers:
39540 @samp{ymm0h} through @samp{ymm7h} for i386
39542 @samp{ymm0h} through @samp{ymm15h} for amd64
39545 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39546 describe a single register, @samp{orig_eax}.
39548 @node MIPS Features
39549 @subsection MIPS Features
39550 @cindex target descriptions, MIPS features
39552 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
39553 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39554 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39557 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39558 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39559 registers. They may be 32-bit or 64-bit depending on the target.
39561 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39562 it may be optional in a future version of @value{GDBN}. It should
39563 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39564 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39566 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39567 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39568 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39569 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39571 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39572 contain a single register, @samp{restart}, which is used by the
39573 Linux kernel to control restartable syscalls.
39575 @node M68K Features
39576 @subsection M68K Features
39577 @cindex target descriptions, M68K features
39580 @item @samp{org.gnu.gdb.m68k.core}
39581 @itemx @samp{org.gnu.gdb.coldfire.core}
39582 @itemx @samp{org.gnu.gdb.fido.core}
39583 One of those features must be always present.
39584 The feature that is present determines which flavor of m68k is
39585 used. The feature that is present should contain registers
39586 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39587 @samp{sp}, @samp{ps} and @samp{pc}.
39589 @item @samp{org.gnu.gdb.coldfire.fp}
39590 This feature is optional. If present, it should contain registers
39591 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39595 @node PowerPC Features
39596 @subsection PowerPC Features
39597 @cindex target descriptions, PowerPC features
39599 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39600 targets. It should contain registers @samp{r0} through @samp{r31},
39601 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39602 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39604 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39605 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39607 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39608 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39611 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39612 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39613 will combine these registers with the floating point registers
39614 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39615 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39616 through @samp{vs63}, the set of vector registers for POWER7.
39618 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39619 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39620 @samp{spefscr}. SPE targets should provide 32-bit registers in
39621 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39622 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39623 these to present registers @samp{ev0} through @samp{ev31} to the
39626 @node TIC6x Features
39627 @subsection TMS320C6x Features
39628 @cindex target descriptions, TIC6x features
39629 @cindex target descriptions, TMS320C6x features
39630 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39631 targets. It should contain registers @samp{A0} through @samp{A15},
39632 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39634 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39635 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39636 through @samp{B31}.
39638 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39639 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39641 @node Operating System Information
39642 @appendix Operating System Information
39643 @cindex operating system information
39649 Users of @value{GDBN} often wish to obtain information about the state of
39650 the operating system running on the target---for example the list of
39651 processes, or the list of open files. This section describes the
39652 mechanism that makes it possible. This mechanism is similar to the
39653 target features mechanism (@pxref{Target Descriptions}), but focuses
39654 on a different aspect of target.
39656 Operating system information is retrived from the target via the
39657 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39658 read}). The object name in the request should be @samp{osdata}, and
39659 the @var{annex} identifies the data to be fetched.
39662 @appendixsection Process list
39663 @cindex operating system information, process list
39665 When requesting the process list, the @var{annex} field in the
39666 @samp{qXfer} request should be @samp{processes}. The returned data is
39667 an XML document. The formal syntax of this document is defined in
39668 @file{gdb/features/osdata.dtd}.
39670 An example document is:
39673 <?xml version="1.0"?>
39674 <!DOCTYPE target SYSTEM "osdata.dtd">
39675 <osdata type="processes">
39677 <column name="pid">1</column>
39678 <column name="user">root</column>
39679 <column name="command">/sbin/init</column>
39680 <column name="cores">1,2,3</column>
39685 Each item should include a column whose name is @samp{pid}. The value
39686 of that column should identify the process on the target. The
39687 @samp{user} and @samp{command} columns are optional, and will be
39688 displayed by @value{GDBN}. The @samp{cores} column, if present,
39689 should contain a comma-separated list of cores that this process
39690 is running on. Target may provide additional columns,
39691 which @value{GDBN} currently ignores.
39693 @node Trace File Format
39694 @appendix Trace File Format
39695 @cindex trace file format
39697 The trace file comes in three parts: a header, a textual description
39698 section, and a trace frame section with binary data.
39700 The header has the form @code{\x7fTRACE0\n}. The first byte is
39701 @code{0x7f} so as to indicate that the file contains binary data,
39702 while the @code{0} is a version number that may have different values
39705 The description section consists of multiple lines of @sc{ascii} text
39706 separated by newline characters (@code{0xa}). The lines may include a
39707 variety of optional descriptive or context-setting information, such
39708 as tracepoint definitions or register set size. @value{GDBN} will
39709 ignore any line that it does not recognize. An empty line marks the end
39712 @c FIXME add some specific types of data
39714 The trace frame section consists of a number of consecutive frames.
39715 Each frame begins with a two-byte tracepoint number, followed by a
39716 four-byte size giving the amount of data in the frame. The data in
39717 the frame consists of a number of blocks, each introduced by a
39718 character indicating its type (at least register, memory, and trace
39719 state variable). The data in this section is raw binary, not a
39720 hexadecimal or other encoding; its endianness matches the target's
39723 @c FIXME bi-arch may require endianness/arch info in description section
39726 @item R @var{bytes}
39727 Register block. The number and ordering of bytes matches that of a
39728 @code{g} packet in the remote protocol. Note that these are the
39729 actual bytes, in target order and @value{GDBN} register order, not a
39730 hexadecimal encoding.
