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 * Dynamic Printf:: Dynamic printf
3345 * Save Breakpoints:: How to save breakpoints in a file
3346 * Static Probe Points:: Listing static probe points
3347 * Error in Breakpoints:: ``Cannot insert breakpoints''
3348 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3352 @subsection Setting Breakpoints
3354 @c FIXME LMB what does GDB do if no code on line of breakpt?
3355 @c consider in particular declaration with/without initialization.
3357 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3360 @kindex b @r{(@code{break})}
3361 @vindex $bpnum@r{, convenience variable}
3362 @cindex latest breakpoint
3363 Breakpoints are set with the @code{break} command (abbreviated
3364 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3365 number of the breakpoint you've set most recently; see @ref{Convenience
3366 Vars,, Convenience Variables}, for a discussion of what you can do with
3367 convenience variables.
3370 @item break @var{location}
3371 Set a breakpoint at the given @var{location}, which can specify a
3372 function name, a line number, or an address of an instruction.
3373 (@xref{Specify Location}, for a list of all the possible ways to
3374 specify a @var{location}.) The breakpoint will stop your program just
3375 before it executes any of the code in the specified @var{location}.
3377 When using source languages that permit overloading of symbols, such as
3378 C@t{++}, a function name may refer to more than one possible place to break.
3379 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3382 It is also possible to insert a breakpoint that will stop the program
3383 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3384 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3387 When called without any arguments, @code{break} sets a breakpoint at
3388 the next instruction to be executed in the selected stack frame
3389 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3390 innermost, this makes your program stop as soon as control
3391 returns to that frame. This is similar to the effect of a
3392 @code{finish} command in the frame inside the selected frame---except
3393 that @code{finish} does not leave an active breakpoint. If you use
3394 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3395 the next time it reaches the current location; this may be useful
3398 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3399 least one instruction has been executed. If it did not do this, you
3400 would be unable to proceed past a breakpoint without first disabling the
3401 breakpoint. This rule applies whether or not the breakpoint already
3402 existed when your program stopped.
3404 @item break @dots{} if @var{cond}
3405 Set a breakpoint with condition @var{cond}; evaluate the expression
3406 @var{cond} each time the breakpoint is reached, and stop only if the
3407 value is nonzero---that is, if @var{cond} evaluates as true.
3408 @samp{@dots{}} stands for one of the possible arguments described
3409 above (or no argument) specifying where to break. @xref{Conditions,
3410 ,Break Conditions}, for more information on breakpoint conditions.
3413 @item tbreak @var{args}
3414 Set a breakpoint enabled only for one stop. @var{args} are the
3415 same as for the @code{break} command, and the breakpoint is set in the same
3416 way, but the breakpoint is automatically deleted after the first time your
3417 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3420 @cindex hardware breakpoints
3421 @item hbreak @var{args}
3422 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3423 @code{break} command and the breakpoint is set in the same way, but the
3424 breakpoint requires hardware support and some target hardware may not
3425 have this support. The main purpose of this is EPROM/ROM code
3426 debugging, so you can set a breakpoint at an instruction without
3427 changing the instruction. This can be used with the new trap-generation
3428 provided by SPARClite DSU and most x86-based targets. These targets
3429 will generate traps when a program accesses some data or instruction
3430 address that is assigned to the debug registers. However the hardware
3431 breakpoint registers can take a limited number of breakpoints. For
3432 example, on the DSU, only two data breakpoints can be set at a time, and
3433 @value{GDBN} will reject this command if more than two are used. Delete
3434 or disable unused hardware breakpoints before setting new ones
3435 (@pxref{Disabling, ,Disabling Breakpoints}).
3436 @xref{Conditions, ,Break Conditions}.
3437 For remote targets, you can restrict the number of hardware
3438 breakpoints @value{GDBN} will use, see @ref{set remote
3439 hardware-breakpoint-limit}.
3442 @item thbreak @var{args}
3443 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3444 are the same as for the @code{hbreak} command and the breakpoint is set in
3445 the same way. However, like the @code{tbreak} command,
3446 the breakpoint is automatically deleted after the
3447 first time your program stops there. Also, like the @code{hbreak}
3448 command, the breakpoint requires hardware support and some target hardware
3449 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3450 See also @ref{Conditions, ,Break Conditions}.
3453 @cindex regular expression
3454 @cindex breakpoints at functions matching a regexp
3455 @cindex set breakpoints in many functions
3456 @item rbreak @var{regex}
3457 Set breakpoints on all functions matching the regular expression
3458 @var{regex}. This command sets an unconditional breakpoint on all
3459 matches, printing a list of all breakpoints it set. Once these
3460 breakpoints are set, they are treated just like the breakpoints set with
3461 the @code{break} command. You can delete them, disable them, or make
3462 them conditional the same way as any other breakpoint.
3464 The syntax of the regular expression is the standard one used with tools
3465 like @file{grep}. Note that this is different from the syntax used by
3466 shells, so for instance @code{foo*} matches all functions that include
3467 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3468 @code{.*} leading and trailing the regular expression you supply, so to
3469 match only functions that begin with @code{foo}, use @code{^foo}.
3471 @cindex non-member C@t{++} functions, set breakpoint in
3472 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3473 breakpoints on overloaded functions that are not members of any special
3476 @cindex set breakpoints on all functions
3477 The @code{rbreak} command can be used to set breakpoints in
3478 @strong{all} the functions in a program, like this:
3481 (@value{GDBP}) rbreak .
3484 @item rbreak @var{file}:@var{regex}
3485 If @code{rbreak} is called with a filename qualification, it limits
3486 the search for functions matching the given regular expression to the
3487 specified @var{file}. This can be used, for example, to set breakpoints on
3488 every function in a given file:
3491 (@value{GDBP}) rbreak file.c:.
3494 The colon separating the filename qualifier from the regex may
3495 optionally be surrounded by spaces.
3497 @kindex info breakpoints
3498 @cindex @code{$_} and @code{info breakpoints}
3499 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3500 @itemx info break @r{[}@var{n}@dots{}@r{]}
3501 Print a table of all breakpoints, watchpoints, and catchpoints set and
3502 not deleted. Optional argument @var{n} means print information only
3503 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3504 For each breakpoint, following columns are printed:
3507 @item Breakpoint Numbers
3509 Breakpoint, watchpoint, or catchpoint.
3511 Whether the breakpoint is marked to be disabled or deleted when hit.
3512 @item Enabled or Disabled
3513 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3514 that are not enabled.
3516 Where the breakpoint is in your program, as a memory address. For a
3517 pending breakpoint whose address is not yet known, this field will
3518 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3519 library that has the symbol or line referred by breakpoint is loaded.
3520 See below for details. A breakpoint with several locations will
3521 have @samp{<MULTIPLE>} in this field---see below for details.
3523 Where the breakpoint is in the source for your program, as a file and
3524 line number. For a pending breakpoint, the original string passed to
3525 the breakpoint command will be listed as it cannot be resolved until
3526 the appropriate shared library is loaded in the future.
3530 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3531 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3532 @value{GDBN} on the host's side. If it is ``target'', then the condition
3533 is evaluated by the target. The @code{info break} command shows
3534 the condition on the line following the affected breakpoint, together with
3535 its condition evaluation mode in between parentheses.
3537 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3538 allowed to have a condition specified for it. The condition is not parsed for
3539 validity until a shared library is loaded that allows the pending
3540 breakpoint to resolve to a valid location.
3543 @code{info break} with a breakpoint
3544 number @var{n} as argument lists only that breakpoint. The
3545 convenience variable @code{$_} and the default examining-address for
3546 the @code{x} command are set to the address of the last breakpoint
3547 listed (@pxref{Memory, ,Examining Memory}).
3550 @code{info break} displays a count of the number of times the breakpoint
3551 has been hit. This is especially useful in conjunction with the
3552 @code{ignore} command. You can ignore a large number of breakpoint
3553 hits, look at the breakpoint info to see how many times the breakpoint
3554 was hit, and then run again, ignoring one less than that number. This
3555 will get you quickly to the last hit of that breakpoint.
3558 For a breakpoints with an enable count (xref) greater than 1,
3559 @code{info break} also displays that count.
3563 @value{GDBN} allows you to set any number of breakpoints at the same place in
3564 your program. There is nothing silly or meaningless about this. When
3565 the breakpoints are conditional, this is even useful
3566 (@pxref{Conditions, ,Break Conditions}).
3568 @cindex multiple locations, breakpoints
3569 @cindex breakpoints, multiple locations
3570 It is possible that a breakpoint corresponds to several locations
3571 in your program. Examples of this situation are:
3575 Multiple functions in the program may have the same name.
3578 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3579 instances of the function body, used in different cases.
3582 For a C@t{++} template function, a given line in the function can
3583 correspond to any number of instantiations.
3586 For an inlined function, a given source line can correspond to
3587 several places where that function is inlined.
3590 In all those cases, @value{GDBN} will insert a breakpoint at all
3591 the relevant locations.
3593 A breakpoint with multiple locations is displayed in the breakpoint
3594 table using several rows---one header row, followed by one row for
3595 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3596 address column. The rows for individual locations contain the actual
3597 addresses for locations, and show the functions to which those
3598 locations belong. The number column for a location is of the form
3599 @var{breakpoint-number}.@var{location-number}.
3604 Num Type Disp Enb Address What
3605 1 breakpoint keep y <MULTIPLE>
3607 breakpoint already hit 1 time
3608 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3609 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3612 Each location can be individually enabled or disabled by passing
3613 @var{breakpoint-number}.@var{location-number} as argument to the
3614 @code{enable} and @code{disable} commands. Note that you cannot
3615 delete the individual locations from the list, you can only delete the
3616 entire list of locations that belong to their parent breakpoint (with
3617 the @kbd{delete @var{num}} command, where @var{num} is the number of
3618 the parent breakpoint, 1 in the above example). Disabling or enabling
3619 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3620 that belong to that breakpoint.
3622 @cindex pending breakpoints
3623 It's quite common to have a breakpoint inside a shared library.
3624 Shared libraries can be loaded and unloaded explicitly,
3625 and possibly repeatedly, as the program is executed. To support
3626 this use case, @value{GDBN} updates breakpoint locations whenever
3627 any shared library is loaded or unloaded. Typically, you would
3628 set a breakpoint in a shared library at the beginning of your
3629 debugging session, when the library is not loaded, and when the
3630 symbols from the library are not available. When you try to set
3631 breakpoint, @value{GDBN} will ask you if you want to set
3632 a so called @dfn{pending breakpoint}---breakpoint whose address
3633 is not yet resolved.
3635 After the program is run, whenever a new shared library is loaded,
3636 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3637 shared library contains the symbol or line referred to by some
3638 pending breakpoint, that breakpoint is resolved and becomes an
3639 ordinary breakpoint. When a library is unloaded, all breakpoints
3640 that refer to its symbols or source lines become pending again.
3642 This logic works for breakpoints with multiple locations, too. For
3643 example, if you have a breakpoint in a C@t{++} template function, and
3644 a newly loaded shared library has an instantiation of that template,
3645 a new location is added to the list of locations for the breakpoint.
3647 Except for having unresolved address, pending breakpoints do not
3648 differ from regular breakpoints. You can set conditions or commands,
3649 enable and disable them and perform other breakpoint operations.
3651 @value{GDBN} provides some additional commands for controlling what
3652 happens when the @samp{break} command cannot resolve breakpoint
3653 address specification to an address:
3655 @kindex set breakpoint pending
3656 @kindex show breakpoint pending
3658 @item set breakpoint pending auto
3659 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3660 location, it queries you whether a pending breakpoint should be created.
3662 @item set breakpoint pending on
3663 This indicates that an unrecognized breakpoint location should automatically
3664 result in a pending breakpoint being created.
3666 @item set breakpoint pending off
3667 This indicates that pending breakpoints are not to be created. Any
3668 unrecognized breakpoint location results in an error. This setting does
3669 not affect any pending breakpoints previously created.
3671 @item show breakpoint pending
3672 Show the current behavior setting for creating pending breakpoints.
3675 The settings above only affect the @code{break} command and its
3676 variants. Once breakpoint is set, it will be automatically updated
3677 as shared libraries are loaded and unloaded.
3679 @cindex automatic hardware breakpoints
3680 For some targets, @value{GDBN} can automatically decide if hardware or
3681 software breakpoints should be used, depending on whether the
3682 breakpoint address is read-only or read-write. This applies to
3683 breakpoints set with the @code{break} command as well as to internal
3684 breakpoints set by commands like @code{next} and @code{finish}. For
3685 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3688 You can control this automatic behaviour with the following commands::
3690 @kindex set breakpoint auto-hw
3691 @kindex show breakpoint auto-hw
3693 @item set breakpoint auto-hw on
3694 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3695 will try to use the target memory map to decide if software or hardware
3696 breakpoint must be used.
3698 @item set breakpoint auto-hw off
3699 This indicates @value{GDBN} should not automatically select breakpoint
3700 type. If the target provides a memory map, @value{GDBN} will warn when
3701 trying to set software breakpoint at a read-only address.
3704 @value{GDBN} normally implements breakpoints by replacing the program code
3705 at the breakpoint address with a special instruction, which, when
3706 executed, given control to the debugger. By default, the program
3707 code is so modified only when the program is resumed. As soon as
3708 the program stops, @value{GDBN} restores the original instructions. This
3709 behaviour guards against leaving breakpoints inserted in the
3710 target should gdb abrubptly disconnect. However, with slow remote
3711 targets, inserting and removing breakpoint can reduce the performance.
3712 This behavior can be controlled with the following commands::
3714 @kindex set breakpoint always-inserted
3715 @kindex show breakpoint always-inserted
3717 @item set breakpoint always-inserted off
3718 All breakpoints, including newly added by the user, are inserted in
3719 the target only when the target is resumed. All breakpoints are
3720 removed from the target when it stops.
3722 @item set breakpoint always-inserted on
3723 Causes all breakpoints to be inserted in the target at all times. If
3724 the user adds a new breakpoint, or changes an existing breakpoint, the
3725 breakpoints in the target are updated immediately. A breakpoint is
3726 removed from the target only when breakpoint itself is removed.
3728 @cindex non-stop mode, and @code{breakpoint always-inserted}
3729 @item set breakpoint always-inserted auto
3730 This is the default mode. If @value{GDBN} is controlling the inferior
3731 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3732 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3733 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3734 @code{breakpoint always-inserted} mode is off.
3737 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3738 when a breakpoint breaks. If the condition is true, then the process being
3739 debugged stops, otherwise the process is resumed.
3741 If the target supports evaluating conditions on its end, @value{GDBN} may
3742 download the breakpoint, together with its conditions, to it.
3744 This feature can be controlled via the following commands:
3746 @kindex set breakpoint condition-evaluation
3747 @kindex show breakpoint condition-evaluation
3749 @item set breakpoint condition-evaluation host
3750 This option commands @value{GDBN} to evaluate the breakpoint
3751 conditions on the host's side. Unconditional breakpoints are sent to
3752 the target which in turn receives the triggers and reports them back to GDB
3753 for condition evaluation. This is the standard evaluation mode.
3755 @item set breakpoint condition-evaluation target
3756 This option commands @value{GDBN} to download breakpoint conditions
3757 to the target at the moment of their insertion. The target
3758 is responsible for evaluating the conditional expression and reporting
3759 breakpoint stop events back to @value{GDBN} whenever the condition
3760 is true. Due to limitations of target-side evaluation, some conditions
3761 cannot be evaluated there, e.g., conditions that depend on local data
3762 that is only known to the host. Examples include
3763 conditional expressions involving convenience variables, complex types
3764 that cannot be handled by the agent expression parser and expressions
3765 that are too long to be sent over to the target, specially when the
3766 target is a remote system. In these cases, the conditions will be
3767 evaluated by @value{GDBN}.
3769 @item set breakpoint condition-evaluation auto
3770 This is the default mode. If the target supports evaluating breakpoint
3771 conditions on its end, @value{GDBN} will download breakpoint conditions to
3772 the target (limitations mentioned previously apply). If the target does
3773 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3774 to evaluating all these conditions on the host's side.
3778 @cindex negative breakpoint numbers
3779 @cindex internal @value{GDBN} breakpoints
3780 @value{GDBN} itself sometimes sets breakpoints in your program for
3781 special purposes, such as proper handling of @code{longjmp} (in C
3782 programs). These internal breakpoints are assigned negative numbers,
3783 starting with @code{-1}; @samp{info breakpoints} does not display them.
3784 You can see these breakpoints with the @value{GDBN} maintenance command
3785 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3788 @node Set Watchpoints
3789 @subsection Setting Watchpoints
3791 @cindex setting watchpoints
3792 You can use a watchpoint to stop execution whenever the value of an
3793 expression changes, without having to predict a particular place where
3794 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3795 The expression may be as simple as the value of a single variable, or
3796 as complex as many variables combined by operators. Examples include:
3800 A reference to the value of a single variable.
3803 An address cast to an appropriate data type. For example,
3804 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3805 address (assuming an @code{int} occupies 4 bytes).
3808 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3809 expression can use any operators valid in the program's native
3810 language (@pxref{Languages}).
3813 You can set a watchpoint on an expression even if the expression can
3814 not be evaluated yet. For instance, you can set a watchpoint on
3815 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3816 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3817 the expression produces a valid value. If the expression becomes
3818 valid in some other way than changing a variable (e.g.@: if the memory
3819 pointed to by @samp{*global_ptr} becomes readable as the result of a
3820 @code{malloc} call), @value{GDBN} may not stop until the next time
3821 the expression changes.
3823 @cindex software watchpoints
3824 @cindex hardware watchpoints
3825 Depending on your system, watchpoints may be implemented in software or
3826 hardware. @value{GDBN} does software watchpointing by single-stepping your
3827 program and testing the variable's value each time, which is hundreds of
3828 times slower than normal execution. (But this may still be worth it, to
3829 catch errors where you have no clue what part of your program is the
3832 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3833 x86-based targets, @value{GDBN} includes support for hardware
3834 watchpoints, which do not slow down the running of your program.
3838 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3839 Set a watchpoint for an expression. @value{GDBN} will break when the
3840 expression @var{expr} is written into by the program and its value
3841 changes. The simplest (and the most popular) use of this command is
3842 to watch the value of a single variable:
3845 (@value{GDBP}) watch foo
3848 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3849 argument, @value{GDBN} breaks only when the thread identified by
3850 @var{threadnum} changes the value of @var{expr}. If any other threads
3851 change the value of @var{expr}, @value{GDBN} will not break. Note
3852 that watchpoints restricted to a single thread in this way only work
3853 with Hardware Watchpoints.
3855 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3856 (see below). The @code{-location} argument tells @value{GDBN} to
3857 instead watch the memory referred to by @var{expr}. In this case,
3858 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3859 and watch the memory at that address. The type of the result is used
3860 to determine the size of the watched memory. If the expression's
3861 result does not have an address, then @value{GDBN} will print an
3864 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3865 of masked watchpoints, if the current architecture supports this
3866 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3867 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3868 to an address to watch. The mask specifies that some bits of an address
3869 (the bits which are reset in the mask) should be ignored when matching
3870 the address accessed by the inferior against the watchpoint address.
3871 Thus, a masked watchpoint watches many addresses simultaneously---those
3872 addresses whose unmasked bits are identical to the unmasked bits in the
3873 watchpoint address. The @code{mask} argument implies @code{-location}.
3877 (@value{GDBP}) watch foo mask 0xffff00ff
3878 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3882 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3883 Set a watchpoint that will break when the value of @var{expr} is read
3887 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3888 Set a watchpoint that will break when @var{expr} is either read from
3889 or written into by the program.
3891 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3892 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3893 This command prints a list of watchpoints, using the same format as
3894 @code{info break} (@pxref{Set Breaks}).
3897 If you watch for a change in a numerically entered address you need to
3898 dereference it, as the address itself is just a constant number which will
3899 never change. @value{GDBN} refuses to create a watchpoint that watches
3900 a never-changing value:
3903 (@value{GDBP}) watch 0x600850
3904 Cannot watch constant value 0x600850.
3905 (@value{GDBP}) watch *(int *) 0x600850
3906 Watchpoint 1: *(int *) 6293584
3909 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3910 watchpoints execute very quickly, and the debugger reports a change in
3911 value at the exact instruction where the change occurs. If @value{GDBN}
3912 cannot set a hardware watchpoint, it sets a software watchpoint, which
3913 executes more slowly and reports the change in value at the next
3914 @emph{statement}, not the instruction, after the change occurs.
3916 @cindex use only software watchpoints
3917 You can force @value{GDBN} to use only software watchpoints with the
3918 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3919 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3920 the underlying system supports them. (Note that hardware-assisted
3921 watchpoints that were set @emph{before} setting
3922 @code{can-use-hw-watchpoints} to zero will still use the hardware
3923 mechanism of watching expression values.)
3926 @item set can-use-hw-watchpoints
3927 @kindex set can-use-hw-watchpoints
3928 Set whether or not to use hardware watchpoints.
3930 @item show can-use-hw-watchpoints
3931 @kindex show can-use-hw-watchpoints
3932 Show the current mode of using hardware watchpoints.
3935 For remote targets, you can restrict the number of hardware
3936 watchpoints @value{GDBN} will use, see @ref{set remote
3937 hardware-breakpoint-limit}.
3939 When you issue the @code{watch} command, @value{GDBN} reports
3942 Hardware watchpoint @var{num}: @var{expr}
3946 if it was able to set a hardware watchpoint.
3948 Currently, the @code{awatch} and @code{rwatch} commands can only set
3949 hardware watchpoints, because accesses to data that don't change the
3950 value of the watched expression cannot be detected without examining
3951 every instruction as it is being executed, and @value{GDBN} does not do
3952 that currently. If @value{GDBN} finds that it is unable to set a
3953 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3954 will print a message like this:
3957 Expression cannot be implemented with read/access watchpoint.
3960 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3961 data type of the watched expression is wider than what a hardware
3962 watchpoint on the target machine can handle. For example, some systems
3963 can only watch regions that are up to 4 bytes wide; on such systems you
3964 cannot set hardware watchpoints for an expression that yields a
3965 double-precision floating-point number (which is typically 8 bytes
3966 wide). As a work-around, it might be possible to break the large region
3967 into a series of smaller ones and watch them with separate watchpoints.
3969 If you set too many hardware watchpoints, @value{GDBN} might be unable
3970 to insert all of them when you resume the execution of your program.
3971 Since the precise number of active watchpoints is unknown until such
3972 time as the program is about to be resumed, @value{GDBN} might not be
3973 able to warn you about this when you set the watchpoints, and the
3974 warning will be printed only when the program is resumed:
3977 Hardware watchpoint @var{num}: Could not insert watchpoint
3981 If this happens, delete or disable some of the watchpoints.
3983 Watching complex expressions that reference many variables can also
3984 exhaust the resources available for hardware-assisted watchpoints.
3985 That's because @value{GDBN} needs to watch every variable in the
3986 expression with separately allocated resources.
3988 If you call a function interactively using @code{print} or @code{call},
3989 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3990 kind of breakpoint or the call completes.
3992 @value{GDBN} automatically deletes watchpoints that watch local
3993 (automatic) variables, or expressions that involve such variables, when
3994 they go out of scope, that is, when the execution leaves the block in
3995 which these variables were defined. In particular, when the program
3996 being debugged terminates, @emph{all} local variables go out of scope,
3997 and so only watchpoints that watch global variables remain set. If you
3998 rerun the program, you will need to set all such watchpoints again. One
3999 way of doing that would be to set a code breakpoint at the entry to the
4000 @code{main} function and when it breaks, set all the watchpoints.
4002 @cindex watchpoints and threads
4003 @cindex threads and watchpoints
4004 In multi-threaded programs, watchpoints will detect changes to the
4005 watched expression from every thread.
4008 @emph{Warning:} In multi-threaded programs, software watchpoints
4009 have only limited usefulness. If @value{GDBN} creates a software
4010 watchpoint, it can only watch the value of an expression @emph{in a
4011 single thread}. If you are confident that the expression can only
4012 change due to the current thread's activity (and if you are also
4013 confident that no other thread can become current), then you can use
4014 software watchpoints as usual. However, @value{GDBN} may not notice
4015 when a non-current thread's activity changes the expression. (Hardware
4016 watchpoints, in contrast, watch an expression in all threads.)
4019 @xref{set remote hardware-watchpoint-limit}.
4021 @node Set Catchpoints
4022 @subsection Setting Catchpoints
4023 @cindex catchpoints, setting
4024 @cindex exception handlers
4025 @cindex event handling
4027 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4028 kinds of program events, such as C@t{++} exceptions or the loading of a
4029 shared library. Use the @code{catch} command to set a catchpoint.
4033 @item catch @var{event}
4034 Stop when @var{event} occurs. @var{event} can be any of the following:
4037 @cindex stop on C@t{++} exceptions
4038 The throwing of a C@t{++} exception.
4041 The catching of a C@t{++} exception.
4044 @cindex Ada exception catching
4045 @cindex catch Ada exceptions
4046 An Ada exception being raised. If an exception name is specified
4047 at the end of the command (eg @code{catch exception Program_Error}),
4048 the debugger will stop only when this specific exception is raised.
4049 Otherwise, the debugger stops execution when any Ada exception is raised.
4051 When inserting an exception catchpoint on a user-defined exception whose
4052 name is identical to one of the exceptions defined by the language, the
4053 fully qualified name must be used as the exception name. Otherwise,
4054 @value{GDBN} will assume that it should stop on the pre-defined exception
4055 rather than the user-defined one. For instance, assuming an exception
4056 called @code{Constraint_Error} is defined in package @code{Pck}, then
4057 the command to use to catch such exceptions is @kbd{catch exception
4058 Pck.Constraint_Error}.
4060 @item exception unhandled
4061 An exception that was raised but is not handled by the program.
4064 A failed Ada assertion.
4067 @cindex break on fork/exec
4068 A call to @code{exec}. This is currently only available for HP-UX
4072 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4073 @cindex break on a system call.
4074 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4075 syscall is a mechanism for application programs to request a service
4076 from the operating system (OS) or one of the OS system services.
4077 @value{GDBN} can catch some or all of the syscalls issued by the
4078 debuggee, and show the related information for each syscall. If no
4079 argument is specified, calls to and returns from all system calls
4082 @var{name} can be any system call name that is valid for the
4083 underlying OS. Just what syscalls are valid depends on the OS. On
4084 GNU and Unix systems, you can find the full list of valid syscall
4085 names on @file{/usr/include/asm/unistd.h}.
4087 @c For MS-Windows, the syscall names and the corresponding numbers
4088 @c can be found, e.g., on this URL:
4089 @c http://www.metasploit.com/users/opcode/syscalls.html
4090 @c but we don't support Windows syscalls yet.
4092 Normally, @value{GDBN} knows in advance which syscalls are valid for
4093 each OS, so you can use the @value{GDBN} command-line completion
4094 facilities (@pxref{Completion,, command completion}) to list the
4097 You may also specify the system call numerically. A syscall's
4098 number is the value passed to the OS's syscall dispatcher to
4099 identify the requested service. When you specify the syscall by its
4100 name, @value{GDBN} uses its database of syscalls to convert the name
4101 into the corresponding numeric code, but using the number directly
4102 may be useful if @value{GDBN}'s database does not have the complete
4103 list of syscalls on your system (e.g., because @value{GDBN} lags
4104 behind the OS upgrades).
4106 The example below illustrates how this command works if you don't provide
4110 (@value{GDBP}) catch syscall
4111 Catchpoint 1 (syscall)
4113 Starting program: /tmp/catch-syscall
4115 Catchpoint 1 (call to syscall 'close'), \
4116 0xffffe424 in __kernel_vsyscall ()
4120 Catchpoint 1 (returned from syscall 'close'), \
4121 0xffffe424 in __kernel_vsyscall ()
4125 Here is an example of catching a system call by name:
4128 (@value{GDBP}) catch syscall chroot
4129 Catchpoint 1 (syscall 'chroot' [61])
4131 Starting program: /tmp/catch-syscall
4133 Catchpoint 1 (call to syscall 'chroot'), \
4134 0xffffe424 in __kernel_vsyscall ()
4138 Catchpoint 1 (returned from syscall 'chroot'), \
4139 0xffffe424 in __kernel_vsyscall ()
4143 An example of specifying a system call numerically. In the case
4144 below, the syscall number has a corresponding entry in the XML
4145 file, so @value{GDBN} finds its name and prints it:
4148 (@value{GDBP}) catch syscall 252
4149 Catchpoint 1 (syscall(s) 'exit_group')
4151 Starting program: /tmp/catch-syscall
4153 Catchpoint 1 (call to syscall 'exit_group'), \
4154 0xffffe424 in __kernel_vsyscall ()
4158 Program exited normally.
4162 However, there can be situations when there is no corresponding name
4163 in XML file for that syscall number. In this case, @value{GDBN} prints
4164 a warning message saying that it was not able to find the syscall name,
4165 but the catchpoint will be set anyway. See the example below:
4168 (@value{GDBP}) catch syscall 764
4169 warning: The number '764' does not represent a known syscall.
4170 Catchpoint 2 (syscall 764)
4174 If you configure @value{GDBN} using the @samp{--without-expat} option,
4175 it will not be able to display syscall names. Also, if your
4176 architecture does not have an XML file describing its system calls,
4177 you will not be able to see the syscall names. It is important to
4178 notice that these two features are used for accessing the syscall
4179 name database. In either case, you will see a warning like this:
4182 (@value{GDBP}) catch syscall
4183 warning: Could not open "syscalls/i386-linux.xml"
4184 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4185 GDB will not be able to display syscall names.
4186 Catchpoint 1 (syscall)
4190 Of course, the file name will change depending on your architecture and system.
4192 Still using the example above, you can also try to catch a syscall by its
4193 number. In this case, you would see something like:
4196 (@value{GDBP}) catch syscall 252
4197 Catchpoint 1 (syscall(s) 252)
4200 Again, in this case @value{GDBN} would not be able to display syscall's names.
4203 A call to @code{fork}. This is currently only available for HP-UX
4207 A call to @code{vfork}. This is currently only available for HP-UX
4210 @item load @r{[}regexp@r{]}
4211 @itemx unload @r{[}regexp@r{]}
4212 The loading or unloading of a shared library. If @var{regexp} is
4213 given, then the catchpoint will stop only if the regular expression
4214 matches one of the affected libraries.
4218 @item tcatch @var{event}
4219 Set a catchpoint that is enabled only for one stop. The catchpoint is
4220 automatically deleted after the first time the event is caught.
4224 Use the @code{info break} command to list the current catchpoints.
4226 There are currently some limitations to C@t{++} exception handling
4227 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4231 If you call a function interactively, @value{GDBN} normally returns
4232 control to you when the function has finished executing. If the call
4233 raises an exception, however, the call may bypass the mechanism that
4234 returns control to you and cause your program either to abort or to
4235 simply continue running until it hits a breakpoint, catches a signal
4236 that @value{GDBN} is listening for, or exits. This is the case even if
4237 you set a catchpoint for the exception; catchpoints on exceptions are
4238 disabled within interactive calls.
4241 You cannot raise an exception interactively.
4244 You cannot install an exception handler interactively.
4247 @cindex raise exceptions
4248 Sometimes @code{catch} is not the best way to debug exception handling:
4249 if you need to know exactly where an exception is raised, it is better to
4250 stop @emph{before} the exception handler is called, since that way you
4251 can see the stack before any unwinding takes place. If you set a
4252 breakpoint in an exception handler instead, it may not be easy to find
4253 out where the exception was raised.
4255 To stop just before an exception handler is called, you need some
4256 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4257 raised by calling a library function named @code{__raise_exception}
4258 which has the following ANSI C interface:
4261 /* @var{addr} is where the exception identifier is stored.
4262 @var{id} is the exception identifier. */
4263 void __raise_exception (void **addr, void *id);
4267 To make the debugger catch all exceptions before any stack
4268 unwinding takes place, set a breakpoint on @code{__raise_exception}
4269 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4271 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4272 that depends on the value of @var{id}, you can stop your program when
4273 a specific exception is raised. You can use multiple conditional
4274 breakpoints to stop your program when any of a number of exceptions are
4279 @subsection Deleting Breakpoints
4281 @cindex clearing breakpoints, watchpoints, catchpoints
4282 @cindex deleting breakpoints, watchpoints, catchpoints
4283 It is often necessary to eliminate a breakpoint, watchpoint, or
4284 catchpoint once it has done its job and you no longer want your program
4285 to stop there. This is called @dfn{deleting} the breakpoint. A
4286 breakpoint that has been deleted no longer exists; it is forgotten.
4288 With the @code{clear} command you can delete breakpoints according to
4289 where they are in your program. With the @code{delete} command you can
4290 delete individual breakpoints, watchpoints, or catchpoints by specifying
4291 their breakpoint numbers.
4293 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4294 automatically ignores breakpoints on the first instruction to be executed
4295 when you continue execution without changing the execution address.
4300 Delete any breakpoints at the next instruction to be executed in the
4301 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4302 the innermost frame is selected, this is a good way to delete a
4303 breakpoint where your program just stopped.
4305 @item clear @var{location}
4306 Delete any breakpoints set at the specified @var{location}.
4307 @xref{Specify Location}, for the various forms of @var{location}; the
4308 most useful ones are listed below:
4311 @item clear @var{function}
4312 @itemx clear @var{filename}:@var{function}
4313 Delete any breakpoints set at entry to the named @var{function}.
4315 @item clear @var{linenum}
4316 @itemx clear @var{filename}:@var{linenum}
4317 Delete any breakpoints set at or within the code of the specified
4318 @var{linenum} of the specified @var{filename}.
4321 @cindex delete breakpoints
4323 @kindex d @r{(@code{delete})}
4324 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4325 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4326 ranges specified as arguments. If no argument is specified, delete all
4327 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4328 confirm off}). You can abbreviate this command as @code{d}.
4332 @subsection Disabling Breakpoints
4334 @cindex enable/disable a breakpoint
4335 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4336 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4337 it had been deleted, but remembers the information on the breakpoint so
4338 that you can @dfn{enable} it again later.
4340 You disable and enable breakpoints, watchpoints, and catchpoints with
4341 the @code{enable} and @code{disable} commands, optionally specifying
4342 one or more breakpoint numbers as arguments. Use @code{info break} to
4343 print a list of all breakpoints, watchpoints, and catchpoints if you
4344 do not know which numbers to use.
4346 Disabling and enabling a breakpoint that has multiple locations
4347 affects all of its locations.
4349 A breakpoint, watchpoint, or catchpoint can have any of several
4350 different states of enablement:
4354 Enabled. The breakpoint stops your program. A breakpoint set
4355 with the @code{break} command starts out in this state.
4357 Disabled. The breakpoint has no effect on your program.
4359 Enabled once. The breakpoint stops your program, but then becomes
4362 Enabled for a count. The breakpoint stops your program for the next
4363 N times, then becomes disabled.
4365 Enabled for deletion. The breakpoint stops your program, but
4366 immediately after it does so it is deleted permanently. A breakpoint
4367 set with the @code{tbreak} command starts out in this state.
4370 You can use the following commands to enable or disable breakpoints,
4371 watchpoints, and catchpoints:
4375 @kindex dis @r{(@code{disable})}
4376 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4377 Disable the specified breakpoints---or all breakpoints, if none are
4378 listed. A disabled breakpoint has no effect but is not forgotten. All
4379 options such as ignore-counts, conditions and commands are remembered in
4380 case the breakpoint is enabled again later. You may abbreviate
4381 @code{disable} as @code{dis}.
4384 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4385 Enable the specified breakpoints (or all defined breakpoints). They
4386 become effective once again in stopping your program.
4388 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4389 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4390 of these breakpoints immediately after stopping your program.
4392 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4393 Enable the specified breakpoints temporarily. @value{GDBN} records
4394 @var{count} with each of the specified breakpoints, and decrements a
4395 breakpoint's count when it is hit. When any count reaches 0,
4396 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4397 count (@pxref{Conditions, ,Break Conditions}), that will be
4398 decremented to 0 before @var{count} is affected.
4400 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4401 Enable the specified breakpoints to work once, then die. @value{GDBN}
4402 deletes any of these breakpoints as soon as your program stops there.
4403 Breakpoints set by the @code{tbreak} command start out in this state.
4406 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4407 @c confusing: tbreak is also initially enabled.
4408 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4409 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4410 subsequently, they become disabled or enabled only when you use one of
4411 the commands above. (The command @code{until} can set and delete a
4412 breakpoint of its own, but it does not change the state of your other
4413 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4417 @subsection Break Conditions
4418 @cindex conditional breakpoints
4419 @cindex breakpoint conditions
4421 @c FIXME what is scope of break condition expr? Context where wanted?
4422 @c in particular for a watchpoint?
4423 The simplest sort of breakpoint breaks every time your program reaches a
4424 specified place. You can also specify a @dfn{condition} for a
4425 breakpoint. A condition is just a Boolean expression in your
4426 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4427 a condition evaluates the expression each time your program reaches it,
4428 and your program stops only if the condition is @emph{true}.
4430 This is the converse of using assertions for program validation; in that
4431 situation, you want to stop when the assertion is violated---that is,
4432 when the condition is false. In C, if you want to test an assertion expressed
4433 by the condition @var{assert}, you should set the condition
4434 @samp{! @var{assert}} on the appropriate breakpoint.
4436 Conditions are also accepted for watchpoints; you may not need them,
4437 since a watchpoint is inspecting the value of an expression anyhow---but
4438 it might be simpler, say, to just set a watchpoint on a variable name,
4439 and specify a condition that tests whether the new value is an interesting
4442 Break conditions can have side effects, and may even call functions in
4443 your program. This can be useful, for example, to activate functions
4444 that log program progress, or to use your own print functions to
4445 format special data structures. The effects are completely predictable
4446 unless there is another enabled breakpoint at the same address. (In
4447 that case, @value{GDBN} might see the other breakpoint first and stop your
4448 program without checking the condition of this one.) Note that
4449 breakpoint commands are usually more convenient and flexible than break
4451 purpose of performing side effects when a breakpoint is reached
4452 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4454 Breakpoint conditions can also be evaluated on the target's side if
4455 the target supports it. Instead of evaluating the conditions locally,
4456 @value{GDBN} encodes the expression into an agent expression
4457 (@pxref{Agent Expressions}) suitable for execution on the target,
4458 independently of @value{GDBN}. Global variables become raw memory
4459 locations, locals become stack accesses, and so forth.
4461 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4462 when its condition evaluates to true. This mechanism may provide faster
4463 response times depending on the performance characteristics of the target
4464 since it does not need to keep @value{GDBN} informed about
4465 every breakpoint trigger, even those with false conditions.
4467 Break conditions can be specified when a breakpoint is set, by using
4468 @samp{if} in the arguments to the @code{break} command. @xref{Set
4469 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4470 with the @code{condition} command.
4472 You can also use the @code{if} keyword with the @code{watch} command.
4473 The @code{catch} command does not recognize the @code{if} keyword;
4474 @code{condition} is the only way to impose a further condition on a
4479 @item condition @var{bnum} @var{expression}
4480 Specify @var{expression} as the break condition for breakpoint,
4481 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4482 breakpoint @var{bnum} stops your program only if the value of
4483 @var{expression} is true (nonzero, in C). When you use
4484 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4485 syntactic correctness, and to determine whether symbols in it have
4486 referents in the context of your breakpoint. If @var{expression} uses
4487 symbols not referenced in the context of the breakpoint, @value{GDBN}
4488 prints an error message:
4491 No symbol "foo" in current context.
4496 not actually evaluate @var{expression} at the time the @code{condition}
4497 command (or a command that sets a breakpoint with a condition, like
4498 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4500 @item condition @var{bnum}
4501 Remove the condition from breakpoint number @var{bnum}. It becomes
4502 an ordinary unconditional breakpoint.
4505 @cindex ignore count (of breakpoint)
4506 A special case of a breakpoint condition is to stop only when the
4507 breakpoint has been reached a certain number of times. This is so
4508 useful that there is a special way to do it, using the @dfn{ignore
4509 count} of the breakpoint. Every breakpoint has an ignore count, which
4510 is an integer. Most of the time, the ignore count is zero, and
4511 therefore has no effect. But if your program reaches a breakpoint whose
4512 ignore count is positive, then instead of stopping, it just decrements
4513 the ignore count by one and continues. As a result, if the ignore count
4514 value is @var{n}, the breakpoint does not stop the next @var{n} times
4515 your program reaches it.
4519 @item ignore @var{bnum} @var{count}
4520 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4521 The next @var{count} times the breakpoint is reached, your program's
4522 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4525 To make the breakpoint stop the next time it is reached, specify
4528 When you use @code{continue} to resume execution of your program from a
4529 breakpoint, you can specify an ignore count directly as an argument to
4530 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4531 Stepping,,Continuing and Stepping}.
4533 If a breakpoint has a positive ignore count and a condition, the
4534 condition is not checked. Once the ignore count reaches zero,
4535 @value{GDBN} resumes checking the condition.
4537 You could achieve the effect of the ignore count with a condition such
4538 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4539 is decremented each time. @xref{Convenience Vars, ,Convenience
4543 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4546 @node Break Commands
4547 @subsection Breakpoint Command Lists
4549 @cindex breakpoint commands
4550 You can give any breakpoint (or watchpoint or catchpoint) a series of
4551 commands to execute when your program stops due to that breakpoint. For
4552 example, you might want to print the values of certain expressions, or
4553 enable other breakpoints.
4557 @kindex end@r{ (breakpoint commands)}
4558 @item commands @r{[}@var{range}@dots{}@r{]}
4559 @itemx @dots{} @var{command-list} @dots{}
4561 Specify a list of commands for the given breakpoints. The commands
4562 themselves appear on the following lines. Type a line containing just
4563 @code{end} to terminate the commands.
4565 To remove all commands from a breakpoint, type @code{commands} and
4566 follow it immediately with @code{end}; that is, give no commands.
4568 With no argument, @code{commands} refers to the last breakpoint,
4569 watchpoint, or catchpoint set (not to the breakpoint most recently
4570 encountered). If the most recent breakpoints were set with a single
4571 command, then the @code{commands} will apply to all the breakpoints
4572 set by that command. This applies to breakpoints set by
4573 @code{rbreak}, and also applies when a single @code{break} command
4574 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4578 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4579 disabled within a @var{command-list}.
4581 You can use breakpoint commands to start your program up again. Simply
4582 use the @code{continue} command, or @code{step}, or any other command
4583 that resumes execution.
4585 Any other commands in the command list, after a command that resumes
4586 execution, are ignored. This is because any time you resume execution
4587 (even with a simple @code{next} or @code{step}), you may encounter
4588 another breakpoint---which could have its own command list, leading to
4589 ambiguities about which list to execute.
4592 If the first command you specify in a command list is @code{silent}, the
4593 usual message about stopping at a breakpoint is not printed. This may
4594 be desirable for breakpoints that are to print a specific message and
4595 then continue. If none of the remaining commands print anything, you
4596 see no sign that the breakpoint was reached. @code{silent} is
4597 meaningful only at the beginning of a breakpoint command list.
4599 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4600 print precisely controlled output, and are often useful in silent
4601 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4603 For example, here is how you could use breakpoint commands to print the
4604 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4610 printf "x is %d\n",x
4615 One application for breakpoint commands is to compensate for one bug so
4616 you can test for another. Put a breakpoint just after the erroneous line
4617 of code, give it a condition to detect the case in which something
4618 erroneous has been done, and give it commands to assign correct values
4619 to any variables that need them. End with the @code{continue} command
4620 so that your program does not stop, and start with the @code{silent}
4621 command so that no output is produced. Here is an example:
4632 @node Dynamic Printf
4633 @subsection Dynamic Printf
4635 @cindex dynamic printf
4637 The dynamic printf command @code{dprintf} combines a breakpoint with
4638 formatted printing of your program's data to give you the effect of
4639 inserting @code{printf} calls into your program on-the-fly, without
4640 having to recompile it.
4642 In its most basic form, the output goes to the GDB console. However,
4643 you can set the variable @code{dprintf-style} for alternate handling.
4644 For instance, you can ask to format the output by calling your
4645 program's @code{printf} function. This has the advantage that the
4646 characters go to the program's output device, so they can recorded in
4647 redirects to files and so forth.
4651 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4652 Whenever execution reaches @var{location}, print the values of one or
4653 more @var{expressions} under the control of the string @var{template}.
4654 To print several values, separate them with commas.
4656 @item set dprintf-style @var{style}
4657 Set the dprintf output to be handled in one of several different
4658 styles enumerated below. A change of style affects all existing
4659 dynamic printfs immediately. (If you need individual control over the
4660 print commands, simply define normal breakpoints with
4661 explicitly-supplied command lists.)
4664 @kindex dprintf-style gdb
4665 Handle the output using the @value{GDBN} @code{printf} command.
4668 @kindex dprintf-style call
4669 Handle the output by calling a function in your program (normally
4672 @item set dprintf-function @var{function}
4673 Set the function to call if the dprintf style is @code{call}. By
4674 default its value is @code{printf}. You may set it to any expression.
4675 that @value{GDBN} can evaluate to a function, as per the @code{call}
4678 @item set dprintf-channel @var{channel}
4679 Set a ``channel'' for dprintf. If set to a non-empty value,
4680 @value{GDBN} will evaluate it as an expression and pass the result as
4681 a first argument to the @code{dprintf-function}, in the manner of
4682 @code{fprintf} and similar functions. Otherwise, the dprintf format
4683 string will be the first argument, in the manner of @code{printf}.
4685 As an example, if you wanted @code{dprintf} output to go to a logfile
4686 that is a standard I/O stream assigned to the variable @code{mylog},
4687 you could do the following:
4690 (gdb) set dprintf-style call
4691 (gdb) set dprintf-function fprintf
4692 (gdb) set dprintf-channel mylog
4693 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4694 Dprintf 1 at 0x123456: file main.c, line 25.
4696 1 dprintf keep y 0x00123456 in main at main.c:25
4697 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4702 Note that the @code{info break} displays the dynamic printf commands
4703 as normal breakpoint commands; you can thus easily see the effect of
4704 the variable settings.
4708 @value{GDBN} does not check the validity of function and channel,
4709 relying on you to supply values that are meaningful for the contexts
4710 in which they are being used. For instance, the function and channel
4711 may be the values of local variables, but if that is the case, then
4712 all enabled dynamic prints must be at locations within the scope of
4713 those locals. If evaluation fails, @value{GDBN} will report an error.
4715 @node Save Breakpoints
4716 @subsection How to save breakpoints to a file
4718 To save breakpoint definitions to a file use the @w{@code{save
4719 breakpoints}} command.
4722 @kindex save breakpoints
4723 @cindex save breakpoints to a file for future sessions
4724 @item save breakpoints [@var{filename}]
4725 This command saves all current breakpoint definitions together with
4726 their commands and ignore counts, into a file @file{@var{filename}}
4727 suitable for use in a later debugging session. This includes all
4728 types of breakpoints (breakpoints, watchpoints, catchpoints,
4729 tracepoints). To read the saved breakpoint definitions, use the
4730 @code{source} command (@pxref{Command Files}). Note that watchpoints
4731 with expressions involving local variables may fail to be recreated
4732 because it may not be possible to access the context where the
4733 watchpoint is valid anymore. Because the saved breakpoint definitions
4734 are simply a sequence of @value{GDBN} commands that recreate the
4735 breakpoints, you can edit the file in your favorite editing program,
4736 and remove the breakpoint definitions you're not interested in, or
4737 that can no longer be recreated.
4740 @node Static Probe Points
4741 @subsection Static Probe Points
4743 @cindex static probe point, SystemTap
4744 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4745 for Statically Defined Tracing, and the probes are designed to have a tiny
4746 runtime code and data footprint, and no dynamic relocations. They are
4747 usable from assembly, C and C@t{++} languages. See
4748 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4749 for a good reference on how the @acronym{SDT} probes are implemented.
4751 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4752 @acronym{SDT} probes are supported on ELF-compatible systems. See
4753 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4754 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4755 in your applications.
4757 @cindex semaphores on static probe points
4758 Some probes have an associated semaphore variable; for instance, this
4759 happens automatically if you defined your probe using a DTrace-style
4760 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4761 automatically enable it when you specify a breakpoint using the
4762 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4763 location by some other method (e.g., @code{break file:line}), then
4764 @value{GDBN} will not automatically set the semaphore.
4766 You can examine the available static static probes using @code{info
4767 probes}, with optional arguments:
4771 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4772 If given, @var{provider} is a regular expression used to match against provider
4773 names when selecting which probes to list. If omitted, probes by all
4774 probes from all providers are listed.
4776 If given, @var{name} is a regular expression to match against probe names
4777 when selecting which probes to list. If omitted, probe names are not
4778 considered when deciding whether to display them.
4780 If given, @var{objfile} is a regular expression used to select which
4781 object files (executable or shared libraries) to examine. If not
4782 given, all object files are considered.
4784 @item info probes all
4785 List the available static probes, from all types.
4788 @vindex $_probe_arg@r{, convenience variable}
4789 A probe may specify up to twelve arguments. These are available at the
4790 point at which the probe is defined---that is, when the current PC is
4791 at the probe's location. The arguments are available using the
4792 convenience variables (@pxref{Convenience Vars})
4793 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4794 an integer of the appropriate size; types are not preserved. The
4795 convenience variable @code{$_probe_argc} holds the number of arguments
4796 at the current probe point.
4798 These variables are always available, but attempts to access them at
4799 any location other than a probe point will cause @value{GDBN} to give
4803 @c @ifclear BARETARGET
4804 @node Error in Breakpoints
4805 @subsection ``Cannot insert breakpoints''
4807 If you request too many active hardware-assisted breakpoints and
4808 watchpoints, you will see this error message:
4810 @c FIXME: the precise wording of this message may change; the relevant
4811 @c source change is not committed yet (Sep 3, 1999).
4813 Stopped; cannot insert breakpoints.
4814 You may have requested too many hardware breakpoints and watchpoints.
4818 This message is printed when you attempt to resume the program, since
4819 only then @value{GDBN} knows exactly how many hardware breakpoints and
4820 watchpoints it needs to insert.
4822 When this message is printed, you need to disable or remove some of the
4823 hardware-assisted breakpoints and watchpoints, and then continue.
4825 @node Breakpoint-related Warnings
4826 @subsection ``Breakpoint address adjusted...''
4827 @cindex breakpoint address adjusted
4829 Some processor architectures place constraints on the addresses at
4830 which breakpoints may be placed. For architectures thus constrained,
4831 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4832 with the constraints dictated by the architecture.
4834 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4835 a VLIW architecture in which a number of RISC-like instructions may be
4836 bundled together for parallel execution. The FR-V architecture
4837 constrains the location of a breakpoint instruction within such a
4838 bundle to the instruction with the lowest address. @value{GDBN}
4839 honors this constraint by adjusting a breakpoint's address to the
4840 first in the bundle.
4842 It is not uncommon for optimized code to have bundles which contain
4843 instructions from different source statements, thus it may happen that
4844 a breakpoint's address will be adjusted from one source statement to
4845 another. Since this adjustment may significantly alter @value{GDBN}'s
4846 breakpoint related behavior from what the user expects, a warning is
4847 printed when the breakpoint is first set and also when the breakpoint
4850 A warning like the one below is printed when setting a breakpoint
4851 that's been subject to address adjustment:
4854 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4857 Such warnings are printed both for user settable and @value{GDBN}'s
4858 internal breakpoints. If you see one of these warnings, you should
4859 verify that a breakpoint set at the adjusted address will have the
4860 desired affect. If not, the breakpoint in question may be removed and
4861 other breakpoints may be set which will have the desired behavior.
4862 E.g., it may be sufficient to place the breakpoint at a later
4863 instruction. A conditional breakpoint may also be useful in some
4864 cases to prevent the breakpoint from triggering too often.
4866 @value{GDBN} will also issue a warning when stopping at one of these
4867 adjusted breakpoints:
4870 warning: Breakpoint 1 address previously adjusted from 0x00010414
4874 When this warning is encountered, it may be too late to take remedial
4875 action except in cases where the breakpoint is hit earlier or more
4876 frequently than expected.
4878 @node Continuing and Stepping
4879 @section Continuing and Stepping
4883 @cindex resuming execution
4884 @dfn{Continuing} means resuming program execution until your program
4885 completes normally. In contrast, @dfn{stepping} means executing just
4886 one more ``step'' of your program, where ``step'' may mean either one
4887 line of source code, or one machine instruction (depending on what
4888 particular command you use). Either when continuing or when stepping,
4889 your program may stop even sooner, due to a breakpoint or a signal. (If
4890 it stops due to a signal, you may want to use @code{handle}, or use
4891 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4895 @kindex c @r{(@code{continue})}
4896 @kindex fg @r{(resume foreground execution)}
4897 @item continue @r{[}@var{ignore-count}@r{]}
4898 @itemx c @r{[}@var{ignore-count}@r{]}
4899 @itemx fg @r{[}@var{ignore-count}@r{]}
4900 Resume program execution, at the address where your program last stopped;
4901 any breakpoints set at that address are bypassed. The optional argument
4902 @var{ignore-count} allows you to specify a further number of times to
4903 ignore a breakpoint at this location; its effect is like that of
4904 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4906 The argument @var{ignore-count} is meaningful only when your program
4907 stopped due to a breakpoint. At other times, the argument to
4908 @code{continue} is ignored.
4910 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4911 debugged program is deemed to be the foreground program) are provided
4912 purely for convenience, and have exactly the same behavior as
4916 To resume execution at a different place, you can use @code{return}
4917 (@pxref{Returning, ,Returning from a Function}) to go back to the
4918 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4919 Different Address}) to go to an arbitrary location in your program.
4921 A typical technique for using stepping is to set a breakpoint
4922 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4923 beginning of the function or the section of your program where a problem
4924 is believed to lie, run your program until it stops at that breakpoint,
4925 and then step through the suspect area, examining the variables that are
4926 interesting, until you see the problem happen.
4930 @kindex s @r{(@code{step})}
4932 Continue running your program until control reaches a different source
4933 line, then stop it and return control to @value{GDBN}. This command is
4934 abbreviated @code{s}.
4937 @c "without debugging information" is imprecise; actually "without line
4938 @c numbers in the debugging information". (gcc -g1 has debugging info but
4939 @c not line numbers). But it seems complex to try to make that
4940 @c distinction here.
4941 @emph{Warning:} If you use the @code{step} command while control is
4942 within a function that was compiled without debugging information,
4943 execution proceeds until control reaches a function that does have
4944 debugging information. Likewise, it will not step into a function which
4945 is compiled without debugging information. To step through functions
4946 without debugging information, use the @code{stepi} command, described
4950 The @code{step} command only stops at the first instruction of a source
4951 line. This prevents the multiple stops that could otherwise occur in
4952 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4953 to stop if a function that has debugging information is called within
4954 the line. In other words, @code{step} @emph{steps inside} any functions
4955 called within the line.
4957 Also, the @code{step} command only enters a function if there is line
4958 number information for the function. Otherwise it acts like the
4959 @code{next} command. This avoids problems when using @code{cc -gl}
4960 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
4961 was any debugging information about the routine.
4963 @item step @var{count}
4964 Continue running as in @code{step}, but do so @var{count} times. If a
4965 breakpoint is reached, or a signal not related to stepping occurs before
4966 @var{count} steps, stepping stops right away.
4969 @kindex n @r{(@code{next})}
4970 @item next @r{[}@var{count}@r{]}
4971 Continue to the next source line in the current (innermost) stack frame.
4972 This is similar to @code{step}, but function calls that appear within
4973 the line of code are executed without stopping. Execution stops when
4974 control reaches a different line of code at the original stack level
4975 that was executing when you gave the @code{next} command. This command
4976 is abbreviated @code{n}.
4978 An argument @var{count} is a repeat count, as for @code{step}.
4981 @c FIX ME!! Do we delete this, or is there a way it fits in with
4982 @c the following paragraph? --- Vctoria
4984 @c @code{next} within a function that lacks debugging information acts like
4985 @c @code{step}, but any function calls appearing within the code of the
4986 @c function are executed without stopping.
4988 The @code{next} command only stops at the first instruction of a
4989 source line. This prevents multiple stops that could otherwise occur in
4990 @code{switch} statements, @code{for} loops, etc.
4992 @kindex set step-mode
4994 @cindex functions without line info, and stepping
4995 @cindex stepping into functions with no line info
4996 @itemx set step-mode on
4997 The @code{set step-mode on} command causes the @code{step} command to
4998 stop at the first instruction of a function which contains no debug line
4999 information rather than stepping over it.
5001 This is useful in cases where you may be interested in inspecting the
5002 machine instructions of a function which has no symbolic info and do not
5003 want @value{GDBN} to automatically skip over this function.
5005 @item set step-mode off
5006 Causes the @code{step} command to step over any functions which contains no
5007 debug information. This is the default.
5009 @item show step-mode
5010 Show whether @value{GDBN} will stop in or step over functions without
5011 source line debug information.
5014 @kindex fin @r{(@code{finish})}
5016 Continue running until just after function in the selected stack frame
5017 returns. Print the returned value (if any). This command can be
5018 abbreviated as @code{fin}.
5020 Contrast this with the @code{return} command (@pxref{Returning,
5021 ,Returning from a Function}).
5024 @kindex u @r{(@code{until})}
5025 @cindex run until specified location
5028 Continue running until a source line past the current line, in the
5029 current stack frame, is reached. This command is used to avoid single
5030 stepping through a loop more than once. It is like the @code{next}
5031 command, except that when @code{until} encounters a jump, it
5032 automatically continues execution until the program counter is greater
5033 than the address of the jump.
5035 This means that when you reach the end of a loop after single stepping
5036 though it, @code{until} makes your program continue execution until it
5037 exits the loop. In contrast, a @code{next} command at the end of a loop
5038 simply steps back to the beginning of the loop, which forces you to step
5039 through the next iteration.
5041 @code{until} always stops your program if it attempts to exit the current
5044 @code{until} may produce somewhat counterintuitive results if the order
5045 of machine code does not match the order of the source lines. For
5046 example, in the following excerpt from a debugging session, the @code{f}
5047 (@code{frame}) command shows that execution is stopped at line
5048 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5052 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5054 (@value{GDBP}) until
5055 195 for ( ; argc > 0; NEXTARG) @{
5058 This happened because, for execution efficiency, the compiler had
5059 generated code for the loop closure test at the end, rather than the
5060 start, of the loop---even though the test in a C @code{for}-loop is
5061 written before the body of the loop. The @code{until} command appeared
5062 to step back to the beginning of the loop when it advanced to this
5063 expression; however, it has not really gone to an earlier
5064 statement---not in terms of the actual machine code.
5066 @code{until} with no argument works by means of single
5067 instruction stepping, and hence is slower than @code{until} with an
5070 @item until @var{location}
5071 @itemx u @var{location}
5072 Continue running your program until either the specified location is
5073 reached, or the current stack frame returns. @var{location} is any of
5074 the forms described in @ref{Specify Location}.
5075 This form of the command uses temporary breakpoints, and
5076 hence is quicker than @code{until} without an argument. The specified
5077 location is actually reached only if it is in the current frame. This
5078 implies that @code{until} can be used to skip over recursive function
5079 invocations. For instance in the code below, if the current location is
5080 line @code{96}, issuing @code{until 99} will execute the program up to
5081 line @code{99} in the same invocation of factorial, i.e., after the inner
5082 invocations have returned.
5085 94 int factorial (int value)
5087 96 if (value > 1) @{
5088 97 value *= factorial (value - 1);
5095 @kindex advance @var{location}
5096 @itemx advance @var{location}
5097 Continue running the program up to the given @var{location}. An argument is
5098 required, which should be of one of the forms described in
5099 @ref{Specify Location}.
5100 Execution will also stop upon exit from the current stack
5101 frame. This command is similar to @code{until}, but @code{advance} will
5102 not skip over recursive function calls, and the target location doesn't
5103 have to be in the same frame as the current one.
5107 @kindex si @r{(@code{stepi})}
5109 @itemx stepi @var{arg}
5111 Execute one machine instruction, then stop and return to the debugger.
5113 It is often useful to do @samp{display/i $pc} when stepping by machine
5114 instructions. This makes @value{GDBN} automatically display the next
5115 instruction to be executed, each time your program stops. @xref{Auto
5116 Display,, Automatic Display}.
5118 An argument is a repeat count, as in @code{step}.
5122 @kindex ni @r{(@code{nexti})}
5124 @itemx nexti @var{arg}
5126 Execute one machine instruction, but if it is a function call,
5127 proceed until the function returns.
5129 An argument is a repeat count, as in @code{next}.
5132 @node Skipping Over Functions and Files
5133 @section Skipping Over Functions and Files
5134 @cindex skipping over functions and files
5136 The program you are debugging may contain some functions which are
5137 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5138 skip a function or all functions in a file when stepping.
5140 For example, consider the following C function:
5151 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5152 are not interested in stepping through @code{boring}. If you run @code{step}
5153 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5154 step over both @code{foo} and @code{boring}!
5156 One solution is to @code{step} into @code{boring} and use the @code{finish}
5157 command to immediately exit it. But this can become tedious if @code{boring}
5158 is called from many places.
5160 A more flexible solution is to execute @kbd{skip boring}. This instructs
5161 @value{GDBN} never to step into @code{boring}. Now when you execute
5162 @code{step} at line 103, you'll step over @code{boring} and directly into
5165 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5166 example, @code{skip file boring.c}.
5169 @kindex skip function
5170 @item skip @r{[}@var{linespec}@r{]}
5171 @itemx skip function @r{[}@var{linespec}@r{]}
5172 After running this command, the function named by @var{linespec} or the
5173 function containing the line named by @var{linespec} will be skipped over when
5174 stepping. @xref{Specify Location}.
5176 If you do not specify @var{linespec}, the function you're currently debugging
5179 (If you have a function called @code{file} that you want to skip, use
5180 @kbd{skip function file}.)
5183 @item skip file @r{[}@var{filename}@r{]}
5184 After running this command, any function whose source lives in @var{filename}
5185 will be skipped over when stepping.
5187 If you do not specify @var{filename}, functions whose source lives in the file
5188 you're currently debugging will be skipped.
5191 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5192 These are the commands for managing your list of skips:
5196 @item info skip @r{[}@var{range}@r{]}
5197 Print details about the specified skip(s). If @var{range} is not specified,
5198 print a table with details about all functions and files marked for skipping.
5199 @code{info skip} prints the following information about each skip:
5203 A number identifying this skip.
5205 The type of this skip, either @samp{function} or @samp{file}.
5206 @item Enabled or Disabled
5207 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5209 For function skips, this column indicates the address in memory of the function
5210 being skipped. If you've set a function skip on a function which has not yet
5211 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5212 which has the function is loaded, @code{info skip} will show the function's
5215 For file skips, this field contains the filename being skipped. For functions
5216 skips, this field contains the function name and its line number in the file
5217 where it is defined.
5221 @item skip delete @r{[}@var{range}@r{]}
5222 Delete the specified skip(s). If @var{range} is not specified, delete all
5226 @item skip enable @r{[}@var{range}@r{]}
5227 Enable the specified skip(s). If @var{range} is not specified, enable all
5230 @kindex skip disable
5231 @item skip disable @r{[}@var{range}@r{]}
5232 Disable the specified skip(s). If @var{range} is not specified, disable all
5241 A signal is an asynchronous event that can happen in a program. The
5242 operating system defines the possible kinds of signals, and gives each
5243 kind a name and a number. For example, in Unix @code{SIGINT} is the
5244 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5245 @code{SIGSEGV} is the signal a program gets from referencing a place in
5246 memory far away from all the areas in use; @code{SIGALRM} occurs when
5247 the alarm clock timer goes off (which happens only if your program has
5248 requested an alarm).
5250 @cindex fatal signals
5251 Some signals, including @code{SIGALRM}, are a normal part of the
5252 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5253 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5254 program has not specified in advance some other way to handle the signal.
5255 @code{SIGINT} does not indicate an error in your program, but it is normally
5256 fatal so it can carry out the purpose of the interrupt: to kill the program.
5258 @value{GDBN} has the ability to detect any occurrence of a signal in your
5259 program. You can tell @value{GDBN} in advance what to do for each kind of
5262 @cindex handling signals
5263 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5264 @code{SIGALRM} be silently passed to your program
5265 (so as not to interfere with their role in the program's functioning)
5266 but to stop your program immediately whenever an error signal happens.
5267 You can change these settings with the @code{handle} command.
5270 @kindex info signals
5274 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5275 handle each one. You can use this to see the signal numbers of all
5276 the defined types of signals.
5278 @item info signals @var{sig}
5279 Similar, but print information only about the specified signal number.
5281 @code{info handle} is an alias for @code{info signals}.
5284 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5285 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5286 can be the number of a signal or its name (with or without the
5287 @samp{SIG} at the beginning); a list of signal numbers of the form
5288 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5289 known signals. Optional arguments @var{keywords}, described below,
5290 say what change to make.
5294 The keywords allowed by the @code{handle} command can be abbreviated.
5295 Their full names are:
5299 @value{GDBN} should not stop your program when this signal happens. It may
5300 still print a message telling you that the signal has come in.
5303 @value{GDBN} should stop your program when this signal happens. This implies
5304 the @code{print} keyword as well.
5307 @value{GDBN} should print a message when this signal happens.
5310 @value{GDBN} should not mention the occurrence of the signal at all. This
5311 implies the @code{nostop} keyword as well.
5315 @value{GDBN} should allow your program to see this signal; your program
5316 can handle the signal, or else it may terminate if the signal is fatal
5317 and not handled. @code{pass} and @code{noignore} are synonyms.
5321 @value{GDBN} should not allow your program to see this signal.
5322 @code{nopass} and @code{ignore} are synonyms.
5326 When a signal stops your program, the signal is not visible to the
5328 continue. Your program sees the signal then, if @code{pass} is in
5329 effect for the signal in question @emph{at that time}. In other words,
5330 after @value{GDBN} reports a signal, you can use the @code{handle}
5331 command with @code{pass} or @code{nopass} to control whether your
5332 program sees that signal when you continue.
5334 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5335 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5336 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5339 You can also use the @code{signal} command to prevent your program from
5340 seeing a signal, or cause it to see a signal it normally would not see,
5341 or to give it any signal at any time. For example, if your program stopped
5342 due to some sort of memory reference error, you might store correct
5343 values into the erroneous variables and continue, hoping to see more
5344 execution; but your program would probably terminate immediately as
5345 a result of the fatal signal once it saw the signal. To prevent this,
5346 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5349 @cindex extra signal information
5350 @anchor{extra signal information}
5352 On some targets, @value{GDBN} can inspect extra signal information
5353 associated with the intercepted signal, before it is actually
5354 delivered to the program being debugged. This information is exported
5355 by the convenience variable @code{$_siginfo}, and consists of data
5356 that is passed by the kernel to the signal handler at the time of the
5357 receipt of a signal. The data type of the information itself is
5358 target dependent. You can see the data type using the @code{ptype
5359 $_siginfo} command. On Unix systems, it typically corresponds to the
5360 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5363 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5364 referenced address that raised a segmentation fault.
5368 (@value{GDBP}) continue
5369 Program received signal SIGSEGV, Segmentation fault.
5370 0x0000000000400766 in main ()
5372 (@value{GDBP}) ptype $_siginfo
5379 struct @{...@} _kill;
5380 struct @{...@} _timer;
5382 struct @{...@} _sigchld;
5383 struct @{...@} _sigfault;
5384 struct @{...@} _sigpoll;
5387 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5391 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5392 $1 = (void *) 0x7ffff7ff7000
5396 Depending on target support, @code{$_siginfo} may also be writable.
5399 @section Stopping and Starting Multi-thread Programs
5401 @cindex stopped threads
5402 @cindex threads, stopped
5404 @cindex continuing threads
5405 @cindex threads, continuing
5407 @value{GDBN} supports debugging programs with multiple threads
5408 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5409 are two modes of controlling execution of your program within the
5410 debugger. In the default mode, referred to as @dfn{all-stop mode},
5411 when any thread in your program stops (for example, at a breakpoint
5412 or while being stepped), all other threads in the program are also stopped by
5413 @value{GDBN}. On some targets, @value{GDBN} also supports
5414 @dfn{non-stop mode}, in which other threads can continue to run freely while
5415 you examine the stopped thread in the debugger.
5418 * All-Stop Mode:: All threads stop when GDB takes control
5419 * Non-Stop Mode:: Other threads continue to execute
5420 * Background Execution:: Running your program asynchronously
5421 * Thread-Specific Breakpoints:: Controlling breakpoints
5422 * Interrupted System Calls:: GDB may interfere with system calls
5423 * Observer Mode:: GDB does not alter program behavior
5427 @subsection All-Stop Mode
5429 @cindex all-stop mode
5431 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5432 @emph{all} threads of execution stop, not just the current thread. This
5433 allows you to examine the overall state of the program, including
5434 switching between threads, without worrying that things may change
5437 Conversely, whenever you restart the program, @emph{all} threads start
5438 executing. @emph{This is true even when single-stepping} with commands
5439 like @code{step} or @code{next}.
5441 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5442 Since thread scheduling is up to your debugging target's operating
5443 system (not controlled by @value{GDBN}), other threads may
5444 execute more than one statement while the current thread completes a
5445 single step. Moreover, in general other threads stop in the middle of a
5446 statement, rather than at a clean statement boundary, when the program
5449 You might even find your program stopped in another thread after
5450 continuing or even single-stepping. This happens whenever some other
5451 thread runs into a breakpoint, a signal, or an exception before the
5452 first thread completes whatever you requested.
5454 @cindex automatic thread selection
5455 @cindex switching threads automatically
5456 @cindex threads, automatic switching
5457 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5458 signal, it automatically selects the thread where that breakpoint or
5459 signal happened. @value{GDBN} alerts you to the context switch with a
5460 message such as @samp{[Switching to Thread @var{n}]} to identify the
5463 On some OSes, you can modify @value{GDBN}'s default behavior by
5464 locking the OS scheduler to allow only a single thread to run.
5467 @item set scheduler-locking @var{mode}
5468 @cindex scheduler locking mode
5469 @cindex lock scheduler
5470 Set the scheduler locking mode. If it is @code{off}, then there is no
5471 locking and any thread may run at any time. If @code{on}, then only the
5472 current thread may run when the inferior is resumed. The @code{step}
5473 mode optimizes for single-stepping; it prevents other threads
5474 from preempting the current thread while you are stepping, so that
5475 the focus of debugging does not change unexpectedly.
5476 Other threads only rarely (or never) get a chance to run
5477 when you step. They are more likely to run when you @samp{next} over a
5478 function call, and they are completely free to run when you use commands
5479 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5480 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5481 the current thread away from the thread that you are debugging.
5483 @item show scheduler-locking
5484 Display the current scheduler locking mode.
5487 @cindex resume threads of multiple processes simultaneously
5488 By default, when you issue one of the execution commands such as
5489 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5490 threads of the current inferior to run. For example, if @value{GDBN}
5491 is attached to two inferiors, each with two threads, the
5492 @code{continue} command resumes only the two threads of the current
5493 inferior. This is useful, for example, when you debug a program that
5494 forks and you want to hold the parent stopped (so that, for instance,
5495 it doesn't run to exit), while you debug the child. In other
5496 situations, you may not be interested in inspecting the current state
5497 of any of the processes @value{GDBN} is attached to, and you may want
5498 to resume them all until some breakpoint is hit. In the latter case,
5499 you can instruct @value{GDBN} to allow all threads of all the
5500 inferiors to run with the @w{@code{set schedule-multiple}} command.
5503 @kindex set schedule-multiple
5504 @item set schedule-multiple
5505 Set the mode for allowing threads of multiple processes to be resumed
5506 when an execution command is issued. When @code{on}, all threads of
5507 all processes are allowed to run. When @code{off}, only the threads
5508 of the current process are resumed. The default is @code{off}. The
5509 @code{scheduler-locking} mode takes precedence when set to @code{on},
5510 or while you are stepping and set to @code{step}.
5512 @item show schedule-multiple
5513 Display the current mode for resuming the execution of threads of
5518 @subsection Non-Stop Mode
5520 @cindex non-stop mode
5522 @c This section is really only a place-holder, and needs to be expanded
5523 @c with more details.
5525 For some multi-threaded targets, @value{GDBN} supports an optional
5526 mode of operation in which you can examine stopped program threads in
5527 the debugger while other threads continue to execute freely. This
5528 minimizes intrusion when debugging live systems, such as programs
5529 where some threads have real-time constraints or must continue to
5530 respond to external events. This is referred to as @dfn{non-stop} mode.
5532 In non-stop mode, when a thread stops to report a debugging event,
5533 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5534 threads as well, in contrast to the all-stop mode behavior. Additionally,
5535 execution commands such as @code{continue} and @code{step} apply by default
5536 only to the current thread in non-stop mode, rather than all threads as
5537 in all-stop mode. This allows you to control threads explicitly in
5538 ways that are not possible in all-stop mode --- for example, stepping
5539 one thread while allowing others to run freely, stepping
5540 one thread while holding all others stopped, or stepping several threads
5541 independently and simultaneously.
5543 To enter non-stop mode, use this sequence of commands before you run
5544 or attach to your program:
5547 # Enable the async interface.
5550 # If using the CLI, pagination breaks non-stop.
5553 # Finally, turn it on!
5557 You can use these commands to manipulate the non-stop mode setting:
5560 @kindex set non-stop
5561 @item set non-stop on
5562 Enable selection of non-stop mode.
5563 @item set non-stop off
5564 Disable selection of non-stop mode.
5565 @kindex show non-stop
5567 Show the current non-stop enablement setting.
5570 Note these commands only reflect whether non-stop mode is enabled,
5571 not whether the currently-executing program is being run in non-stop mode.
5572 In particular, the @code{set non-stop} preference is only consulted when
5573 @value{GDBN} starts or connects to the target program, and it is generally
5574 not possible to switch modes once debugging has started. Furthermore,
5575 since not all targets support non-stop mode, even when you have enabled
5576 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5579 In non-stop mode, all execution commands apply only to the current thread
5580 by default. That is, @code{continue} only continues one thread.
5581 To continue all threads, issue @code{continue -a} or @code{c -a}.
5583 You can use @value{GDBN}'s background execution commands
5584 (@pxref{Background Execution}) to run some threads in the background
5585 while you continue to examine or step others from @value{GDBN}.
5586 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5587 always executed asynchronously in non-stop mode.
5589 Suspending execution is done with the @code{interrupt} command when
5590 running in the background, or @kbd{Ctrl-c} during foreground execution.
5591 In all-stop mode, this stops the whole process;
5592 but in non-stop mode the interrupt applies only to the current thread.
5593 To stop the whole program, use @code{interrupt -a}.
5595 Other execution commands do not currently support the @code{-a} option.
5597 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5598 that thread current, as it does in all-stop mode. This is because the
5599 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5600 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5601 changed to a different thread just as you entered a command to operate on the
5602 previously current thread.
5604 @node Background Execution
5605 @subsection Background Execution
5607 @cindex foreground execution
5608 @cindex background execution
5609 @cindex asynchronous execution
5610 @cindex execution, foreground, background and asynchronous
5612 @value{GDBN}'s execution commands have two variants: the normal
5613 foreground (synchronous) behavior, and a background
5614 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5615 the program to report that some thread has stopped before prompting for
5616 another command. In background execution, @value{GDBN} immediately gives
5617 a command prompt so that you can issue other commands while your program runs.
5619 You need to explicitly enable asynchronous mode before you can use
5620 background execution commands. You can use these commands to
5621 manipulate the asynchronous mode setting:
5624 @kindex set target-async
5625 @item set target-async on
5626 Enable asynchronous mode.
5627 @item set target-async off
5628 Disable asynchronous mode.
5629 @kindex show target-async
5630 @item show target-async
5631 Show the current target-async setting.
5634 If the target doesn't support async mode, @value{GDBN} issues an error
5635 message if you attempt to use the background execution commands.
5637 To specify background execution, add a @code{&} to the command. For example,
5638 the background form of the @code{continue} command is @code{continue&}, or
5639 just @code{c&}. The execution commands that accept background execution
5645 @xref{Starting, , Starting your Program}.
5649 @xref{Attach, , Debugging an Already-running Process}.
5653 @xref{Continuing and Stepping, step}.
5657 @xref{Continuing and Stepping, stepi}.
5661 @xref{Continuing and Stepping, next}.
5665 @xref{Continuing and Stepping, nexti}.
5669 @xref{Continuing and Stepping, continue}.
5673 @xref{Continuing and Stepping, finish}.
5677 @xref{Continuing and Stepping, until}.
5681 Background execution is especially useful in conjunction with non-stop
5682 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5683 However, you can also use these commands in the normal all-stop mode with
5684 the restriction that you cannot issue another execution command until the
5685 previous one finishes. Examples of commands that are valid in all-stop
5686 mode while the program is running include @code{help} and @code{info break}.
5688 You can interrupt your program while it is running in the background by
5689 using the @code{interrupt} command.
5696 Suspend execution of the running program. In all-stop mode,
5697 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5698 only the current thread. To stop the whole program in non-stop mode,
5699 use @code{interrupt -a}.
5702 @node Thread-Specific Breakpoints
5703 @subsection Thread-Specific Breakpoints
5705 When your program has multiple threads (@pxref{Threads,, Debugging
5706 Programs with Multiple Threads}), you can choose whether to set
5707 breakpoints on all threads, or on a particular thread.
5710 @cindex breakpoints and threads
5711 @cindex thread breakpoints
5712 @kindex break @dots{} thread @var{threadno}
5713 @item break @var{linespec} thread @var{threadno}
5714 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5715 @var{linespec} specifies source lines; there are several ways of
5716 writing them (@pxref{Specify Location}), but the effect is always to
5717 specify some source line.
5719 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5720 to specify that you only want @value{GDBN} to stop the program when a
5721 particular thread reaches this breakpoint. @var{threadno} is one of the
5722 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5723 column of the @samp{info threads} display.
5725 If you do not specify @samp{thread @var{threadno}} when you set a
5726 breakpoint, the breakpoint applies to @emph{all} threads of your
5729 You can use the @code{thread} qualifier on conditional breakpoints as
5730 well; in this case, place @samp{thread @var{threadno}} before or
5731 after the breakpoint condition, like this:
5734 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5739 @node Interrupted System Calls
5740 @subsection Interrupted System Calls
5742 @cindex thread breakpoints and system calls
5743 @cindex system calls and thread breakpoints
5744 @cindex premature return from system calls
5745 There is an unfortunate side effect when using @value{GDBN} to debug
5746 multi-threaded programs. If one thread stops for a
5747 breakpoint, or for some other reason, and another thread is blocked in a
5748 system call, then the system call may return prematurely. This is a
5749 consequence of the interaction between multiple threads and the signals
5750 that @value{GDBN} uses to implement breakpoints and other events that
5753 To handle this problem, your program should check the return value of
5754 each system call and react appropriately. This is good programming
5757 For example, do not write code like this:
5763 The call to @code{sleep} will return early if a different thread stops
5764 at a breakpoint or for some other reason.
5766 Instead, write this:
5771 unslept = sleep (unslept);
5774 A system call is allowed to return early, so the system is still
5775 conforming to its specification. But @value{GDBN} does cause your
5776 multi-threaded program to behave differently than it would without
5779 Also, @value{GDBN} uses internal breakpoints in the thread library to
5780 monitor certain events such as thread creation and thread destruction.
5781 When such an event happens, a system call in another thread may return
5782 prematurely, even though your program does not appear to stop.
5785 @subsection Observer Mode
5787 If you want to build on non-stop mode and observe program behavior
5788 without any chance of disruption by @value{GDBN}, you can set
5789 variables to disable all of the debugger's attempts to modify state,
5790 whether by writing memory, inserting breakpoints, etc. These operate
5791 at a low level, intercepting operations from all commands.
5793 When all of these are set to @code{off}, then @value{GDBN} is said to
5794 be @dfn{observer mode}. As a convenience, the variable
5795 @code{observer} can be set to disable these, plus enable non-stop
5798 Note that @value{GDBN} will not prevent you from making nonsensical
5799 combinations of these settings. For instance, if you have enabled
5800 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5801 then breakpoints that work by writing trap instructions into the code
5802 stream will still not be able to be placed.
5807 @item set observer on
5808 @itemx set observer off
5809 When set to @code{on}, this disables all the permission variables
5810 below (except for @code{insert-fast-tracepoints}), plus enables
5811 non-stop debugging. Setting this to @code{off} switches back to
5812 normal debugging, though remaining in non-stop mode.
5815 Show whether observer mode is on or off.
5817 @kindex may-write-registers
5818 @item set may-write-registers on
5819 @itemx set may-write-registers off
5820 This controls whether @value{GDBN} will attempt to alter the values of
5821 registers, such as with assignment expressions in @code{print}, or the
5822 @code{jump} command. It defaults to @code{on}.
5824 @item show may-write-registers
5825 Show the current permission to write registers.
5827 @kindex may-write-memory
5828 @item set may-write-memory on
5829 @itemx set may-write-memory off
5830 This controls whether @value{GDBN} will attempt to alter the contents
5831 of memory, such as with assignment expressions in @code{print}. It
5832 defaults to @code{on}.
5834 @item show may-write-memory
5835 Show the current permission to write memory.
5837 @kindex may-insert-breakpoints
5838 @item set may-insert-breakpoints on
5839 @itemx set may-insert-breakpoints off
5840 This controls whether @value{GDBN} will attempt to insert breakpoints.
5841 This affects all breakpoints, including internal breakpoints defined
5842 by @value{GDBN}. It defaults to @code{on}.
5844 @item show may-insert-breakpoints
5845 Show the current permission to insert breakpoints.
5847 @kindex may-insert-tracepoints
5848 @item set may-insert-tracepoints on
5849 @itemx set may-insert-tracepoints off
5850 This controls whether @value{GDBN} will attempt to insert (regular)
5851 tracepoints at the beginning of a tracing experiment. It affects only
5852 non-fast tracepoints, fast tracepoints being under the control of
5853 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5855 @item show may-insert-tracepoints
5856 Show the current permission to insert tracepoints.
5858 @kindex may-insert-fast-tracepoints
5859 @item set may-insert-fast-tracepoints on
5860 @itemx set may-insert-fast-tracepoints off
5861 This controls whether @value{GDBN} will attempt to insert fast
5862 tracepoints at the beginning of a tracing experiment. It affects only
5863 fast tracepoints, regular (non-fast) tracepoints being under the
5864 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5866 @item show may-insert-fast-tracepoints
5867 Show the current permission to insert fast tracepoints.
5869 @kindex may-interrupt
5870 @item set may-interrupt on
5871 @itemx set may-interrupt off
5872 This controls whether @value{GDBN} will attempt to interrupt or stop
5873 program execution. When this variable is @code{off}, the
5874 @code{interrupt} command will have no effect, nor will
5875 @kbd{Ctrl-c}. It defaults to @code{on}.
5877 @item show may-interrupt
5878 Show the current permission to interrupt or stop the program.
5882 @node Reverse Execution
5883 @chapter Running programs backward
5884 @cindex reverse execution
5885 @cindex running programs backward
5887 When you are debugging a program, it is not unusual to realize that
5888 you have gone too far, and some event of interest has already happened.
5889 If the target environment supports it, @value{GDBN} can allow you to
5890 ``rewind'' the program by running it backward.
5892 A target environment that supports reverse execution should be able
5893 to ``undo'' the changes in machine state that have taken place as the
5894 program was executing normally. Variables, registers etc.@: should
5895 revert to their previous values. Obviously this requires a great
5896 deal of sophistication on the part of the target environment; not
5897 all target environments can support reverse execution.
5899 When a program is executed in reverse, the instructions that
5900 have most recently been executed are ``un-executed'', in reverse
5901 order. The program counter runs backward, following the previous
5902 thread of execution in reverse. As each instruction is ``un-executed'',
5903 the values of memory and/or registers that were changed by that
5904 instruction are reverted to their previous states. After executing
5905 a piece of source code in reverse, all side effects of that code
5906 should be ``undone'', and all variables should be returned to their
5907 prior values@footnote{
5908 Note that some side effects are easier to undo than others. For instance,
5909 memory and registers are relatively easy, but device I/O is hard. Some
5910 targets may be able undo things like device I/O, and some may not.
5912 The contract between @value{GDBN} and the reverse executing target
5913 requires only that the target do something reasonable when
5914 @value{GDBN} tells it to execute backwards, and then report the
5915 results back to @value{GDBN}. Whatever the target reports back to
5916 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5917 assumes that the memory and registers that the target reports are in a
5918 consistant state, but @value{GDBN} accepts whatever it is given.
5921 If you are debugging in a target environment that supports
5922 reverse execution, @value{GDBN} provides the following commands.
5925 @kindex reverse-continue
5926 @kindex rc @r{(@code{reverse-continue})}
5927 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5928 @itemx rc @r{[}@var{ignore-count}@r{]}
5929 Beginning at the point where your program last stopped, start executing
5930 in reverse. Reverse execution will stop for breakpoints and synchronous
5931 exceptions (signals), just like normal execution. Behavior of
5932 asynchronous signals depends on the target environment.
5934 @kindex reverse-step
5935 @kindex rs @r{(@code{step})}
5936 @item reverse-step @r{[}@var{count}@r{]}
5937 Run the program backward until control reaches the start of a
5938 different source line; then stop it, and return control to @value{GDBN}.
5940 Like the @code{step} command, @code{reverse-step} will only stop
5941 at the beginning of a source line. It ``un-executes'' the previously
5942 executed source line. If the previous source line included calls to
5943 debuggable functions, @code{reverse-step} will step (backward) into
5944 the called function, stopping at the beginning of the @emph{last}
5945 statement in the called function (typically a return statement).
5947 Also, as with the @code{step} command, if non-debuggable functions are
5948 called, @code{reverse-step} will run thru them backward without stopping.
5950 @kindex reverse-stepi
5951 @kindex rsi @r{(@code{reverse-stepi})}
5952 @item reverse-stepi @r{[}@var{count}@r{]}
5953 Reverse-execute one machine instruction. Note that the instruction
5954 to be reverse-executed is @emph{not} the one pointed to by the program
5955 counter, but the instruction executed prior to that one. For instance,
5956 if the last instruction was a jump, @code{reverse-stepi} will take you
5957 back from the destination of the jump to the jump instruction itself.
5959 @kindex reverse-next
5960 @kindex rn @r{(@code{reverse-next})}
5961 @item reverse-next @r{[}@var{count}@r{]}
5962 Run backward to the beginning of the previous line executed in
5963 the current (innermost) stack frame. If the line contains function
5964 calls, they will be ``un-executed'' without stopping. Starting from
5965 the first line of a function, @code{reverse-next} will take you back
5966 to the caller of that function, @emph{before} the function was called,
5967 just as the normal @code{next} command would take you from the last
5968 line of a function back to its return to its caller
5969 @footnote{Unless the code is too heavily optimized.}.
5971 @kindex reverse-nexti
5972 @kindex rni @r{(@code{reverse-nexti})}
5973 @item reverse-nexti @r{[}@var{count}@r{]}
5974 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5975 in reverse, except that called functions are ``un-executed'' atomically.
5976 That is, if the previously executed instruction was a return from
5977 another function, @code{reverse-nexti} will continue to execute
5978 in reverse until the call to that function (from the current stack
5981 @kindex reverse-finish
5982 @item reverse-finish
5983 Just as the @code{finish} command takes you to the point where the
5984 current function returns, @code{reverse-finish} takes you to the point
5985 where it was called. Instead of ending up at the end of the current
5986 function invocation, you end up at the beginning.
5988 @kindex set exec-direction
5989 @item set exec-direction
5990 Set the direction of target execution.
5991 @itemx set exec-direction reverse
5992 @cindex execute forward or backward in time
5993 @value{GDBN} will perform all execution commands in reverse, until the
5994 exec-direction mode is changed to ``forward''. Affected commands include
5995 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5996 command cannot be used in reverse mode.
5997 @item set exec-direction forward
5998 @value{GDBN} will perform all execution commands in the normal fashion.
5999 This is the default.
6003 @node Process Record and Replay
6004 @chapter Recording Inferior's Execution and Replaying It
6005 @cindex process record and replay
6006 @cindex recording inferior's execution and replaying it
6008 On some platforms, @value{GDBN} provides a special @dfn{process record
6009 and replay} target that can record a log of the process execution, and
6010 replay it later with both forward and reverse execution commands.
6013 When this target is in use, if the execution log includes the record
6014 for the next instruction, @value{GDBN} will debug in @dfn{replay
6015 mode}. In the replay mode, the inferior does not really execute code
6016 instructions. Instead, all the events that normally happen during
6017 code execution are taken from the execution log. While code is not
6018 really executed in replay mode, the values of registers (including the
6019 program counter register) and the memory of the inferior are still
6020 changed as they normally would. Their contents are taken from the
6024 If the record for the next instruction is not in the execution log,
6025 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6026 inferior executes normally, and @value{GDBN} records the execution log
6029 The process record and replay target supports reverse execution
6030 (@pxref{Reverse Execution}), even if the platform on which the
6031 inferior runs does not. However, the reverse execution is limited in
6032 this case by the range of the instructions recorded in the execution
6033 log. In other words, reverse execution on platforms that don't
6034 support it directly can only be done in the replay mode.
6036 When debugging in the reverse direction, @value{GDBN} will work in
6037 replay mode as long as the execution log includes the record for the
6038 previous instruction; otherwise, it will work in record mode, if the
6039 platform supports reverse execution, or stop if not.
6041 For architecture environments that support process record and replay,
6042 @value{GDBN} provides the following commands:
6045 @kindex target record
6049 This command starts the process record and replay target. The process
6050 record and replay target can only debug a process that is already
6051 running. Therefore, you need first to start the process with the
6052 @kbd{run} or @kbd{start} commands, and then start the recording with
6053 the @kbd{target record} command.