39732 @item M @var{address} @var{length} @var{bytes}...
39733 Memory block. This is a contiguous block of memory, at the 8-byte
39734 address @var{address}, with a 2-byte length @var{length}, followed by
39735 @var{length} bytes.
39737 @item V @var{number} @var{value}
39738 Trace state variable block. This records the 8-byte signed value
39739 @var{value} of trace state variable numbered @var{number}.
39743 Future enhancements of the trace file format may include additional types
39746 @node Index Section Format
39747 @appendix @code{.gdb_index} section format
39748 @cindex .gdb_index section format
39749 @cindex index section format
39751 This section documents the index section that is created by @code{save
39752 gdb-index} (@pxref{Index Files}). The index section is
39753 DWARF-specific; some knowledge of DWARF is assumed in this
39756 The mapped index file format is designed to be directly
39757 @code{mmap}able on any architecture. In most cases, a datum is
39758 represented using a little-endian 32-bit integer value, called an
39759 @code{offset_type}. Big endian machines must byte-swap the values
39760 before using them. Exceptions to this rule are noted. The data is
39761 laid out such that alignment is always respected.
39763 A mapped index consists of several areas, laid out in order.
39767 The file header. This is a sequence of values, of @code{offset_type}
39768 unless otherwise noted:
39772 The version number, currently 6. Versions 1, 2 and 3 are obsolete.
39773 Version 4 uses a different hashing function from versions 5 and 6.
39774 Version 6 includes symbols for inlined functions, whereas versions
39775 4 and 5 do not. @value{GDBN} will only read version 4 and 5 indices
39776 if the @code{--use-deprecated-index-sections} option is used.
39779 The offset, from the start of the file, of the CU list.
39782 The offset, from the start of the file, of the types CU list. Note
39783 that this area can be empty, in which case this offset will be equal
39784 to the next offset.
39787 The offset, from the start of the file, of the address area.
39790 The offset, from the start of the file, of the symbol table.
39793 The offset, from the start of the file, of the constant pool.
39797 The CU list. This is a sequence of pairs of 64-bit little-endian
39798 values, sorted by the CU offset. The first element in each pair is
39799 the offset of a CU in the @code{.debug_info} section. The second
39800 element in each pair is the length of that CU. References to a CU
39801 elsewhere in the map are done using a CU index, which is just the
39802 0-based index into this table. Note that if there are type CUs, then
39803 conceptually CUs and type CUs form a single list for the purposes of
39807 The types CU list. This is a sequence of triplets of 64-bit
39808 little-endian values. In a triplet, the first value is the CU offset,
39809 the second value is the type offset in the CU, and the third value is
39810 the type signature. The types CU list is not sorted.
39813 The address area. The address area consists of a sequence of address
39814 entries. Each address entry has three elements:
39818 The low address. This is a 64-bit little-endian value.
39821 The high address. This is a 64-bit little-endian value. Like
39822 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39825 The CU index. This is an @code{offset_type} value.
39829 The symbol table. This is an open-addressed hash table. The size of
39830 the hash table is always a power of 2.
39832 Each slot in the hash table consists of a pair of @code{offset_type}
39833 values. The first value is the offset of the symbol's name in the
39834 constant pool. The second value is the offset of the CU vector in the
39837 If both values are 0, then this slot in the hash table is empty. This
39838 is ok because while 0 is a valid constant pool index, it cannot be a
39839 valid index for both a string and a CU vector.
39841 The hash value for a table entry is computed by applying an
39842 iterative hash function to the symbol's name. Starting with an
39843 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39844 the string is incorporated into the hash using the formula depending on the
39849 The formula is @code{r = r * 67 + c - 113}.
39851 @item Versions 5 and 6
39852 The formula is @code{r = r * 67 + tolower (c) - 113}.
39855 The terminating @samp{\0} is not incorporated into the hash.
39857 The step size used in the hash table is computed via
39858 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39859 value, and @samp{size} is the size of the hash table. The step size
39860 is used to find the next candidate slot when handling a hash
39863 The names of C@t{++} symbols in the hash table are canonicalized. We
39864 don't currently have a simple description of the canonicalization
39865 algorithm; if you intend to create new index sections, you must read
39869 The constant pool. This is simply a bunch of bytes. It is organized
39870 so that alignment is correct: CU vectors are stored first, followed by
39873 A CU vector in the constant pool is a sequence of @code{offset_type}
39874 values. The first value is the number of CU indices in the vector.
39875 Each subsequent value is the index of a CU in the CU list. This
39876 element in the hash table is used to indicate which CUs define the
39879 A string in the constant pool is zero-terminated.
39884 @node GNU Free Documentation License
39885 @appendix GNU Free Documentation License
39894 % I think something like @colophon should be in texinfo. In the
39896 \long\def\colophon{\hbox to0pt{}\vfill
39897 \centerline{The body of this manual is set in}
39898 \centerline{\fontname\tenrm,}
39899 \centerline{with headings in {\bf\fontname\tenbf}}
39900 \centerline{and examples in {\tt\fontname\tentt}.}
39901 \centerline{{\it\fontname\tenit\/},}
39902 \centerline{{\bf\fontname\tenbf}, and}
39903 \centerline{{\sl\fontname\tensl\/}}
39904 \centerline{are used for emphasis.}\vfill}
39906 % Blame: doc@cygnus.com, 1991.