6055 Both @code{record} and @code{rec} are aliases of @code{target record}.
6057 @cindex displaced stepping, and process record and replay
6058 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6059 will be automatically disabled when process record and replay target
6060 is started. That's because the process record and replay target
6061 doesn't support displaced stepping.
6063 @cindex non-stop mode, and process record and replay
6064 @cindex asynchronous execution, and process record and replay
6065 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6066 the asynchronous execution mode (@pxref{Background Execution}), the
6067 process record and replay target cannot be started because it doesn't
6068 support these two modes.
6073 Stop the process record and replay target. When process record and
6074 replay target stops, the entire execution log will be deleted and the
6075 inferior will either be terminated, or will remain in its final state.
6077 When you stop the process record and replay target in record mode (at
6078 the end of the execution log), the inferior will be stopped at the
6079 next instruction that would have been recorded. In other words, if
6080 you record for a while and then stop recording, the inferior process
6081 will be left in the same state as if the recording never happened.
6083 On the other hand, if the process record and replay target is stopped
6084 while in replay mode (that is, not at the end of the execution log,
6085 but at some earlier point), the inferior process will become ``live''
6086 at that earlier state, and it will then be possible to continue the
6087 usual ``live'' debugging of the process from that state.
6089 When the inferior process exits, or @value{GDBN} detaches from it,
6090 process record and replay target will automatically stop itself.
6093 @item record save @var{filename}
6094 Save the execution log to a file @file{@var{filename}}.
6095 Default filename is @file{gdb_record.@var{process_id}}, where
6096 @var{process_id} is the process ID of the inferior.
6098 @kindex record restore
6099 @item record restore @var{filename}
6100 Restore the execution log from a file @file{@var{filename}}.
6101 File must have been created with @code{record save}.
6103 @kindex set record insn-number-max
6104 @item set record insn-number-max @var{limit}
6105 Set the limit of instructions to be recorded. Default value is 200000.
6107 If @var{limit} is a positive number, then @value{GDBN} will start
6108 deleting instructions from the log once the number of the record
6109 instructions becomes greater than @var{limit}. For every new recorded
6110 instruction, @value{GDBN} will delete the earliest recorded
6111 instruction to keep the number of recorded instructions at the limit.
6112 (Since deleting recorded instructions loses information, @value{GDBN}
6113 lets you control what happens when the limit is reached, by means of
6114 the @code{stop-at-limit} option, described below.)
6116 If @var{limit} is zero, @value{GDBN} will never delete recorded
6117 instructions from the execution log. The number of recorded
6118 instructions is unlimited in this case.
6120 @kindex show record insn-number-max
6121 @item show record insn-number-max
6122 Show the limit of instructions to be recorded.
6124 @kindex set record stop-at-limit
6125 @item set record stop-at-limit
6126 Control the behavior when the number of recorded instructions reaches
6127 the limit. If ON (the default), @value{GDBN} will stop when the limit
6128 is reached for the first time and ask you whether you want to stop the
6129 inferior or continue running it and recording the execution log. If
6130 you decide to continue recording, each new recorded instruction will
6131 cause the oldest one to be deleted.
6133 If this option is OFF, @value{GDBN} will automatically delete the
6134 oldest record to make room for each new one, without asking.
6136 @kindex show record stop-at-limit
6137 @item show record stop-at-limit
6138 Show the current setting of @code{stop-at-limit}.
6140 @kindex set record memory-query
6141 @item set record memory-query
6142 Control the behavior when @value{GDBN} is unable to record memory
6143 changes caused by an instruction. If ON, @value{GDBN} will query
6144 whether to stop the inferior in that case.
6146 If this option is OFF (the default), @value{GDBN} will automatically
6147 ignore the effect of such instructions on memory. Later, when
6148 @value{GDBN} replays this execution log, it will mark the log of this
6149 instruction as not accessible, and it will not affect the replay
6152 @kindex show record memory-query
6153 @item show record memory-query
6154 Show the current setting of @code{memory-query}.
6158 Show various statistics about the state of process record and its
6159 in-memory execution log buffer, including:
6163 Whether in record mode or replay mode.
6165 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6167 Highest recorded instruction number.
6169 Current instruction about to be replayed (if in replay mode).
6171 Number of instructions contained in the execution log.
6173 Maximum number of instructions that may be contained in the execution log.
6176 @kindex record delete
6179 When record target runs in replay mode (``in the past''), delete the
6180 subsequent execution log and begin to record a new execution log starting
6181 from the current address. This means you will abandon the previously
6182 recorded ``future'' and begin recording a new ``future''.
6187 @chapter Examining the Stack
6189 When your program has stopped, the first thing you need to know is where it
6190 stopped and how it got there.
6193 Each time your program performs a function call, information about the call
6195 That information includes the location of the call in your program,
6196 the arguments of the call,
6197 and the local variables of the function being called.
6198 The information is saved in a block of data called a @dfn{stack frame}.
6199 The stack frames are allocated in a region of memory called the @dfn{call
6202 When your program stops, the @value{GDBN} commands for examining the
6203 stack allow you to see all of this information.
6205 @cindex selected frame
6206 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6207 @value{GDBN} commands refer implicitly to the selected frame. In
6208 particular, whenever you ask @value{GDBN} for the value of a variable in
6209 your program, the value is found in the selected frame. There are
6210 special @value{GDBN} commands to select whichever frame you are
6211 interested in. @xref{Selection, ,Selecting a Frame}.
6213 When your program stops, @value{GDBN} automatically selects the
6214 currently executing frame and describes it briefly, similar to the
6215 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6218 * Frames:: Stack frames
6219 * Backtrace:: Backtraces
6220 * Selection:: Selecting a frame
6221 * Frame Info:: Information on a frame
6226 @section Stack Frames
6228 @cindex frame, definition
6230 The call stack is divided up into contiguous pieces called @dfn{stack
6231 frames}, or @dfn{frames} for short; each frame is the data associated
6232 with one call to one function. The frame contains the arguments given
6233 to the function, the function's local variables, and the address at
6234 which the function is executing.
6236 @cindex initial frame
6237 @cindex outermost frame
6238 @cindex innermost frame
6239 When your program is started, the stack has only one frame, that of the
6240 function @code{main}. This is called the @dfn{initial} frame or the
6241 @dfn{outermost} frame. Each time a function is called, a new frame is
6242 made. Each time a function returns, the frame for that function invocation
6243 is eliminated. If a function is recursive, there can be many frames for
6244 the same function. The frame for the function in which execution is
6245 actually occurring is called the @dfn{innermost} frame. This is the most
6246 recently created of all the stack frames that still exist.
6248 @cindex frame pointer
6249 Inside your program, stack frames are identified by their addresses. A
6250 stack frame consists of many bytes, each of which has its own address; each
6251 kind of computer has a convention for choosing one byte whose
6252 address serves as the address of the frame. Usually this address is kept
6253 in a register called the @dfn{frame pointer register}
6254 (@pxref{Registers, $fp}) while execution is going on in that frame.
6256 @cindex frame number
6257 @value{GDBN} assigns numbers to all existing stack frames, starting with
6258 zero for the innermost frame, one for the frame that called it,
6259 and so on upward. These numbers do not really exist in your program;
6260 they are assigned by @value{GDBN} to give you a way of designating stack
6261 frames in @value{GDBN} commands.
6263 @c The -fomit-frame-pointer below perennially causes hbox overflow
6264 @c underflow problems.
6265 @cindex frameless execution
6266 Some compilers provide a way to compile functions so that they operate
6267 without stack frames. (For example, the @value{NGCC} option
6269 @samp{-fomit-frame-pointer}
6271 generates functions without a frame.)
6272 This is occasionally done with heavily used library functions to save
6273 the frame setup time. @value{GDBN} has limited facilities for dealing
6274 with these function invocations. If the innermost function invocation
6275 has no stack frame, @value{GDBN} nevertheless regards it as though
6276 it had a separate frame, which is numbered zero as usual, allowing
6277 correct tracing of the function call chain. However, @value{GDBN} has
6278 no provision for frameless functions elsewhere in the stack.
6281 @kindex frame@r{, command}
6282 @cindex current stack frame
6283 @item frame @var{args}
6284 The @code{frame} command allows you to move from one stack frame to another,
6285 and to print the stack frame you select. @var{args} may be either the
6286 address of the frame or the stack frame number. Without an argument,
6287 @code{frame} prints the current stack frame.
6289 @kindex select-frame
6290 @cindex selecting frame silently
6292 The @code{select-frame} command allows you to move from one stack frame
6293 to another without printing the frame. This is the silent version of
6301 @cindex call stack traces
6302 A backtrace is a summary of how your program got where it is. It shows one
6303 line per frame, for many frames, starting with the currently executing
6304 frame (frame zero), followed by its caller (frame one), and on up the
6309 @kindex bt @r{(@code{backtrace})}
6312 Print a backtrace of the entire stack: one line per frame for all
6313 frames in the stack.
6315 You can stop the backtrace at any time by typing the system interrupt
6316 character, normally @kbd{Ctrl-c}.
6318 @item backtrace @var{n}
6320 Similar, but print only the innermost @var{n} frames.
6322 @item backtrace -@var{n}
6324 Similar, but print only the outermost @var{n} frames.
6326 @item backtrace full
6328 @itemx bt full @var{n}
6329 @itemx bt full -@var{n}
6330 Print the values of the local variables also. @var{n} specifies the
6331 number of frames to print, as described above.
6336 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6337 are additional aliases for @code{backtrace}.
6339 @cindex multiple threads, backtrace
6340 In a multi-threaded program, @value{GDBN} by default shows the
6341 backtrace only for the current thread. To display the backtrace for
6342 several or all of the threads, use the command @code{thread apply}
6343 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6344 apply all backtrace}, @value{GDBN} will display the backtrace for all
6345 the threads; this is handy when you debug a core dump of a
6346 multi-threaded program.
6348 Each line in the backtrace shows the frame number and the function name.
6349 The program counter value is also shown---unless you use @code{set
6350 print address off}. The backtrace also shows the source file name and
6351 line number, as well as the arguments to the function. The program
6352 counter value is omitted if it is at the beginning of the code for that
6355 Here is an example of a backtrace. It was made with the command
6356 @samp{bt 3}, so it shows the innermost three frames.
6360 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6362 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6363 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6365 (More stack frames follow...)
6370 The display for frame zero does not begin with a program counter
6371 value, indicating that your program has stopped at the beginning of the
6372 code for line @code{993} of @code{builtin.c}.
6375 The value of parameter @code{data} in frame 1 has been replaced by
6376 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6377 only if it is a scalar (integer, pointer, enumeration, etc). See command
6378 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6379 on how to configure the way function parameter values are printed.
6381 @cindex optimized out, in backtrace
6382 @cindex function call arguments, optimized out
6383 If your program was compiled with optimizations, some compilers will
6384 optimize away arguments passed to functions if those arguments are
6385 never used after the call. Such optimizations generate code that
6386 passes arguments through registers, but doesn't store those arguments
6387 in the stack frame. @value{GDBN} has no way of displaying such
6388 arguments in stack frames other than the innermost one. Here's what
6389 such a backtrace might look like:
6393 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6395 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6396 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6398 (More stack frames follow...)
6403 The values of arguments that were not saved in their stack frames are
6404 shown as @samp{<optimized out>}.
6406 If you need to display the values of such optimized-out arguments,
6407 either deduce that from other variables whose values depend on the one
6408 you are interested in, or recompile without optimizations.
6410 @cindex backtrace beyond @code{main} function
6411 @cindex program entry point
6412 @cindex startup code, and backtrace
6413 Most programs have a standard user entry point---a place where system
6414 libraries and startup code transition into user code. For C this is
6415 @code{main}@footnote{
6416 Note that embedded programs (the so-called ``free-standing''
6417 environment) are not required to have a @code{main} function as the
6418 entry point. They could even have multiple entry points.}.
6419 When @value{GDBN} finds the entry function in a backtrace
6420 it will terminate the backtrace, to avoid tracing into highly
6421 system-specific (and generally uninteresting) code.
6423 If you need to examine the startup code, or limit the number of levels
6424 in a backtrace, you can change this behavior:
6427 @item set backtrace past-main
6428 @itemx set backtrace past-main on
6429 @kindex set backtrace
6430 Backtraces will continue past the user entry point.
6432 @item set backtrace past-main off
6433 Backtraces will stop when they encounter the user entry point. This is the
6436 @item show backtrace past-main
6437 @kindex show backtrace
6438 Display the current user entry point backtrace policy.
6440 @item set backtrace past-entry
6441 @itemx set backtrace past-entry on
6442 Backtraces will continue past the internal entry point of an application.
6443 This entry point is encoded by the linker when the application is built,
6444 and is likely before the user entry point @code{main} (or equivalent) is called.
6446 @item set backtrace past-entry off
6447 Backtraces will stop when they encounter the internal entry point of an
6448 application. This is the default.
6450 @item show backtrace past-entry
6451 Display the current internal entry point backtrace policy.
6453 @item set backtrace limit @var{n}
6454 @itemx set backtrace limit 0
6455 @cindex backtrace limit
6456 Limit the backtrace to @var{n} levels. A value of zero means
6459 @item show backtrace limit
6460 Display the current limit on backtrace levels.
6464 @section Selecting a Frame
6466 Most commands for examining the stack and other data in your program work on
6467 whichever stack frame is selected at the moment. Here are the commands for
6468 selecting a stack frame; all of them finish by printing a brief description
6469 of the stack frame just selected.
6472 @kindex frame@r{, selecting}
6473 @kindex f @r{(@code{frame})}
6476 Select frame number @var{n}. Recall that frame zero is the innermost
6477 (currently executing) frame, frame one is the frame that called the
6478 innermost one, and so on. The highest-numbered frame is the one for
6481 @item frame @var{addr}
6483 Select the frame at address @var{addr}. This is useful mainly if the
6484 chaining of stack frames has been damaged by a bug, making it
6485 impossible for @value{GDBN} to assign numbers properly to all frames. In
6486 addition, this can be useful when your program has multiple stacks and
6487 switches between them.
6489 On the SPARC architecture, @code{frame} needs two addresses to
6490 select an arbitrary frame: a frame pointer and a stack pointer.
6492 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6493 pointer and a program counter.
6495 On the 29k architecture, it needs three addresses: a register stack
6496 pointer, a program counter, and a memory stack pointer.
6500 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6501 advances toward the outermost frame, to higher frame numbers, to frames
6502 that have existed longer. @var{n} defaults to one.
6505 @kindex do @r{(@code{down})}
6507 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6508 advances toward the innermost frame, to lower frame numbers, to frames
6509 that were created more recently. @var{n} defaults to one. You may
6510 abbreviate @code{down} as @code{do}.
6513 All of these commands end by printing two lines of output describing the
6514 frame. The first line shows the frame number, the function name, the
6515 arguments, and the source file and line number of execution in that
6516 frame. The second line shows the text of that source line.
6524 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6526 10 read_input_file (argv[i]);
6530 After such a printout, the @code{list} command with no arguments
6531 prints ten lines centered on the point of execution in the frame.
6532 You can also edit the program at the point of execution with your favorite
6533 editing program by typing @code{edit}.
6534 @xref{List, ,Printing Source Lines},
6538 @kindex down-silently
6540 @item up-silently @var{n}
6541 @itemx down-silently @var{n}
6542 These two commands are variants of @code{up} and @code{down},
6543 respectively; they differ in that they do their work silently, without
6544 causing display of the new frame. They are intended primarily for use
6545 in @value{GDBN} command scripts, where the output might be unnecessary and
6550 @section Information About a Frame
6552 There are several other commands to print information about the selected
6558 When used without any argument, this command does not change which
6559 frame is selected, but prints a brief description of the currently
6560 selected stack frame. It can be abbreviated @code{f}. With an
6561 argument, this command is used to select a stack frame.
6562 @xref{Selection, ,Selecting a Frame}.
6565 @kindex info f @r{(@code{info frame})}
6568 This command prints a verbose description of the selected stack frame,
6573 the address of the frame
6575 the address of the next frame down (called by this frame)
6577 the address of the next frame up (caller of this frame)
6579 the language in which the source code corresponding to this frame is written
6581 the address of the frame's arguments
6583 the address of the frame's local variables
6585 the program counter saved in it (the address of execution in the caller frame)
6587 which registers were saved in the frame
6590 @noindent The verbose description is useful when
6591 something has gone wrong that has made the stack format fail to fit
6592 the usual conventions.
6594 @item info frame @var{addr}
6595 @itemx info f @var{addr}
6596 Print a verbose description of the frame at address @var{addr}, without
6597 selecting that frame. The selected frame remains unchanged by this
6598 command. This requires the same kind of address (more than one for some
6599 architectures) that you specify in the @code{frame} command.
6600 @xref{Selection, ,Selecting a Frame}.
6604 Print the arguments of the selected frame, each on a separate line.
6608 Print the local variables of the selected frame, each on a separate
6609 line. These are all variables (declared either static or automatic)
6610 accessible at the point of execution of the selected frame.
6616 @chapter Examining Source Files
6618 @value{GDBN} can print parts of your program's source, since the debugging
6619 information recorded in the program tells @value{GDBN} what source files were
6620 used to build it. When your program stops, @value{GDBN} spontaneously prints
6621 the line where it stopped. Likewise, when you select a stack frame
6622 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6623 execution in that frame has stopped. You can print other portions of
6624 source files by explicit command.
6626 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6627 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6628 @value{GDBN} under @sc{gnu} Emacs}.
6631 * List:: Printing source lines
6632 * Specify Location:: How to specify code locations
6633 * Edit:: Editing source files
6634 * Search:: Searching source files
6635 * Source Path:: Specifying source directories
6636 * Machine Code:: Source and machine code
6640 @section Printing Source Lines
6643 @kindex l @r{(@code{list})}
6644 To print lines from a source file, use the @code{list} command
6645 (abbreviated @code{l}). By default, ten lines are printed.
6646 There are several ways to specify what part of the file you want to
6647 print; see @ref{Specify Location}, for the full list.
6649 Here are the forms of the @code{list} command most commonly used:
6652 @item list @var{linenum}
6653 Print lines centered around line number @var{linenum} in the
6654 current source file.
6656 @item list @var{function}
6657 Print lines centered around the beginning of function
6661 Print more lines. If the last lines printed were printed with a
6662 @code{list} command, this prints lines following the last lines
6663 printed; however, if the last line printed was a solitary line printed
6664 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6665 Stack}), this prints lines centered around that line.
6668 Print lines just before the lines last printed.
6671 @cindex @code{list}, how many lines to display
6672 By default, @value{GDBN} prints ten source lines with any of these forms of
6673 the @code{list} command. You can change this using @code{set listsize}:
6676 @kindex set listsize
6677 @item set listsize @var{count}
6678 Make the @code{list} command display @var{count} source lines (unless
6679 the @code{list} argument explicitly specifies some other number).
6681 @kindex show listsize
6683 Display the number of lines that @code{list} prints.
6686 Repeating a @code{list} command with @key{RET} discards the argument,
6687 so it is equivalent to typing just @code{list}. This is more useful
6688 than listing the same lines again. An exception is made for an
6689 argument of @samp{-}; that argument is preserved in repetition so that
6690 each repetition moves up in the source file.
6692 In general, the @code{list} command expects you to supply zero, one or two
6693 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6694 of writing them (@pxref{Specify Location}), but the effect is always
6695 to specify some source line.
6697 Here is a complete description of the possible arguments for @code{list}:
6700 @item list @var{linespec}
6701 Print lines centered around the line specified by @var{linespec}.
6703 @item list @var{first},@var{last}
6704 Print lines from @var{first} to @var{last}. Both arguments are
6705 linespecs. When a @code{list} command has two linespecs, and the
6706 source file of the second linespec is omitted, this refers to
6707 the same source file as the first linespec.
6709 @item list ,@var{last}
6710 Print lines ending with @var{last}.
6712 @item list @var{first},
6713 Print lines starting with @var{first}.
6716 Print lines just after the lines last printed.
6719 Print lines just before the lines last printed.
6722 As described in the preceding table.
6725 @node Specify Location
6726 @section Specifying a Location
6727 @cindex specifying location
6730 Several @value{GDBN} commands accept arguments that specify a location
6731 of your program's code. Since @value{GDBN} is a source-level
6732 debugger, a location usually specifies some line in the source code;
6733 for that reason, locations are also known as @dfn{linespecs}.
6735 Here are all the different ways of specifying a code location that
6736 @value{GDBN} understands:
6740 Specifies the line number @var{linenum} of the current source file.
6743 @itemx +@var{offset}
6744 Specifies the line @var{offset} lines before or after the @dfn{current
6745 line}. For the @code{list} command, the current line is the last one
6746 printed; for the breakpoint commands, this is the line at which
6747 execution stopped in the currently selected @dfn{stack frame}
6748 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6749 used as the second of the two linespecs in a @code{list} command,
6750 this specifies the line @var{offset} lines up or down from the first
6753 @item @var{filename}:@var{linenum}
6754 Specifies the line @var{linenum} in the source file @var{filename}.
6755 If @var{filename} is a relative file name, then it will match any
6756 source file name with the same trailing components. For example, if
6757 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6758 name of @file{/build/trunk/gcc/expr.c}, but not
6759 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6761 @item @var{function}
6762 Specifies the line that begins the body of the function @var{function}.
6763 For example, in C, this is the line with the open brace.
6765 @item @var{function}:@var{label}
6766 Specifies the line where @var{label} appears in @var{function}.
6768 @item @var{filename}:@var{function}
6769 Specifies the line that begins the body of the function @var{function}
6770 in the file @var{filename}. You only need the file name with a
6771 function name to avoid ambiguity when there are identically named
6772 functions in different source files.
6775 Specifies the line at which the label named @var{label} appears.
6776 @value{GDBN} searches for the label in the function corresponding to
6777 the currently selected stack frame. If there is no current selected
6778 stack frame (for instance, if the inferior is not running), then
6779 @value{GDBN} will not search for a label.
6781 @item *@var{address}
6782 Specifies the program address @var{address}. For line-oriented
6783 commands, such as @code{list} and @code{edit}, this specifies a source
6784 line that contains @var{address}. For @code{break} and other
6785 breakpoint oriented commands, this can be used to set breakpoints in
6786 parts of your program which do not have debugging information or
6789 Here @var{address} may be any expression valid in the current working
6790 language (@pxref{Languages, working language}) that specifies a code
6791 address. In addition, as a convenience, @value{GDBN} extends the
6792 semantics of expressions used in locations to cover the situations
6793 that frequently happen during debugging. Here are the various forms
6797 @item @var{expression}
6798 Any expression valid in the current working language.
6800 @item @var{funcaddr}
6801 An address of a function or procedure derived from its name. In C,
6802 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6803 simply the function's name @var{function} (and actually a special case
6804 of a valid expression). In Pascal and Modula-2, this is
6805 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6806 (although the Pascal form also works).
6808 This form specifies the address of the function's first instruction,
6809 before the stack frame and arguments have been set up.
6811 @item '@var{filename}'::@var{funcaddr}
6812 Like @var{funcaddr} above, but also specifies the name of the source
6813 file explicitly. This is useful if the name of the function does not
6814 specify the function unambiguously, e.g., if there are several
6815 functions with identical names in different source files.
6818 @cindex breakpoint at static probe point
6819 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
6820 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
6821 applications to embed static probes. @xref{Static Probe Points}, for more
6822 information on finding and using static probes. This form of linespec
6823 specifies the location of such a static probe.
6825 If @var{objfile} is given, only probes coming from that shared library
6826 or executable matching @var{objfile} as a regular expression are considered.
6827 If @var{provider} is given, then only probes from that provider are considered.
6828 If several probes match the spec, @value{GDBN} will insert a breakpoint at
6829 each one of those probes.
6835 @section Editing Source Files
6836 @cindex editing source files
6839 @kindex e @r{(@code{edit})}
6840 To edit the lines in a source file, use the @code{edit} command.
6841 The editing program of your choice
6842 is invoked with the current line set to
6843 the active line in the program.
6844 Alternatively, there are several ways to specify what part of the file you
6845 want to print if you want to see other parts of the program:
6848 @item edit @var{location}
6849 Edit the source file specified by @code{location}. Editing starts at
6850 that @var{location}, e.g., at the specified source line of the
6851 specified file. @xref{Specify Location}, for all the possible forms
6852 of the @var{location} argument; here are the forms of the @code{edit}
6853 command most commonly used:
6856 @item edit @var{number}
6857 Edit the current source file with @var{number} as the active line number.
6859 @item edit @var{function}
6860 Edit the file containing @var{function} at the beginning of its definition.
6865 @subsection Choosing your Editor
6866 You can customize @value{GDBN} to use any editor you want
6868 The only restriction is that your editor (say @code{ex}), recognizes the
6869 following command-line syntax:
6871 ex +@var{number} file
6873 The optional numeric value +@var{number} specifies the number of the line in
6874 the file where to start editing.}.
6875 By default, it is @file{@value{EDITOR}}, but you can change this
6876 by setting the environment variable @code{EDITOR} before using
6877 @value{GDBN}. For example, to configure @value{GDBN} to use the
6878 @code{vi} editor, you could use these commands with the @code{sh} shell:
6884 or in the @code{csh} shell,
6886 setenv EDITOR /usr/bin/vi
6891 @section Searching Source Files
6892 @cindex searching source files
6894 There are two commands for searching through the current source file for a
6899 @kindex forward-search
6900 @item forward-search @var{regexp}
6901 @itemx search @var{regexp}
6902 The command @samp{forward-search @var{regexp}} checks each line,
6903 starting with the one following the last line listed, for a match for
6904 @var{regexp}. It lists the line that is found. You can use the
6905 synonym @samp{search @var{regexp}} or abbreviate the command name as
6908 @kindex reverse-search
6909 @item reverse-search @var{regexp}
6910 The command @samp{reverse-search @var{regexp}} checks each line, starting
6911 with the one before the last line listed and going backward, for a match
6912 for @var{regexp}. It lists the line that is found. You can abbreviate
6913 this command as @code{rev}.
6917 @section Specifying Source Directories
6920 @cindex directories for source files
6921 Executable programs sometimes do not record the directories of the source
6922 files from which they were compiled, just the names. Even when they do,
6923 the directories could be moved between the compilation and your debugging
6924 session. @value{GDBN} has a list of directories to search for source files;
6925 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6926 it tries all the directories in the list, in the order they are present
6927 in the list, until it finds a file with the desired name.
6929 For example, suppose an executable references the file
6930 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6931 @file{/mnt/cross}. The file is first looked up literally; if this
6932 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6933 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6934 message is printed. @value{GDBN} does not look up the parts of the
6935 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6936 Likewise, the subdirectories of the source path are not searched: if
6937 the source path is @file{/mnt/cross}, and the binary refers to
6938 @file{foo.c}, @value{GDBN} would not find it under
6939 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6941 Plain file names, relative file names with leading directories, file
6942 names containing dots, etc.@: are all treated as described above; for
6943 instance, if the source path is @file{/mnt/cross}, and the source file
6944 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6945 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6946 that---@file{/mnt/cross/foo.c}.
6948 Note that the executable search path is @emph{not} used to locate the
6951 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6952 any information it has cached about where source files are found and where
6953 each line is in the file.
6957 When you start @value{GDBN}, its source path includes only @samp{cdir}
6958 and @samp{cwd}, in that order.
6959 To add other directories, use the @code{directory} command.
6961 The search path is used to find both program source files and @value{GDBN}
6962 script files (read using the @samp{-command} option and @samp{source} command).
6964 In addition to the source path, @value{GDBN} provides a set of commands
6965 that manage a list of source path substitution rules. A @dfn{substitution
6966 rule} specifies how to rewrite source directories stored in the program's
6967 debug information in case the sources were moved to a different
6968 directory between compilation and debugging. A rule is made of
6969 two strings, the first specifying what needs to be rewritten in
6970 the path, and the second specifying how it should be rewritten.
6971 In @ref{set substitute-path}, we name these two parts @var{from} and
6972 @var{to} respectively. @value{GDBN} does a simple string replacement
6973 of @var{from} with @var{to} at the start of the directory part of the
6974 source file name, and uses that result instead of the original file
6975 name to look up the sources.
6977 Using the previous example, suppose the @file{foo-1.0} tree has been
6978 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6979 @value{GDBN} to replace @file{/usr/src} in all source path names with
6980 @file{/mnt/cross}. The first lookup will then be
6981 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6982 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6983 substitution rule, use the @code{set substitute-path} command
6984 (@pxref{set substitute-path}).
6986 To avoid unexpected substitution results, a rule is applied only if the
6987 @var{from} part of the directory name ends at a directory separator.
6988 For instance, a rule substituting @file{/usr/source} into
6989 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6990 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6991 is applied only at the beginning of the directory name, this rule will
6992 not be applied to @file{/root/usr/source/baz.c} either.
6994 In many cases, you can achieve the same result using the @code{directory}
6995 command. However, @code{set substitute-path} can be more efficient in
6996 the case where the sources are organized in a complex tree with multiple
6997 subdirectories. With the @code{directory} command, you need to add each
6998 subdirectory of your project. If you moved the entire tree while
6999 preserving its internal organization, then @code{set substitute-path}
7000 allows you to direct the debugger to all the sources with one single
7003 @code{set substitute-path} is also more than just a shortcut command.
7004 The source path is only used if the file at the original location no
7005 longer exists. On the other hand, @code{set substitute-path} modifies
7006 the debugger behavior to look at the rewritten location instead. So, if
7007 for any reason a source file that is not relevant to your executable is
7008 located at the original location, a substitution rule is the only
7009 method available to point @value{GDBN} at the new location.
7011 @cindex @samp{--with-relocated-sources}
7012 @cindex default source path substitution
7013 You can configure a default source path substitution rule by
7014 configuring @value{GDBN} with the
7015 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7016 should be the name of a directory under @value{GDBN}'s configured
7017 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7018 directory names in debug information under @var{dir} will be adjusted
7019 automatically if the installed @value{GDBN} is moved to a new
7020 location. This is useful if @value{GDBN}, libraries or executables
7021 with debug information and corresponding source code are being moved
7025 @item directory @var{dirname} @dots{}
7026 @item dir @var{dirname} @dots{}
7027 Add directory @var{dirname} to the front of the source path. Several
7028 directory names may be given to this command, separated by @samp{:}
7029 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7030 part of absolute file names) or
7031 whitespace. You may specify a directory that is already in the source
7032 path; this moves it forward, so @value{GDBN} searches it sooner.
7036 @vindex $cdir@r{, convenience variable}
7037 @vindex $cwd@r{, convenience variable}
7038 @cindex compilation directory
7039 @cindex current directory
7040 @cindex working directory
7041 @cindex directory, current
7042 @cindex directory, compilation
7043 You can use the string @samp{$cdir} to refer to the compilation
7044 directory (if one is recorded), and @samp{$cwd} to refer to the current
7045 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7046 tracks the current working directory as it changes during your @value{GDBN}
7047 session, while the latter is immediately expanded to the current
7048 directory at the time you add an entry to the source path.
7051 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7053 @c RET-repeat for @code{directory} is explicitly disabled, but since
7054 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7056 @item set directories @var{path-list}
7057 @kindex set directories
7058 Set the source path to @var{path-list}.
7059 @samp{$cdir:$cwd} are added if missing.
7061 @item show directories
7062 @kindex show directories
7063 Print the source path: show which directories it contains.
7065 @anchor{set substitute-path}
7066 @item set substitute-path @var{from} @var{to}
7067 @kindex set substitute-path
7068 Define a source path substitution rule, and add it at the end of the
7069 current list of existing substitution rules. If a rule with the same
7070 @var{from} was already defined, then the old rule is also deleted.
7072 For example, if the file @file{/foo/bar/baz.c} was moved to
7073 @file{/mnt/cross/baz.c}, then the command
7076 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7080 will tell @value{GDBN} to replace @samp{/usr/src} with
7081 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7082 @file{baz.c} even though it was moved.
7084 In the case when more than one substitution rule have been defined,
7085 the rules are evaluated one by one in the order where they have been
7086 defined. The first one matching, if any, is selected to perform
7089 For instance, if we had entered the following commands:
7092 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7093 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7097 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7098 @file{/mnt/include/defs.h} by using the first rule. However, it would
7099 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7100 @file{/mnt/src/lib/foo.c}.
7103 @item unset substitute-path [path]
7104 @kindex unset substitute-path
7105 If a path is specified, search the current list of substitution rules
7106 for a rule that would rewrite that path. Delete that rule if found.
7107 A warning is emitted by the debugger if no rule could be found.
7109 If no path is specified, then all substitution rules are deleted.
7111 @item show substitute-path [path]
7112 @kindex show substitute-path
7113 If a path is specified, then print the source path substitution rule
7114 which would rewrite that path, if any.
7116 If no path is specified, then print all existing source path substitution
7121 If your source path is cluttered with directories that are no longer of
7122 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7123 versions of source. You can correct the situation as follows:
7127 Use @code{directory} with no argument to reset the source path to its default value.
7130 Use @code{directory} with suitable arguments to reinstall the
7131 directories you want in the source path. You can add all the
7132 directories in one command.
7136 @section Source and Machine Code
7137 @cindex source line and its code address
7139 You can use the command @code{info line} to map source lines to program
7140 addresses (and vice versa), and the command @code{disassemble} to display
7141 a range of addresses as machine instructions. You can use the command
7142 @code{set disassemble-next-line} to set whether to disassemble next
7143 source line when execution stops. When run under @sc{gnu} Emacs
7144 mode, the @code{info line} command causes the arrow to point to the
7145 line specified. Also, @code{info line} prints addresses in symbolic form as
7150 @item info line @var{linespec}
7151 Print the starting and ending addresses of the compiled code for
7152 source line @var{linespec}. You can specify source lines in any of
7153 the ways documented in @ref{Specify Location}.
7156 For example, we can use @code{info line} to discover the location of
7157 the object code for the first line of function
7158 @code{m4_changequote}:
7160 @c FIXME: I think this example should also show the addresses in
7161 @c symbolic form, as they usually would be displayed.
7163 (@value{GDBP}) info line m4_changequote
7164 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7168 @cindex code address and its source line
7169 We can also inquire (using @code{*@var{addr}} as the form for
7170 @var{linespec}) what source line covers a particular address:
7172 (@value{GDBP}) info line *0x63ff
7173 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7176 @cindex @code{$_} and @code{info line}
7177 @cindex @code{x} command, default address
7178 @kindex x@r{(examine), and} info line
7179 After @code{info line}, the default address for the @code{x} command
7180 is changed to the starting address of the line, so that @samp{x/i} is
7181 sufficient to begin examining the machine code (@pxref{Memory,
7182 ,Examining Memory}). Also, this address is saved as the value of the
7183 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7188 @cindex assembly instructions
7189 @cindex instructions, assembly
7190 @cindex machine instructions
7191 @cindex listing machine instructions
7193 @itemx disassemble /m
7194 @itemx disassemble /r
7195 This specialized command dumps a range of memory as machine
7196 instructions. It can also print mixed source+disassembly by specifying
7197 the @code{/m} modifier and print the raw instructions in hex as well as
7198 in symbolic form by specifying the @code{/r}.
7199 The default memory range is the function surrounding the
7200 program counter of the selected frame. A single argument to this
7201 command is a program counter value; @value{GDBN} dumps the function
7202 surrounding this value. When two arguments are given, they should
7203 be separated by a comma, possibly surrounded by whitespace. The
7204 arguments specify a range of addresses to dump, in one of two forms:
7207 @item @var{start},@var{end}
7208 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7209 @item @var{start},+@var{length}
7210 the addresses from @var{start} (inclusive) to
7211 @code{@var{start}+@var{length}} (exclusive).
7215 When 2 arguments are specified, the name of the function is also
7216 printed (since there could be several functions in the given range).
7218 The argument(s) can be any expression yielding a numeric value, such as
7219 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7221 If the range of memory being disassembled contains current program counter,
7222 the instruction at that location is shown with a @code{=>} marker.
7225 The following example shows the disassembly of a range of addresses of
7226 HP PA-RISC 2.0 code:
7229 (@value{GDBP}) disas 0x32c4, 0x32e4
7230 Dump of assembler code from 0x32c4 to 0x32e4:
7231 0x32c4 <main+204>: addil 0,dp
7232 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7233 0x32cc <main+212>: ldil 0x3000,r31
7234 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7235 0x32d4 <main+220>: ldo 0(r31),rp
7236 0x32d8 <main+224>: addil -0x800,dp
7237 0x32dc <main+228>: ldo 0x588(r1),r26
7238 0x32e0 <main+232>: ldil 0x3000,r31
7239 End of assembler dump.
7242 Here is an example showing mixed source+assembly for Intel x86, when the
7243 program is stopped just after function prologue:
7246 (@value{GDBP}) disas /m main
7247 Dump of assembler code for function main:
7249 0x08048330 <+0>: push %ebp
7250 0x08048331 <+1>: mov %esp,%ebp
7251 0x08048333 <+3>: sub $0x8,%esp
7252 0x08048336 <+6>: and $0xfffffff0,%esp
7253 0x08048339 <+9>: sub $0x10,%esp
7255 6 printf ("Hello.\n");
7256 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7257 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7261 0x08048348 <+24>: mov $0x0,%eax
7262 0x0804834d <+29>: leave
7263 0x0804834e <+30>: ret
7265 End of assembler dump.
7268 Here is another example showing raw instructions in hex for AMD x86-64,
7271 (gdb) disas /r 0x400281,+10
7272 Dump of assembler code from 0x400281 to 0x40028b:
7273 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7274 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7275 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7276 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7277 End of assembler dump.
7280 Some architectures have more than one commonly-used set of instruction
7281 mnemonics or other syntax.
7283 For programs that were dynamically linked and use shared libraries,
7284 instructions that call functions or branch to locations in the shared
7285 libraries might show a seemingly bogus location---it's actually a
7286 location of the relocation table. On some architectures, @value{GDBN}
7287 might be able to resolve these to actual function names.
7290 @kindex set disassembly-flavor
7291 @cindex Intel disassembly flavor
7292 @cindex AT&T disassembly flavor
7293 @item set disassembly-flavor @var{instruction-set}
7294 Select the instruction set to use when disassembling the
7295 program via the @code{disassemble} or @code{x/i} commands.
7297 Currently this command is only defined for the Intel x86 family. You
7298 can set @var{instruction-set} to either @code{intel} or @code{att}.
7299 The default is @code{att}, the AT&T flavor used by default by Unix
7300 assemblers for x86-based targets.
7302 @kindex show disassembly-flavor
7303 @item show disassembly-flavor
7304 Show the current setting of the disassembly flavor.
7308 @kindex set disassemble-next-line
7309 @kindex show disassemble-next-line
7310 @item set disassemble-next-line
7311 @itemx show disassemble-next-line
7312 Control whether or not @value{GDBN} will disassemble the next source
7313 line or instruction when execution stops. If ON, @value{GDBN} will
7314 display disassembly of the next source line when execution of the
7315 program being debugged stops. This is @emph{in addition} to
7316 displaying the source line itself, which @value{GDBN} always does if
7317 possible. If the next source line cannot be displayed for some reason
7318 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7319 info in the debug info), @value{GDBN} will display disassembly of the
7320 next @emph{instruction} instead of showing the next source line. If
7321 AUTO, @value{GDBN} will display disassembly of next instruction only
7322 if the source line cannot be displayed. This setting causes
7323 @value{GDBN} to display some feedback when you step through a function
7324 with no line info or whose source file is unavailable. The default is
7325 OFF, which means never display the disassembly of the next line or
7331 @chapter Examining Data
7333 @cindex printing data
7334 @cindex examining data
7337 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7338 @c document because it is nonstandard... Under Epoch it displays in a
7339 @c different window or something like that.
7340 The usual way to examine data in your program is with the @code{print}
7341 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7342 evaluates and prints the value of an expression of the language your
7343 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7344 Different Languages}). It may also print the expression using a
7345 Python-based pretty-printer (@pxref{Pretty Printing}).
7348 @item print @var{expr}
7349 @itemx print /@var{f} @var{expr}
7350 @var{expr} is an expression (in the source language). By default the
7351 value of @var{expr} is printed in a format appropriate to its data type;
7352 you can choose a different format by specifying @samp{/@var{f}}, where
7353 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7357 @itemx print /@var{f}
7358 @cindex reprint the last value
7359 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7360 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7361 conveniently inspect the same value in an alternative format.
7364 A more low-level way of examining data is with the @code{x} command.
7365 It examines data in memory at a specified address and prints it in a
7366 specified format. @xref{Memory, ,Examining Memory}.
7368 If you are interested in information about types, or about how the
7369 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7370 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7373 @cindex exploring hierarchical data structures
7375 Another way of examining values of expressions and type information is
7376 through the Python extension command @code{explore} (available only if
7377 the @value{GDBN} build is configured with @code{--with-python}). It
7378 offers an interactive way to start at the highest level (or, the most
7379 abstract level) of the data type of an expression (or, the data type
7380 itself) and explore all the way down to leaf scalar values/fields
7381 embedded in the higher level data types.
7384 @item explore @var{arg}
7385 @var{arg} is either an expression (in the source language), or a type
7386 visible in the current context of the program being debugged.
7389 The working of the @code{explore} command can be illustrated with an
7390 example. If a data type @code{struct ComplexStruct} is defined in your
7400 struct ComplexStruct
7402 struct SimpleStruct *ss_p;
7408 followed by variable declarations as
7411 struct SimpleStruct ss = @{ 10, 1.11 @};
7412 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7416 then, the value of the variable @code{cs} can be explored using the
7417 @code{explore} command as follows.
7421 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7422 the following fields:
7424 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7425 arr = <Enter 1 to explore this field of type `int [10]'>
7427 Enter the field number of choice:
7431 Since the fields of @code{cs} are not scalar values, you are being
7432 prompted to chose the field you want to explore. Let's say you choose
7433 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7434 pointer, you will be asked if it is pointing to a single value. From
7435 the declaration of @code{cs} above, it is indeed pointing to a single
7436 value, hence you enter @code{y}. If you enter @code{n}, then you will
7437 be asked if it were pointing to an array of values, in which case this
7438 field will be explored as if it were an array.
7441 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7442 Continue exploring it as a pointer to a single value [y/n]: y
7443 The value of `*(cs.ss_p)' is a struct/class of type `struct
7444 SimpleStruct' with the following fields:
7446 i = 10 .. (Value of type `int')
7447 d = 1.1100000000000001 .. (Value of type `double')
7449 Press enter to return to parent value:
7453 If the field @code{arr} of @code{cs} was chosen for exploration by
7454 entering @code{1} earlier, then since it is as array, you will be
7455 prompted to enter the index of the element in the array that you want
7459 `cs.arr' is an array of `int'.
7460 Enter the index of the element you want to explore in `cs.arr': 5
7462 `(cs.arr)[5]' is a scalar value of type `int'.
7466 Press enter to return to parent value:
7469 In general, at any stage of exploration, you can go deeper towards the
7470 leaf values by responding to the prompts appropriately, or hit the
7471 return key to return to the enclosing data structure (the @i{higher}
7472 level data structure).
7474 Similar to exploring values, you can use the @code{explore} command to
7475 explore types. Instead of specifying a value (which is typically a
7476 variable name or an expression valid in the current context of the
7477 program being debugged), you specify a type name. If you consider the
7478 same example as above, your can explore the type
7479 @code{struct ComplexStruct} by passing the argument
7480 @code{struct ComplexStruct} to the @code{explore} command.
7483 (gdb) explore struct ComplexStruct
7487 By responding to the prompts appropriately in the subsequent interactive
7488 session, you can explore the type @code{struct ComplexStruct} in a
7489 manner similar to how the value @code{cs} was explored in the above
7492 The @code{explore} command also has two sub-commands,
7493 @code{explore value} and @code{explore type}. The former sub-command is
7494 a way to explicitly specify that value exploration of the argument is
7495 being invoked, while the latter is a way to explicitly specify that type
7496 exploration of the argument is being invoked.
7499 @item explore value @var{expr}
7500 @cindex explore value
7501 This sub-command of @code{explore} explores the value of the
7502 expression @var{expr} (if @var{expr} is an expression valid in the
7503 current context of the program being debugged). The behavior of this
7504 command is identical to that of the behavior of the @code{explore}
7505 command being passed the argument @var{expr}.
7507 @item explore type @var{arg}
7508 @cindex explore type
7509 This sub-command of @code{explore} explores the type of @var{arg} (if
7510 @var{arg} is a type visible in the current context of program being
7511 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7512 is an expression valid in the current context of the program being
7513 debugged). If @var{arg} is a type, then the behavior of this command is
7514 identical to that of the @code{explore} command being passed the
7515 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7516 this command will be identical to that of the @code{explore} command
7517 being passed the type of @var{arg} as the argument.
7521 * Expressions:: Expressions
7522 * Ambiguous Expressions:: Ambiguous Expressions
7523 * Variables:: Program variables
7524 * Arrays:: Artificial arrays
7525 * Output Formats:: Output formats
7526 * Memory:: Examining memory
7527 * Auto Display:: Automatic display
7528 * Print Settings:: Print settings
7529 * Pretty Printing:: Python pretty printing
7530 * Value History:: Value history
7531 * Convenience Vars:: Convenience variables
7532 * Registers:: Registers
7533 * Floating Point Hardware:: Floating point hardware
7534 * Vector Unit:: Vector Unit
7535 * OS Information:: Auxiliary data provided by operating system
7536 * Memory Region Attributes:: Memory region attributes
7537 * Dump/Restore Files:: Copy between memory and a file
7538 * Core File Generation:: Cause a program dump its core
7539 * Character Sets:: Debugging programs that use a different
7540 character set than GDB does
7541 * Caching Remote Data:: Data caching for remote targets
7542 * Searching Memory:: Searching memory for a sequence of bytes
7546 @section Expressions
7549 @code{print} and many other @value{GDBN} commands accept an expression and
7550 compute its value. Any kind of constant, variable or operator defined
7551 by the programming language you are using is valid in an expression in
7552 @value{GDBN}. This includes conditional expressions, function calls,
7553 casts, and string constants. It also includes preprocessor macros, if
7554 you compiled your program to include this information; see
7557 @cindex arrays in expressions
7558 @value{GDBN} supports array constants in expressions input by
7559 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7560 you can use the command @code{print @{1, 2, 3@}} to create an array
7561 of three integers. If you pass an array to a function or assign it
7562 to a program variable, @value{GDBN} copies the array to memory that
7563 is @code{malloc}ed in the target program.
7565 Because C is so widespread, most of the expressions shown in examples in
7566 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7567 Languages}, for information on how to use expressions in other
7570 In this section, we discuss operators that you can use in @value{GDBN}
7571 expressions regardless of your programming language.
7573 @cindex casts, in expressions
7574 Casts are supported in all languages, not just in C, because it is so
7575 useful to cast a number into a pointer in order to examine a structure
7576 at that address in memory.
7577 @c FIXME: casts supported---Mod2 true?
7579 @value{GDBN} supports these operators, in addition to those common
7580 to programming languages:
7584 @samp{@@} is a binary operator for treating parts of memory as arrays.
7585 @xref{Arrays, ,Artificial Arrays}, for more information.
7588 @samp{::} allows you to specify a variable in terms of the file or
7589 function where it is defined. @xref{Variables, ,Program Variables}.
7591 @cindex @{@var{type}@}
7592 @cindex type casting memory
7593 @cindex memory, viewing as typed object
7594 @cindex casts, to view memory
7595 @item @{@var{type}@} @var{addr}
7596 Refers to an object of type @var{type} stored at address @var{addr} in
7597 memory. @var{addr} may be any expression whose value is an integer or
7598 pointer (but parentheses are required around binary operators, just as in
7599 a cast). This construct is allowed regardless of what kind of data is
7600 normally supposed to reside at @var{addr}.
7603 @node Ambiguous Expressions
7604 @section Ambiguous Expressions
7605 @cindex ambiguous expressions
7607 Expressions can sometimes contain some ambiguous elements. For instance,
7608 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7609 a single function name to be defined several times, for application in
7610 different contexts. This is called @dfn{overloading}. Another example
7611 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7612 templates and is typically instantiated several times, resulting in
7613 the same function name being defined in different contexts.
7615 In some cases and depending on the language, it is possible to adjust
7616 the expression to remove the ambiguity. For instance in C@t{++}, you
7617 can specify the signature of the function you want to break on, as in
7618 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7619 qualified name of your function often makes the expression unambiguous
7622 When an ambiguity that needs to be resolved is detected, the debugger
7623 has the capability to display a menu of numbered choices for each
7624 possibility, and then waits for the selection with the prompt @samp{>}.
7625 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7626 aborts the current command. If the command in which the expression was
7627 used allows more than one choice to be selected, the next option in the
7628 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7631 For example, the following session excerpt shows an attempt to set a
7632 breakpoint at the overloaded symbol @code{String::after}.
7633 We choose three particular definitions of that function name:
7635 @c FIXME! This is likely to change to show arg type lists, at least
7638 (@value{GDBP}) b String::after
7641 [2] file:String.cc; line number:867
7642 [3] file:String.cc; line number:860
7643 [4] file:String.cc; line number:875
7644 [5] file:String.cc; line number:853
7645 [6] file:String.cc; line number:846
7646 [7] file:String.cc; line number:735
7648 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7649 Breakpoint 2 at 0xb344: file String.cc, line 875.
7650 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7651 Multiple breakpoints were set.
7652 Use the "delete" command to delete unwanted
7659 @kindex set multiple-symbols
7660 @item set multiple-symbols @var{mode}
7661 @cindex multiple-symbols menu
7663 This option allows you to adjust the debugger behavior when an expression
7666 By default, @var{mode} is set to @code{all}. If the command with which
7667 the expression is used allows more than one choice, then @value{GDBN}
7668 automatically selects all possible choices. For instance, inserting
7669 a breakpoint on a function using an ambiguous name results in a breakpoint
7670 inserted on each possible match. However, if a unique choice must be made,
7671 then @value{GDBN} uses the menu to help you disambiguate the expression.
7672 For instance, printing the address of an overloaded function will result
7673 in the use of the menu.
7675 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7676 when an ambiguity is detected.
7678 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7679 an error due to the ambiguity and the command is aborted.
7681 @kindex show multiple-symbols
7682 @item show multiple-symbols
7683 Show the current value of the @code{multiple-symbols} setting.
7687 @section Program Variables
7689 The most common kind of expression to use is the name of a variable
7692 Variables in expressions are understood in the selected stack frame
7693 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7697 global (or file-static)
7704 visible according to the scope rules of the
7705 programming language from the point of execution in that frame
7708 @noindent This means that in the function
7723 you can examine and use the variable @code{a} whenever your program is
7724 executing within the function @code{foo}, but you can only use or
7725 examine the variable @code{b} while your program is executing inside
7726 the block where @code{b} is declared.
7728 @cindex variable name conflict
7729 There is an exception: you can refer to a variable or function whose
7730 scope is a single source file even if the current execution point is not
7731 in this file. But it is possible to have more than one such variable or
7732 function with the same name (in different source files). If that
7733 happens, referring to that name has unpredictable effects. If you wish,
7734 you can specify a static variable in a particular function or file by
7735 using the colon-colon (@code{::}) notation:
7737 @cindex colon-colon, context for variables/functions
7739 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7740 @cindex @code{::}, context for variables/functions
7743 @var{file}::@var{variable}
7744 @var{function}::@var{variable}
7748 Here @var{file} or @var{function} is the name of the context for the
7749 static @var{variable}. In the case of file names, you can use quotes to
7750 make sure @value{GDBN} parses the file name as a single word---for example,
7751 to print a global value of @code{x} defined in @file{f2.c}:
7754 (@value{GDBP}) p 'f2.c'::x
7757 The @code{::} notation is normally used for referring to
7758 static variables, since you typically disambiguate uses of local variables
7759 in functions by selecting the appropriate frame and using the
7760 simple name of the variable. However, you may also use this notation
7761 to refer to local variables in frames enclosing the selected frame:
7770 process (a); /* Stop here */
7781 For example, if there is a breakpoint at the commented line,
7782 here is what you might see
7783 when the program stops after executing the call @code{bar(0)}:
7788 (@value{GDBP}) p bar::a
7791 #2 0x080483d0 in foo (a=5) at foobar.c:12
7794 (@value{GDBP}) p bar::a
7798 @cindex C@t{++} scope resolution
7799 These uses of @samp{::} are very rarely in conflict with the very similar
7800 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7801 scope resolution operator in @value{GDBN} expressions.
7802 @c FIXME: Um, so what happens in one of those rare cases where it's in
7805 @cindex wrong values
7806 @cindex variable values, wrong
7807 @cindex function entry/exit, wrong values of variables
7808 @cindex optimized code, wrong values of variables
7810 @emph{Warning:} Occasionally, a local variable may appear to have the
7811 wrong value at certain points in a function---just after entry to a new
7812 scope, and just before exit.
7814 You may see this problem when you are stepping by machine instructions.
7815 This is because, on most machines, it takes more than one instruction to
7816 set up a stack frame (including local variable definitions); if you are
7817 stepping by machine instructions, variables may appear to have the wrong
7818 values until the stack frame is completely built. On exit, it usually
7819 also takes more than one machine instruction to destroy a stack frame;
7820 after you begin stepping through that group of instructions, local
7821 variable definitions may be gone.
7823 This may also happen when the compiler does significant optimizations.
7824 To be sure of always seeing accurate values, turn off all optimization
7827 @cindex ``No symbol "foo" in current context''
7828 Another possible effect of compiler optimizations is to optimize
7829 unused variables out of existence, or assign variables to registers (as
7830 opposed to memory addresses). Depending on the support for such cases
7831 offered by the debug info format used by the compiler, @value{GDBN}
7832 might not be able to display values for such local variables. If that
7833 happens, @value{GDBN} will print a message like this:
7836 No symbol "foo" in current context.
7839 To solve such problems, either recompile without optimizations, or use a
7840 different debug info format, if the compiler supports several such
7841 formats. @xref{Compilation}, for more information on choosing compiler
7842 options. @xref{C, ,C and C@t{++}}, for more information about debug
7843 info formats that are best suited to C@t{++} programs.
7845 If you ask to print an object whose contents are unknown to
7846 @value{GDBN}, e.g., because its data type is not completely specified
7847 by the debug information, @value{GDBN} will say @samp{<incomplete
7848 type>}. @xref{Symbols, incomplete type}, for more about this.
7850 If you append @kbd{@@entry} string to a function parameter name you get its
7851 value at the time the function got called. If the value is not available an
7852 error message is printed. Entry values are available only with some compilers.
7853 Entry values are normally also printed at the function parameter list according
7854 to @ref{set print entry-values}.
7857 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7863 (gdb) print i@@entry
7867 Strings are identified as arrays of @code{char} values without specified
7868 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7869 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7870 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7871 defines literal string type @code{"char"} as @code{char} without a sign.
7876 signed char var1[] = "A";
7879 You get during debugging
7884 $2 = @{65 'A', 0 '\0'@}
7888 @section Artificial Arrays
7890 @cindex artificial array
7892 @kindex @@@r{, referencing memory as an array}
7893 It is often useful to print out several successive objects of the
7894 same type in memory; a section of an array, or an array of
7895 dynamically determined size for which only a pointer exists in the
7898 You can do this by referring to a contiguous span of memory as an
7899 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7900 operand of @samp{@@} should be the first element of the desired array
7901 and be an individual object. The right operand should be the desired length
7902 of the array. The result is an array value whose elements are all of
7903 the type of the left argument. The first element is actually the left
7904 argument; the second element comes from bytes of memory immediately
7905 following those that hold the first element, and so on. Here is an
7906 example. If a program says
7909 int *array = (int *) malloc (len * sizeof (int));
7913 you can print the contents of @code{array} with
7919 The left operand of @samp{@@} must reside in memory. Array values made
7920 with @samp{@@} in this way behave just like other arrays in terms of
7921 subscripting, and are coerced to pointers when used in expressions.
7922 Artificial arrays most often appear in expressions via the value history
7923 (@pxref{Value History, ,Value History}), after printing one out.
7925 Another way to create an artificial array is to use a cast.
7926 This re-interprets a value as if it were an array.
7927 The value need not be in memory:
7929 (@value{GDBP}) p/x (short[2])0x12345678
7930 $1 = @{0x1234, 0x5678@}
7933 As a convenience, if you leave the array length out (as in
7934 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7935 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7937 (@value{GDBP}) p/x (short[])0x12345678
7938 $2 = @{0x1234, 0x5678@}
7941 Sometimes the artificial array mechanism is not quite enough; in
7942 moderately complex data structures, the elements of interest may not
7943 actually be adjacent---for example, if you are interested in the values
7944 of pointers in an array. One useful work-around in this situation is
7945 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7946 Variables}) as a counter in an expression that prints the first
7947 interesting value, and then repeat that expression via @key{RET}. For
7948 instance, suppose you have an array @code{dtab} of pointers to
7949 structures, and you are interested in the values of a field @code{fv}
7950 in each structure. Here is an example of what you might type:
7960 @node Output Formats
7961 @section Output Formats
7963 @cindex formatted output
7964 @cindex output formats
7965 By default, @value{GDBN} prints a value according to its data type. Sometimes
7966 this is not what you want. For example, you might want to print a number
7967 in hex, or a pointer in decimal. Or you might want to view data in memory
7968 at a certain address as a character string or as an instruction. To do
7969 these things, specify an @dfn{output format} when you print a value.
7971 The simplest use of output formats is to say how to print a value
7972 already computed. This is done by starting the arguments of the
7973 @code{print} command with a slash and a format letter. The format
7974 letters supported are:
7978 Regard the bits of the value as an integer, and print the integer in
7982 Print as integer in signed decimal.
7985 Print as integer in unsigned decimal.
7988 Print as integer in octal.
7991 Print as integer in binary. The letter @samp{t} stands for ``two''.
7992 @footnote{@samp{b} cannot be used because these format letters are also
7993 used with the @code{x} command, where @samp{b} stands for ``byte'';
7994 see @ref{Memory,,Examining Memory}.}
7997 @cindex unknown address, locating
7998 @cindex locate address
7999 Print as an address, both absolute in hexadecimal and as an offset from
8000 the nearest preceding symbol. You can use this format used to discover
8001 where (in what function) an unknown address is located:
8004 (@value{GDBP}) p/a 0x54320
8005 $3 = 0x54320 <_initialize_vx+396>
8009 The command @code{info symbol 0x54320} yields similar results.
8010 @xref{Symbols, info symbol}.
8013 Regard as an integer and print it as a character constant. This
8014 prints both the numerical value and its character representation. The
8015 character representation is replaced with the octal escape @samp{\nnn}
8016 for characters outside the 7-bit @sc{ascii} range.
8018 Without this format, @value{GDBN} displays @code{char},
8019 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8020 constants. Single-byte members of vectors are displayed as integer
8024 Regard the bits of the value as a floating point number and print
8025 using typical floating point syntax.
8028 @cindex printing strings
8029 @cindex printing byte arrays
8030 Regard as a string, if possible. With this format, pointers to single-byte
8031 data are displayed as null-terminated strings and arrays of single-byte data
8032 are displayed as fixed-length strings. Other values are displayed in their
8035 Without this format, @value{GDBN} displays pointers to and arrays of
8036 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8037 strings. Single-byte members of a vector are displayed as an integer
8041 @cindex raw printing
8042 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8043 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8044 Printing}). This typically results in a higher-level display of the
8045 value's contents. The @samp{r} format bypasses any Python
8046 pretty-printer which might exist.
8049 For example, to print the program counter in hex (@pxref{Registers}), type
8056 Note that no space is required before the slash; this is because command
8057 names in @value{GDBN} cannot contain a slash.
8059 To reprint the last value in the value history with a different format,
8060 you can use the @code{print} command with just a format and no
8061 expression. For example, @samp{p/x} reprints the last value in hex.
8064 @section Examining Memory
8066 You can use the command @code{x} (for ``examine'') to examine memory in
8067 any of several formats, independently of your program's data types.
8069 @cindex examining memory
8071 @kindex x @r{(examine memory)}
8072 @item x/@var{nfu} @var{addr}
8075 Use the @code{x} command to examine memory.
8078 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8079 much memory to display and how to format it; @var{addr} is an
8080 expression giving the address where you want to start displaying memory.
8081 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8082 Several commands set convenient defaults for @var{addr}.
8085 @item @var{n}, the repeat count
8086 The repeat count is a decimal integer; the default is 1. It specifies
8087 how much memory (counting by units @var{u}) to display.
8088 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8091 @item @var{f}, the display format
8092 The display format is one of the formats used by @code{print}
8093 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8094 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8095 The default is @samp{x} (hexadecimal) initially. The default changes
8096 each time you use either @code{x} or @code{print}.
8098 @item @var{u}, the unit size
8099 The unit size is any of
8105 Halfwords (two bytes).
8107 Words (four bytes). This is the initial default.
8109 Giant words (eight bytes).
8112 Each time you specify a unit size with @code{x}, that size becomes the
8113 default unit the next time you use @code{x}. For the @samp{i} format,
8114 the unit size is ignored and is normally not written. For the @samp{s} format,
8115 the unit size defaults to @samp{b}, unless it is explicitly given.
8116 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8117 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8118 Note that the results depend on the programming language of the
8119 current compilation unit. If the language is C, the @samp{s}
8120 modifier will use the UTF-16 encoding while @samp{w} will use
8121 UTF-32. The encoding is set by the programming language and cannot
8124 @item @var{addr}, starting display address
8125 @var{addr} is the address where you want @value{GDBN} to begin displaying
8126 memory. The expression need not have a pointer value (though it may);
8127 it is always interpreted as an integer address of a byte of memory.
8128 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8129 @var{addr} is usually just after the last address examined---but several
8130 other commands also set the default address: @code{info breakpoints} (to
8131 the address of the last breakpoint listed), @code{info line} (to the
8132 starting address of a line), and @code{print} (if you use it to display
8133 a value from memory).
8136 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8137 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8138 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8139 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8140 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8142 Since the letters indicating unit sizes are all distinct from the
8143 letters specifying output formats, you do not have to remember whether
8144 unit size or format comes first; either order works. The output
8145 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8146 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8148 Even though the unit size @var{u} is ignored for the formats @samp{s}
8149 and @samp{i}, you might still want to use a count @var{n}; for example,
8150 @samp{3i} specifies that you want to see three machine instructions,
8151 including any operands. For convenience, especially when used with
8152 the @code{display} command, the @samp{i} format also prints branch delay
8153 slot instructions, if any, beyond the count specified, which immediately
8154 follow the last instruction that is within the count. The command
8155 @code{disassemble} gives an alternative way of inspecting machine
8156 instructions; see @ref{Machine Code,,Source and Machine Code}.
8158 All the defaults for the arguments to @code{x} are designed to make it
8159 easy to continue scanning memory with minimal specifications each time
8160 you use @code{x}. For example, after you have inspected three machine
8161 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8162 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8163 the repeat count @var{n} is used again; the other arguments default as
8164 for successive uses of @code{x}.
8166 When examining machine instructions, the instruction at current program
8167 counter is shown with a @code{=>} marker. For example:
8170 (@value{GDBP}) x/5i $pc-6
8171 0x804837f <main+11>: mov %esp,%ebp
8172 0x8048381 <main+13>: push %ecx
8173 0x8048382 <main+14>: sub $0x4,%esp
8174 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8175 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8178 @cindex @code{$_}, @code{$__}, and value history
8179 The addresses and contents printed by the @code{x} command are not saved
8180 in the value history because there is often too much of them and they
8181 would get in the way. Instead, @value{GDBN} makes these values available for
8182 subsequent use in expressions as values of the convenience variables
8183 @code{$_} and @code{$__}. After an @code{x} command, the last address
8184 examined is available for use in expressions in the convenience variable
8185 @code{$_}. The contents of that address, as examined, are available in
8186 the convenience variable @code{$__}.
8188 If the @code{x} command has a repeat count, the address and contents saved
8189 are from the last memory unit printed; this is not the same as the last
8190 address printed if several units were printed on the last line of output.
8192 @cindex remote memory comparison
8193 @cindex verify remote memory image
8194 When you are debugging a program running on a remote target machine
8195 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8196 remote machine's memory against the executable file you downloaded to
8197 the target. The @code{compare-sections} command is provided for such
8201 @kindex compare-sections
8202 @item compare-sections @r{[}@var{section-name}@r{]}
8203 Compare the data of a loadable section @var{section-name} in the
8204 executable file of the program being debugged with the same section in
8205 the remote machine's memory, and report any mismatches. With no
8206 arguments, compares all loadable sections. This command's
8207 availability depends on the target's support for the @code{"qCRC"}
8212 @section Automatic Display
8213 @cindex automatic display
8214 @cindex display of expressions
8216 If you find that you want to print the value of an expression frequently
8217 (to see how it changes), you might want to add it to the @dfn{automatic
8218 display list} so that @value{GDBN} prints its value each time your program stops.
8219 Each expression added to the list is given a number to identify it;
8220 to remove an expression from the list, you specify that number.
8221 The automatic display looks like this:
8225 3: bar[5] = (struct hack *) 0x3804
8229 This display shows item numbers, expressions and their current values. As with
8230 displays you request manually using @code{x} or @code{print}, you can
8231 specify the output format you prefer; in fact, @code{display} decides
8232 whether to use @code{print} or @code{x} depending your format
8233 specification---it uses @code{x} if you specify either the @samp{i}
8234 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8238 @item display @var{expr}
8239 Add the expression @var{expr} to the list of expressions to display
8240 each time your program stops. @xref{Expressions, ,Expressions}.
8242 @code{display} does not repeat if you press @key{RET} again after using it.
8244 @item display/@var{fmt} @var{expr}
8245 For @var{fmt} specifying only a display format and not a size or
8246 count, add the expression @var{expr} to the auto-display list but
8247 arrange to display it each time in the specified format @var{fmt}.
8248 @xref{Output Formats,,Output Formats}.
8250 @item display/@var{fmt} @var{addr}
8251 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8252 number of units, add the expression @var{addr} as a memory address to
8253 be examined each time your program stops. Examining means in effect
8254 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8257 For example, @samp{display/i $pc} can be helpful, to see the machine
8258 instruction about to be executed each time execution stops (@samp{$pc}
8259 is a common name for the program counter; @pxref{Registers, ,Registers}).
8262 @kindex delete display
8264 @item undisplay @var{dnums}@dots{}
8265 @itemx delete display @var{dnums}@dots{}
8266 Remove items from the list of expressions to display. Specify the
8267 numbers of the displays that you want affected with the command
8268 argument @var{dnums}. It can be a single display number, one of the
8269 numbers shown in the first field of the @samp{info display} display;
8270 or it could be a range of display numbers, as in @code{2-4}.
8272 @code{undisplay} does not repeat if you press @key{RET} after using it.
8273 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8275 @kindex disable display
8276 @item disable display @var{dnums}@dots{}
8277 Disable the display of item numbers @var{dnums}. A disabled display
8278 item is not printed automatically, but is not forgotten. It may be
8279 enabled again later. Specify the numbers of the displays that you
8280 want affected with the command argument @var{dnums}. It can be a
8281 single display number, one of the numbers shown in the first field of
8282 the @samp{info display} display; or it could be a range of display
8283 numbers, as in @code{2-4}.
8285 @kindex enable display
8286 @item enable display @var{dnums}@dots{}
8287 Enable display of item numbers @var{dnums}. It becomes effective once
8288 again in auto display of its expression, until you specify otherwise.
8289 Specify the numbers of the displays that you want affected with the
8290 command argument @var{dnums}. It can be a single display number, one
8291 of the numbers shown in the first field of the @samp{info display}
8292 display; or it could be a range of display numbers, as in @code{2-4}.
8295 Display the current values of the expressions on the list, just as is
8296 done when your program stops.
8298 @kindex info display
8300 Print the list of expressions previously set up to display
8301 automatically, each one with its item number, but without showing the
8302 values. This includes disabled expressions, which are marked as such.
8303 It also includes expressions which would not be displayed right now
8304 because they refer to automatic variables not currently available.
8307 @cindex display disabled out of scope
8308 If a display expression refers to local variables, then it does not make
8309 sense outside the lexical context for which it was set up. Such an
8310 expression is disabled when execution enters a context where one of its
8311 variables is not defined. For example, if you give the command
8312 @code{display last_char} while inside a function with an argument
8313 @code{last_char}, @value{GDBN} displays this argument while your program
8314 continues to stop inside that function. When it stops elsewhere---where
8315 there is no variable @code{last_char}---the display is disabled
8316 automatically. The next time your program stops where @code{last_char}
8317 is meaningful, you can enable the display expression once again.
8319 @node Print Settings
8320 @section Print Settings
8322 @cindex format options
8323 @cindex print settings
8324 @value{GDBN} provides the following ways to control how arrays, structures,
8325 and symbols are printed.
8328 These settings are useful for debugging programs in any language:
8332 @item set print address
8333 @itemx set print address on
8334 @cindex print/don't print memory addresses
8335 @value{GDBN} prints memory addresses showing the location of stack
8336 traces, structure values, pointer values, breakpoints, and so forth,
8337 even when it also displays the contents of those addresses. The default
8338 is @code{on}. For example, this is what a stack frame display looks like with
8339 @code{set print address on}:
8344 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8346 530 if (lquote != def_lquote)
8350 @item set print address off
8351 Do not print addresses when displaying their contents. For example,
8352 this is the same stack frame displayed with @code{set print address off}:
8356 (@value{GDBP}) set print addr off
8358 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8359 530 if (lquote != def_lquote)
8363 You can use @samp{set print address off} to eliminate all machine
8364 dependent displays from the @value{GDBN} interface. For example, with
8365 @code{print address off}, you should get the same text for backtraces on
8366 all machines---whether or not they involve pointer arguments.
8369 @item show print address
8370 Show whether or not addresses are to be printed.
8373 When @value{GDBN} prints a symbolic address, it normally prints the
8374 closest earlier symbol plus an offset. If that symbol does not uniquely
8375 identify the address (for example, it is a name whose scope is a single
8376 source file), you may need to clarify. One way to do this is with
8377 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8378 you can set @value{GDBN} to print the source file and line number when
8379 it prints a symbolic address:
8382 @item set print symbol-filename on
8383 @cindex source file and line of a symbol
8384 @cindex symbol, source file and line
8385 Tell @value{GDBN} to print the source file name and line number of a
8386 symbol in the symbolic form of an address.
8388 @item set print symbol-filename off
8389 Do not print source file name and line number of a symbol. This is the
8392 @item show print symbol-filename
8393 Show whether or not @value{GDBN} will print the source file name and
8394 line number of a symbol in the symbolic form of an address.
8397 Another situation where it is helpful to show symbol filenames and line
8398 numbers is when disassembling code; @value{GDBN} shows you the line
8399 number and source file that corresponds to each instruction.
8401 Also, you may wish to see the symbolic form only if the address being
8402 printed is reasonably close to the closest earlier symbol:
8405 @item set print max-symbolic-offset @var{max-offset}
8406 @cindex maximum value for offset of closest symbol
8407 Tell @value{GDBN} to only display the symbolic form of an address if the
8408 offset between the closest earlier symbol and the address is less than
8409 @var{max-offset}. The default is 0, which tells @value{GDBN}
8410 to always print the symbolic form of an address if any symbol precedes it.
8412 @item show print max-symbolic-offset
8413 Ask how large the maximum offset is that @value{GDBN} prints in a
8417 @cindex wild pointer, interpreting
8418 @cindex pointer, finding referent
8419 If you have a pointer and you are not sure where it points, try
8420 @samp{set print symbol-filename on}. Then you can determine the name
8421 and source file location of the variable where it points, using
8422 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8423 For example, here @value{GDBN} shows that a variable @code{ptt} points
8424 at another variable @code{t}, defined in @file{hi2.c}:
8427 (@value{GDBP}) set print symbol-filename on
8428 (@value{GDBP}) p/a ptt
8429 $4 = 0xe008 <t in hi2.c>
8433 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8434 does not show the symbol name and filename of the referent, even with
8435 the appropriate @code{set print} options turned on.
8438 You can also enable @samp{/a}-like formatting all the time using
8439 @samp{set print symbol on}:
8442 @item set print symbol on
8443 Tell @value{GDBN} to print the symbol corresponding to an address, if
8446 @item set print symbol off
8447 Tell @value{GDBN} not to print the symbol corresponding to an
8448 address. In this mode, @value{GDBN} will still print the symbol
8449 corresponding to pointers to functions. This is the default.
8451 @item show print symbol
8452 Show whether @value{GDBN} will display the symbol corresponding to an
8456 Other settings control how different kinds of objects are printed:
8459 @item set print array
8460 @itemx set print array on
8461 @cindex pretty print arrays
8462 Pretty print arrays. This format is more convenient to read,
8463 but uses more space. The default is off.
8465 @item set print array off
8466 Return to compressed format for arrays.
8468 @item show print array
8469 Show whether compressed or pretty format is selected for displaying
8472 @cindex print array indexes
8473 @item set print array-indexes
8474 @itemx set print array-indexes on
8475 Print the index of each element when displaying arrays. May be more
8476 convenient to locate a given element in the array or quickly find the
8477 index of a given element in that printed array. The default is off.
8479 @item set print array-indexes off
8480 Stop printing element indexes when displaying arrays.
8482 @item show print array-indexes
8483 Show whether the index of each element is printed when displaying
8486 @item set print elements @var{number-of-elements}
8487 @cindex number of array elements to print
8488 @cindex limit on number of printed array elements
8489 Set a limit on how many elements of an array @value{GDBN} will print.
8490 If @value{GDBN} is printing a large array, it stops printing after it has
8491 printed the number of elements set by the @code{set print elements} command.
8492 This limit also applies to the display of strings.
8493 When @value{GDBN} starts, this limit is set to 200.
8494 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8496 @item show print elements
8497 Display the number of elements of a large array that @value{GDBN} will print.
8498 If the number is 0, then the printing is unlimited.
8500 @item set print frame-arguments @var{value}
8501 @kindex set print frame-arguments
8502 @cindex printing frame argument values
8503 @cindex print all frame argument values
8504 @cindex print frame argument values for scalars only
8505 @cindex do not print frame argument values
8506 This command allows to control how the values of arguments are printed
8507 when the debugger prints a frame (@pxref{Frames}). The possible
8512 The values of all arguments are printed.
8515 Print the value of an argument only if it is a scalar. The value of more
8516 complex arguments such as arrays, structures, unions, etc, is replaced
8517 by @code{@dots{}}. This is the default. Here is an example where
8518 only scalar arguments are shown:
8521 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8526 None of the argument values are printed. Instead, the value of each argument
8527 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8530 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8535 By default, only scalar arguments are printed. This command can be used
8536 to configure the debugger to print the value of all arguments, regardless
8537 of their type. However, it is often advantageous to not print the value
8538 of more complex parameters. For instance, it reduces the amount of
8539 information printed in each frame, making the backtrace more readable.
8540 Also, it improves performance when displaying Ada frames, because
8541 the computation of large arguments can sometimes be CPU-intensive,
8542 especially in large applications. Setting @code{print frame-arguments}
8543 to @code{scalars} (the default) or @code{none} avoids this computation,
8544 thus speeding up the display of each Ada frame.
8546 @item show print frame-arguments
8547 Show how the value of arguments should be displayed when printing a frame.
8549 @anchor{set print entry-values}
8550 @item set print entry-values @var{value}
8551 @kindex set print entry-values
8552 Set printing of frame argument values at function entry. In some cases
8553 @value{GDBN} can determine the value of function argument which was passed by
8554 the function caller, even if the value was modified inside the called function
8555 and therefore is different. With optimized code, the current value could be
8556 unavailable, but the entry value may still be known.
8558 The default value is @code{default} (see below for its description). Older
8559 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8560 this feature will behave in the @code{default} setting the same way as with the
8563 This functionality is currently supported only by DWARF 2 debugging format and
8564 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8565 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8568 The @var{value} parameter can be one of the following:
8572 Print only actual parameter values, never print values from function entry
8576 #0 different (val=6)
8577 #0 lost (val=<optimized out>)
8579 #0 invalid (val=<optimized out>)
8583 Print only parameter values from function entry point. The actual parameter
8584 values are never printed.
8586 #0 equal (val@@entry=5)
8587 #0 different (val@@entry=5)
8588 #0 lost (val@@entry=5)
8589 #0 born (val@@entry=<optimized out>)
8590 #0 invalid (val@@entry=<optimized out>)
8594 Print only parameter values from function entry point. If value from function
8595 entry point is not known while the actual value is known, print the actual
8596 value for such parameter.
8598 #0 equal (val@@entry=5)
8599 #0 different (val@@entry=5)
8600 #0 lost (val@@entry=5)
8602 #0 invalid (val@@entry=<optimized out>)
8606 Print actual parameter values. If actual parameter value is not known while
8607 value from function entry point is known, print the entry point value for such
8611 #0 different (val=6)
8612 #0 lost (val@@entry=5)
8614 #0 invalid (val=<optimized out>)
8618 Always print both the actual parameter value and its value from function entry
8619 point, even if values of one or both are not available due to compiler
8622 #0 equal (val=5, val@@entry=5)
8623 #0 different (val=6, val@@entry=5)
8624 #0 lost (val=<optimized out>, val@@entry=5)
8625 #0 born (val=10, val@@entry=<optimized out>)
8626 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8630 Print the actual parameter value if it is known and also its value from
8631 function entry point if it is known. If neither is known, print for the actual
8632 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8633 values are known and identical, print the shortened
8634 @code{param=param@@entry=VALUE} notation.
8636 #0 equal (val=val@@entry=5)
8637 #0 different (val=6, val@@entry=5)
8638 #0 lost (val@@entry=5)
8640 #0 invalid (val=<optimized out>)
8644 Always print the actual parameter value. Print also its value from function
8645 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8646 if both values are known and identical, print the shortened
8647 @code{param=param@@entry=VALUE} notation.
8649 #0 equal (val=val@@entry=5)
8650 #0 different (val=6, val@@entry=5)
8651 #0 lost (val=<optimized out>, val@@entry=5)
8653 #0 invalid (val=<optimized out>)
8657 For analysis messages on possible failures of frame argument values at function
8658 entry resolution see @ref{set debug entry-values}.
8660 @item show print entry-values
8661 Show the method being used for printing of frame argument values at function
8664 @item set print repeats
8665 @cindex repeated array elements
8666 Set the threshold for suppressing display of repeated array
8667 elements. When the number of consecutive identical elements of an
8668 array exceeds the threshold, @value{GDBN} prints the string
8669 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8670 identical repetitions, instead of displaying the identical elements
8671 themselves. Setting the threshold to zero will cause all elements to
8672 be individually printed. The default threshold is 10.
8674 @item show print repeats
8675 Display the current threshold for printing repeated identical
8678 @item set print null-stop
8679 @cindex @sc{null} elements in arrays
8680 Cause @value{GDBN} to stop printing the characters of an array when the first
8681 @sc{null} is encountered. This is useful when large arrays actually
8682 contain only short strings.
8685 @item show print null-stop
8686 Show whether @value{GDBN} stops printing an array on the first
8687 @sc{null} character.
8689 @item set print pretty on
8690 @cindex print structures in indented form
8691 @cindex indentation in structure display
8692 Cause @value{GDBN} to print structures in an indented format with one member
8693 per line, like this:
8708 @item set print pretty off
8709 Cause @value{GDBN} to print structures in a compact format, like this:
8713 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8714 meat = 0x54 "Pork"@}
8719 This is the default format.
8721 @item show print pretty
8722 Show which format @value{GDBN} is using to print structures.
8724 @item set print sevenbit-strings on
8725 @cindex eight-bit characters in strings
8726 @cindex octal escapes in strings
8727 Print using only seven-bit characters; if this option is set,
8728 @value{GDBN} displays any eight-bit characters (in strings or
8729 character values) using the notation @code{\}@var{nnn}. This setting is
8730 best if you are working in English (@sc{ascii}) and you use the
8731 high-order bit of characters as a marker or ``meta'' bit.
8733 @item set print sevenbit-strings off
8734 Print full eight-bit characters. This allows the use of more
8735 international character sets, and is the default.
8737 @item show print sevenbit-strings
8738 Show whether or not @value{GDBN} is printing only seven-bit characters.
8740 @item set print union on
8741 @cindex unions in structures, printing
8742 Tell @value{GDBN} to print unions which are contained in structures
8743 and other unions. This is the default setting.
8745 @item set print union off
8746 Tell @value{GDBN} not to print unions which are contained in
8747 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8750 @item show print union
8751 Ask @value{GDBN} whether or not it will print unions which are contained in
8752 structures and other unions.
8754 For example, given the declarations
8757 typedef enum @{Tree, Bug@} Species;
8758 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8759 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8770 struct thing foo = @{Tree, @{Acorn@}@};
8774 with @code{set print union on} in effect @samp{p foo} would print
8777 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8781 and with @code{set print union off} in effect it would print
8784 $1 = @{it = Tree, form = @{...@}@}
8788 @code{set print union} affects programs written in C-like languages
8794 These settings are of interest when debugging C@t{++} programs:
8797 @cindex demangling C@t{++} names
8798 @item set print demangle
8799 @itemx set print demangle on
8800 Print C@t{++} names in their source form rather than in the encoded
8801 (``mangled'') form passed to the assembler and linker for type-safe
8802 linkage. The default is on.
8804 @item show print demangle
8805 Show whether C@t{++} names are printed in mangled or demangled form.
8807 @item set print asm-demangle
8808 @itemx set print asm-demangle on
8809 Print C@t{++} names in their source form rather than their mangled form, even
8810 in assembler code printouts such as instruction disassemblies.
8813 @item show print asm-demangle
8814 Show whether C@t{++} names in assembly listings are printed in mangled
8817 @cindex C@t{++} symbol decoding style
8818 @cindex symbol decoding style, C@t{++}
8819 @kindex set demangle-style
8820 @item set demangle-style @var{style}
8821 Choose among several encoding schemes used by different compilers to
8822 represent C@t{++} names. The choices for @var{style} are currently:
8826 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8829 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8830 This is the default.
8833 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8836 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8839 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8840 @strong{Warning:} this setting alone is not sufficient to allow
8841 debugging @code{cfront}-generated executables. @value{GDBN} would
8842 require further enhancement to permit that.
8845 If you omit @var{style}, you will see a list of possible formats.
8847 @item show demangle-style
8848 Display the encoding style currently in use for decoding C@t{++} symbols.
8850 @item set print object
8851 @itemx set print object on
8852 @cindex derived type of an object, printing
8853 @cindex display derived types
8854 When displaying a pointer to an object, identify the @emph{actual}
8855 (derived) type of the object rather than the @emph{declared} type, using
8856 the virtual function table. Note that the virtual function table is
8857 required---this feature can only work for objects that have run-time
8858 type identification; a single virtual method in the object's declared
8859 type is sufficient. Note that this setting is also taken into account when
8860 working with variable objects via MI (@pxref{GDB/MI}).
8862 @item set print object off
8863 Display only the declared type of objects, without reference to the
8864 virtual function table. This is the default setting.
8866 @item show print object
8867 Show whether actual, or declared, object types are displayed.
8869 @item set print static-members
8870 @itemx set print static-members on
8871 @cindex static members of C@t{++} objects
8872 Print static members when displaying a C@t{++} object. The default is on.
8874 @item set print static-members off
8875 Do not print static members when displaying a C@t{++} object.
8877 @item show print static-members
8878 Show whether C@t{++} static members are printed or not.
8880 @item set print pascal_static-members
8881 @itemx set print pascal_static-members on
8882 @cindex static members of Pascal objects
8883 @cindex Pascal objects, static members display
8884 Print static members when displaying a Pascal object. The default is on.
8886 @item set print pascal_static-members off
8887 Do not print static members when displaying a Pascal object.
8889 @item show print pascal_static-members
8890 Show whether Pascal static members are printed or not.
8892 @c These don't work with HP ANSI C++ yet.
8893 @item set print vtbl
8894 @itemx set print vtbl on
8895 @cindex pretty print C@t{++} virtual function tables
8896 @cindex virtual functions (C@t{++}) display
8897 @cindex VTBL display
8898 Pretty print C@t{++} virtual function tables. The default is off.
8899 (The @code{vtbl} commands do not work on programs compiled with the HP
8900 ANSI C@t{++} compiler (@code{aCC}).)
8902 @item set print vtbl off
8903 Do not pretty print C@t{++} virtual function tables.
8905 @item show print vtbl
8906 Show whether C@t{++} virtual function tables are pretty printed, or not.
8909 @node Pretty Printing
8910 @section Pretty Printing
8912 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8913 Python code. It greatly simplifies the display of complex objects. This
8914 mechanism works for both MI and the CLI.
8917 * Pretty-Printer Introduction:: Introduction to pretty-printers
8918 * Pretty-Printer Example:: An example pretty-printer
8919 * Pretty-Printer Commands:: Pretty-printer commands
8922 @node Pretty-Printer Introduction
8923 @subsection Pretty-Printer Introduction
8925 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8926 registered for the value. If there is then @value{GDBN} invokes the
8927 pretty-printer to print the value. Otherwise the value is printed normally.
8929 Pretty-printers are normally named. This makes them easy to manage.
8930 The @samp{info pretty-printer} command will list all the installed
8931 pretty-printers with their names.
8932 If a pretty-printer can handle multiple data types, then its
8933 @dfn{subprinters} are the printers for the individual data types.
8934 Each such subprinter has its own name.
8935 The format of the name is @var{printer-name};@var{subprinter-name}.
8937 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8938 Typically they are automatically loaded and registered when the corresponding
8939 debug information is loaded, thus making them available without having to
8940 do anything special.
8942 There are three places where a pretty-printer can be registered.
8946 Pretty-printers registered globally are available when debugging
8950 Pretty-printers registered with a program space are available only
8951 when debugging that program.
8952 @xref{Progspaces In Python}, for more details on program spaces in Python.
8955 Pretty-printers registered with an objfile are loaded and unloaded
8956 with the corresponding objfile (e.g., shared library).
8957 @xref{Objfiles In Python}, for more details on objfiles in Python.
8960 @xref{Selecting Pretty-Printers}, for further information on how
8961 pretty-printers are selected,
8963 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8966 @node Pretty-Printer Example
8967 @subsection Pretty-Printer Example
8969 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8972 (@value{GDBP}) print s
8974 static npos = 4294967295,
8976 <std::allocator<char>> = @{
8977 <__gnu_cxx::new_allocator<char>> = @{
8978 <No data fields>@}, <No data fields>
8980 members of std::basic_string<char, std::char_traits<char>,
8981 std::allocator<char> >::_Alloc_hider:
8982 _M_p = 0x804a014 "abcd"
8987 With a pretty-printer for @code{std::string} only the contents are printed:
8990 (@value{GDBP}) print s
8994 @node Pretty-Printer Commands
8995 @subsection Pretty-Printer Commands
8996 @cindex pretty-printer commands
8999 @kindex info pretty-printer
9000 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9001 Print the list of installed pretty-printers.
9002 This includes disabled pretty-printers, which are marked as such.
9004 @var{object-regexp} is a regular expression matching the objects
9005 whose pretty-printers to list.
9006 Objects can be @code{global}, the program space's file
9007 (@pxref{Progspaces In Python}),
9008 and the object files within that program space (@pxref{Objfiles In Python}).
9009 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9010 looks up a printer from these three objects.
9012 @var{name-regexp} is a regular expression matching the name of the printers
9015 @kindex disable pretty-printer
9016 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9017 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9018 A disabled pretty-printer is not forgotten, it may be enabled again later.
9020 @kindex enable pretty-printer
9021 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9022 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9027 Suppose we have three pretty-printers installed: one from library1.so
9028 named @code{foo} that prints objects of type @code{foo}, and
9029 another from library2.so named @code{bar} that prints two types of objects,
9030 @code{bar1} and @code{bar2}.
9033 (gdb) info pretty-printer
9040 (gdb) info pretty-printer library2
9045 (gdb) disable pretty-printer library1
9047 2 of 3 printers enabled
9048 (gdb) info pretty-printer
9055 (gdb) disable pretty-printer library2 bar:bar1
9057 1 of 3 printers enabled
9058 (gdb) info pretty-printer library2
9065 (gdb) disable pretty-printer library2 bar
9067 0 of 3 printers enabled
9068 (gdb) info pretty-printer library2
9077 Note that for @code{bar} the entire printer can be disabled,
9078 as can each individual subprinter.
9081 @section Value History
9083 @cindex value history
9084 @cindex history of values printed by @value{GDBN}
9085 Values printed by the @code{print} command are saved in the @value{GDBN}
9086 @dfn{value history}. This allows you to refer to them in other expressions.
9087 Values are kept until the symbol table is re-read or discarded
9088 (for example with the @code{file} or @code{symbol-file} commands).
9089 When the symbol table changes, the value history is discarded,
9090 since the values may contain pointers back to the types defined in the
9095 @cindex history number
9096 The values printed are given @dfn{history numbers} by which you can
9097 refer to them. These are successive integers starting with one.
9098 @code{print} shows you the history number assigned to a value by
9099 printing @samp{$@var{num} = } before the value; here @var{num} is the
9102 To refer to any previous value, use @samp{$} followed by the value's
9103 history number. The way @code{print} labels its output is designed to
9104 remind you of this. Just @code{$} refers to the most recent value in
9105 the history, and @code{$$} refers to the value before that.
9106 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9107 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9108 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9110 For example, suppose you have just printed a pointer to a structure and
9111 want to see the contents of the structure. It suffices to type
9117 If you have a chain of structures where the component @code{next} points
9118 to the next one, you can print the contents of the next one with this:
9125 You can print successive links in the chain by repeating this
9126 command---which you can do by just typing @key{RET}.
9128 Note that the history records values, not expressions. If the value of
9129 @code{x} is 4 and you type these commands:
9137 then the value recorded in the value history by the @code{print} command
9138 remains 4 even though the value of @code{x} has changed.
9143 Print the last ten values in the value history, with their item numbers.
9144 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9145 values} does not change the history.
9147 @item show values @var{n}
9148 Print ten history values centered on history item number @var{n}.
9151 Print ten history values just after the values last printed. If no more
9152 values are available, @code{show values +} produces no display.
9155 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9156 same effect as @samp{show values +}.
9158 @node Convenience Vars
9159 @section Convenience Variables
9161 @cindex convenience variables
9162 @cindex user-defined variables
9163 @value{GDBN} provides @dfn{convenience variables} that you can use within
9164 @value{GDBN} to hold on to a value and refer to it later. These variables
9165 exist entirely within @value{GDBN}; they are not part of your program, and
9166 setting a convenience variable has no direct effect on further execution
9167 of your program. That is why you can use them freely.
9169 Convenience variables are prefixed with @samp{$}. Any name preceded by
9170 @samp{$} can be used for a convenience variable, unless it is one of
9171 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9172 (Value history references, in contrast, are @emph{numbers} preceded
9173 by @samp{$}. @xref{Value History, ,Value History}.)
9175 You can save a value in a convenience variable with an assignment
9176 expression, just as you would set a variable in your program.
9180 set $foo = *object_ptr
9184 would save in @code{$foo} the value contained in the object pointed to by
9187 Using a convenience variable for the first time creates it, but its
9188 value is @code{void} until you assign a new value. You can alter the
9189 value with another assignment at any time.
9191 Convenience variables have no fixed types. You can assign a convenience
9192 variable any type of value, including structures and arrays, even if
9193 that variable already has a value of a different type. The convenience
9194 variable, when used as an expression, has the type of its current value.
9197 @kindex show convenience
9198 @cindex show all user variables
9199 @item show convenience
9200 Print a list of convenience variables used so far, and their values.
9201 Abbreviated @code{show conv}.
9203 @kindex init-if-undefined
9204 @cindex convenience variables, initializing
9205 @item init-if-undefined $@var{variable} = @var{expression}
9206 Set a convenience variable if it has not already been set. This is useful
9207 for user-defined commands that keep some state. It is similar, in concept,
9208 to using local static variables with initializers in C (except that
9209 convenience variables are global). It can also be used to allow users to
9210 override default values used in a command script.
9212 If the variable is already defined then the expression is not evaluated so
9213 any side-effects do not occur.
9216 One of the ways to use a convenience variable is as a counter to be
9217 incremented or a pointer to be advanced. For example, to print
9218 a field from successive elements of an array of structures:
9222 print bar[$i++]->contents
9226 Repeat that command by typing @key{RET}.
9228 Some convenience variables are created automatically by @value{GDBN} and given
9229 values likely to be useful.
9232 @vindex $_@r{, convenience variable}
9234 The variable @code{$_} is automatically set by the @code{x} command to
9235 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9236 commands which provide a default address for @code{x} to examine also
9237 set @code{$_} to that address; these commands include @code{info line}
9238 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9239 except when set by the @code{x} command, in which case it is a pointer
9240 to the type of @code{$__}.
9242 @vindex $__@r{, convenience variable}
9244 The variable @code{$__} is automatically set by the @code{x} command
9245 to the value found in the last address examined. Its type is chosen
9246 to match the format in which the data was printed.
9249 @vindex $_exitcode@r{, convenience variable}
9250 The variable @code{$_exitcode} is automatically set to the exit code when
9251 the program being debugged terminates.
9254 @itemx $_probe_arg0@dots{}$_probe_arg11
9255 Arguments to a static probe. @xref{Static Probe Points}.
9258 @vindex $_sdata@r{, inspect, convenience variable}
9259 The variable @code{$_sdata} contains extra collected static tracepoint
9260 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9261 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9262 if extra static tracepoint data has not been collected.
9265 @vindex $_siginfo@r{, convenience variable}
9266 The variable @code{$_siginfo} contains extra signal information
9267 (@pxref{extra signal information}). Note that @code{$_siginfo}
9268 could be empty, if the application has not yet received any signals.
9269 For example, it will be empty before you execute the @code{run} command.
9272 @vindex $_tlb@r{, convenience variable}
9273 The variable @code{$_tlb} is automatically set when debugging
9274 applications running on MS-Windows in native mode or connected to
9275 gdbserver that supports the @code{qGetTIBAddr} request.
9276 @xref{General Query Packets}.
9277 This variable contains the address of the thread information block.
9281 On HP-UX systems, if you refer to a function or variable name that
9282 begins with a dollar sign, @value{GDBN} searches for a user or system
9283 name first, before it searches for a convenience variable.
9285 @cindex convenience functions
9286 @value{GDBN} also supplies some @dfn{convenience functions}. These
9287 have a syntax similar to convenience variables. A convenience
9288 function can be used in an expression just like an ordinary function;
9289 however, a convenience function is implemented internally to
9294 @kindex help function
9295 @cindex show all convenience functions
9296 Print a list of all convenience functions.
9303 You can refer to machine register contents, in expressions, as variables
9304 with names starting with @samp{$}. The names of registers are different
9305 for each machine; use @code{info registers} to see the names used on
9309 @kindex info registers
9310 @item info registers
9311 Print the names and values of all registers except floating-point
9312 and vector registers (in the selected stack frame).
9314 @kindex info all-registers
9315 @cindex floating point registers
9316 @item info all-registers
9317 Print the names and values of all registers, including floating-point
9318 and vector registers (in the selected stack frame).
9320 @item info registers @var{regname} @dots{}
9321 Print the @dfn{relativized} value of each specified register @var{regname}.
9322 As discussed in detail below, register values are normally relative to
9323 the selected stack frame. @var{regname} may be any register name valid on
9324 the machine you are using, with or without the initial @samp{$}.
9327 @cindex stack pointer register
9328 @cindex program counter register
9329 @cindex process status register
9330 @cindex frame pointer register
9331 @cindex standard registers
9332 @value{GDBN} has four ``standard'' register names that are available (in
9333 expressions) on most machines---whenever they do not conflict with an
9334 architecture's canonical mnemonics for registers. The register names
9335 @code{$pc} and @code{$sp} are used for the program counter register and
9336 the stack pointer. @code{$fp} is used for a register that contains a
9337 pointer to the current stack frame, and @code{$ps} is used for a
9338 register that contains the processor status. For example,
9339 you could print the program counter in hex with
9346 or print the instruction to be executed next with
9353 or add four to the stack pointer@footnote{This is a way of removing
9354 one word from the stack, on machines where stacks grow downward in
9355 memory (most machines, nowadays). This assumes that the innermost
9356 stack frame is selected; setting @code{$sp} is not allowed when other
9357 stack frames are selected. To pop entire frames off the stack,
9358 regardless of machine architecture, use @code{return};
9359 see @ref{Returning, ,Returning from a Function}.} with
9365 Whenever possible, these four standard register names are available on
9366 your machine even though the machine has different canonical mnemonics,
9367 so long as there is no conflict. The @code{info registers} command
9368 shows the canonical names. For example, on the SPARC, @code{info
9369 registers} displays the processor status register as @code{$psr} but you
9370 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9371 is an alias for the @sc{eflags} register.
9373 @value{GDBN} always considers the contents of an ordinary register as an
9374 integer when the register is examined in this way. Some machines have
9375 special registers which can hold nothing but floating point; these
9376 registers are considered to have floating point values. There is no way
9377 to refer to the contents of an ordinary register as floating point value
9378 (although you can @emph{print} it as a floating point value with
9379 @samp{print/f $@var{regname}}).
9381 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9382 means that the data format in which the register contents are saved by
9383 the operating system is not the same one that your program normally
9384 sees. For example, the registers of the 68881 floating point
9385 coprocessor are always saved in ``extended'' (raw) format, but all C
9386 programs expect to work with ``double'' (virtual) format. In such
9387 cases, @value{GDBN} normally works with the virtual format only (the format
9388 that makes sense for your program), but the @code{info registers} command
9389 prints the data in both formats.
9391 @cindex SSE registers (x86)
9392 @cindex MMX registers (x86)
9393 Some machines have special registers whose contents can be interpreted
9394 in several different ways. For example, modern x86-based machines
9395 have SSE and MMX registers that can hold several values packed
9396 together in several different formats. @value{GDBN} refers to such
9397 registers in @code{struct} notation:
9400 (@value{GDBP}) print $xmm1
9402 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9403 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9404 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9405 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9406 v4_int32 = @{0, 20657912, 11, 13@},
9407 v2_int64 = @{88725056443645952, 55834574859@},
9408 uint128 = 0x0000000d0000000b013b36f800000000
9413 To set values of such registers, you need to tell @value{GDBN} which
9414 view of the register you wish to change, as if you were assigning
9415 value to a @code{struct} member:
9418 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9421 Normally, register values are relative to the selected stack frame
9422 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9423 value that the register would contain if all stack frames farther in
9424 were exited and their saved registers restored. In order to see the
9425 true contents of hardware registers, you must select the innermost
9426 frame (with @samp{frame 0}).
9428 However, @value{GDBN} must deduce where registers are saved, from the machine
9429 code generated by your compiler. If some registers are not saved, or if
9430 @value{GDBN} is unable to locate the saved registers, the selected stack
9431 frame makes no difference.
9433 @node Floating Point Hardware
9434 @section Floating Point Hardware
9435 @cindex floating point
9437 Depending on the configuration, @value{GDBN} may be able to give
9438 you more information about the status of the floating point hardware.
9443 Display hardware-dependent information about the floating
9444 point unit. The exact contents and layout vary depending on the
9445 floating point chip. Currently, @samp{info float} is supported on
9446 the ARM and x86 machines.
9450 @section Vector Unit
9453 Depending on the configuration, @value{GDBN} may be able to give you
9454 more information about the status of the vector unit.
9459 Display information about the vector unit. The exact contents and
9460 layout vary depending on the hardware.
9463 @node OS Information
9464 @section Operating System Auxiliary Information
9465 @cindex OS information
9467 @value{GDBN} provides interfaces to useful OS facilities that can help
9468 you debug your program.
9470 @cindex @code{ptrace} system call
9471 @cindex @code{struct user} contents
9472 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9473 machines), it interfaces with the inferior via the @code{ptrace}
9474 system call. The operating system creates a special sata structure,
9475 called @code{struct user}, for this interface. You can use the
9476 command @code{info udot} to display the contents of this data
9482 Display the contents of the @code{struct user} maintained by the OS
9483 kernel for the program being debugged. @value{GDBN} displays the
9484 contents of @code{struct user} as a list of hex numbers, similar to
9485 the @code{examine} command.
9488 @cindex auxiliary vector
9489 @cindex vector, auxiliary
9490 Some operating systems supply an @dfn{auxiliary vector} to programs at
9491 startup. This is akin to the arguments and environment that you
9492 specify for a program, but contains a system-dependent variety of
9493 binary values that tell system libraries important details about the
9494 hardware, operating system, and process. Each value's purpose is
9495 identified by an integer tag; the meanings are well-known but system-specific.
9496 Depending on the configuration and operating system facilities,
9497 @value{GDBN} may be able to show you this information. For remote
9498 targets, this functionality may further depend on the remote stub's
9499 support of the @samp{qXfer:auxv:read} packet, see
9500 @ref{qXfer auxiliary vector read}.
9505 Display the auxiliary vector of the inferior, which can be either a
9506 live process or a core dump file. @value{GDBN} prints each tag value
9507 numerically, and also shows names and text descriptions for recognized
9508 tags. Some values in the vector are numbers, some bit masks, and some
9509 pointers to strings or other data. @value{GDBN} displays each value in the
9510 most appropriate form for a recognized tag, and in hexadecimal for
9511 an unrecognized tag.
9514 On some targets, @value{GDBN} can access operating system-specific
9515 information and show it to you. The types of information available
9516 will differ depending on the type of operating system running on the
9517 target. The mechanism used to fetch the data is described in
9518 @ref{Operating System Information}. For remote targets, this
9519 functionality depends on the remote stub's support of the
9520 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9524 @item info os @var{infotype}
9526 Display OS information of the requested type.
9528 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9530 @anchor{linux info os infotypes}
9532 @kindex info os processes
9534 Display the list of processes on the target. For each process,
9535 @value{GDBN} prints the process identifier, the name of the user, the
9536 command corresponding to the process, and the list of processor cores
9537 that the process is currently running on. (To understand what these
9538 properties mean, for this and the following info types, please consult
9539 the general @sc{gnu}/Linux documentation.)
9541 @kindex info os procgroups
9543 Display the list of process groups on the target. For each process,
9544 @value{GDBN} prints the identifier of the process group that it belongs
9545 to, the command corresponding to the process group leader, the process
9546 identifier, and the command line of the process. The list is sorted
9547 first by the process group identifier, then by the process identifier,
9548 so that processes belonging to the same process group are grouped together
9549 and the process group leader is listed first.
9551 @kindex info os threads
9553 Display the list of threads running on the target. For each thread,
9554 @value{GDBN} prints the identifier of the process that the thread
9555 belongs to, the command of the process, the thread identifier, and the
9556 processor core that it is currently running on. The main thread of a
9557 process is not listed.
9559 @kindex info os files
9561 Display the list of open file descriptors on the target. For each
9562 file descriptor, @value{GDBN} prints the identifier of the process
9563 owning the descriptor, the command of the owning process, the value
9564 of the descriptor, and the target of the descriptor.
9566 @kindex info os sockets
9568 Display the list of Internet-domain sockets on the target. For each
9569 socket, @value{GDBN} prints the address and port of the local and
9570 remote endpoints, the current state of the connection, the creator of
9571 the socket, the IP address family of the socket, and the type of the
9576 Display the list of all System V shared-memory regions on the target.
9577 For each shared-memory region, @value{GDBN} prints the region key,
9578 the shared-memory identifier, the access permissions, the size of the
9579 region, the process that created the region, the process that last
9580 attached to or detached from the region, the current number of live
9581 attaches to the region, and the times at which the region was last
9582 attached to, detach from, and changed.
9584 @kindex info os semaphores
9586 Display the list of all System V semaphore sets on the target. For each
9587 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9588 set identifier, the access permissions, the number of semaphores in the
9589 set, the user and group of the owner and creator of the semaphore set,
9590 and the times at which the semaphore set was operated upon and changed.
9594 Display the list of all System V message queues on the target. For each
9595 message queue, @value{GDBN} prints the message queue key, the message
9596 queue identifier, the access permissions, the current number of bytes
9597 on the queue, the current number of messages on the queue, the processes
9598 that last sent and received a message on the queue, the user and group
9599 of the owner and creator of the message queue, the times at which a
9600 message was last sent and received on the queue, and the time at which
9601 the message queue was last changed.
9603 @kindex info os modules
9605 Display the list of all loaded kernel modules on the target. For each
9606 module, @value{GDBN} prints the module name, the size of the module in
9607 bytes, the number of times the module is used, the dependencies of the
9608 module, the status of the module, and the address of the loaded module
9613 If @var{infotype} is omitted, then list the possible values for
9614 @var{infotype} and the kind of OS information available for each
9615 @var{infotype}. If the target does not return a list of possible
9616 types, this command will report an error.
9619 @node Memory Region Attributes
9620 @section Memory Region Attributes
9621 @cindex memory region attributes
9623 @dfn{Memory region attributes} allow you to describe special handling
9624 required by regions of your target's memory. @value{GDBN} uses
9625 attributes to determine whether to allow certain types of memory
9626 accesses; whether to use specific width accesses; and whether to cache
9627 target memory. By default the description of memory regions is
9628 fetched from the target (if the current target supports this), but the
9629 user can override the fetched regions.
9631 Defined memory regions can be individually enabled and disabled. When a
9632 memory region is disabled, @value{GDBN} uses the default attributes when
9633 accessing memory in that region. Similarly, if no memory regions have
9634 been defined, @value{GDBN} uses the default attributes when accessing
9637 When a memory region is defined, it is given a number to identify it;
9638 to enable, disable, or remove a memory region, you specify that number.
9642 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9643 Define a memory region bounded by @var{lower} and @var{upper} with
9644 attributes @var{attributes}@dots{}, and add it to the list of regions
9645 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9646 case: it is treated as the target's maximum memory address.
9647 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9650 Discard any user changes to the memory regions and use target-supplied
9651 regions, if available, or no regions if the target does not support.
9654 @item delete mem @var{nums}@dots{}
9655 Remove memory regions @var{nums}@dots{} from the list of regions
9656 monitored by @value{GDBN}.
9659 @item disable mem @var{nums}@dots{}
9660 Disable monitoring of memory regions @var{nums}@dots{}.
9661 A disabled memory region is not forgotten.
9662 It may be enabled again later.
9665 @item enable mem @var{nums}@dots{}
9666 Enable monitoring of memory regions @var{nums}@dots{}.
9670 Print a table of all defined memory regions, with the following columns
9674 @item Memory Region Number
9675 @item Enabled or Disabled.
9676 Enabled memory regions are marked with @samp{y}.
9677 Disabled memory regions are marked with @samp{n}.
9680 The address defining the inclusive lower bound of the memory region.
9683 The address defining the exclusive upper bound of the memory region.
9686 The list of attributes set for this memory region.
9691 @subsection Attributes
9693 @subsubsection Memory Access Mode
9694 The access mode attributes set whether @value{GDBN} may make read or
9695 write accesses to a memory region.
9697 While these attributes prevent @value{GDBN} from performing invalid
9698 memory accesses, they do nothing to prevent the target system, I/O DMA,
9699 etc.@: from accessing memory.
9703 Memory is read only.
9705 Memory is write only.
9707 Memory is read/write. This is the default.
9710 @subsubsection Memory Access Size
9711 The access size attribute tells @value{GDBN} to use specific sized
9712 accesses in the memory region. Often memory mapped device registers
9713 require specific sized accesses. If no access size attribute is
9714 specified, @value{GDBN} may use accesses of any size.
9718 Use 8 bit memory accesses.
9720 Use 16 bit memory accesses.
9722 Use 32 bit memory accesses.
9724 Use 64 bit memory accesses.
9727 @c @subsubsection Hardware/Software Breakpoints
9728 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9729 @c will use hardware or software breakpoints for the internal breakpoints
9730 @c used by the step, next, finish, until, etc. commands.
9734 @c Always use hardware breakpoints
9735 @c @item swbreak (default)
9738 @subsubsection Data Cache
9739 The data cache attributes set whether @value{GDBN} will cache target
9740 memory. While this generally improves performance by reducing debug
9741 protocol overhead, it can lead to incorrect results because @value{GDBN}
9742 does not know about volatile variables or memory mapped device
9747 Enable @value{GDBN} to cache target memory.
9749 Disable @value{GDBN} from caching target memory. This is the default.
9752 @subsection Memory Access Checking
9753 @value{GDBN} can be instructed to refuse accesses to memory that is
9754 not explicitly described. This can be useful if accessing such
9755 regions has undesired effects for a specific target, or to provide
9756 better error checking. The following commands control this behaviour.
9759 @kindex set mem inaccessible-by-default
9760 @item set mem inaccessible-by-default [on|off]
9761 If @code{on} is specified, make @value{GDBN} treat memory not
9762 explicitly described by the memory ranges as non-existent and refuse accesses
9763 to such memory. The checks are only performed if there's at least one
9764 memory range defined. If @code{off} is specified, make @value{GDBN}
9765 treat the memory not explicitly described by the memory ranges as RAM.
9766 The default value is @code{on}.
9767 @kindex show mem inaccessible-by-default
9768 @item show mem inaccessible-by-default
9769 Show the current handling of accesses to unknown memory.
9773 @c @subsubsection Memory Write Verification
9774 @c The memory write verification attributes set whether @value{GDBN}
9775 @c will re-reads data after each write to verify the write was successful.
9779 @c @item noverify (default)
9782 @node Dump/Restore Files
9783 @section Copy Between Memory and a File
9784 @cindex dump/restore files
9785 @cindex append data to a file
9786 @cindex dump data to a file
9787 @cindex restore data from a file
9789 You can use the commands @code{dump}, @code{append}, and
9790 @code{restore} to copy data between target memory and a file. The
9791 @code{dump} and @code{append} commands write data to a file, and the
9792 @code{restore} command reads data from a file back into the inferior's
9793 memory. Files may be in binary, Motorola S-record, Intel hex, or
9794 Tektronix Hex format; however, @value{GDBN} can only append to binary
9800 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9801 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9802 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9803 or the value of @var{expr}, to @var{filename} in the given format.
9805 The @var{format} parameter may be any one of:
9812 Motorola S-record format.
9814 Tektronix Hex format.
9817 @value{GDBN} uses the same definitions of these formats as the
9818 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9819 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9823 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9824 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9825 Append the contents of memory from @var{start_addr} to @var{end_addr},
9826 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9827 (@value{GDBN} can only append data to files in raw binary form.)
9830 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9831 Restore the contents of file @var{filename} into memory. The
9832 @code{restore} command can automatically recognize any known @sc{bfd}
9833 file format, except for raw binary. To restore a raw binary file you
9834 must specify the optional keyword @code{binary} after the filename.
9836 If @var{bias} is non-zero, its value will be added to the addresses
9837 contained in the file. Binary files always start at address zero, so
9838 they will be restored at address @var{bias}. Other bfd files have
9839 a built-in location; they will be restored at offset @var{bias}
9842 If @var{start} and/or @var{end} are non-zero, then only data between
9843 file offset @var{start} and file offset @var{end} will be restored.
9844 These offsets are relative to the addresses in the file, before
9845 the @var{bias} argument is applied.
9849 @node Core File Generation
9850 @section How to Produce a Core File from Your Program
9851 @cindex dump core from inferior
9853 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9854 image of a running process and its process status (register values
9855 etc.). Its primary use is post-mortem debugging of a program that
9856 crashed while it ran outside a debugger. A program that crashes
9857 automatically produces a core file, unless this feature is disabled by
9858 the user. @xref{Files}, for information on invoking @value{GDBN} in
9859 the post-mortem debugging mode.
9861 Occasionally, you may wish to produce a core file of the program you
9862 are debugging in order to preserve a snapshot of its state.
9863 @value{GDBN} has a special command for that.
9867 @kindex generate-core-file
9868 @item generate-core-file [@var{file}]
9869 @itemx gcore [@var{file}]
9870 Produce a core dump of the inferior process. The optional argument
9871 @var{file} specifies the file name where to put the core dump. If not
9872 specified, the file name defaults to @file{core.@var{pid}}, where
9873 @var{pid} is the inferior process ID.
9875 Note that this command is implemented only for some systems (as of
9876 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9879 @node Character Sets
9880 @section Character Sets
9881 @cindex character sets
9883 @cindex translating between character sets
9884 @cindex host character set
9885 @cindex target character set
9887 If the program you are debugging uses a different character set to
9888 represent characters and strings than the one @value{GDBN} uses itself,
9889 @value{GDBN} can automatically translate between the character sets for
9890 you. The character set @value{GDBN} uses we call the @dfn{host
9891 character set}; the one the inferior program uses we call the
9892 @dfn{target character set}.
9894 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9895 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9896 remote protocol (@pxref{Remote Debugging}) to debug a program
9897 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9898 then the host character set is Latin-1, and the target character set is
9899 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9900 target-charset EBCDIC-US}, then @value{GDBN} translates between
9901 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9902 character and string literals in expressions.
9904 @value{GDBN} has no way to automatically recognize which character set
9905 the inferior program uses; you must tell it, using the @code{set
9906 target-charset} command, described below.
9908 Here are the commands for controlling @value{GDBN}'s character set
9912 @item set target-charset @var{charset}
9913 @kindex set target-charset
9914 Set the current target character set to @var{charset}. To display the
9915 list of supported target character sets, type
9916 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9918 @item set host-charset @var{charset}
9919 @kindex set host-charset
9920 Set the current host character set to @var{charset}.
9922 By default, @value{GDBN} uses a host character set appropriate to the
9923 system it is running on; you can override that default using the
9924 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9925 automatically determine the appropriate host character set. In this
9926 case, @value{GDBN} uses @samp{UTF-8}.
9928 @value{GDBN} can only use certain character sets as its host character
9929 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9930 @value{GDBN} will list the host character sets it supports.
9932 @item set charset @var{charset}
9934 Set the current host and target character sets to @var{charset}. As
9935 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9936 @value{GDBN} will list the names of the character sets that can be used
9937 for both host and target.
9940 @kindex show charset
9941 Show the names of the current host and target character sets.
9943 @item show host-charset
9944 @kindex show host-charset
9945 Show the name of the current host character set.
9947 @item show target-charset
9948 @kindex show target-charset
9949 Show the name of the current target character set.
9951 @item set target-wide-charset @var{charset}
9952 @kindex set target-wide-charset
9953 Set the current target's wide character set to @var{charset}. This is
9954 the character set used by the target's @code{wchar_t} type. To
9955 display the list of supported wide character sets, type
9956 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9958 @item show target-wide-charset
9959 @kindex show target-wide-charset
9960 Show the name of the current target's wide character set.
9963 Here is an example of @value{GDBN}'s character set support in action.
9964 Assume that the following source code has been placed in the file
9965 @file{charset-test.c}:
9971 = @{72, 101, 108, 108, 111, 44, 32, 119,
9972 111, 114, 108, 100, 33, 10, 0@};
9973 char ibm1047_hello[]
9974 = @{200, 133, 147, 147, 150, 107, 64, 166,
9975 150, 153, 147, 132, 90, 37, 0@};
9979 printf ("Hello, world!\n");
9983 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9984 containing the string @samp{Hello, world!} followed by a newline,
9985 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9987 We compile the program, and invoke the debugger on it:
9990 $ gcc -g charset-test.c -o charset-test
9991 $ gdb -nw charset-test
9992 GNU gdb 2001-12-19-cvs
9993 Copyright 2001 Free Software Foundation, Inc.
9998 We can use the @code{show charset} command to see what character sets
9999 @value{GDBN} is currently using to interpret and display characters and
10003 (@value{GDBP}) show charset
10004 The current host and target character set is `ISO-8859-1'.
10008 For the sake of printing this manual, let's use @sc{ascii} as our
10009 initial character set:
10011 (@value{GDBP}) set charset ASCII
10012 (@value{GDBP}) show charset
10013 The current host and target character set is `ASCII'.
10017 Let's assume that @sc{ascii} is indeed the correct character set for our
10018 host system --- in other words, let's assume that if @value{GDBN} prints
10019 characters using the @sc{ascii} character set, our terminal will display
10020 them properly. Since our current target character set is also
10021 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10024 (@value{GDBP}) print ascii_hello
10025 $1 = 0x401698 "Hello, world!\n"
10026 (@value{GDBP}) print ascii_hello[0]
10031 @value{GDBN} uses the target character set for character and string
10032 literals you use in expressions:
10035 (@value{GDBP}) print '+'
10040 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10043 @value{GDBN} relies on the user to tell it which character set the
10044 target program uses. If we print @code{ibm1047_hello} while our target
10045 character set is still @sc{ascii}, we get jibberish:
10048 (@value{GDBP}) print ibm1047_hello
10049 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10050 (@value{GDBP}) print ibm1047_hello[0]
10055 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10056 @value{GDBN} tells us the character sets it supports:
10059 (@value{GDBP}) set target-charset
10060 ASCII EBCDIC-US IBM1047 ISO-8859-1
10061 (@value{GDBP}) set target-charset
10064 We can select @sc{ibm1047} as our target character set, and examine the
10065 program's strings again. Now the @sc{ascii} string is wrong, but
10066 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10067 target character set, @sc{ibm1047}, to the host character set,
10068 @sc{ascii}, and they display correctly:
10071 (@value{GDBP}) set target-charset IBM1047
10072 (@value{GDBP}) show charset
10073 The current host character set is `ASCII'.
10074 The current target character set is `IBM1047'.
10075 (@value{GDBP}) print ascii_hello
10076 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10077 (@value{GDBP}) print ascii_hello[0]
10079 (@value{GDBP}) print ibm1047_hello
10080 $8 = 0x4016a8 "Hello, world!\n"
10081 (@value{GDBP}) print ibm1047_hello[0]
10086 As above, @value{GDBN} uses the target character set for character and
10087 string literals you use in expressions:
10090 (@value{GDBP}) print '+'
10095 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10098 @node Caching Remote Data
10099 @section Caching Data of Remote Targets
10100 @cindex caching data of remote targets
10102 @value{GDBN} caches data exchanged between the debugger and a
10103 remote target (@pxref{Remote Debugging}). Such caching generally improves
10104 performance, because it reduces the overhead of the remote protocol by
10105 bundling memory reads and writes into large chunks. Unfortunately, simply
10106 caching everything would lead to incorrect results, since @value{GDBN}
10107 does not necessarily know anything about volatile values, memory-mapped I/O
10108 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10109 memory can be changed @emph{while} a gdb command is executing.
10110 Therefore, by default, @value{GDBN} only caches data
10111 known to be on the stack@footnote{In non-stop mode, it is moderately
10112 rare for a running thread to modify the stack of a stopped thread
10113 in a way that would interfere with a backtrace, and caching of
10114 stack reads provides a significant speed up of remote backtraces.}.
10115 Other regions of memory can be explicitly marked as
10116 cacheable; see @pxref{Memory Region Attributes}.
10119 @kindex set remotecache
10120 @item set remotecache on
10121 @itemx set remotecache off
10122 This option no longer does anything; it exists for compatibility
10125 @kindex show remotecache
10126 @item show remotecache
10127 Show the current state of the obsolete remotecache flag.
10129 @kindex set stack-cache
10130 @item set stack-cache on
10131 @itemx set stack-cache off
10132 Enable or disable caching of stack accesses. When @code{ON}, use
10133 caching. By default, this option is @code{ON}.
10135 @kindex show stack-cache
10136 @item show stack-cache
10137 Show the current state of data caching for memory accesses.
10139 @kindex info dcache
10140 @item info dcache @r{[}line@r{]}
10141 Print the information about the data cache performance. The
10142 information displayed includes the dcache width and depth, and for
10143 each cache line, its number, address, and how many times it was
10144 referenced. This command is useful for debugging the data cache
10147 If a line number is specified, the contents of that line will be
10150 @item set dcache size @var{size}
10151 @cindex dcache size
10152 @kindex set dcache size
10153 Set maximum number of entries in dcache (dcache depth above).
10155 @item set dcache line-size @var{line-size}
10156 @cindex dcache line-size
10157 @kindex set dcache line-size
10158 Set number of bytes each dcache entry caches (dcache width above).
10159 Must be a power of 2.
10161 @item show dcache size
10162 @kindex show dcache size
10163 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10165 @item show dcache line-size
10166 @kindex show dcache line-size
10167 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10171 @node Searching Memory
10172 @section Search Memory
10173 @cindex searching memory
10175 Memory can be searched for a particular sequence of bytes with the
10176 @code{find} command.
10180 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10181 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10182 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10183 etc. The search begins at address @var{start_addr} and continues for either
10184 @var{len} bytes or through to @var{end_addr} inclusive.
10187 @var{s} and @var{n} are optional parameters.
10188 They may be specified in either order, apart or together.
10191 @item @var{s}, search query size
10192 The size of each search query value.
10198 halfwords (two bytes)
10202 giant words (eight bytes)
10205 All values are interpreted in the current language.
10206 This means, for example, that if the current source language is C/C@t{++}
10207 then searching for the string ``hello'' includes the trailing '\0'.
10209 If the value size is not specified, it is taken from the
10210 value's type in the current language.
10211 This is useful when one wants to specify the search
10212 pattern as a mixture of types.
10213 Note that this means, for example, that in the case of C-like languages
10214 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10215 which is typically four bytes.
10217 @item @var{n}, maximum number of finds
10218 The maximum number of matches to print. The default is to print all finds.
10221 You can use strings as search values. Quote them with double-quotes
10223 The string value is copied into the search pattern byte by byte,
10224 regardless of the endianness of the target and the size specification.
10226 The address of each match found is printed as well as a count of the
10227 number of matches found.
10229 The address of the last value found is stored in convenience variable
10231 A count of the number of matches is stored in @samp{$numfound}.
10233 For example, if stopped at the @code{printf} in this function:
10239 static char hello[] = "hello-hello";
10240 static struct @{ char c; short s; int i; @}
10241 __attribute__ ((packed)) mixed
10242 = @{ 'c', 0x1234, 0x87654321 @};
10243 printf ("%s\n", hello);
10248 you get during debugging:
10251 (gdb) find &hello[0], +sizeof(hello), "hello"
10252 0x804956d <hello.1620+6>
10254 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10255 0x8049567 <hello.1620>
10256 0x804956d <hello.1620+6>
10258 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10259 0x8049567 <hello.1620>
10261 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10262 0x8049560 <mixed.1625>
10264 (gdb) print $numfound
10267 $2 = (void *) 0x8049560
10270 @node Optimized Code
10271 @chapter Debugging Optimized Code
10272 @cindex optimized code, debugging
10273 @cindex debugging optimized code
10275 Almost all compilers support optimization. With optimization
10276 disabled, the compiler generates assembly code that corresponds
10277 directly to your source code, in a simplistic way. As the compiler
10278 applies more powerful optimizations, the generated assembly code
10279 diverges from your original source code. With help from debugging
10280 information generated by the compiler, @value{GDBN} can map from
10281 the running program back to constructs from your original source.
10283 @value{GDBN} is more accurate with optimization disabled. If you
10284 can recompile without optimization, it is easier to follow the
10285 progress of your program during debugging. But, there are many cases
10286 where you may need to debug an optimized version.
10288 When you debug a program compiled with @samp{-g -O}, remember that the
10289 optimizer has rearranged your code; the debugger shows you what is
10290 really there. Do not be too surprised when the execution path does not
10291 exactly match your source file! An extreme example: if you define a
10292 variable, but never use it, @value{GDBN} never sees that
10293 variable---because the compiler optimizes it out of existence.
10295 Some things do not work as well with @samp{-g -O} as with just
10296 @samp{-g}, particularly on machines with instruction scheduling. If in
10297 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10298 please report it to us as a bug (including a test case!).
10299 @xref{Variables}, for more information about debugging optimized code.
10302 * Inline Functions:: How @value{GDBN} presents inlining
10303 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10306 @node Inline Functions
10307 @section Inline Functions
10308 @cindex inline functions, debugging
10310 @dfn{Inlining} is an optimization that inserts a copy of the function
10311 body directly at each call site, instead of jumping to a shared
10312 routine. @value{GDBN} displays inlined functions just like
10313 non-inlined functions. They appear in backtraces. You can view their
10314 arguments and local variables, step into them with @code{step}, skip
10315 them with @code{next}, and escape from them with @code{finish}.
10316 You can check whether a function was inlined by using the
10317 @code{info frame} command.
10319 For @value{GDBN} to support inlined functions, the compiler must
10320 record information about inlining in the debug information ---
10321 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10322 other compilers do also. @value{GDBN} only supports inlined functions
10323 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10324 do not emit two required attributes (@samp{DW_AT_call_file} and
10325 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10326 function calls with earlier versions of @value{NGCC}. It instead
10327 displays the arguments and local variables of inlined functions as
10328 local variables in the caller.
10330 The body of an inlined function is directly included at its call site;
10331 unlike a non-inlined function, there are no instructions devoted to
10332 the call. @value{GDBN} still pretends that the call site and the
10333 start of the inlined function are different instructions. Stepping to
10334 the call site shows the call site, and then stepping again shows
10335 the first line of the inlined function, even though no additional
10336 instructions are executed.
10338 This makes source-level debugging much clearer; you can see both the
10339 context of the call and then the effect of the call. Only stepping by
10340 a single instruction using @code{stepi} or @code{nexti} does not do
10341 this; single instruction steps always show the inlined body.
10343 There are some ways that @value{GDBN} does not pretend that inlined
10344 function calls are the same as normal calls:
10348 Setting breakpoints at the call site of an inlined function may not
10349 work, because the call site does not contain any code. @value{GDBN}
10350 may incorrectly move the breakpoint to the next line of the enclosing
10351 function, after the call. This limitation will be removed in a future
10352 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10353 or inside the inlined function instead.
10356 @value{GDBN} cannot locate the return value of inlined calls after
10357 using the @code{finish} command. This is a limitation of compiler-generated
10358 debugging information; after @code{finish}, you can step to the next line
10359 and print a variable where your program stored the return value.
10363 @node Tail Call Frames
10364 @section Tail Call Frames
10365 @cindex tail call frames, debugging
10367 Function @code{B} can call function @code{C} in its very last statement. In
10368 unoptimized compilation the call of @code{C} is immediately followed by return
10369 instruction at the end of @code{B} code. Optimizing compiler may replace the
10370 call and return in function @code{B} into one jump to function @code{C}
10371 instead. Such use of a jump instruction is called @dfn{tail call}.
10373 During execution of function @code{C}, there will be no indication in the
10374 function call stack frames that it was tail-called from @code{B}. If function
10375 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10376 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10377 some cases @value{GDBN} can determine that @code{C} was tail-called from
10378 @code{B}, and it will then create fictitious call frame for that, with the
10379 return address set up as if @code{B} called @code{C} normally.
10381 This functionality is currently supported only by DWARF 2 debugging format and
10382 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10383 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10386 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10387 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10391 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10393 Stack level 1, frame at 0x7fffffffda30:
10394 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10395 tail call frame, caller of frame at 0x7fffffffda30
10396 source language c++.
10397 Arglist at unknown address.
10398 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10401 The detection of all the possible code path executions can find them ambiguous.
10402 There is no execution history stored (possible @ref{Reverse Execution} is never
10403 used for this purpose) and the last known caller could have reached the known
10404 callee by multiple different jump sequences. In such case @value{GDBN} still
10405 tries to show at least all the unambiguous top tail callers and all the
10406 unambiguous bottom tail calees, if any.
10409 @anchor{set debug entry-values}
10410 @item set debug entry-values
10411 @kindex set debug entry-values
10412 When set to on, enables printing of analysis messages for both frame argument
10413 values at function entry and tail calls. It will show all the possible valid
10414 tail calls code paths it has considered. It will also print the intersection
10415 of them with the final unambiguous (possibly partial or even empty) code path
10418 @item show debug entry-values
10419 @kindex show debug entry-values
10420 Show the current state of analysis messages printing for both frame argument
10421 values at function entry and tail calls.
10424 The analysis messages for tail calls can for example show why the virtual tail
10425 call frame for function @code{c} has not been recognized (due to the indirect
10426 reference by variable @code{x}):
10429 static void __attribute__((noinline, noclone)) c (void);
10430 void (*x) (void) = c;
10431 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10432 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10433 int main (void) @{ x (); return 0; @}
10435 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10436 DW_TAG_GNU_call_site 0x40039a in main
10438 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10441 #1 0x000000000040039a in main () at t.c:5
10444 Another possibility is an ambiguous virtual tail call frames resolution:
10448 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10449 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10450 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10451 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10452 static void __attribute__((noinline, noclone)) b (void)
10453 @{ if (i) c (); else e (); @}
10454 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10455 int main (void) @{ a (); return 0; @}
10457 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10458 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10459 tailcall: reduced: 0x4004d2(a) |
10462 #1 0x00000000004004d2 in a () at t.c:8
10463 #2 0x0000000000400395 in main () at t.c:9
10466 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10467 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10469 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10470 @ifset HAVE_MAKEINFO_CLICK
10471 @set ARROW @click{}
10472 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10473 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10475 @ifclear HAVE_MAKEINFO_CLICK
10477 @set CALLSEQ1B @value{CALLSEQ1A}
10478 @set CALLSEQ2B @value{CALLSEQ2A}
10481 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10482 The code can have possible execution paths @value{CALLSEQ1B} or
10483 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10485 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10486 has found. It then finds another possible calling sequcen - that one is
10487 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10488 printed as the @code{reduced:} calling sequence. That one could have many
10489 futher @code{compare:} and @code{reduced:} statements as long as there remain
10490 any non-ambiguous sequence entries.
10492 For the frame of function @code{b} in both cases there are different possible
10493 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10494 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10495 therefore this one is displayed to the user while the ambiguous frames are
10498 There can be also reasons why printing of frame argument values at function
10503 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10504 static void __attribute__((noinline, noclone)) a (int i);
10505 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10506 static void __attribute__((noinline, noclone)) a (int i)
10507 @{ if (i) b (i - 1); else c (0); @}
10508 int main (void) @{ a (5); return 0; @}
10511 #0 c (i=i@@entry=0) at t.c:2
10512 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10513 function "a" at 0x400420 can call itself via tail calls
10514 i=<optimized out>) at t.c:6
10515 #2 0x000000000040036e in main () at t.c:7
10518 @value{GDBN} cannot find out from the inferior state if and how many times did
10519 function @code{a} call itself (via function @code{b}) as these calls would be
10520 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10521 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10522 prints @code{<optimized out>} instead.
10525 @chapter C Preprocessor Macros
10527 Some languages, such as C and C@t{++}, provide a way to define and invoke
10528 ``preprocessor macros'' which expand into strings of tokens.
10529 @value{GDBN} can evaluate expressions containing macro invocations, show
10530 the result of macro expansion, and show a macro's definition, including
10531 where it was defined.
10533 You may need to compile your program specially to provide @value{GDBN}
10534 with information about preprocessor macros. Most compilers do not
10535 include macros in their debugging information, even when you compile
10536 with the @option{-g} flag. @xref{Compilation}.
10538 A program may define a macro at one point, remove that definition later,
10539 and then provide a different definition after that. Thus, at different
10540 points in the program, a macro may have different definitions, or have
10541 no definition at all. If there is a current stack frame, @value{GDBN}
10542 uses the macros in scope at that frame's source code line. Otherwise,
10543 @value{GDBN} uses the macros in scope at the current listing location;
10546 Whenever @value{GDBN} evaluates an expression, it always expands any
10547 macro invocations present in the expression. @value{GDBN} also provides
10548 the following commands for working with macros explicitly.
10552 @kindex macro expand
10553 @cindex macro expansion, showing the results of preprocessor
10554 @cindex preprocessor macro expansion, showing the results of
10555 @cindex expanding preprocessor macros
10556 @item macro expand @var{expression}
10557 @itemx macro exp @var{expression}
10558 Show the results of expanding all preprocessor macro invocations in
10559 @var{expression}. Since @value{GDBN} simply expands macros, but does
10560 not parse the result, @var{expression} need not be a valid expression;
10561 it can be any string of tokens.
10564 @item macro expand-once @var{expression}
10565 @itemx macro exp1 @var{expression}
10566 @cindex expand macro once
10567 @i{(This command is not yet implemented.)} Show the results of
10568 expanding those preprocessor macro invocations that appear explicitly in
10569 @var{expression}. Macro invocations appearing in that expansion are
10570 left unchanged. This command allows you to see the effect of a
10571 particular macro more clearly, without being confused by further
10572 expansions. Since @value{GDBN} simply expands macros, but does not
10573 parse the result, @var{expression} need not be a valid expression; it
10574 can be any string of tokens.
10577 @cindex macro definition, showing
10578 @cindex definition of a macro, showing
10579 @cindex macros, from debug info
10580 @item info macro [-a|-all] [--] @var{macro}
10581 Show the current definition or all definitions of the named @var{macro},
10582 and describe the source location or compiler command-line where that
10583 definition was established. The optional double dash is to signify the end of
10584 argument processing and the beginning of @var{macro} for non C-like macros where
10585 the macro may begin with a hyphen.
10587 @kindex info macros
10588 @item info macros @var{linespec}
10589 Show all macro definitions that are in effect at the location specified
10590 by @var{linespec}, and describe the source location or compiler
10591 command-line where those definitions were established.
10593 @kindex macro define
10594 @cindex user-defined macros
10595 @cindex defining macros interactively
10596 @cindex macros, user-defined
10597 @item macro define @var{macro} @var{replacement-list}
10598 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10599 Introduce a definition for a preprocessor macro named @var{macro},
10600 invocations of which are replaced by the tokens given in
10601 @var{replacement-list}. The first form of this command defines an
10602 ``object-like'' macro, which takes no arguments; the second form
10603 defines a ``function-like'' macro, which takes the arguments given in
10606 A definition introduced by this command is in scope in every
10607 expression evaluated in @value{GDBN}, until it is removed with the
10608 @code{macro undef} command, described below. The definition overrides
10609 all definitions for @var{macro} present in the program being debugged,
10610 as well as any previous user-supplied definition.
10612 @kindex macro undef
10613 @item macro undef @var{macro}
10614 Remove any user-supplied definition for the macro named @var{macro}.
10615 This command only affects definitions provided with the @code{macro
10616 define} command, described above; it cannot remove definitions present
10617 in the program being debugged.
10621 List all the macros defined using the @code{macro define} command.
10624 @cindex macros, example of debugging with
10625 Here is a transcript showing the above commands in action. First, we
10626 show our source files:
10631 #include "sample.h"
10634 #define ADD(x) (M + x)
10639 printf ("Hello, world!\n");
10641 printf ("We're so creative.\n");
10643 printf ("Goodbye, world!\n");
10650 Now, we compile the program using the @sc{gnu} C compiler,
10651 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10652 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10653 and @option{-gdwarf-4}; we recommend always choosing the most recent
10654 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10655 includes information about preprocessor macros in the debugging
10659 $ gcc -gdwarf-2 -g3 sample.c -o sample
10663 Now, we start @value{GDBN} on our sample program:
10667 GNU gdb 2002-05-06-cvs
10668 Copyright 2002 Free Software Foundation, Inc.
10669 GDB is free software, @dots{}
10673 We can expand macros and examine their definitions, even when the
10674 program is not running. @value{GDBN} uses the current listing position
10675 to decide which macro definitions are in scope:
10678 (@value{GDBP}) list main
10681 5 #define ADD(x) (M + x)
10686 10 printf ("Hello, world!\n");
10688 12 printf ("We're so creative.\n");
10689 (@value{GDBP}) info macro ADD
10690 Defined at /home/jimb/gdb/macros/play/sample.c:5
10691 #define ADD(x) (M + x)
10692 (@value{GDBP}) info macro Q
10693 Defined at /home/jimb/gdb/macros/play/sample.h:1
10694 included at /home/jimb/gdb/macros/play/sample.c:2
10696 (@value{GDBP}) macro expand ADD(1)
10697 expands to: (42 + 1)
10698 (@value{GDBP}) macro expand-once ADD(1)
10699 expands to: once (M + 1)
10703 In the example above, note that @code{macro expand-once} expands only
10704 the macro invocation explicit in the original text --- the invocation of
10705 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10706 which was introduced by @code{ADD}.
10708 Once the program is running, @value{GDBN} uses the macro definitions in
10709 force at the source line of the current stack frame:
10712 (@value{GDBP}) break main
10713 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10715 Starting program: /home/jimb/gdb/macros/play/sample
10717 Breakpoint 1, main () at sample.c:10
10718 10 printf ("Hello, world!\n");
10722 At line 10, the definition of the macro @code{N} at line 9 is in force:
10725 (@value{GDBP}) info macro N
10726 Defined at /home/jimb/gdb/macros/play/sample.c:9
10728 (@value{GDBP}) macro expand N Q M
10729 expands to: 28 < 42
10730 (@value{GDBP}) print N Q M
10735 As we step over directives that remove @code{N}'s definition, and then
10736 give it a new definition, @value{GDBN} finds the definition (or lack
10737 thereof) in force at each point:
10740 (@value{GDBP}) next
10742 12 printf ("We're so creative.\n");
10743 (@value{GDBP}) info macro N
10744 The symbol `N' has no definition as a C/C++ preprocessor macro
10745 at /home/jimb/gdb/macros/play/sample.c:12
10746 (@value{GDBP}) next
10748 14 printf ("Goodbye, world!\n");
10749 (@value{GDBP}) info macro N
10750 Defined at /home/jimb/gdb/macros/play/sample.c:13
10752 (@value{GDBP}) macro expand N Q M
10753 expands to: 1729 < 42
10754 (@value{GDBP}) print N Q M
10759 In addition to source files, macros can be defined on the compilation command
10760 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10761 such a way, @value{GDBN} displays the location of their definition as line zero
10762 of the source file submitted to the compiler.
10765 (@value{GDBP}) info macro __STDC__
10766 Defined at /home/jimb/gdb/macros/play/sample.c:0
10773 @chapter Tracepoints
10774 @c This chapter is based on the documentation written by Michael
10775 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10777 @cindex tracepoints
10778 In some applications, it is not feasible for the debugger to interrupt
10779 the program's execution long enough for the developer to learn
10780 anything helpful about its behavior. If the program's correctness
10781 depends on its real-time behavior, delays introduced by a debugger
10782 might cause the program to change its behavior drastically, or perhaps
10783 fail, even when the code itself is correct. It is useful to be able
10784 to observe the program's behavior without interrupting it.
10786 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10787 specify locations in the program, called @dfn{tracepoints}, and
10788 arbitrary expressions to evaluate when those tracepoints are reached.
10789 Later, using the @code{tfind} command, you can examine the values
10790 those expressions had when the program hit the tracepoints. The
10791 expressions may also denote objects in memory---structures or arrays,
10792 for example---whose values @value{GDBN} should record; while visiting
10793 a particular tracepoint, you may inspect those objects as if they were
10794 in memory at that moment. However, because @value{GDBN} records these
10795 values without interacting with you, it can do so quickly and
10796 unobtrusively, hopefully not disturbing the program's behavior.
10798 The tracepoint facility is currently available only for remote
10799 targets. @xref{Targets}. In addition, your remote target must know
10800 how to collect trace data. This functionality is implemented in the
10801 remote stub; however, none of the stubs distributed with @value{GDBN}
10802 support tracepoints as of this writing. The format of the remote
10803 packets used to implement tracepoints are described in @ref{Tracepoint
10806 It is also possible to get trace data from a file, in a manner reminiscent
10807 of corefiles; you specify the filename, and use @code{tfind} to search
10808 through the file. @xref{Trace Files}, for more details.
10810 This chapter describes the tracepoint commands and features.
10813 * Set Tracepoints::
10814 * Analyze Collected Data::
10815 * Tracepoint Variables::
10819 @node Set Tracepoints
10820 @section Commands to Set Tracepoints
10822 Before running such a @dfn{trace experiment}, an arbitrary number of
10823 tracepoints can be set. A tracepoint is actually a special type of
10824 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10825 standard breakpoint commands. For instance, as with breakpoints,
10826 tracepoint numbers are successive integers starting from one, and many
10827 of the commands associated with tracepoints take the tracepoint number
10828 as their argument, to identify which tracepoint to work on.
10830 For each tracepoint, you can specify, in advance, some arbitrary set
10831 of data that you want the target to collect in the trace buffer when
10832 it hits that tracepoint. The collected data can include registers,
10833 local variables, or global data. Later, you can use @value{GDBN}
10834 commands to examine the values these data had at the time the
10835 tracepoint was hit.
10837 Tracepoints do not support every breakpoint feature. Ignore counts on
10838 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10839 commands when they are hit. Tracepoints may not be thread-specific
10842 @cindex fast tracepoints
10843 Some targets may support @dfn{fast tracepoints}, which are inserted in
10844 a different way (such as with a jump instead of a trap), that is
10845 faster but possibly restricted in where they may be installed.
10847 @cindex static tracepoints
10848 @cindex markers, static tracepoints
10849 @cindex probing markers, static tracepoints
10850 Regular and fast tracepoints are dynamic tracing facilities, meaning
10851 that they can be used to insert tracepoints at (almost) any location
10852 in the target. Some targets may also support controlling @dfn{static
10853 tracepoints} from @value{GDBN}. With static tracing, a set of
10854 instrumentation points, also known as @dfn{markers}, are embedded in
10855 the target program, and can be activated or deactivated by name or
10856 address. These are usually placed at locations which facilitate
10857 investigating what the target is actually doing. @value{GDBN}'s
10858 support for static tracing includes being able to list instrumentation
10859 points, and attach them with @value{GDBN} defined high level
10860 tracepoints that expose the whole range of convenience of
10861 @value{GDBN}'s tracepoints support. Namely, support for collecting
10862 registers values and values of global or local (to the instrumentation
10863 point) variables; tracepoint conditions and trace state variables.
10864 The act of installing a @value{GDBN} static tracepoint on an
10865 instrumentation point, or marker, is referred to as @dfn{probing} a
10866 static tracepoint marker.
10868 @code{gdbserver} supports tracepoints on some target systems.
10869 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10871 This section describes commands to set tracepoints and associated
10872 conditions and actions.
10875 * Create and Delete Tracepoints::
10876 * Enable and Disable Tracepoints::
10877 * Tracepoint Passcounts::
10878 * Tracepoint Conditions::
10879 * Trace State Variables::
10880 * Tracepoint Actions::
10881 * Listing Tracepoints::
10882 * Listing Static Tracepoint Markers::
10883 * Starting and Stopping Trace Experiments::
10884 * Tracepoint Restrictions::
10887 @node Create and Delete Tracepoints
10888 @subsection Create and Delete Tracepoints
10891 @cindex set tracepoint
10893 @item trace @var{location}
10894 The @code{trace} command is very similar to the @code{break} command.
10895 Its argument @var{location} can be a source line, a function name, or
10896 an address in the target program. @xref{Specify Location}. The
10897 @code{trace} command defines a tracepoint, which is a point in the
10898 target program where the debugger will briefly stop, collect some
10899 data, and then allow the program to continue. Setting a tracepoint or
10900 changing its actions takes effect immediately if the remote stub
10901 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10903 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10904 these changes don't take effect until the next @code{tstart}
10905 command, and once a trace experiment is running, further changes will
10906 not have any effect until the next trace experiment starts. In addition,
10907 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10908 address is not yet resolved. (This is similar to pending breakpoints.)
10909 Pending tracepoints are not downloaded to the target and not installed
10910 until they are resolved. The resolution of pending tracepoints requires
10911 @value{GDBN} support---when debugging with the remote target, and
10912 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10913 tracing}), pending tracepoints can not be resolved (and downloaded to
10914 the remote stub) while @value{GDBN} is disconnected.
10916 Here are some examples of using the @code{trace} command:
10919 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10921 (@value{GDBP}) @b{trace +2} // 2 lines forward
10923 (@value{GDBP}) @b{trace my_function} // first source line of function
10925 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10927 (@value{GDBP}) @b{trace *0x2117c4} // an address
10931 You can abbreviate @code{trace} as @code{tr}.
10933 @item trace @var{location} if @var{cond}
10934 Set a tracepoint with condition @var{cond}; evaluate the expression
10935 @var{cond} each time the tracepoint is reached, and collect data only
10936 if the value is nonzero---that is, if @var{cond} evaluates as true.
10937 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10938 information on tracepoint conditions.
10940 @item ftrace @var{location} [ if @var{cond} ]
10941 @cindex set fast tracepoint
10942 @cindex fast tracepoints, setting
10944 The @code{ftrace} command sets a fast tracepoint. For targets that
10945 support them, fast tracepoints will use a more efficient but possibly
10946 less general technique to trigger data collection, such as a jump
10947 instruction instead of a trap, or some sort of hardware support. It
10948 may not be possible to create a fast tracepoint at the desired
10949 location, in which case the command will exit with an explanatory
10952 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10955 On 32-bit x86-architecture systems, fast tracepoints normally need to
10956 be placed at an instruction that is 5 bytes or longer, but can be
10957 placed at 4-byte instructions if the low 64K of memory of the target
10958 program is available to install trampolines. Some Unix-type systems,
10959 such as @sc{gnu}/Linux, exclude low addresses from the program's
10960 address space; but for instance with the Linux kernel it is possible
10961 to let @value{GDBN} use this area by doing a @command{sysctl} command
10962 to set the @code{mmap_min_addr} kernel parameter, as in
10965 sudo sysctl -w vm.mmap_min_addr=32768
10969 which sets the low address to 32K, which leaves plenty of room for
10970 trampolines. The minimum address should be set to a page boundary.
10972 @item strace @var{location} [ if @var{cond} ]
10973 @cindex set static tracepoint
10974 @cindex static tracepoints, setting
10975 @cindex probe static tracepoint marker
10977 The @code{strace} command sets a static tracepoint. For targets that
10978 support it, setting a static tracepoint probes a static
10979 instrumentation point, or marker, found at @var{location}. It may not
10980 be possible to set a static tracepoint at the desired location, in
10981 which case the command will exit with an explanatory message.
10983 @value{GDBN} handles arguments to @code{strace} exactly as for
10984 @code{trace}, with the addition that the user can also specify
10985 @code{-m @var{marker}} as @var{location}. This probes the marker
10986 identified by the @var{marker} string identifier. This identifier
10987 depends on the static tracepoint backend library your program is
10988 using. You can find all the marker identifiers in the @samp{ID} field
10989 of the @code{info static-tracepoint-markers} command output.
10990 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10991 Markers}. For example, in the following small program using the UST
10997 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11002 the marker id is composed of joining the first two arguments to the
11003 @code{trace_mark} call with a slash, which translates to:
11006 (@value{GDBP}) info static-tracepoint-markers
11007 Cnt Enb ID Address What
11008 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11014 so you may probe the marker above with:
11017 (@value{GDBP}) strace -m ust/bar33
11020 Static tracepoints accept an extra collect action --- @code{collect
11021 $_sdata}. This collects arbitrary user data passed in the probe point
11022 call to the tracing library. In the UST example above, you'll see
11023 that the third argument to @code{trace_mark} is a printf-like format
11024 string. The user data is then the result of running that formating
11025 string against the following arguments. Note that @code{info
11026 static-tracepoint-markers} command output lists that format string in
11027 the @samp{Data:} field.
11029 You can inspect this data when analyzing the trace buffer, by printing
11030 the $_sdata variable like any other variable available to
11031 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11034 @cindex last tracepoint number
11035 @cindex recent tracepoint number
11036 @cindex tracepoint number
11037 The convenience variable @code{$tpnum} records the tracepoint number
11038 of the most recently set tracepoint.
11040 @kindex delete tracepoint
11041 @cindex tracepoint deletion
11042 @item delete tracepoint @r{[}@var{num}@r{]}
11043 Permanently delete one or more tracepoints. With no argument, the
11044 default is to delete all tracepoints. Note that the regular
11045 @code{delete} command can remove tracepoints also.
11050 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11052 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11056 You can abbreviate this command as @code{del tr}.
11059 @node Enable and Disable Tracepoints
11060 @subsection Enable and Disable Tracepoints
11062 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11065 @kindex disable tracepoint
11066 @item disable tracepoint @r{[}@var{num}@r{]}
11067 Disable tracepoint @var{num}, or all tracepoints if no argument
11068 @var{num} is given. A disabled tracepoint will have no effect during
11069 a trace experiment, but it is not forgotten. You can re-enable
11070 a disabled tracepoint using the @code{enable tracepoint} command.
11071 If the command is issued during a trace experiment and the debug target
11072 has support for disabling tracepoints during a trace experiment, then the
11073 change will be effective immediately. Otherwise, it will be applied to the
11074 next trace experiment.
11076 @kindex enable tracepoint
11077 @item enable tracepoint @r{[}@var{num}@r{]}
11078 Enable tracepoint @var{num}, or all tracepoints. If this command is
11079 issued during a trace experiment and the debug target supports enabling
11080 tracepoints during a trace experiment, then the enabled tracepoints will
11081 become effective immediately. Otherwise, they will become effective the
11082 next time a trace experiment is run.
11085 @node Tracepoint Passcounts
11086 @subsection Tracepoint Passcounts
11090 @cindex tracepoint pass count
11091 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11092 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11093 automatically stop a trace experiment. If a tracepoint's passcount is
11094 @var{n}, then the trace experiment will be automatically stopped on
11095 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11096 @var{num} is not specified, the @code{passcount} command sets the
11097 passcount of the most recently defined tracepoint. If no passcount is
11098 given, the trace experiment will run until stopped explicitly by the
11104 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11105 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11107 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11108 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11109 (@value{GDBP}) @b{trace foo}
11110 (@value{GDBP}) @b{pass 3}
11111 (@value{GDBP}) @b{trace bar}
11112 (@value{GDBP}) @b{pass 2}
11113 (@value{GDBP}) @b{trace baz}
11114 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11115 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11116 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11117 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11121 @node Tracepoint Conditions
11122 @subsection Tracepoint Conditions
11123 @cindex conditional tracepoints
11124 @cindex tracepoint conditions
11126 The simplest sort of tracepoint collects data every time your program
11127 reaches a specified place. You can also specify a @dfn{condition} for
11128 a tracepoint. A condition is just a Boolean expression in your
11129 programming language (@pxref{Expressions, ,Expressions}). A
11130 tracepoint with a condition evaluates the expression each time your
11131 program reaches it, and data collection happens only if the condition
11134 Tracepoint conditions can be specified when a tracepoint is set, by
11135 using @samp{if} in the arguments to the @code{trace} command.
11136 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11137 also be set or changed at any time with the @code{condition} command,
11138 just as with breakpoints.
11140 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11141 the conditional expression itself. Instead, @value{GDBN} encodes the
11142 expression into an agent expression (@pxref{Agent Expressions})
11143 suitable for execution on the target, independently of @value{GDBN}.
11144 Global variables become raw memory locations, locals become stack
11145 accesses, and so forth.
11147 For instance, suppose you have a function that is usually called
11148 frequently, but should not be called after an error has occurred. You
11149 could use the following tracepoint command to collect data about calls
11150 of that function that happen while the error code is propagating
11151 through the program; an unconditional tracepoint could end up
11152 collecting thousands of useless trace frames that you would have to
11156 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11159 @node Trace State Variables
11160 @subsection Trace State Variables
11161 @cindex trace state variables
11163 A @dfn{trace state variable} is a special type of variable that is
11164 created and managed by target-side code. The syntax is the same as
11165 that for GDB's convenience variables (a string prefixed with ``$''),
11166 but they are stored on the target. They must be created explicitly,
11167 using a @code{tvariable} command. They are always 64-bit signed
11170 Trace state variables are remembered by @value{GDBN}, and downloaded
11171 to the target along with tracepoint information when the trace
11172 experiment starts. There are no intrinsic limits on the number of
11173 trace state variables, beyond memory limitations of the target.
11175 @cindex convenience variables, and trace state variables
11176 Although trace state variables are managed by the target, you can use
11177 them in print commands and expressions as if they were convenience
11178 variables; @value{GDBN} will get the current value from the target
11179 while the trace experiment is running. Trace state variables share
11180 the same namespace as other ``$'' variables, which means that you
11181 cannot have trace state variables with names like @code{$23} or
11182 @code{$pc}, nor can you have a trace state variable and a convenience
11183 variable with the same name.
11187 @item tvariable $@var{name} [ = @var{expression} ]
11189 The @code{tvariable} command creates a new trace state variable named
11190 @code{$@var{name}}, and optionally gives it an initial value of
11191 @var{expression}. @var{expression} is evaluated when this command is
11192 entered; the result will be converted to an integer if possible,
11193 otherwise @value{GDBN} will report an error. A subsequent
11194 @code{tvariable} command specifying the same name does not create a
11195 variable, but instead assigns the supplied initial value to the
11196 existing variable of that name, overwriting any previous initial
11197 value. The default initial value is 0.
11199 @item info tvariables
11200 @kindex info tvariables
11201 List all the trace state variables along with their initial values.
11202 Their current values may also be displayed, if the trace experiment is
11205 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11206 @kindex delete tvariable
11207 Delete the given trace state variables, or all of them if no arguments
11212 @node Tracepoint Actions
11213 @subsection Tracepoint Action Lists
11217 @cindex tracepoint actions
11218 @item actions @r{[}@var{num}@r{]}
11219 This command will prompt for a list of actions to be taken when the
11220 tracepoint is hit. If the tracepoint number @var{num} is not
11221 specified, this command sets the actions for the one that was most
11222 recently defined (so that you can define a tracepoint and then say
11223 @code{actions} without bothering about its number). You specify the
11224 actions themselves on the following lines, one action at a time, and
11225 terminate the actions list with a line containing just @code{end}. So
11226 far, the only defined actions are @code{collect}, @code{teval}, and
11227 @code{while-stepping}.
11229 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11230 Commands, ,Breakpoint Command Lists}), except that only the defined
11231 actions are allowed; any other @value{GDBN} command is rejected.
11233 @cindex remove actions from a tracepoint
11234 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11235 and follow it immediately with @samp{end}.
11238 (@value{GDBP}) @b{collect @var{data}} // collect some data
11240 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11242 (@value{GDBP}) @b{end} // signals the end of actions.
11245 In the following example, the action list begins with @code{collect}
11246 commands indicating the things to be collected when the tracepoint is
11247 hit. Then, in order to single-step and collect additional data
11248 following the tracepoint, a @code{while-stepping} command is used,
11249 followed by the list of things to be collected after each step in a
11250 sequence of single steps. The @code{while-stepping} command is
11251 terminated by its own separate @code{end} command. Lastly, the action
11252 list is terminated by an @code{end} command.
11255 (@value{GDBP}) @b{trace foo}
11256 (@value{GDBP}) @b{actions}
11257 Enter actions for tracepoint 1, one per line:
11260 > while-stepping 12
11261 > collect $pc, arr[i]
11266 @kindex collect @r{(tracepoints)}
11267 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11268 Collect values of the given expressions when the tracepoint is hit.
11269 This command accepts a comma-separated list of any valid expressions.
11270 In addition to global, static, or local variables, the following
11271 special arguments are supported:
11275 Collect all registers.
11278 Collect all function arguments.
11281 Collect all local variables.
11284 Collect the return address. This is helpful if you want to see more
11288 Collects the number of arguments from the static probe at which the
11289 tracepoint is located.
11290 @xref{Static Probe Points}.
11292 @item $_probe_arg@var{n}
11293 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11294 from the static probe at which the tracepoint is located.
11295 @xref{Static Probe Points}.
11298 @vindex $_sdata@r{, collect}
11299 Collect static tracepoint marker specific data. Only available for
11300 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11301 Lists}. On the UST static tracepoints library backend, an
11302 instrumentation point resembles a @code{printf} function call. The
11303 tracing library is able to collect user specified data formatted to a
11304 character string using the format provided by the programmer that
11305 instrumented the program. Other backends have similar mechanisms.
11306 Here's an example of a UST marker call:
11309 const char master_name[] = "$your_name";
11310 trace_mark(channel1, marker1, "hello %s", master_name)
11313 In this case, collecting @code{$_sdata} collects the string
11314 @samp{hello $yourname}. When analyzing the trace buffer, you can
11315 inspect @samp{$_sdata} like any other variable available to
11319 You can give several consecutive @code{collect} commands, each one
11320 with a single argument, or one @code{collect} command with several
11321 arguments separated by commas; the effect is the same.
11323 The optional @var{mods} changes the usual handling of the arguments.
11324 @code{s} requests that pointers to chars be handled as strings, in
11325 particular collecting the contents of the memory being pointed at, up
11326 to the first zero. The upper bound is by default the value of the
11327 @code{print elements} variable; if @code{s} is followed by a decimal
11328 number, that is the upper bound instead. So for instance
11329 @samp{collect/s25 mystr} collects as many as 25 characters at
11332 The command @code{info scope} (@pxref{Symbols, info scope}) is
11333 particularly useful for figuring out what data to collect.
11335 @kindex teval @r{(tracepoints)}
11336 @item teval @var{expr1}, @var{expr2}, @dots{}
11337 Evaluate the given expressions when the tracepoint is hit. This
11338 command accepts a comma-separated list of expressions. The results
11339 are discarded, so this is mainly useful for assigning values to trace
11340 state variables (@pxref{Trace State Variables}) without adding those
11341 values to the trace buffer, as would be the case if the @code{collect}
11344 @kindex while-stepping @r{(tracepoints)}
11345 @item while-stepping @var{n}
11346 Perform @var{n} single-step instruction traces after the tracepoint,
11347 collecting new data after each step. The @code{while-stepping}
11348 command is followed by the list of what to collect while stepping
11349 (followed by its own @code{end} command):
11352 > while-stepping 12
11353 > collect $regs, myglobal
11359 Note that @code{$pc} is not automatically collected by
11360 @code{while-stepping}; you need to explicitly collect that register if
11361 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11364 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11365 @kindex set default-collect
11366 @cindex default collection action
11367 This variable is a list of expressions to collect at each tracepoint
11368 hit. It is effectively an additional @code{collect} action prepended
11369 to every tracepoint action list. The expressions are parsed
11370 individually for each tracepoint, so for instance a variable named
11371 @code{xyz} may be interpreted as a global for one tracepoint, and a
11372 local for another, as appropriate to the tracepoint's location.
11374 @item show default-collect
11375 @kindex show default-collect
11376 Show the list of expressions that are collected by default at each
11381 @node Listing Tracepoints
11382 @subsection Listing Tracepoints
11385 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11386 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11387 @cindex information about tracepoints
11388 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11389 Display information about the tracepoint @var{num}. If you don't
11390 specify a tracepoint number, displays information about all the
11391 tracepoints defined so far. The format is similar to that used for
11392 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11393 command, simply restricting itself to tracepoints.
11395 A tracepoint's listing may include additional information specific to
11400 its passcount as given by the @code{passcount @var{n}} command
11404 (@value{GDBP}) @b{info trace}
11405 Num Type Disp Enb Address What
11406 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11408 collect globfoo, $regs
11417 This command can be abbreviated @code{info tp}.
11420 @node Listing Static Tracepoint Markers
11421 @subsection Listing Static Tracepoint Markers
11424 @kindex info static-tracepoint-markers
11425 @cindex information about static tracepoint markers
11426 @item info static-tracepoint-markers
11427 Display information about all static tracepoint markers defined in the
11430 For each marker, the following columns are printed:
11434 An incrementing counter, output to help readability. This is not a
11437 The marker ID, as reported by the target.
11438 @item Enabled or Disabled
11439 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11440 that are not enabled.
11442 Where the marker is in your program, as a memory address.
11444 Where the marker is in the source for your program, as a file and line
11445 number. If the debug information included in the program does not
11446 allow @value{GDBN} to locate the source of the marker, this column
11447 will be left blank.
11451 In addition, the following information may be printed for each marker:
11455 User data passed to the tracing library by the marker call. In the
11456 UST backend, this is the format string passed as argument to the
11458 @item Static tracepoints probing the marker
11459 The list of static tracepoints attached to the marker.
11463 (@value{GDBP}) info static-tracepoint-markers
11464 Cnt ID Enb Address What
11465 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11466 Data: number1 %d number2 %d
11467 Probed by static tracepoints: #2
11468 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11474 @node Starting and Stopping Trace Experiments
11475 @subsection Starting and Stopping Trace Experiments
11478 @kindex tstart [ @var{notes} ]
11479 @cindex start a new trace experiment
11480 @cindex collected data discarded
11482 This command starts the trace experiment, and begins collecting data.
11483 It has the side effect of discarding all the data collected in the
11484 trace buffer during the previous trace experiment. If any arguments
11485 are supplied, they are taken as a note and stored with the trace
11486 experiment's state. The notes may be arbitrary text, and are
11487 especially useful with disconnected tracing in a multi-user context;
11488 the notes can explain what the trace is doing, supply user contact
11489 information, and so forth.
11491 @kindex tstop [ @var{notes} ]
11492 @cindex stop a running trace experiment
11494 This command stops the trace experiment. If any arguments are
11495 supplied, they are recorded with the experiment as a note. This is
11496 useful if you are stopping a trace started by someone else, for
11497 instance if the trace is interfering with the system's behavior and
11498 needs to be stopped quickly.
11500 @strong{Note}: a trace experiment and data collection may stop
11501 automatically if any tracepoint's passcount is reached
11502 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11505 @cindex status of trace data collection
11506 @cindex trace experiment, status of
11508 This command displays the status of the current trace data
11512 Here is an example of the commands we described so far:
11515 (@value{GDBP}) @b{trace gdb_c_test}
11516 (@value{GDBP}) @b{actions}
11517 Enter actions for tracepoint #1, one per line.
11518 > collect $regs,$locals,$args
11519 > while-stepping 11
11523 (@value{GDBP}) @b{tstart}
11524 [time passes @dots{}]
11525 (@value{GDBP}) @b{tstop}
11528 @anchor{disconnected tracing}
11529 @cindex disconnected tracing
11530 You can choose to continue running the trace experiment even if
11531 @value{GDBN} disconnects from the target, voluntarily or
11532 involuntarily. For commands such as @code{detach}, the debugger will
11533 ask what you want to do with the trace. But for unexpected
11534 terminations (@value{GDBN} crash, network outage), it would be
11535 unfortunate to lose hard-won trace data, so the variable
11536 @code{disconnected-tracing} lets you decide whether the trace should
11537 continue running without @value{GDBN}.
11540 @item set disconnected-tracing on
11541 @itemx set disconnected-tracing off
11542 @kindex set disconnected-tracing
11543 Choose whether a tracing run should continue to run if @value{GDBN}
11544 has disconnected from the target. Note that @code{detach} or
11545 @code{quit} will ask you directly what to do about a running trace no
11546 matter what this variable's setting, so the variable is mainly useful
11547 for handling unexpected situations, such as loss of the network.
11549 @item show disconnected-tracing
11550 @kindex show disconnected-tracing
11551 Show the current choice for disconnected tracing.
11555 When you reconnect to the target, the trace experiment may or may not
11556 still be running; it might have filled the trace buffer in the
11557 meantime, or stopped for one of the other reasons. If it is running,
11558 it will continue after reconnection.
11560 Upon reconnection, the target will upload information about the
11561 tracepoints in effect. @value{GDBN} will then compare that
11562 information to the set of tracepoints currently defined, and attempt
11563 to match them up, allowing for the possibility that the numbers may
11564 have changed due to creation and deletion in the meantime. If one of
11565 the target's tracepoints does not match any in @value{GDBN}, the
11566 debugger will create a new tracepoint, so that you have a number with
11567 which to specify that tracepoint. This matching-up process is
11568 necessarily heuristic, and it may result in useless tracepoints being
11569 created; you may simply delete them if they are of no use.
11571 @cindex circular trace buffer
11572 If your target agent supports a @dfn{circular trace buffer}, then you
11573 can run a trace experiment indefinitely without filling the trace
11574 buffer; when space runs out, the agent deletes already-collected trace
11575 frames, oldest first, until there is enough room to continue
11576 collecting. This is especially useful if your tracepoints are being
11577 hit too often, and your trace gets terminated prematurely because the
11578 buffer is full. To ask for a circular trace buffer, simply set
11579 @samp{circular-trace-buffer} to on. You can set this at any time,
11580 including during tracing; if the agent can do it, it will change
11581 buffer handling on the fly, otherwise it will not take effect until
11585 @item set circular-trace-buffer on
11586 @itemx set circular-trace-buffer off
11587 @kindex set circular-trace-buffer
11588 Choose whether a tracing run should use a linear or circular buffer
11589 for trace data. A linear buffer will not lose any trace data, but may
11590 fill up prematurely, while a circular buffer will discard old trace
11591 data, but it will have always room for the latest tracepoint hits.
11593 @item show circular-trace-buffer
11594 @kindex show circular-trace-buffer
11595 Show the current choice for the trace buffer. Note that this may not
11596 match the agent's current buffer handling, nor is it guaranteed to
11597 match the setting that might have been in effect during a past run,
11598 for instance if you are looking at frames from a trace file.
11603 @item set trace-user @var{text}
11604 @kindex set trace-user
11606 @item show trace-user
11607 @kindex show trace-user
11609 @item set trace-notes @var{text}
11610 @kindex set trace-notes
11611 Set the trace run's notes.
11613 @item show trace-notes
11614 @kindex show trace-notes
11615 Show the trace run's notes.
11617 @item set trace-stop-notes @var{text}
11618 @kindex set trace-stop-notes
11619 Set the trace run's stop notes. The handling of the note is as for
11620 @code{tstop} arguments; the set command is convenient way to fix a
11621 stop note that is mistaken or incomplete.
11623 @item show trace-stop-notes
11624 @kindex show trace-stop-notes
11625 Show the trace run's stop notes.
11629 @node Tracepoint Restrictions
11630 @subsection Tracepoint Restrictions
11632 @cindex tracepoint restrictions
11633 There are a number of restrictions on the use of tracepoints. As
11634 described above, tracepoint data gathering occurs on the target
11635 without interaction from @value{GDBN}. Thus the full capabilities of
11636 the debugger are not available during data gathering, and then at data
11637 examination time, you will be limited by only having what was
11638 collected. The following items describe some common problems, but it
11639 is not exhaustive, and you may run into additional difficulties not
11645 Tracepoint expressions are intended to gather objects (lvalues). Thus
11646 the full flexibility of GDB's expression evaluator is not available.
11647 You cannot call functions, cast objects to aggregate types, access
11648 convenience variables or modify values (except by assignment to trace
11649 state variables). Some language features may implicitly call
11650 functions (for instance Objective-C fields with accessors), and therefore
11651 cannot be collected either.
11654 Collection of local variables, either individually or in bulk with
11655 @code{$locals} or @code{$args}, during @code{while-stepping} may
11656 behave erratically. The stepping action may enter a new scope (for
11657 instance by stepping into a function), or the location of the variable
11658 may change (for instance it is loaded into a register). The
11659 tracepoint data recorded uses the location information for the
11660 variables that is correct for the tracepoint location. When the
11661 tracepoint is created, it is not possible, in general, to determine
11662 where the steps of a @code{while-stepping} sequence will advance the
11663 program---particularly if a conditional branch is stepped.
11666 Collection of an incompletely-initialized or partially-destroyed object
11667 may result in something that @value{GDBN} cannot display, or displays
11668 in a misleading way.
11671 When @value{GDBN} displays a pointer to character it automatically
11672 dereferences the pointer to also display characters of the string
11673 being pointed to. However, collecting the pointer during tracing does
11674 not automatically collect the string. You need to explicitly
11675 dereference the pointer and provide size information if you want to
11676 collect not only the pointer, but the memory pointed to. For example,
11677 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11681 It is not possible to collect a complete stack backtrace at a
11682 tracepoint. Instead, you may collect the registers and a few hundred
11683 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11684 (adjust to use the name of the actual stack pointer register on your
11685 target architecture, and the amount of stack you wish to capture).
11686 Then the @code{backtrace} command will show a partial backtrace when
11687 using a trace frame. The number of stack frames that can be examined
11688 depends on the sizes of the frames in the collected stack. Note that
11689 if you ask for a block so large that it goes past the bottom of the
11690 stack, the target agent may report an error trying to read from an
11694 If you do not collect registers at a tracepoint, @value{GDBN} can
11695 infer that the value of @code{$pc} must be the same as the address of
11696 the tracepoint and use that when you are looking at a trace frame
11697 for that tracepoint. However, this cannot work if the tracepoint has
11698 multiple locations (for instance if it was set in a function that was
11699 inlined), or if it has a @code{while-stepping} loop. In those cases
11700 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11705 @node Analyze Collected Data
11706 @section Using the Collected Data
11708 After the tracepoint experiment ends, you use @value{GDBN} commands
11709 for examining the trace data. The basic idea is that each tracepoint
11710 collects a trace @dfn{snapshot} every time it is hit and another
11711 snapshot every time it single-steps. All these snapshots are
11712 consecutively numbered from zero and go into a buffer, and you can
11713 examine them later. The way you examine them is to @dfn{focus} on a
11714 specific trace snapshot. When the remote stub is focused on a trace
11715 snapshot, it will respond to all @value{GDBN} requests for memory and
11716 registers by reading from the buffer which belongs to that snapshot,
11717 rather than from @emph{real} memory or registers of the program being
11718 debugged. This means that @strong{all} @value{GDBN} commands
11719 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11720 behave as if we were currently debugging the program state as it was
11721 when the tracepoint occurred. Any requests for data that are not in
11722 the buffer will fail.
11725 * tfind:: How to select a trace snapshot
11726 * tdump:: How to display all data for a snapshot
11727 * save tracepoints:: How to save tracepoints for a future run
11731 @subsection @code{tfind @var{n}}
11734 @cindex select trace snapshot
11735 @cindex find trace snapshot
11736 The basic command for selecting a trace snapshot from the buffer is
11737 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11738 counting from zero. If no argument @var{n} is given, the next
11739 snapshot is selected.
11741 Here are the various forms of using the @code{tfind} command.
11745 Find the first snapshot in the buffer. This is a synonym for
11746 @code{tfind 0} (since 0 is the number of the first snapshot).
11749 Stop debugging trace snapshots, resume @emph{live} debugging.
11752 Same as @samp{tfind none}.
11755 No argument means find the next trace snapshot.
11758 Find the previous trace snapshot before the current one. This permits
11759 retracing earlier steps.
11761 @item tfind tracepoint @var{num}
11762 Find the next snapshot associated with tracepoint @var{num}. Search
11763 proceeds forward from the last examined trace snapshot. If no
11764 argument @var{num} is given, it means find the next snapshot collected
11765 for the same tracepoint as the current snapshot.
11767 @item tfind pc @var{addr}
11768 Find the next snapshot associated with the value @var{addr} of the
11769 program counter. Search proceeds forward from the last examined trace
11770 snapshot. If no argument @var{addr} is given, it means find the next
11771 snapshot with the same value of PC as the current snapshot.
11773 @item tfind outside @var{addr1}, @var{addr2}
11774 Find the next snapshot whose PC is outside the given range of
11775 addresses (exclusive).
11777 @item tfind range @var{addr1}, @var{addr2}
11778 Find the next snapshot whose PC is between @var{addr1} and
11779 @var{addr2} (inclusive).
11781 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11782 Find the next snapshot associated with the source line @var{n}. If
11783 the optional argument @var{file} is given, refer to line @var{n} in
11784 that source file. Search proceeds forward from the last examined
11785 trace snapshot. If no argument @var{n} is given, it means find the
11786 next line other than the one currently being examined; thus saying
11787 @code{tfind line} repeatedly can appear to have the same effect as
11788 stepping from line to line in a @emph{live} debugging session.
11791 The default arguments for the @code{tfind} commands are specifically
11792 designed to make it easy to scan through the trace buffer. For
11793 instance, @code{tfind} with no argument selects the next trace
11794 snapshot, and @code{tfind -} with no argument selects the previous
11795 trace snapshot. So, by giving one @code{tfind} command, and then
11796 simply hitting @key{RET} repeatedly you can examine all the trace
11797 snapshots in order. Or, by saying @code{tfind -} and then hitting
11798 @key{RET} repeatedly you can examine the snapshots in reverse order.
11799 The @code{tfind line} command with no argument selects the snapshot
11800 for the next source line executed. The @code{tfind pc} command with
11801 no argument selects the next snapshot with the same program counter
11802 (PC) as the current frame. The @code{tfind tracepoint} command with
11803 no argument selects the next trace snapshot collected by the same
11804 tracepoint as the current one.
11806 In addition to letting you scan through the trace buffer manually,
11807 these commands make it easy to construct @value{GDBN} scripts that
11808 scan through the trace buffer and print out whatever collected data
11809 you are interested in. Thus, if we want to examine the PC, FP, and SP
11810 registers from each trace frame in the buffer, we can say this:
11813 (@value{GDBP}) @b{tfind start}
11814 (@value{GDBP}) @b{while ($trace_frame != -1)}
11815 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11816 $trace_frame, $pc, $sp, $fp
11820 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11821 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11822 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11823 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11824 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11825 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11826 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11827 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11828 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11829 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11830 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11833 Or, if we want to examine the variable @code{X} at each source line in
11837 (@value{GDBP}) @b{tfind start}
11838 (@value{GDBP}) @b{while ($trace_frame != -1)}
11839 > printf "Frame %d, X == %d\n", $trace_frame, X
11849 @subsection @code{tdump}
11851 @cindex dump all data collected at tracepoint
11852 @cindex tracepoint data, display
11854 This command takes no arguments. It prints all the data collected at
11855 the current trace snapshot.
11858 (@value{GDBP}) @b{trace 444}
11859 (@value{GDBP}) @b{actions}
11860 Enter actions for tracepoint #2, one per line:
11861 > collect $regs, $locals, $args, gdb_long_test
11864 (@value{GDBP}) @b{tstart}
11866 (@value{GDBP}) @b{tfind line 444}
11867 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11869 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11871 (@value{GDBP}) @b{tdump}
11872 Data collected at tracepoint 2, trace frame 1:
11873 d0 0xc4aa0085 -995491707
11877 d4 0x71aea3d 119204413
11880 d7 0x380035 3670069
11881 a0 0x19e24a 1696330
11882 a1 0x3000668 50333288
11884 a3 0x322000 3284992
11885 a4 0x3000698 50333336
11886 a5 0x1ad3cc 1758156
11887 fp 0x30bf3c 0x30bf3c
11888 sp 0x30bf34 0x30bf34
11890 pc 0x20b2c8 0x20b2c8
11894 p = 0x20e5b4 "gdb-test"
11901 gdb_long_test = 17 '\021'
11906 @code{tdump} works by scanning the tracepoint's current collection
11907 actions and printing the value of each expression listed. So
11908 @code{tdump} can fail, if after a run, you change the tracepoint's
11909 actions to mention variables that were not collected during the run.
11911 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11912 uses the collected value of @code{$pc} to distinguish between trace
11913 frames that were collected at the tracepoint hit, and frames that were
11914 collected while stepping. This allows it to correctly choose whether
11915 to display the basic list of collections, or the collections from the
11916 body of the while-stepping loop. However, if @code{$pc} was not collected,
11917 then @code{tdump} will always attempt to dump using the basic collection
11918 list, and may fail if a while-stepping frame does not include all the
11919 same data that is collected at the tracepoint hit.
11920 @c This is getting pretty arcane, example would be good.
11922 @node save tracepoints
11923 @subsection @code{save tracepoints @var{filename}}
11924 @kindex save tracepoints
11925 @kindex save-tracepoints
11926 @cindex save tracepoints for future sessions
11928 This command saves all current tracepoint definitions together with
11929 their actions and passcounts, into a file @file{@var{filename}}
11930 suitable for use in a later debugging session. To read the saved
11931 tracepoint definitions, use the @code{source} command (@pxref{Command
11932 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11933 alias for @w{@code{save tracepoints}}
11935 @node Tracepoint Variables
11936 @section Convenience Variables for Tracepoints
11937 @cindex tracepoint variables
11938 @cindex convenience variables for tracepoints
11941 @vindex $trace_frame
11942 @item (int) $trace_frame
11943 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11944 snapshot is selected.
11946 @vindex $tracepoint
11947 @item (int) $tracepoint
11948 The tracepoint for the current trace snapshot.
11950 @vindex $trace_line
11951 @item (int) $trace_line
11952 The line number for the current trace snapshot.
11954 @vindex $trace_file
11955 @item (char []) $trace_file
11956 The source file for the current trace snapshot.
11958 @vindex $trace_func
11959 @item (char []) $trace_func
11960 The name of the function containing @code{$tracepoint}.
11963 Note: @code{$trace_file} is not suitable for use in @code{printf},
11964 use @code{output} instead.
11966 Here's a simple example of using these convenience variables for
11967 stepping through all the trace snapshots and printing some of their
11968 data. Note that these are not the same as trace state variables,
11969 which are managed by the target.
11972 (@value{GDBP}) @b{tfind start}
11974 (@value{GDBP}) @b{while $trace_frame != -1}
11975 > output $trace_file
11976 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11982 @section Using Trace Files
11983 @cindex trace files
11985 In some situations, the target running a trace experiment may no
11986 longer be available; perhaps it crashed, or the hardware was needed
11987 for a different activity. To handle these cases, you can arrange to
11988 dump the trace data into a file, and later use that file as a source
11989 of trace data, via the @code{target tfile} command.
11994 @item tsave [ -r ] @var{filename}
11995 Save the trace data to @var{filename}. By default, this command
11996 assumes that @var{filename} refers to the host filesystem, so if
11997 necessary @value{GDBN} will copy raw trace data up from the target and
11998 then save it. If the target supports it, you can also supply the
11999 optional argument @code{-r} (``remote'') to direct the target to save
12000 the data directly into @var{filename} in its own filesystem, which may be
12001 more efficient if the trace buffer is very large. (Note, however, that
12002 @code{target tfile} can only read from files accessible to the host.)
12004 @kindex target tfile
12006 @item target tfile @var{filename}
12007 Use the file named @var{filename} as a source of trace data. Commands
12008 that examine data work as they do with a live target, but it is not
12009 possible to run any new trace experiments. @code{tstatus} will report
12010 the state of the trace run at the moment the data was saved, as well
12011 as the current trace frame you are examining. @var{filename} must be
12012 on a filesystem accessible to the host.
12017 @chapter Debugging Programs That Use Overlays
12020 If your program is too large to fit completely in your target system's
12021 memory, you can sometimes use @dfn{overlays} to work around this
12022 problem. @value{GDBN} provides some support for debugging programs that
12026 * How Overlays Work:: A general explanation of overlays.
12027 * Overlay Commands:: Managing overlays in @value{GDBN}.
12028 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12029 mapped by asking the inferior.
12030 * Overlay Sample Program:: A sample program using overlays.
12033 @node How Overlays Work
12034 @section How Overlays Work
12035 @cindex mapped overlays
12036 @cindex unmapped overlays
12037 @cindex load address, overlay's
12038 @cindex mapped address
12039 @cindex overlay area
12041 Suppose you have a computer whose instruction address space is only 64
12042 kilobytes long, but which has much more memory which can be accessed by
12043 other means: special instructions, segment registers, or memory
12044 management hardware, for example. Suppose further that you want to
12045 adapt a program which is larger than 64 kilobytes to run on this system.
12047 One solution is to identify modules of your program which are relatively
12048 independent, and need not call each other directly; call these modules
12049 @dfn{overlays}. Separate the overlays from the main program, and place
12050 their machine code in the larger memory. Place your main program in
12051 instruction memory, but leave at least enough space there to hold the
12052 largest overlay as well.
12054 Now, to call a function located in an overlay, you must first copy that
12055 overlay's machine code from the large memory into the space set aside
12056 for it in the instruction memory, and then jump to its entry point
12059 @c NB: In the below the mapped area's size is greater or equal to the
12060 @c size of all overlays. This is intentional to remind the developer
12061 @c that overlays don't necessarily need to be the same size.
12065 Data Instruction Larger
12066 Address Space Address Space Address Space
12067 +-----------+ +-----------+ +-----------+
12069 +-----------+ +-----------+ +-----------+<-- overlay 1
12070 | program | | main | .----| overlay 1 | load address
12071 | variables | | program | | +-----------+
12072 | and heap | | | | | |
12073 +-----------+ | | | +-----------+<-- overlay 2
12074 | | +-----------+ | | | load address
12075 +-----------+ | | | .-| overlay 2 |
12077 mapped --->+-----------+ | | +-----------+
12078 address | | | | | |
12079 | overlay | <-' | | |
12080 | area | <---' +-----------+<-- overlay 3
12081 | | <---. | | load address
12082 +-----------+ `--| overlay 3 |
12089 @anchor{A code overlay}A code overlay
12093 The diagram (@pxref{A code overlay}) shows a system with separate data
12094 and instruction address spaces. To map an overlay, the program copies
12095 its code from the larger address space to the instruction address space.
12096 Since the overlays shown here all use the same mapped address, only one
12097 may be mapped at a time. For a system with a single address space for
12098 data and instructions, the diagram would be similar, except that the
12099 program variables and heap would share an address space with the main
12100 program and the overlay area.
12102 An overlay loaded into instruction memory and ready for use is called a
12103 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12104 instruction memory. An overlay not present (or only partially present)
12105 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12106 is its address in the larger memory. The mapped address is also called
12107 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12108 called the @dfn{load memory address}, or @dfn{LMA}.
12110 Unfortunately, overlays are not a completely transparent way to adapt a
12111 program to limited instruction memory. They introduce a new set of
12112 global constraints you must keep in mind as you design your program:
12117 Before calling or returning to a function in an overlay, your program
12118 must make sure that overlay is actually mapped. Otherwise, the call or
12119 return will transfer control to the right address, but in the wrong
12120 overlay, and your program will probably crash.
12123 If the process of mapping an overlay is expensive on your system, you
12124 will need to choose your overlays carefully to minimize their effect on
12125 your program's performance.
12128 The executable file you load onto your system must contain each
12129 overlay's instructions, appearing at the overlay's load address, not its
12130 mapped address. However, each overlay's instructions must be relocated
12131 and its symbols defined as if the overlay were at its mapped address.
12132 You can use GNU linker scripts to specify different load and relocation
12133 addresses for pieces of your program; see @ref{Overlay Description,,,
12134 ld.info, Using ld: the GNU linker}.
12137 The procedure for loading executable files onto your system must be able
12138 to load their contents into the larger address space as well as the
12139 instruction and data spaces.
12143 The overlay system described above is rather simple, and could be
12144 improved in many ways:
12149 If your system has suitable bank switch registers or memory management
12150 hardware, you could use those facilities to make an overlay's load area
12151 contents simply appear at their mapped address in instruction space.
12152 This would probably be faster than copying the overlay to its mapped
12153 area in the usual way.
12156 If your overlays are small enough, you could set aside more than one
12157 overlay area, and have more than one overlay mapped at a time.
12160 You can use overlays to manage data, as well as instructions. In
12161 general, data overlays are even less transparent to your design than
12162 code overlays: whereas code overlays only require care when you call or
12163 return to functions, data overlays require care every time you access
12164 the data. Also, if you change the contents of a data overlay, you
12165 must copy its contents back out to its load address before you can copy a
12166 different data overlay into the same mapped area.
12171 @node Overlay Commands
12172 @section Overlay Commands
12174 To use @value{GDBN}'s overlay support, each overlay in your program must
12175 correspond to a separate section of the executable file. The section's
12176 virtual memory address and load memory address must be the overlay's
12177 mapped and load addresses. Identifying overlays with sections allows
12178 @value{GDBN} to determine the appropriate address of a function or
12179 variable, depending on whether the overlay is mapped or not.
12181 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12182 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12187 Disable @value{GDBN}'s overlay support. When overlay support is
12188 disabled, @value{GDBN} assumes that all functions and variables are
12189 always present at their mapped addresses. By default, @value{GDBN}'s
12190 overlay support is disabled.
12192 @item overlay manual
12193 @cindex manual overlay debugging
12194 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12195 relies on you to tell it which overlays are mapped, and which are not,
12196 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12197 commands described below.
12199 @item overlay map-overlay @var{overlay}
12200 @itemx overlay map @var{overlay}
12201 @cindex map an overlay
12202 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12203 be the name of the object file section containing the overlay. When an
12204 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12205 functions and variables at their mapped addresses. @value{GDBN} assumes
12206 that any other overlays whose mapped ranges overlap that of
12207 @var{overlay} are now unmapped.
12209 @item overlay unmap-overlay @var{overlay}
12210 @itemx overlay unmap @var{overlay}
12211 @cindex unmap an overlay
12212 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12213 must be the name of the object file section containing the overlay.
12214 When an overlay is unmapped, @value{GDBN} assumes it can find the
12215 overlay's functions and variables at their load addresses.
12218 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12219 consults a data structure the overlay manager maintains in the inferior
12220 to see which overlays are mapped. For details, see @ref{Automatic
12221 Overlay Debugging}.
12223 @item overlay load-target
12224 @itemx overlay load
12225 @cindex reloading the overlay table
12226 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12227 re-reads the table @value{GDBN} automatically each time the inferior
12228 stops, so this command should only be necessary if you have changed the
12229 overlay mapping yourself using @value{GDBN}. This command is only
12230 useful when using automatic overlay debugging.
12232 @item overlay list-overlays
12233 @itemx overlay list
12234 @cindex listing mapped overlays
12235 Display a list of the overlays currently mapped, along with their mapped
12236 addresses, load addresses, and sizes.
12240 Normally, when @value{GDBN} prints a code address, it includes the name
12241 of the function the address falls in:
12244 (@value{GDBP}) print main
12245 $3 = @{int ()@} 0x11a0 <main>
12248 When overlay debugging is enabled, @value{GDBN} recognizes code in
12249 unmapped overlays, and prints the names of unmapped functions with
12250 asterisks around them. For example, if @code{foo} is a function in an
12251 unmapped overlay, @value{GDBN} prints it this way:
12254 (@value{GDBP}) overlay list
12255 No sections are mapped.
12256 (@value{GDBP}) print foo
12257 $5 = @{int (int)@} 0x100000 <*foo*>
12260 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12264 (@value{GDBP}) overlay list
12265 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12266 mapped at 0x1016 - 0x104a
12267 (@value{GDBP}) print foo
12268 $6 = @{int (int)@} 0x1016 <foo>
12271 When overlay debugging is enabled, @value{GDBN} can find the correct
12272 address for functions and variables in an overlay, whether or not the
12273 overlay is mapped. This allows most @value{GDBN} commands, like
12274 @code{break} and @code{disassemble}, to work normally, even on unmapped
12275 code. However, @value{GDBN}'s breakpoint support has some limitations:
12279 @cindex breakpoints in overlays
12280 @cindex overlays, setting breakpoints in
12281 You can set breakpoints in functions in unmapped overlays, as long as
12282 @value{GDBN} can write to the overlay at its load address.
12284 @value{GDBN} can not set hardware or simulator-based breakpoints in
12285 unmapped overlays. However, if you set a breakpoint at the end of your
12286 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12287 you are using manual overlay management), @value{GDBN} will re-set its
12288 breakpoints properly.
12292 @node Automatic Overlay Debugging
12293 @section Automatic Overlay Debugging
12294 @cindex automatic overlay debugging
12296 @value{GDBN} can automatically track which overlays are mapped and which
12297 are not, given some simple co-operation from the overlay manager in the
12298 inferior. If you enable automatic overlay debugging with the
12299 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12300 looks in the inferior's memory for certain variables describing the
12301 current state of the overlays.
12303 Here are the variables your overlay manager must define to support
12304 @value{GDBN}'s automatic overlay debugging:
12308 @item @code{_ovly_table}:
12309 This variable must be an array of the following structures:
12314 /* The overlay's mapped address. */
12317 /* The size of the overlay, in bytes. */
12318 unsigned long size;
12320 /* The overlay's load address. */
12323 /* Non-zero if the overlay is currently mapped;
12325 unsigned long mapped;
12329 @item @code{_novlys}:
12330 This variable must be a four-byte signed integer, holding the total
12331 number of elements in @code{_ovly_table}.
12335 To decide whether a particular overlay is mapped or not, @value{GDBN}
12336 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12337 @code{lma} members equal the VMA and LMA of the overlay's section in the
12338 executable file. When @value{GDBN} finds a matching entry, it consults
12339 the entry's @code{mapped} member to determine whether the overlay is
12342 In addition, your overlay manager may define a function called
12343 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12344 will silently set a breakpoint there. If the overlay manager then
12345 calls this function whenever it has changed the overlay table, this
12346 will enable @value{GDBN} to accurately keep track of which overlays
12347 are in program memory, and update any breakpoints that may be set
12348 in overlays. This will allow breakpoints to work even if the
12349 overlays are kept in ROM or other non-writable memory while they
12350 are not being executed.
12352 @node Overlay Sample Program
12353 @section Overlay Sample Program
12354 @cindex overlay example program
12356 When linking a program which uses overlays, you must place the overlays
12357 at their load addresses, while relocating them to run at their mapped
12358 addresses. To do this, you must write a linker script (@pxref{Overlay
12359 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12360 since linker scripts are specific to a particular host system, target
12361 architecture, and target memory layout, this manual cannot provide
12362 portable sample code demonstrating @value{GDBN}'s overlay support.
12364 However, the @value{GDBN} source distribution does contain an overlaid
12365 program, with linker scripts for a few systems, as part of its test
12366 suite. The program consists of the following files from
12367 @file{gdb/testsuite/gdb.base}:
12371 The main program file.
12373 A simple overlay manager, used by @file{overlays.c}.
12378 Overlay modules, loaded and used by @file{overlays.c}.
12381 Linker scripts for linking the test program on the @code{d10v-elf}
12382 and @code{m32r-elf} targets.
12385 You can build the test program using the @code{d10v-elf} GCC
12386 cross-compiler like this:
12389 $ d10v-elf-gcc -g -c overlays.c
12390 $ d10v-elf-gcc -g -c ovlymgr.c
12391 $ d10v-elf-gcc -g -c foo.c
12392 $ d10v-elf-gcc -g -c bar.c
12393 $ d10v-elf-gcc -g -c baz.c
12394 $ d10v-elf-gcc -g -c grbx.c
12395 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12396 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12399 The build process is identical for any other architecture, except that
12400 you must substitute the appropriate compiler and linker script for the
12401 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12405 @chapter Using @value{GDBN} with Different Languages
12408 Although programming languages generally have common aspects, they are
12409 rarely expressed in the same manner. For instance, in ANSI C,
12410 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12411 Modula-2, it is accomplished by @code{p^}. Values can also be
12412 represented (and displayed) differently. Hex numbers in C appear as
12413 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12415 @cindex working language
12416 Language-specific information is built into @value{GDBN} for some languages,
12417 allowing you to express operations like the above in your program's
12418 native language, and allowing @value{GDBN} to output values in a manner
12419 consistent with the syntax of your program's native language. The
12420 language you use to build expressions is called the @dfn{working
12424 * Setting:: Switching between source languages
12425 * Show:: Displaying the language
12426 * Checks:: Type and range checks
12427 * Supported Languages:: Supported languages
12428 * Unsupported Languages:: Unsupported languages
12432 @section Switching Between Source Languages
12434 There are two ways to control the working language---either have @value{GDBN}
12435 set it automatically, or select it manually yourself. You can use the
12436 @code{set language} command for either purpose. On startup, @value{GDBN}
12437 defaults to setting the language automatically. The working language is
12438 used to determine how expressions you type are interpreted, how values
12441 In addition to the working language, every source file that
12442 @value{GDBN} knows about has its own working language. For some object
12443 file formats, the compiler might indicate which language a particular
12444 source file is in. However, most of the time @value{GDBN} infers the
12445 language from the name of the file. The language of a source file
12446 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12447 show each frame appropriately for its own language. There is no way to
12448 set the language of a source file from within @value{GDBN}, but you can
12449 set the language associated with a filename extension. @xref{Show, ,
12450 Displaying the Language}.
12452 This is most commonly a problem when you use a program, such
12453 as @code{cfront} or @code{f2c}, that generates C but is written in
12454 another language. In that case, make the
12455 program use @code{#line} directives in its C output; that way
12456 @value{GDBN} will know the correct language of the source code of the original
12457 program, and will display that source code, not the generated C code.
12460 * Filenames:: Filename extensions and languages.
12461 * Manually:: Setting the working language manually
12462 * Automatically:: Having @value{GDBN} infer the source language
12466 @subsection List of Filename Extensions and Languages
12468 If a source file name ends in one of the following extensions, then
12469 @value{GDBN} infers that its language is the one indicated.
12487 C@t{++} source file
12493 Objective-C source file
12497 Fortran source file
12500 Modula-2 source file
12504 Assembler source file. This actually behaves almost like C, but
12505 @value{GDBN} does not skip over function prologues when stepping.
12508 In addition, you may set the language associated with a filename
12509 extension. @xref{Show, , Displaying the Language}.
12512 @subsection Setting the Working Language
12514 If you allow @value{GDBN} to set the language automatically,
12515 expressions are interpreted the same way in your debugging session and
12518 @kindex set language
12519 If you wish, you may set the language manually. To do this, issue the
12520 command @samp{set language @var{lang}}, where @var{lang} is the name of
12521 a language, such as
12522 @code{c} or @code{modula-2}.
12523 For a list of the supported languages, type @samp{set language}.
12525 Setting the language manually prevents @value{GDBN} from updating the working
12526 language automatically. This can lead to confusion if you try
12527 to debug a program when the working language is not the same as the
12528 source language, when an expression is acceptable to both
12529 languages---but means different things. For instance, if the current
12530 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12538 might not have the effect you intended. In C, this means to add
12539 @code{b} and @code{c} and place the result in @code{a}. The result
12540 printed would be the value of @code{a}. In Modula-2, this means to compare
12541 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12543 @node Automatically
12544 @subsection Having @value{GDBN} Infer the Source Language
12546 To have @value{GDBN} set the working language automatically, use
12547 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12548 then infers the working language. That is, when your program stops in a
12549 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12550 working language to the language recorded for the function in that
12551 frame. If the language for a frame is unknown (that is, if the function
12552 or block corresponding to the frame was defined in a source file that
12553 does not have a recognized extension), the current working language is
12554 not changed, and @value{GDBN} issues a warning.
12556 This may not seem necessary for most programs, which are written
12557 entirely in one source language. However, program modules and libraries
12558 written in one source language can be used by a main program written in
12559 a different source language. Using @samp{set language auto} in this
12560 case frees you from having to set the working language manually.
12563 @section Displaying the Language
12565 The following commands help you find out which language is the
12566 working language, and also what language source files were written in.
12569 @item show language
12570 @kindex show language
12571 Display the current working language. This is the
12572 language you can use with commands such as @code{print} to
12573 build and compute expressions that may involve variables in your program.
12576 @kindex info frame@r{, show the source language}
12577 Display the source language for this frame. This language becomes the
12578 working language if you use an identifier from this frame.
12579 @xref{Frame Info, ,Information about a Frame}, to identify the other
12580 information listed here.
12583 @kindex info source@r{, show the source language}
12584 Display the source language of this source file.
12585 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12586 information listed here.
12589 In unusual circumstances, you may have source files with extensions
12590 not in the standard list. You can then set the extension associated
12591 with a language explicitly:
12594 @item set extension-language @var{ext} @var{language}
12595 @kindex set extension-language
12596 Tell @value{GDBN} that source files with extension @var{ext} are to be
12597 assumed as written in the source language @var{language}.
12599 @item info extensions
12600 @kindex info extensions
12601 List all the filename extensions and the associated languages.
12605 @section Type and Range Checking
12608 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12609 checking are included, but they do not yet have any effect. This
12610 section documents the intended facilities.
12612 @c FIXME remove warning when type/range code added
12614 Some languages are designed to guard you against making seemingly common
12615 errors through a series of compile- and run-time checks. These include
12616 checking the type of arguments to functions and operators, and making
12617 sure mathematical overflows are caught at run time. Checks such as
12618 these help to ensure a program's correctness once it has been compiled
12619 by eliminating type mismatches, and providing active checks for range
12620 errors when your program is running.
12622 @value{GDBN} can check for conditions like the above if you wish.
12623 Although @value{GDBN} does not check the statements in your program,
12624 it can check expressions entered directly into @value{GDBN} for
12625 evaluation via the @code{print} command, for example. As with the
12626 working language, @value{GDBN} can also decide whether or not to check
12627 automatically based on your program's source language.
12628 @xref{Supported Languages, ,Supported Languages}, for the default
12629 settings of supported languages.
12632 * Type Checking:: An overview of type checking
12633 * Range Checking:: An overview of range checking
12636 @cindex type checking
12637 @cindex checks, type
12638 @node Type Checking
12639 @subsection An Overview of Type Checking
12641 Some languages, such as Modula-2, are strongly typed, meaning that the
12642 arguments to operators and functions have to be of the correct type,
12643 otherwise an error occurs. These checks prevent type mismatch
12644 errors from ever causing any run-time problems. For example,
12652 The second example fails because the @code{CARDINAL} 1 is not
12653 type-compatible with the @code{REAL} 2.3.
12655 For the expressions you use in @value{GDBN} commands, you can tell the
12656 @value{GDBN} type checker to skip checking;
12657 to treat any mismatches as errors and abandon the expression;
12658 or to only issue warnings when type mismatches occur,
12659 but evaluate the expression anyway. When you choose the last of
12660 these, @value{GDBN} evaluates expressions like the second example above, but
12661 also issues a warning.
12663 Even if you turn type checking off, there may be other reasons
12664 related to type that prevent @value{GDBN} from evaluating an expression.
12665 For instance, @value{GDBN} does not know how to add an @code{int} and
12666 a @code{struct foo}. These particular type errors have nothing to do
12667 with the language in use, and usually arise from expressions, such as
12668 the one described above, which make little sense to evaluate anyway.
12670 Each language defines to what degree it is strict about type. For
12671 instance, both Modula-2 and C require the arguments to arithmetical
12672 operators to be numbers. In C, enumerated types and pointers can be
12673 represented as numbers, so that they are valid arguments to mathematical
12674 operators. @xref{Supported Languages, ,Supported Languages}, for further
12675 details on specific languages.
12677 @value{GDBN} provides some additional commands for controlling the type checker:
12679 @kindex set check type
12680 @kindex show check type
12682 @item set check type auto
12683 Set type checking on or off based on the current working language.
12684 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12687 @item set check type on
12688 @itemx set check type off
12689 Set type checking on or off, overriding the default setting for the
12690 current working language. Issue a warning if the setting does not
12691 match the language default. If any type mismatches occur in
12692 evaluating an expression while type checking is on, @value{GDBN} prints a
12693 message and aborts evaluation of the expression.
12695 @item set check type warn
12696 Cause the type checker to issue warnings, but to always attempt to
12697 evaluate the expression. Evaluating the expression may still
12698 be impossible for other reasons. For example, @value{GDBN} cannot add
12699 numbers and structures.
12702 Show the current setting of the type checker, and whether or not @value{GDBN}
12703 is setting it automatically.
12706 @cindex range checking
12707 @cindex checks, range
12708 @node Range Checking
12709 @subsection An Overview of Range Checking
12711 In some languages (such as Modula-2), it is an error to exceed the
12712 bounds of a type; this is enforced with run-time checks. Such range
12713 checking is meant to ensure program correctness by making sure
12714 computations do not overflow, or indices on an array element access do
12715 not exceed the bounds of the array.
12717 For expressions you use in @value{GDBN} commands, you can tell
12718 @value{GDBN} to treat range errors in one of three ways: ignore them,
12719 always treat them as errors and abandon the expression, or issue
12720 warnings but evaluate the expression anyway.
12722 A range error can result from numerical overflow, from exceeding an
12723 array index bound, or when you type a constant that is not a member
12724 of any type. Some languages, however, do not treat overflows as an
12725 error. In many implementations of C, mathematical overflow causes the
12726 result to ``wrap around'' to lower values---for example, if @var{m} is
12727 the largest integer value, and @var{s} is the smallest, then
12730 @var{m} + 1 @result{} @var{s}
12733 This, too, is specific to individual languages, and in some cases
12734 specific to individual compilers or machines. @xref{Supported Languages, ,
12735 Supported Languages}, for further details on specific languages.
12737 @value{GDBN} provides some additional commands for controlling the range checker:
12739 @kindex set check range
12740 @kindex show check range
12742 @item set check range auto
12743 Set range checking on or off based on the current working language.
12744 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12747 @item set check range on
12748 @itemx set check range off
12749 Set range checking on or off, overriding the default setting for the
12750 current working language. A warning is issued if the setting does not
12751 match the language default. If a range error occurs and range checking is on,
12752 then a message is printed and evaluation of the expression is aborted.
12754 @item set check range warn
12755 Output messages when the @value{GDBN} range checker detects a range error,
12756 but attempt to evaluate the expression anyway. Evaluating the
12757 expression may still be impossible for other reasons, such as accessing
12758 memory that the process does not own (a typical example from many Unix
12762 Show the current setting of the range checker, and whether or not it is
12763 being set automatically by @value{GDBN}.
12766 @node Supported Languages
12767 @section Supported Languages
12769 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
12770 OpenCL C, Pascal, assembly, Modula-2, and Ada.
12771 @c This is false ...
12772 Some @value{GDBN} features may be used in expressions regardless of the
12773 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12774 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12775 ,Expressions}) can be used with the constructs of any supported
12778 The following sections detail to what degree each source language is
12779 supported by @value{GDBN}. These sections are not meant to be language
12780 tutorials or references, but serve only as a reference guide to what the
12781 @value{GDBN} expression parser accepts, and what input and output
12782 formats should look like for different languages. There are many good
12783 books written on each of these languages; please look to these for a
12784 language reference or tutorial.
12787 * C:: C and C@t{++}
12790 * Objective-C:: Objective-C
12791 * OpenCL C:: OpenCL C
12792 * Fortran:: Fortran
12794 * Modula-2:: Modula-2
12799 @subsection C and C@t{++}
12801 @cindex C and C@t{++}
12802 @cindex expressions in C or C@t{++}
12804 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12805 to both languages. Whenever this is the case, we discuss those languages
12809 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12810 @cindex @sc{gnu} C@t{++}
12811 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12812 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12813 effectively, you must compile your C@t{++} programs with a supported
12814 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12815 compiler (@code{aCC}).
12818 * C Operators:: C and C@t{++} operators
12819 * C Constants:: C and C@t{++} constants
12820 * C Plus Plus Expressions:: C@t{++} expressions
12821 * C Defaults:: Default settings for C and C@t{++}
12822 * C Checks:: C and C@t{++} type and range checks
12823 * Debugging C:: @value{GDBN} and C
12824 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12825 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12829 @subsubsection C and C@t{++} Operators
12831 @cindex C and C@t{++} operators
12833 Operators must be defined on values of specific types. For instance,
12834 @code{+} is defined on numbers, but not on structures. Operators are
12835 often defined on groups of types.
12837 For the purposes of C and C@t{++}, the following definitions hold:
12842 @emph{Integral types} include @code{int} with any of its storage-class
12843 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12846 @emph{Floating-point types} include @code{float}, @code{double}, and
12847 @code{long double} (if supported by the target platform).
12850 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12853 @emph{Scalar types} include all of the above.
12858 The following operators are supported. They are listed here
12859 in order of increasing precedence:
12863 The comma or sequencing operator. Expressions in a comma-separated list
12864 are evaluated from left to right, with the result of the entire
12865 expression being the last expression evaluated.
12868 Assignment. The value of an assignment expression is the value
12869 assigned. Defined on scalar types.
12872 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12873 and translated to @w{@code{@var{a} = @var{a op b}}}.
12874 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12875 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12876 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12879 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12880 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12884 Logical @sc{or}. Defined on integral types.
12887 Logical @sc{and}. Defined on integral types.
12890 Bitwise @sc{or}. Defined on integral types.
12893 Bitwise exclusive-@sc{or}. Defined on integral types.
12896 Bitwise @sc{and}. Defined on integral types.
12899 Equality and inequality. Defined on scalar types. The value of these
12900 expressions is 0 for false and non-zero for true.
12902 @item <@r{, }>@r{, }<=@r{, }>=
12903 Less than, greater than, less than or equal, greater than or equal.
12904 Defined on scalar types. The value of these expressions is 0 for false
12905 and non-zero for true.
12908 left shift, and right shift. Defined on integral types.
12911 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12914 Addition and subtraction. Defined on integral types, floating-point types and
12917 @item *@r{, }/@r{, }%
12918 Multiplication, division, and modulus. Multiplication and division are
12919 defined on integral and floating-point types. Modulus is defined on
12923 Increment and decrement. When appearing before a variable, the
12924 operation is performed before the variable is used in an expression;
12925 when appearing after it, the variable's value is used before the
12926 operation takes place.
12929 Pointer dereferencing. Defined on pointer types. Same precedence as
12933 Address operator. Defined on variables. Same precedence as @code{++}.
12935 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12936 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12937 to examine the address
12938 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12942 Negative. Defined on integral and floating-point types. Same
12943 precedence as @code{++}.
12946 Logical negation. Defined on integral types. Same precedence as
12950 Bitwise complement operator. Defined on integral types. Same precedence as
12955 Structure member, and pointer-to-structure member. For convenience,
12956 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12957 pointer based on the stored type information.
12958 Defined on @code{struct} and @code{union} data.
12961 Dereferences of pointers to members.
12964 Array indexing. @code{@var{a}[@var{i}]} is defined as
12965 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12968 Function parameter list. Same precedence as @code{->}.
12971 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12972 and @code{class} types.
12975 Doubled colons also represent the @value{GDBN} scope operator
12976 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12980 If an operator is redefined in the user code, @value{GDBN} usually
12981 attempts to invoke the redefined version instead of using the operator's
12982 predefined meaning.
12985 @subsubsection C and C@t{++} Constants
12987 @cindex C and C@t{++} constants
12989 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12994 Integer constants are a sequence of digits. Octal constants are
12995 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12996 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12997 @samp{l}, specifying that the constant should be treated as a
13001 Floating point constants are a sequence of digits, followed by a decimal
13002 point, followed by a sequence of digits, and optionally followed by an
13003 exponent. An exponent is of the form:
13004 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13005 sequence of digits. The @samp{+} is optional for positive exponents.
13006 A floating-point constant may also end with a letter @samp{f} or
13007 @samp{F}, specifying that the constant should be treated as being of
13008 the @code{float} (as opposed to the default @code{double}) type; or with
13009 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13013 Enumerated constants consist of enumerated identifiers, or their
13014 integral equivalents.
13017 Character constants are a single character surrounded by single quotes
13018 (@code{'}), or a number---the ordinal value of the corresponding character
13019 (usually its @sc{ascii} value). Within quotes, the single character may
13020 be represented by a letter or by @dfn{escape sequences}, which are of
13021 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13022 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13023 @samp{@var{x}} is a predefined special character---for example,
13024 @samp{\n} for newline.
13026 Wide character constants can be written by prefixing a character
13027 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13028 form of @samp{x}. The target wide character set is used when
13029 computing the value of this constant (@pxref{Character Sets}).
13032 String constants are a sequence of character constants surrounded by
13033 double quotes (@code{"}). Any valid character constant (as described
13034 above) may appear. Double quotes within the string must be preceded by
13035 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13038 Wide string constants can be written by prefixing a string constant
13039 with @samp{L}, as in C. The target wide character set is used when
13040 computing the value of this constant (@pxref{Character Sets}).
13043 Pointer constants are an integral value. You can also write pointers
13044 to constants using the C operator @samp{&}.
13047 Array constants are comma-separated lists surrounded by braces @samp{@{}
13048 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13049 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13050 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13053 @node C Plus Plus Expressions
13054 @subsubsection C@t{++} Expressions
13056 @cindex expressions in C@t{++}
13057 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13059 @cindex debugging C@t{++} programs
13060 @cindex C@t{++} compilers
13061 @cindex debug formats and C@t{++}
13062 @cindex @value{NGCC} and C@t{++}
13064 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13065 the proper compiler and the proper debug format. Currently,
13066 @value{GDBN} works best when debugging C@t{++} code that is compiled
13067 with the most recent version of @value{NGCC} possible. The DWARF
13068 debugging format is preferred; @value{NGCC} defaults to this on most
13069 popular platforms. Other compilers and/or debug formats are likely to
13070 work badly or not at all when using @value{GDBN} to debug C@t{++}
13071 code. @xref{Compilation}.
13076 @cindex member functions
13078 Member function calls are allowed; you can use expressions like
13081 count = aml->GetOriginal(x, y)
13084 @vindex this@r{, inside C@t{++} member functions}
13085 @cindex namespace in C@t{++}
13087 While a member function is active (in the selected stack frame), your
13088 expressions have the same namespace available as the member function;
13089 that is, @value{GDBN} allows implicit references to the class instance
13090 pointer @code{this} following the same rules as C@t{++}. @code{using}
13091 declarations in the current scope are also respected by @value{GDBN}.
13093 @cindex call overloaded functions
13094 @cindex overloaded functions, calling
13095 @cindex type conversions in C@t{++}
13097 You can call overloaded functions; @value{GDBN} resolves the function
13098 call to the right definition, with some restrictions. @value{GDBN} does not
13099 perform overload resolution involving user-defined type conversions,
13100 calls to constructors, or instantiations of templates that do not exist
13101 in the program. It also cannot handle ellipsis argument lists or
13104 It does perform integral conversions and promotions, floating-point
13105 promotions, arithmetic conversions, pointer conversions, conversions of
13106 class objects to base classes, and standard conversions such as those of
13107 functions or arrays to pointers; it requires an exact match on the
13108 number of function arguments.
13110 Overload resolution is always performed, unless you have specified
13111 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13112 ,@value{GDBN} Features for C@t{++}}.
13114 You must specify @code{set overload-resolution off} in order to use an
13115 explicit function signature to call an overloaded function, as in
13117 p 'foo(char,int)'('x', 13)
13120 The @value{GDBN} command-completion facility can simplify this;
13121 see @ref{Completion, ,Command Completion}.
13123 @cindex reference declarations
13125 @value{GDBN} understands variables declared as C@t{++} references; you can use
13126 them in expressions just as you do in C@t{++} source---they are automatically
13129 In the parameter list shown when @value{GDBN} displays a frame, the values of
13130 reference variables are not displayed (unlike other variables); this
13131 avoids clutter, since references are often used for large structures.
13132 The @emph{address} of a reference variable is always shown, unless
13133 you have specified @samp{set print address off}.
13136 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13137 expressions can use it just as expressions in your program do. Since
13138 one scope may be defined in another, you can use @code{::} repeatedly if
13139 necessary, for example in an expression like
13140 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13141 resolving name scope by reference to source files, in both C and C@t{++}
13142 debugging (@pxref{Variables, ,Program Variables}).
13145 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13150 @subsubsection C and C@t{++} Defaults
13152 @cindex C and C@t{++} defaults
13154 If you allow @value{GDBN} to set type and range checking automatically, they
13155 both default to @code{off} whenever the working language changes to
13156 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13157 selects the working language.
13159 If you allow @value{GDBN} to set the language automatically, it
13160 recognizes source files whose names end with @file{.c}, @file{.C}, or
13161 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13162 these files, it sets the working language to C or C@t{++}.
13163 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13164 for further details.
13166 @c Type checking is (a) primarily motivated by Modula-2, and (b)
13167 @c unimplemented. If (b) changes, it might make sense to let this node
13168 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
13171 @subsubsection C and C@t{++} Type and Range Checks
13173 @cindex C and C@t{++} checks
13175 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
13176 is not used. However, if you turn type checking on, @value{GDBN}
13177 considers two variables type equivalent if:
13181 The two variables are structured and have the same structure, union, or
13185 The two variables have the same type name, or types that have been
13186 declared equivalent through @code{typedef}.
13189 @c leaving this out because neither J Gilmore nor R Pesch understand it.
13192 The two @code{struct}, @code{union}, or @code{enum} variables are
13193 declared in the same declaration. (Note: this may not be true for all C
13198 Range checking, if turned on, is done on mathematical operations. Array
13199 indices are not checked, since they are often used to index a pointer
13200 that is not itself an array.
13203 @subsubsection @value{GDBN} and C
13205 The @code{set print union} and @code{show print union} commands apply to
13206 the @code{union} type. When set to @samp{on}, any @code{union} that is
13207 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13208 appears as @samp{@{...@}}.
13210 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13211 with pointers and a memory allocation function. @xref{Expressions,
13214 @node Debugging C Plus Plus
13215 @subsubsection @value{GDBN} Features for C@t{++}
13217 @cindex commands for C@t{++}
13219 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13220 designed specifically for use with C@t{++}. Here is a summary:
13223 @cindex break in overloaded functions
13224 @item @r{breakpoint menus}
13225 When you want a breakpoint in a function whose name is overloaded,
13226 @value{GDBN} has the capability to display a menu of possible breakpoint
13227 locations to help you specify which function definition you want.
13228 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13230 @cindex overloading in C@t{++}
13231 @item rbreak @var{regex}
13232 Setting breakpoints using regular expressions is helpful for setting
13233 breakpoints on overloaded functions that are not members of any special
13235 @xref{Set Breaks, ,Setting Breakpoints}.
13237 @cindex C@t{++} exception handling
13240 Debug C@t{++} exception handling using these commands. @xref{Set
13241 Catchpoints, , Setting Catchpoints}.
13243 @cindex inheritance
13244 @item ptype @var{typename}
13245 Print inheritance relationships as well as other information for type
13247 @xref{Symbols, ,Examining the Symbol Table}.
13249 @item info vtbl @var{expression}.
13250 The @code{info vtbl} command can be used to display the virtual
13251 method tables of the object computed by @var{expression}. This shows
13252 one entry per virtual table; there may be multiple virtual tables when
13253 multiple inheritance is in use.
13255 @cindex C@t{++} symbol display
13256 @item set print demangle
13257 @itemx show print demangle
13258 @itemx set print asm-demangle
13259 @itemx show print asm-demangle
13260 Control whether C@t{++} symbols display in their source form, both when
13261 displaying code as C@t{++} source and when displaying disassemblies.
13262 @xref{Print Settings, ,Print Settings}.
13264 @item set print object
13265 @itemx show print object
13266 Choose whether to print derived (actual) or declared types of objects.
13267 @xref{Print Settings, ,Print Settings}.
13269 @item set print vtbl
13270 @itemx show print vtbl
13271 Control the format for printing virtual function tables.
13272 @xref{Print Settings, ,Print Settings}.
13273 (The @code{vtbl} commands do not work on programs compiled with the HP
13274 ANSI C@t{++} compiler (@code{aCC}).)
13276 @kindex set overload-resolution
13277 @cindex overloaded functions, overload resolution
13278 @item set overload-resolution on
13279 Enable overload resolution for C@t{++} expression evaluation. The default
13280 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13281 and searches for a function whose signature matches the argument types,
13282 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13283 Expressions, ,C@t{++} Expressions}, for details).
13284 If it cannot find a match, it emits a message.
13286 @item set overload-resolution off
13287 Disable overload resolution for C@t{++} expression evaluation. For
13288 overloaded functions that are not class member functions, @value{GDBN}
13289 chooses the first function of the specified name that it finds in the
13290 symbol table, whether or not its arguments are of the correct type. For
13291 overloaded functions that are class member functions, @value{GDBN}
13292 searches for a function whose signature @emph{exactly} matches the
13295 @kindex show overload-resolution
13296 @item show overload-resolution
13297 Show the current setting of overload resolution.
13299 @item @r{Overloaded symbol names}
13300 You can specify a particular definition of an overloaded symbol, using
13301 the same notation that is used to declare such symbols in C@t{++}: type
13302 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13303 also use the @value{GDBN} command-line word completion facilities to list the
13304 available choices, or to finish the type list for you.
13305 @xref{Completion,, Command Completion}, for details on how to do this.
13308 @node Decimal Floating Point
13309 @subsubsection Decimal Floating Point format
13310 @cindex decimal floating point format
13312 @value{GDBN} can examine, set and perform computations with numbers in
13313 decimal floating point format, which in the C language correspond to the
13314 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13315 specified by the extension to support decimal floating-point arithmetic.
13317 There are two encodings in use, depending on the architecture: BID (Binary
13318 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13319 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13322 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13323 to manipulate decimal floating point numbers, it is not possible to convert
13324 (using a cast, for example) integers wider than 32-bit to decimal float.
13326 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13327 point computations, error checking in decimal float operations ignores
13328 underflow, overflow and divide by zero exceptions.
13330 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13331 to inspect @code{_Decimal128} values stored in floating point registers.
13332 See @ref{PowerPC,,PowerPC} for more details.
13338 @value{GDBN} can be used to debug programs written in D and compiled with
13339 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13340 specific feature --- dynamic arrays.
13345 @cindex Go (programming language)
13346 @value{GDBN} can be used to debug programs written in Go and compiled with
13347 @file{gccgo} or @file{6g} compilers.
13349 Here is a summary of the Go-specific features and restrictions:
13352 @cindex current Go package
13353 @item The current Go package
13354 The name of the current package does not need to be specified when
13355 specifying global variables and functions.
13357 For example, given the program:
13361 var myglob = "Shall we?"
13367 When stopped inside @code{main} either of these work:
13371 (gdb) p main.myglob
13374 @cindex builtin Go types
13375 @item Builtin Go types
13376 The @code{string} type is recognized by @value{GDBN} and is printed
13379 @cindex builtin Go functions
13380 @item Builtin Go functions
13381 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13382 function and handles it internally.
13384 @cindex restrictions on Go expressions
13385 @item Restrictions on Go expressions
13386 All Go operators are supported except @code{&^}.
13387 The Go @code{_} ``blank identifier'' is not supported.
13388 Automatic dereferencing of pointers is not supported.
13392 @subsection Objective-C
13394 @cindex Objective-C
13395 This section provides information about some commands and command
13396 options that are useful for debugging Objective-C code. See also
13397 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13398 few more commands specific to Objective-C support.
13401 * Method Names in Commands::
13402 * The Print Command with Objective-C::
13405 @node Method Names in Commands
13406 @subsubsection Method Names in Commands
13408 The following commands have been extended to accept Objective-C method
13409 names as line specifications:
13411 @kindex clear@r{, and Objective-C}
13412 @kindex break@r{, and Objective-C}
13413 @kindex info line@r{, and Objective-C}
13414 @kindex jump@r{, and Objective-C}
13415 @kindex list@r{, and Objective-C}
13419 @item @code{info line}
13424 A fully qualified Objective-C method name is specified as
13427 -[@var{Class} @var{methodName}]
13430 where the minus sign is used to indicate an instance method and a
13431 plus sign (not shown) is used to indicate a class method. The class
13432 name @var{Class} and method name @var{methodName} are enclosed in
13433 brackets, similar to the way messages are specified in Objective-C
13434 source code. For example, to set a breakpoint at the @code{create}
13435 instance method of class @code{Fruit} in the program currently being
13439 break -[Fruit create]
13442 To list ten program lines around the @code{initialize} class method,
13446 list +[NSText initialize]
13449 In the current version of @value{GDBN}, the plus or minus sign is
13450 required. In future versions of @value{GDBN}, the plus or minus
13451 sign will be optional, but you can use it to narrow the search. It
13452 is also possible to specify just a method name:
13458 You must specify the complete method name, including any colons. If
13459 your program's source files contain more than one @code{create} method,
13460 you'll be presented with a numbered list of classes that implement that
13461 method. Indicate your choice by number, or type @samp{0} to exit if
13464 As another example, to clear a breakpoint established at the
13465 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13468 clear -[NSWindow makeKeyAndOrderFront:]
13471 @node The Print Command with Objective-C
13472 @subsubsection The Print Command With Objective-C
13473 @cindex Objective-C, print objects
13474 @kindex print-object
13475 @kindex po @r{(@code{print-object})}
13477 The print command has also been extended to accept methods. For example:
13480 print -[@var{object} hash]
13483 @cindex print an Objective-C object description
13484 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13486 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13487 and print the result. Also, an additional command has been added,
13488 @code{print-object} or @code{po} for short, which is meant to print
13489 the description of an object. However, this command may only work
13490 with certain Objective-C libraries that have a particular hook
13491 function, @code{_NSPrintForDebugger}, defined.
13494 @subsection OpenCL C
13497 This section provides information about @value{GDBN}s OpenCL C support.
13500 * OpenCL C Datatypes::
13501 * OpenCL C Expressions::
13502 * OpenCL C Operators::
13505 @node OpenCL C Datatypes
13506 @subsubsection OpenCL C Datatypes
13508 @cindex OpenCL C Datatypes
13509 @value{GDBN} supports the builtin scalar and vector datatypes specified
13510 by OpenCL 1.1. In addition the half- and double-precision floating point
13511 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13512 extensions are also known to @value{GDBN}.
13514 @node OpenCL C Expressions
13515 @subsubsection OpenCL C Expressions
13517 @cindex OpenCL C Expressions
13518 @value{GDBN} supports accesses to vector components including the access as
13519 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13520 supported by @value{GDBN} can be used as well.
13522 @node OpenCL C Operators
13523 @subsubsection OpenCL C Operators
13525 @cindex OpenCL C Operators
13526 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13530 @subsection Fortran
13531 @cindex Fortran-specific support in @value{GDBN}
13533 @value{GDBN} can be used to debug programs written in Fortran, but it
13534 currently supports only the features of Fortran 77 language.
13536 @cindex trailing underscore, in Fortran symbols
13537 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13538 among them) append an underscore to the names of variables and
13539 functions. When you debug programs compiled by those compilers, you
13540 will need to refer to variables and functions with a trailing
13544 * Fortran Operators:: Fortran operators and expressions
13545 * Fortran Defaults:: Default settings for Fortran
13546 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13549 @node Fortran Operators
13550 @subsubsection Fortran Operators and Expressions
13552 @cindex Fortran operators and expressions
13554 Operators must be defined on values of specific types. For instance,
13555 @code{+} is defined on numbers, but not on characters or other non-
13556 arithmetic types. Operators are often defined on groups of types.
13560 The exponentiation operator. It raises the first operand to the power
13564 The range operator. Normally used in the form of array(low:high) to
13565 represent a section of array.
13568 The access component operator. Normally used to access elements in derived
13569 types. Also suitable for unions. As unions aren't part of regular Fortran,
13570 this can only happen when accessing a register that uses a gdbarch-defined
13574 @node Fortran Defaults
13575 @subsubsection Fortran Defaults
13577 @cindex Fortran Defaults
13579 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13580 default uses case-insensitive matches for Fortran symbols. You can
13581 change that with the @samp{set case-insensitive} command, see
13582 @ref{Symbols}, for the details.
13584 @node Special Fortran Commands
13585 @subsubsection Special Fortran Commands
13587 @cindex Special Fortran commands
13589 @value{GDBN} has some commands to support Fortran-specific features,
13590 such as displaying common blocks.
13593 @cindex @code{COMMON} blocks, Fortran
13594 @kindex info common
13595 @item info common @r{[}@var{common-name}@r{]}
13596 This command prints the values contained in the Fortran @code{COMMON}
13597 block whose name is @var{common-name}. With no argument, the names of
13598 all @code{COMMON} blocks visible at the current program location are
13605 @cindex Pascal support in @value{GDBN}, limitations
13606 Debugging Pascal programs which use sets, subranges, file variables, or
13607 nested functions does not currently work. @value{GDBN} does not support
13608 entering expressions, printing values, or similar features using Pascal
13611 The Pascal-specific command @code{set print pascal_static-members}
13612 controls whether static members of Pascal objects are displayed.
13613 @xref{Print Settings, pascal_static-members}.
13616 @subsection Modula-2
13618 @cindex Modula-2, @value{GDBN} support
13620 The extensions made to @value{GDBN} to support Modula-2 only support
13621 output from the @sc{gnu} Modula-2 compiler (which is currently being
13622 developed). Other Modula-2 compilers are not currently supported, and
13623 attempting to debug executables produced by them is most likely
13624 to give an error as @value{GDBN} reads in the executable's symbol
13627 @cindex expressions in Modula-2
13629 * M2 Operators:: Built-in operators
13630 * Built-In Func/Proc:: Built-in functions and procedures
13631 * M2 Constants:: Modula-2 constants
13632 * M2 Types:: Modula-2 types
13633 * M2 Defaults:: Default settings for Modula-2
13634 * Deviations:: Deviations from standard Modula-2
13635 * M2 Checks:: Modula-2 type and range checks
13636 * M2 Scope:: The scope operators @code{::} and @code{.}
13637 * GDB/M2:: @value{GDBN} and Modula-2
13641 @subsubsection Operators
13642 @cindex Modula-2 operators
13644 Operators must be defined on values of specific types. For instance,
13645 @code{+} is defined on numbers, but not on structures. Operators are
13646 often defined on groups of types. For the purposes of Modula-2, the
13647 following definitions hold:
13652 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13656 @emph{Character types} consist of @code{CHAR} and its subranges.
13659 @emph{Floating-point types} consist of @code{REAL}.
13662 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13666 @emph{Scalar types} consist of all of the above.
13669 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13672 @emph{Boolean types} consist of @code{BOOLEAN}.
13676 The following operators are supported, and appear in order of
13677 increasing precedence:
13681 Function argument or array index separator.
13684 Assignment. The value of @var{var} @code{:=} @var{value} is
13688 Less than, greater than on integral, floating-point, or enumerated
13692 Less than or equal to, greater than or equal to
13693 on integral, floating-point and enumerated types, or set inclusion on
13694 set types. Same precedence as @code{<}.
13696 @item =@r{, }<>@r{, }#
13697 Equality and two ways of expressing inequality, valid on scalar types.
13698 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13699 available for inequality, since @code{#} conflicts with the script
13703 Set membership. Defined on set types and the types of their members.
13704 Same precedence as @code{<}.
13707 Boolean disjunction. Defined on boolean types.
13710 Boolean conjunction. Defined on boolean types.
13713 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13716 Addition and subtraction on integral and floating-point types, or union
13717 and difference on set types.
13720 Multiplication on integral and floating-point types, or set intersection
13724 Division on floating-point types, or symmetric set difference on set
13725 types. Same precedence as @code{*}.
13728 Integer division and remainder. Defined on integral types. Same
13729 precedence as @code{*}.
13732 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13735 Pointer dereferencing. Defined on pointer types.
13738 Boolean negation. Defined on boolean types. Same precedence as
13742 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13743 precedence as @code{^}.
13746 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13749 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13753 @value{GDBN} and Modula-2 scope operators.
13757 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13758 treats the use of the operator @code{IN}, or the use of operators
13759 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13760 @code{<=}, and @code{>=} on sets as an error.
13764 @node Built-In Func/Proc
13765 @subsubsection Built-in Functions and Procedures
13766 @cindex Modula-2 built-ins
13768 Modula-2 also makes available several built-in procedures and functions.
13769 In describing these, the following metavariables are used:
13774 represents an @code{ARRAY} variable.
13777 represents a @code{CHAR} constant or variable.
13780 represents a variable or constant of integral type.
13783 represents an identifier that belongs to a set. Generally used in the
13784 same function with the metavariable @var{s}. The type of @var{s} should
13785 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13788 represents a variable or constant of integral or floating-point type.
13791 represents a variable or constant of floating-point type.
13797 represents a variable.
13800 represents a variable or constant of one of many types. See the
13801 explanation of the function for details.
13804 All Modula-2 built-in procedures also return a result, described below.
13808 Returns the absolute value of @var{n}.
13811 If @var{c} is a lower case letter, it returns its upper case
13812 equivalent, otherwise it returns its argument.
13815 Returns the character whose ordinal value is @var{i}.
13818 Decrements the value in the variable @var{v} by one. Returns the new value.
13820 @item DEC(@var{v},@var{i})
13821 Decrements the value in the variable @var{v} by @var{i}. Returns the
13824 @item EXCL(@var{m},@var{s})
13825 Removes the element @var{m} from the set @var{s}. Returns the new
13828 @item FLOAT(@var{i})
13829 Returns the floating point equivalent of the integer @var{i}.
13831 @item HIGH(@var{a})
13832 Returns the index of the last member of @var{a}.
13835 Increments the value in the variable @var{v} by one. Returns the new value.
13837 @item INC(@var{v},@var{i})
13838 Increments the value in the variable @var{v} by @var{i}. Returns the
13841 @item INCL(@var{m},@var{s})
13842 Adds the element @var{m} to the set @var{s} if it is not already
13843 there. Returns the new set.
13846 Returns the maximum value of the type @var{t}.
13849 Returns the minimum value of the type @var{t}.
13852 Returns boolean TRUE if @var{i} is an odd number.
13855 Returns the ordinal value of its argument. For example, the ordinal
13856 value of a character is its @sc{ascii} value (on machines supporting the
13857 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13858 integral, character and enumerated types.
13860 @item SIZE(@var{x})
13861 Returns the size of its argument. @var{x} can be a variable or a type.
13863 @item TRUNC(@var{r})
13864 Returns the integral part of @var{r}.
13866 @item TSIZE(@var{x})
13867 Returns the size of its argument. @var{x} can be a variable or a type.
13869 @item VAL(@var{t},@var{i})
13870 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13874 @emph{Warning:} Sets and their operations are not yet supported, so
13875 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13879 @cindex Modula-2 constants
13881 @subsubsection Constants
13883 @value{GDBN} allows you to express the constants of Modula-2 in the following
13889 Integer constants are simply a sequence of digits. When used in an
13890 expression, a constant is interpreted to be type-compatible with the
13891 rest of the expression. Hexadecimal integers are specified by a
13892 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13895 Floating point constants appear as a sequence of digits, followed by a
13896 decimal point and another sequence of digits. An optional exponent can
13897 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13898 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13899 digits of the floating point constant must be valid decimal (base 10)
13903 Character constants consist of a single character enclosed by a pair of
13904 like quotes, either single (@code{'}) or double (@code{"}). They may
13905 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13906 followed by a @samp{C}.
13909 String constants consist of a sequence of characters enclosed by a
13910 pair of like quotes, either single (@code{'}) or double (@code{"}).
13911 Escape sequences in the style of C are also allowed. @xref{C
13912 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13916 Enumerated constants consist of an enumerated identifier.
13919 Boolean constants consist of the identifiers @code{TRUE} and
13923 Pointer constants consist of integral values only.
13926 Set constants are not yet supported.
13930 @subsubsection Modula-2 Types
13931 @cindex Modula-2 types
13933 Currently @value{GDBN} can print the following data types in Modula-2
13934 syntax: array types, record types, set types, pointer types, procedure
13935 types, enumerated types, subrange types and base types. You can also
13936 print the contents of variables declared using these type.
13937 This section gives a number of simple source code examples together with
13938 sample @value{GDBN} sessions.
13940 The first example contains the following section of code:
13949 and you can request @value{GDBN} to interrogate the type and value of
13950 @code{r} and @code{s}.
13953 (@value{GDBP}) print s
13955 (@value{GDBP}) ptype s
13957 (@value{GDBP}) print r
13959 (@value{GDBP}) ptype r
13964 Likewise if your source code declares @code{s} as:
13968 s: SET ['A'..'Z'] ;
13972 then you may query the type of @code{s} by:
13975 (@value{GDBP}) ptype s
13976 type = SET ['A'..'Z']
13980 Note that at present you cannot interactively manipulate set
13981 expressions using the debugger.
13983 The following example shows how you might declare an array in Modula-2
13984 and how you can interact with @value{GDBN} to print its type and contents:
13988 s: ARRAY [-10..10] OF CHAR ;
13992 (@value{GDBP}) ptype s
13993 ARRAY [-10..10] OF CHAR
13996 Note that the array handling is not yet complete and although the type
13997 is printed correctly, expression handling still assumes that all
13998 arrays have a lower bound of zero and not @code{-10} as in the example
14001 Here are some more type related Modula-2 examples:
14005 colour = (blue, red, yellow, green) ;
14006 t = [blue..yellow] ;
14014 The @value{GDBN} interaction shows how you can query the data type
14015 and value of a variable.
14018 (@value{GDBP}) print s
14020 (@value{GDBP}) ptype t
14021 type = [blue..yellow]
14025 In this example a Modula-2 array is declared and its contents
14026 displayed. Observe that the contents are written in the same way as
14027 their @code{C} counterparts.
14031 s: ARRAY [1..5] OF CARDINAL ;
14037 (@value{GDBP}) print s
14038 $1 = @{1, 0, 0, 0, 0@}
14039 (@value{GDBP}) ptype s
14040 type = ARRAY [1..5] OF CARDINAL
14043 The Modula-2 language interface to @value{GDBN} also understands
14044 pointer types as shown in this example:
14048 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14055 and you can request that @value{GDBN} describes the type of @code{s}.
14058 (@value{GDBP}) ptype s
14059 type = POINTER TO ARRAY [1..5] OF CARDINAL
14062 @value{GDBN} handles compound types as we can see in this example.
14063 Here we combine array types, record types, pointer types and subrange
14074 myarray = ARRAY myrange OF CARDINAL ;
14075 myrange = [-2..2] ;
14077 s: POINTER TO ARRAY myrange OF foo ;
14081 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14085 (@value{GDBP}) ptype s
14086 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14089 f3 : ARRAY [-2..2] OF CARDINAL;
14094 @subsubsection Modula-2 Defaults
14095 @cindex Modula-2 defaults
14097 If type and range checking are set automatically by @value{GDBN}, they
14098 both default to @code{on} whenever the working language changes to
14099 Modula-2. This happens regardless of whether you or @value{GDBN}
14100 selected the working language.
14102 If you allow @value{GDBN} to set the language automatically, then entering
14103 code compiled from a file whose name ends with @file{.mod} sets the
14104 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14105 Infer the Source Language}, for further details.
14108 @subsubsection Deviations from Standard Modula-2
14109 @cindex Modula-2, deviations from
14111 A few changes have been made to make Modula-2 programs easier to debug.
14112 This is done primarily via loosening its type strictness:
14116 Unlike in standard Modula-2, pointer constants can be formed by
14117 integers. This allows you to modify pointer variables during
14118 debugging. (In standard Modula-2, the actual address contained in a
14119 pointer variable is hidden from you; it can only be modified
14120 through direct assignment to another pointer variable or expression that
14121 returned a pointer.)
14124 C escape sequences can be used in strings and characters to represent
14125 non-printable characters. @value{GDBN} prints out strings with these
14126 escape sequences embedded. Single non-printable characters are
14127 printed using the @samp{CHR(@var{nnn})} format.
14130 The assignment operator (@code{:=}) returns the value of its right-hand
14134 All built-in procedures both modify @emph{and} return their argument.
14138 @subsubsection Modula-2 Type and Range Checks
14139 @cindex Modula-2 checks
14142 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14145 @c FIXME remove warning when type/range checks added
14147 @value{GDBN} considers two Modula-2 variables type equivalent if:
14151 They are of types that have been declared equivalent via a @code{TYPE
14152 @var{t1} = @var{t2}} statement
14155 They have been declared on the same line. (Note: This is true of the
14156 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14159 As long as type checking is enabled, any attempt to combine variables
14160 whose types are not equivalent is an error.
14162 Range checking is done on all mathematical operations, assignment, array
14163 index bounds, and all built-in functions and procedures.
14166 @subsubsection The Scope Operators @code{::} and @code{.}
14168 @cindex @code{.}, Modula-2 scope operator
14169 @cindex colon, doubled as scope operator
14171 @vindex colon-colon@r{, in Modula-2}
14172 @c Info cannot handle :: but TeX can.
14175 @vindex ::@r{, in Modula-2}
14178 There are a few subtle differences between the Modula-2 scope operator
14179 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14184 @var{module} . @var{id}
14185 @var{scope} :: @var{id}
14189 where @var{scope} is the name of a module or a procedure,
14190 @var{module} the name of a module, and @var{id} is any declared
14191 identifier within your program, except another module.
14193 Using the @code{::} operator makes @value{GDBN} search the scope
14194 specified by @var{scope} for the identifier @var{id}. If it is not
14195 found in the specified scope, then @value{GDBN} searches all scopes
14196 enclosing the one specified by @var{scope}.
14198 Using the @code{.} operator makes @value{GDBN} search the current scope for
14199 the identifier specified by @var{id} that was imported from the
14200 definition module specified by @var{module}. With this operator, it is
14201 an error if the identifier @var{id} was not imported from definition
14202 module @var{module}, or if @var{id} is not an identifier in
14206 @subsubsection @value{GDBN} and Modula-2
14208 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14209 Five subcommands of @code{set print} and @code{show print} apply
14210 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14211 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14212 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14213 analogue in Modula-2.
14215 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14216 with any language, is not useful with Modula-2. Its
14217 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14218 created in Modula-2 as they can in C or C@t{++}. However, because an
14219 address can be specified by an integral constant, the construct
14220 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14222 @cindex @code{#} in Modula-2
14223 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14224 interpreted as the beginning of a comment. Use @code{<>} instead.
14230 The extensions made to @value{GDBN} for Ada only support
14231 output from the @sc{gnu} Ada (GNAT) compiler.
14232 Other Ada compilers are not currently supported, and
14233 attempting to debug executables produced by them is most likely
14237 @cindex expressions in Ada
14239 * Ada Mode Intro:: General remarks on the Ada syntax
14240 and semantics supported by Ada mode
14242 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14243 * Additions to Ada:: Extensions of the Ada expression syntax.
14244 * Stopping Before Main Program:: Debugging the program during elaboration.
14245 * Ada Tasks:: Listing and setting breakpoints in tasks.
14246 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14247 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14249 * Ada Glitches:: Known peculiarities of Ada mode.
14252 @node Ada Mode Intro
14253 @subsubsection Introduction
14254 @cindex Ada mode, general
14256 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14257 syntax, with some extensions.
14258 The philosophy behind the design of this subset is
14262 That @value{GDBN} should provide basic literals and access to operations for
14263 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14264 leaving more sophisticated computations to subprograms written into the
14265 program (which therefore may be called from @value{GDBN}).
14268 That type safety and strict adherence to Ada language restrictions
14269 are not particularly important to the @value{GDBN} user.
14272 That brevity is important to the @value{GDBN} user.
14275 Thus, for brevity, the debugger acts as if all names declared in
14276 user-written packages are directly visible, even if they are not visible
14277 according to Ada rules, thus making it unnecessary to fully qualify most
14278 names with their packages, regardless of context. Where this causes
14279 ambiguity, @value{GDBN} asks the user's intent.
14281 The debugger will start in Ada mode if it detects an Ada main program.
14282 As for other languages, it will enter Ada mode when stopped in a program that
14283 was translated from an Ada source file.
14285 While in Ada mode, you may use `@t{--}' for comments. This is useful
14286 mostly for documenting command files. The standard @value{GDBN} comment
14287 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14288 middle (to allow based literals).
14290 The debugger supports limited overloading. Given a subprogram call in which
14291 the function symbol has multiple definitions, it will use the number of
14292 actual parameters and some information about their types to attempt to narrow
14293 the set of definitions. It also makes very limited use of context, preferring
14294 procedures to functions in the context of the @code{call} command, and
14295 functions to procedures elsewhere.
14297 @node Omissions from Ada
14298 @subsubsection Omissions from Ada
14299 @cindex Ada, omissions from
14301 Here are the notable omissions from the subset:
14305 Only a subset of the attributes are supported:
14309 @t{'First}, @t{'Last}, and @t{'Length}
14310 on array objects (not on types and subtypes).
14313 @t{'Min} and @t{'Max}.
14316 @t{'Pos} and @t{'Val}.
14322 @t{'Range} on array objects (not subtypes), but only as the right
14323 operand of the membership (@code{in}) operator.
14326 @t{'Access}, @t{'Unchecked_Access}, and
14327 @t{'Unrestricted_Access} (a GNAT extension).
14335 @code{Characters.Latin_1} are not available and
14336 concatenation is not implemented. Thus, escape characters in strings are
14337 not currently available.
14340 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14341 equality of representations. They will generally work correctly
14342 for strings and arrays whose elements have integer or enumeration types.
14343 They may not work correctly for arrays whose element
14344 types have user-defined equality, for arrays of real values
14345 (in particular, IEEE-conformant floating point, because of negative
14346 zeroes and NaNs), and for arrays whose elements contain unused bits with
14347 indeterminate values.
14350 The other component-by-component array operations (@code{and}, @code{or},
14351 @code{xor}, @code{not}, and relational tests other than equality)
14352 are not implemented.
14355 @cindex array aggregates (Ada)
14356 @cindex record aggregates (Ada)
14357 @cindex aggregates (Ada)
14358 There is limited support for array and record aggregates. They are
14359 permitted only on the right sides of assignments, as in these examples:
14362 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14363 (@value{GDBP}) set An_Array := (1, others => 0)
14364 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14365 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14366 (@value{GDBP}) set A_Record := (1, "Peter", True);
14367 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14371 discriminant's value by assigning an aggregate has an
14372 undefined effect if that discriminant is used within the record.
14373 However, you can first modify discriminants by directly assigning to
14374 them (which normally would not be allowed in Ada), and then performing an
14375 aggregate assignment. For example, given a variable @code{A_Rec}
14376 declared to have a type such as:
14379 type Rec (Len : Small_Integer := 0) is record
14381 Vals : IntArray (1 .. Len);
14385 you can assign a value with a different size of @code{Vals} with two
14389 (@value{GDBP}) set A_Rec.Len := 4
14390 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14393 As this example also illustrates, @value{GDBN} is very loose about the usual
14394 rules concerning aggregates. You may leave out some of the
14395 components of an array or record aggregate (such as the @code{Len}
14396 component in the assignment to @code{A_Rec} above); they will retain their
14397 original values upon assignment. You may freely use dynamic values as
14398 indices in component associations. You may even use overlapping or
14399 redundant component associations, although which component values are
14400 assigned in such cases is not defined.
14403 Calls to dispatching subprograms are not implemented.
14406 The overloading algorithm is much more limited (i.e., less selective)
14407 than that of real Ada. It makes only limited use of the context in
14408 which a subexpression appears to resolve its meaning, and it is much
14409 looser in its rules for allowing type matches. As a result, some
14410 function calls will be ambiguous, and the user will be asked to choose
14411 the proper resolution.
14414 The @code{new} operator is not implemented.
14417 Entry calls are not implemented.
14420 Aside from printing, arithmetic operations on the native VAX floating-point
14421 formats are not supported.
14424 It is not possible to slice a packed array.
14427 The names @code{True} and @code{False}, when not part of a qualified name,
14428 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14430 Should your program
14431 redefine these names in a package or procedure (at best a dubious practice),
14432 you will have to use fully qualified names to access their new definitions.
14435 @node Additions to Ada
14436 @subsubsection Additions to Ada
14437 @cindex Ada, deviations from
14439 As it does for other languages, @value{GDBN} makes certain generic
14440 extensions to Ada (@pxref{Expressions}):
14444 If the expression @var{E} is a variable residing in memory (typically
14445 a local variable or array element) and @var{N} is a positive integer,
14446 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14447 @var{N}-1 adjacent variables following it in memory as an array. In
14448 Ada, this operator is generally not necessary, since its prime use is
14449 in displaying parts of an array, and slicing will usually do this in
14450 Ada. However, there are occasional uses when debugging programs in
14451 which certain debugging information has been optimized away.
14454 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14455 appears in function or file @var{B}.'' When @var{B} is a file name,
14456 you must typically surround it in single quotes.
14459 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14460 @var{type} that appears at address @var{addr}.''
14463 A name starting with @samp{$} is a convenience variable
14464 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14467 In addition, @value{GDBN} provides a few other shortcuts and outright
14468 additions specific to Ada:
14472 The assignment statement is allowed as an expression, returning
14473 its right-hand operand as its value. Thus, you may enter
14476 (@value{GDBP}) set x := y + 3
14477 (@value{GDBP}) print A(tmp := y + 1)
14481 The semicolon is allowed as an ``operator,'' returning as its value
14482 the value of its right-hand operand.
14483 This allows, for example,
14484 complex conditional breaks:
14487 (@value{GDBP}) break f
14488 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14492 Rather than use catenation and symbolic character names to introduce special
14493 characters into strings, one may instead use a special bracket notation,
14494 which is also used to print strings. A sequence of characters of the form
14495 @samp{["@var{XX}"]} within a string or character literal denotes the
14496 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14497 sequence of characters @samp{["""]} also denotes a single quotation mark
14498 in strings. For example,
14500 "One line.["0a"]Next line.["0a"]"
14503 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14507 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14508 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14512 (@value{GDBP}) print 'max(x, y)
14516 When printing arrays, @value{GDBN} uses positional notation when the
14517 array has a lower bound of 1, and uses a modified named notation otherwise.
14518 For example, a one-dimensional array of three integers with a lower bound
14519 of 3 might print as
14526 That is, in contrast to valid Ada, only the first component has a @code{=>}
14530 You may abbreviate attributes in expressions with any unique,
14531 multi-character subsequence of
14532 their names (an exact match gets preference).
14533 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14534 in place of @t{a'length}.
14537 @cindex quoting Ada internal identifiers
14538 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14539 to lower case. The GNAT compiler uses upper-case characters for
14540 some of its internal identifiers, which are normally of no interest to users.
14541 For the rare occasions when you actually have to look at them,
14542 enclose them in angle brackets to avoid the lower-case mapping.
14545 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14549 Printing an object of class-wide type or dereferencing an
14550 access-to-class-wide value will display all the components of the object's
14551 specific type (as indicated by its run-time tag). Likewise, component
14552 selection on such a value will operate on the specific type of the
14557 @node Stopping Before Main Program
14558 @subsubsection Stopping at the Very Beginning
14560 @cindex breakpointing Ada elaboration code
14561 It is sometimes necessary to debug the program during elaboration, and
14562 before reaching the main procedure.
14563 As defined in the Ada Reference
14564 Manual, the elaboration code is invoked from a procedure called
14565 @code{adainit}. To run your program up to the beginning of
14566 elaboration, simply use the following two commands:
14567 @code{tbreak adainit} and @code{run}.
14570 @subsubsection Extensions for Ada Tasks
14571 @cindex Ada, tasking
14573 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14574 @value{GDBN} provides the following task-related commands:
14579 This command shows a list of current Ada tasks, as in the following example:
14586 (@value{GDBP}) info tasks
14587 ID TID P-ID Pri State Name
14588 1 8088000 0 15 Child Activation Wait main_task
14589 2 80a4000 1 15 Accept Statement b
14590 3 809a800 1 15 Child Activation Wait a
14591 * 4 80ae800 3 15 Runnable c
14596 In this listing, the asterisk before the last task indicates it to be the
14597 task currently being inspected.
14601 Represents @value{GDBN}'s internal task number.
14607 The parent's task ID (@value{GDBN}'s internal task number).
14610 The base priority of the task.
14613 Current state of the task.
14617 The task has been created but has not been activated. It cannot be
14621 The task is not blocked for any reason known to Ada. (It may be waiting
14622 for a mutex, though.) It is conceptually "executing" in normal mode.
14625 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14626 that were waiting on terminate alternatives have been awakened and have
14627 terminated themselves.
14629 @item Child Activation Wait
14630 The task is waiting for created tasks to complete activation.
14632 @item Accept Statement
14633 The task is waiting on an accept or selective wait statement.
14635 @item Waiting on entry call
14636 The task is waiting on an entry call.
14638 @item Async Select Wait
14639 The task is waiting to start the abortable part of an asynchronous
14643 The task is waiting on a select statement with only a delay
14646 @item Child Termination Wait
14647 The task is sleeping having completed a master within itself, and is
14648 waiting for the tasks dependent on that master to become terminated or
14649 waiting on a terminate Phase.
14651 @item Wait Child in Term Alt
14652 The task is sleeping waiting for tasks on terminate alternatives to
14653 finish terminating.
14655 @item Accepting RV with @var{taskno}
14656 The task is accepting a rendez-vous with the task @var{taskno}.
14660 Name of the task in the program.
14664 @kindex info task @var{taskno}
14665 @item info task @var{taskno}
14666 This command shows detailled informations on the specified task, as in
14667 the following example:
14672 (@value{GDBP}) info tasks
14673 ID TID P-ID Pri State Name
14674 1 8077880 0 15 Child Activation Wait main_task
14675 * 2 807c468 1 15 Runnable task_1
14676 (@value{GDBP}) info task 2
14677 Ada Task: 0x807c468
14680 Parent: 1 (main_task)
14686 @kindex task@r{ (Ada)}
14687 @cindex current Ada task ID
14688 This command prints the ID of the current task.
14694 (@value{GDBP}) info tasks
14695 ID TID P-ID Pri State Name
14696 1 8077870 0 15 Child Activation Wait main_task
14697 * 2 807c458 1 15 Runnable t
14698 (@value{GDBP}) task
14699 [Current task is 2]
14702 @item task @var{taskno}
14703 @cindex Ada task switching
14704 This command is like the @code{thread @var{threadno}}
14705 command (@pxref{Threads}). It switches the context of debugging
14706 from the current task to the given task.
14712 (@value{GDBP}) info tasks
14713 ID TID P-ID Pri State Name
14714 1 8077870 0 15 Child Activation Wait main_task
14715 * 2 807c458 1 15 Runnable t
14716 (@value{GDBP}) task 1
14717 [Switching to task 1]
14718 #0 0x8067726 in pthread_cond_wait ()
14720 #0 0x8067726 in pthread_cond_wait ()
14721 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14722 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14723 #3 0x806153e in system.tasking.stages.activate_tasks ()
14724 #4 0x804aacc in un () at un.adb:5
14727 @item break @var{linespec} task @var{taskno}
14728 @itemx break @var{linespec} task @var{taskno} if @dots{}
14729 @cindex breakpoints and tasks, in Ada
14730 @cindex task breakpoints, in Ada
14731 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14732 These commands are like the @code{break @dots{} thread @dots{}}
14733 command (@pxref{Thread Stops}).
14734 @var{linespec} specifies source lines, as described
14735 in @ref{Specify Location}.
14737 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14738 to specify that you only want @value{GDBN} to stop the program when a
14739 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14740 numeric task identifiers assigned by @value{GDBN}, shown in the first
14741 column of the @samp{info tasks} display.
14743 If you do not specify @samp{task @var{taskno}} when you set a
14744 breakpoint, the breakpoint applies to @emph{all} tasks of your
14747 You can use the @code{task} qualifier on conditional breakpoints as
14748 well; in this case, place @samp{task @var{taskno}} before the
14749 breakpoint condition (before the @code{if}).
14757 (@value{GDBP}) info tasks
14758 ID TID P-ID Pri State Name
14759 1 140022020 0 15 Child Activation Wait main_task
14760 2 140045060 1 15 Accept/Select Wait t2
14761 3 140044840 1 15 Runnable t1
14762 * 4 140056040 1 15 Runnable t3
14763 (@value{GDBP}) b 15 task 2
14764 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14765 (@value{GDBP}) cont
14770 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14772 (@value{GDBP}) info tasks
14773 ID TID P-ID Pri State Name
14774 1 140022020 0 15 Child Activation Wait main_task
14775 * 2 140045060 1 15 Runnable t2
14776 3 140044840 1 15 Runnable t1
14777 4 140056040 1 15 Delay Sleep t3
14781 @node Ada Tasks and Core Files
14782 @subsubsection Tasking Support when Debugging Core Files
14783 @cindex Ada tasking and core file debugging
14785 When inspecting a core file, as opposed to debugging a live program,
14786 tasking support may be limited or even unavailable, depending on
14787 the platform being used.
14788 For instance, on x86-linux, the list of tasks is available, but task
14789 switching is not supported. On Tru64, however, task switching will work
14792 On certain platforms, including Tru64, the debugger needs to perform some
14793 memory writes in order to provide Ada tasking support. When inspecting
14794 a core file, this means that the core file must be opened with read-write
14795 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14796 Under these circumstances, you should make a backup copy of the core
14797 file before inspecting it with @value{GDBN}.
14799 @node Ravenscar Profile
14800 @subsubsection Tasking Support when using the Ravenscar Profile
14801 @cindex Ravenscar Profile
14803 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14804 specifically designed for systems with safety-critical real-time
14808 @kindex set ravenscar task-switching on
14809 @cindex task switching with program using Ravenscar Profile
14810 @item set ravenscar task-switching on
14811 Allows task switching when debugging a program that uses the Ravenscar
14812 Profile. This is the default.
14814 @kindex set ravenscar task-switching off
14815 @item set ravenscar task-switching off
14816 Turn off task switching when debugging a program that uses the Ravenscar
14817 Profile. This is mostly intended to disable the code that adds support
14818 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14819 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14820 To be effective, this command should be run before the program is started.
14822 @kindex show ravenscar task-switching
14823 @item show ravenscar task-switching
14824 Show whether it is possible to switch from task to task in a program
14825 using the Ravenscar Profile.
14830 @subsubsection Known Peculiarities of Ada Mode
14831 @cindex Ada, problems
14833 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14834 we know of several problems with and limitations of Ada mode in
14836 some of which will be fixed with planned future releases of the debugger
14837 and the GNU Ada compiler.
14841 Static constants that the compiler chooses not to materialize as objects in
14842 storage are invisible to the debugger.
14845 Named parameter associations in function argument lists are ignored (the
14846 argument lists are treated as positional).
14849 Many useful library packages are currently invisible to the debugger.
14852 Fixed-point arithmetic, conversions, input, and output is carried out using
14853 floating-point arithmetic, and may give results that only approximate those on
14857 The GNAT compiler never generates the prefix @code{Standard} for any of
14858 the standard symbols defined by the Ada language. @value{GDBN} knows about
14859 this: it will strip the prefix from names when you use it, and will never
14860 look for a name you have so qualified among local symbols, nor match against
14861 symbols in other packages or subprograms. If you have
14862 defined entities anywhere in your program other than parameters and
14863 local variables whose simple names match names in @code{Standard},
14864 GNAT's lack of qualification here can cause confusion. When this happens,
14865 you can usually resolve the confusion
14866 by qualifying the problematic names with package
14867 @code{Standard} explicitly.
14870 Older versions of the compiler sometimes generate erroneous debugging
14871 information, resulting in the debugger incorrectly printing the value
14872 of affected entities. In some cases, the debugger is able to work
14873 around an issue automatically. In other cases, the debugger is able
14874 to work around the issue, but the work-around has to be specifically
14877 @kindex set ada trust-PAD-over-XVS
14878 @kindex show ada trust-PAD-over-XVS
14881 @item set ada trust-PAD-over-XVS on
14882 Configure GDB to strictly follow the GNAT encoding when computing the
14883 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14884 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14885 a complete description of the encoding used by the GNAT compiler).
14886 This is the default.
14888 @item set ada trust-PAD-over-XVS off
14889 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14890 sometimes prints the wrong value for certain entities, changing @code{ada
14891 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14892 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14893 @code{off}, but this incurs a slight performance penalty, so it is
14894 recommended to leave this setting to @code{on} unless necessary.
14898 @node Unsupported Languages
14899 @section Unsupported Languages
14901 @cindex unsupported languages
14902 @cindex minimal language
14903 In addition to the other fully-supported programming languages,
14904 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14905 It does not represent a real programming language, but provides a set
14906 of capabilities close to what the C or assembly languages provide.
14907 This should allow most simple operations to be performed while debugging
14908 an application that uses a language currently not supported by @value{GDBN}.
14910 If the language is set to @code{auto}, @value{GDBN} will automatically
14911 select this language if the current frame corresponds to an unsupported
14915 @chapter Examining the Symbol Table
14917 The commands described in this chapter allow you to inquire about the
14918 symbols (names of variables, functions and types) defined in your
14919 program. This information is inherent in the text of your program and
14920 does not change as your program executes. @value{GDBN} finds it in your
14921 program's symbol table, in the file indicated when you started @value{GDBN}
14922 (@pxref{File Options, ,Choosing Files}), or by one of the
14923 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14925 @cindex symbol names
14926 @cindex names of symbols
14927 @cindex quoting names
14928 Occasionally, you may need to refer to symbols that contain unusual
14929 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14930 most frequent case is in referring to static variables in other
14931 source files (@pxref{Variables,,Program Variables}). File names
14932 are recorded in object files as debugging symbols, but @value{GDBN} would
14933 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14934 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14935 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14942 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14945 @cindex case-insensitive symbol names
14946 @cindex case sensitivity in symbol names
14947 @kindex set case-sensitive
14948 @item set case-sensitive on
14949 @itemx set case-sensitive off
14950 @itemx set case-sensitive auto
14951 Normally, when @value{GDBN} looks up symbols, it matches their names
14952 with case sensitivity determined by the current source language.
14953 Occasionally, you may wish to control that. The command @code{set
14954 case-sensitive} lets you do that by specifying @code{on} for
14955 case-sensitive matches or @code{off} for case-insensitive ones. If
14956 you specify @code{auto}, case sensitivity is reset to the default
14957 suitable for the source language. The default is case-sensitive
14958 matches for all languages except for Fortran, for which the default is
14959 case-insensitive matches.
14961 @kindex show case-sensitive
14962 @item show case-sensitive
14963 This command shows the current setting of case sensitivity for symbols
14966 @kindex info address
14967 @cindex address of a symbol
14968 @item info address @var{symbol}
14969 Describe where the data for @var{symbol} is stored. For a register
14970 variable, this says which register it is kept in. For a non-register
14971 local variable, this prints the stack-frame offset at which the variable
14974 Note the contrast with @samp{print &@var{symbol}}, which does not work
14975 at all for a register variable, and for a stack local variable prints
14976 the exact address of the current instantiation of the variable.
14978 @kindex info symbol
14979 @cindex symbol from address
14980 @cindex closest symbol and offset for an address
14981 @item info symbol @var{addr}
14982 Print the name of a symbol which is stored at the address @var{addr}.
14983 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14984 nearest symbol and an offset from it:
14987 (@value{GDBP}) info symbol 0x54320
14988 _initialize_vx + 396 in section .text
14992 This is the opposite of the @code{info address} command. You can use
14993 it to find out the name of a variable or a function given its address.
14995 For dynamically linked executables, the name of executable or shared
14996 library containing the symbol is also printed:
14999 (@value{GDBP}) info symbol 0x400225
15000 _start + 5 in section .text of /tmp/a.out
15001 (@value{GDBP}) info symbol 0x2aaaac2811cf
15002 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15006 @item whatis [@var{arg}]
15007 Print the data type of @var{arg}, which can be either an expression
15008 or a name of a data type. With no argument, print the data type of
15009 @code{$}, the last value in the value history.
15011 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15012 is not actually evaluated, and any side-effecting operations (such as
15013 assignments or function calls) inside it do not take place.
15015 If @var{arg} is a variable or an expression, @code{whatis} prints its
15016 literal type as it is used in the source code. If the type was
15017 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15018 the data type underlying the @code{typedef}. If the type of the
15019 variable or the expression is a compound data type, such as
15020 @code{struct} or @code{class}, @code{whatis} never prints their
15021 fields or methods. It just prints the @code{struct}/@code{class}
15022 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15023 such a compound data type, use @code{ptype}.
15025 If @var{arg} is a type name that was defined using @code{typedef},
15026 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15027 Unrolling means that @code{whatis} will show the underlying type used
15028 in the @code{typedef} declaration of @var{arg}. However, if that
15029 underlying type is also a @code{typedef}, @code{whatis} will not
15032 For C code, the type names may also have the form @samp{class
15033 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15034 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15037 @item ptype [@var{arg}]
15038 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15039 detailed description of the type, instead of just the name of the type.
15040 @xref{Expressions, ,Expressions}.
15042 Contrary to @code{whatis}, @code{ptype} always unrolls any
15043 @code{typedef}s in its argument declaration, whether the argument is
15044 a variable, expression, or a data type. This means that @code{ptype}
15045 of a variable or an expression will not print literally its type as
15046 present in the source code---use @code{whatis} for that. @code{typedef}s at
15047 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15048 fields, methods and inner @code{class typedef}s of @code{struct}s,
15049 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15051 For example, for this variable declaration:
15054 typedef double real_t;
15055 struct complex @{ real_t real; double imag; @};
15056 typedef struct complex complex_t;
15058 real_t *real_pointer_var;
15062 the two commands give this output:
15066 (@value{GDBP}) whatis var
15068 (@value{GDBP}) ptype var
15069 type = struct complex @{
15073 (@value{GDBP}) whatis complex_t
15074 type = struct complex
15075 (@value{GDBP}) whatis struct complex
15076 type = struct complex
15077 (@value{GDBP}) ptype struct complex
15078 type = struct complex @{
15082 (@value{GDBP}) whatis real_pointer_var
15084 (@value{GDBP}) ptype real_pointer_var
15090 As with @code{whatis}, using @code{ptype} without an argument refers to
15091 the type of @code{$}, the last value in the value history.
15093 @cindex incomplete type
15094 Sometimes, programs use opaque data types or incomplete specifications
15095 of complex data structure. If the debug information included in the
15096 program does not allow @value{GDBN} to display a full declaration of
15097 the data type, it will say @samp{<incomplete type>}. For example,
15098 given these declarations:
15102 struct foo *fooptr;
15106 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15109 (@value{GDBP}) ptype foo
15110 $1 = <incomplete type>
15114 ``Incomplete type'' is C terminology for data types that are not
15115 completely specified.
15118 @item info types @var{regexp}
15120 Print a brief description of all types whose names match the regular
15121 expression @var{regexp} (or all types in your program, if you supply
15122 no argument). Each complete typename is matched as though it were a
15123 complete line; thus, @samp{i type value} gives information on all
15124 types in your program whose names include the string @code{value}, but
15125 @samp{i type ^value$} gives information only on types whose complete
15126 name is @code{value}.
15128 This command differs from @code{ptype} in two ways: first, like
15129 @code{whatis}, it does not print a detailed description; second, it
15130 lists all source files where a type is defined.
15133 @cindex local variables
15134 @item info scope @var{location}
15135 List all the variables local to a particular scope. This command
15136 accepts a @var{location} argument---a function name, a source line, or
15137 an address preceded by a @samp{*}, and prints all the variables local
15138 to the scope defined by that location. (@xref{Specify Location}, for
15139 details about supported forms of @var{location}.) For example:
15142 (@value{GDBP}) @b{info scope command_line_handler}
15143 Scope for command_line_handler:
15144 Symbol rl is an argument at stack/frame offset 8, length 4.
15145 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15146 Symbol linelength is in static storage at address 0x150a1c, length 4.
15147 Symbol p is a local variable in register $esi, length 4.
15148 Symbol p1 is a local variable in register $ebx, length 4.
15149 Symbol nline is a local variable in register $edx, length 4.
15150 Symbol repeat is a local variable at frame offset -8, length 4.
15154 This command is especially useful for determining what data to collect
15155 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15158 @kindex info source
15160 Show information about the current source file---that is, the source file for
15161 the function containing the current point of execution:
15164 the name of the source file, and the directory containing it,
15166 the directory it was compiled in,
15168 its length, in lines,
15170 which programming language it is written in,
15172 whether the executable includes debugging information for that file, and
15173 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15175 whether the debugging information includes information about
15176 preprocessor macros.
15180 @kindex info sources
15182 Print the names of all source files in your program for which there is
15183 debugging information, organized into two lists: files whose symbols
15184 have already been read, and files whose symbols will be read when needed.
15186 @kindex info functions
15187 @item info functions
15188 Print the names and data types of all defined functions.
15190 @item info functions @var{regexp}
15191 Print the names and data types of all defined functions
15192 whose names contain a match for regular expression @var{regexp}.
15193 Thus, @samp{info fun step} finds all functions whose names
15194 include @code{step}; @samp{info fun ^step} finds those whose names
15195 start with @code{step}. If a function name contains characters
15196 that conflict with the regular expression language (e.g.@:
15197 @samp{operator*()}), they may be quoted with a backslash.
15199 @kindex info variables
15200 @item info variables
15201 Print the names and data types of all variables that are defined
15202 outside of functions (i.e.@: excluding local variables).
15204 @item info variables @var{regexp}
15205 Print the names and data types of all variables (except for local
15206 variables) whose names contain a match for regular expression
15209 @kindex info classes
15210 @cindex Objective-C, classes and selectors
15212 @itemx info classes @var{regexp}
15213 Display all Objective-C classes in your program, or
15214 (with the @var{regexp} argument) all those matching a particular regular
15217 @kindex info selectors
15218 @item info selectors
15219 @itemx info selectors @var{regexp}
15220 Display all Objective-C selectors in your program, or
15221 (with the @var{regexp} argument) all those matching a particular regular
15225 This was never implemented.
15226 @kindex info methods
15228 @itemx info methods @var{regexp}
15229 The @code{info methods} command permits the user to examine all defined
15230 methods within C@t{++} program, or (with the @var{regexp} argument) a
15231 specific set of methods found in the various C@t{++} classes. Many
15232 C@t{++} classes provide a large number of methods. Thus, the output
15233 from the @code{ptype} command can be overwhelming and hard to use. The
15234 @code{info-methods} command filters the methods, printing only those
15235 which match the regular-expression @var{regexp}.
15238 @cindex opaque data types
15239 @kindex set opaque-type-resolution
15240 @item set opaque-type-resolution on
15241 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15242 declared as a pointer to a @code{struct}, @code{class}, or
15243 @code{union}---for example, @code{struct MyType *}---that is used in one
15244 source file although the full declaration of @code{struct MyType} is in
15245 another source file. The default is on.
15247 A change in the setting of this subcommand will not take effect until
15248 the next time symbols for a file are loaded.
15250 @item set opaque-type-resolution off
15251 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15252 is printed as follows:
15254 @{<no data fields>@}
15257 @kindex show opaque-type-resolution
15258 @item show opaque-type-resolution
15259 Show whether opaque types are resolved or not.
15261 @kindex maint print symbols
15262 @cindex symbol dump
15263 @kindex maint print psymbols
15264 @cindex partial symbol dump
15265 @item maint print symbols @var{filename}
15266 @itemx maint print psymbols @var{filename}
15267 @itemx maint print msymbols @var{filename}
15268 Write a dump of debugging symbol data into the file @var{filename}.
15269 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15270 symbols with debugging data are included. If you use @samp{maint print
15271 symbols}, @value{GDBN} includes all the symbols for which it has already
15272 collected full details: that is, @var{filename} reflects symbols for
15273 only those files whose symbols @value{GDBN} has read. You can use the
15274 command @code{info sources} to find out which files these are. If you
15275 use @samp{maint print psymbols} instead, the dump shows information about
15276 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15277 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15278 @samp{maint print msymbols} dumps just the minimal symbol information
15279 required for each object file from which @value{GDBN} has read some symbols.
15280 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15281 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15283 @kindex maint info symtabs
15284 @kindex maint info psymtabs
15285 @cindex listing @value{GDBN}'s internal symbol tables
15286 @cindex symbol tables, listing @value{GDBN}'s internal
15287 @cindex full symbol tables, listing @value{GDBN}'s internal
15288 @cindex partial symbol tables, listing @value{GDBN}'s internal
15289 @item maint info symtabs @r{[} @var{regexp} @r{]}
15290 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15292 List the @code{struct symtab} or @code{struct partial_symtab}
15293 structures whose names match @var{regexp}. If @var{regexp} is not
15294 given, list them all. The output includes expressions which you can
15295 copy into a @value{GDBN} debugging this one to examine a particular
15296 structure in more detail. For example:
15299 (@value{GDBP}) maint info psymtabs dwarf2read
15300 @{ objfile /home/gnu/build/gdb/gdb
15301 ((struct objfile *) 0x82e69d0)
15302 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15303 ((struct partial_symtab *) 0x8474b10)
15306 text addresses 0x814d3c8 -- 0x8158074
15307 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15308 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15309 dependencies (none)
15312 (@value{GDBP}) maint info symtabs
15316 We see that there is one partial symbol table whose filename contains
15317 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15318 and we see that @value{GDBN} has not read in any symtabs yet at all.
15319 If we set a breakpoint on a function, that will cause @value{GDBN} to
15320 read the symtab for the compilation unit containing that function:
15323 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15324 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15326 (@value{GDBP}) maint info symtabs
15327 @{ objfile /home/gnu/build/gdb/gdb
15328 ((struct objfile *) 0x82e69d0)
15329 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15330 ((struct symtab *) 0x86c1f38)
15333 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15334 linetable ((struct linetable *) 0x8370fa0)
15335 debugformat DWARF 2
15344 @chapter Altering Execution
15346 Once you think you have found an error in your program, you might want to
15347 find out for certain whether correcting the apparent error would lead to
15348 correct results in the rest of the run. You can find the answer by
15349 experiment, using the @value{GDBN} features for altering execution of the
15352 For example, you can store new values into variables or memory
15353 locations, give your program a signal, restart it at a different
15354 address, or even return prematurely from a function.
15357 * Assignment:: Assignment to variables
15358 * Jumping:: Continuing at a different address
15359 * Signaling:: Giving your program a signal
15360 * Returning:: Returning from a function
15361 * Calling:: Calling your program's functions
15362 * Patching:: Patching your program
15366 @section Assignment to Variables
15369 @cindex setting variables
15370 To alter the value of a variable, evaluate an assignment expression.
15371 @xref{Expressions, ,Expressions}. For example,
15378 stores the value 4 into the variable @code{x}, and then prints the
15379 value of the assignment expression (which is 4).
15380 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15381 information on operators in supported languages.
15383 @kindex set variable
15384 @cindex variables, setting
15385 If you are not interested in seeing the value of the assignment, use the
15386 @code{set} command instead of the @code{print} command. @code{set} is
15387 really the same as @code{print} except that the expression's value is
15388 not printed and is not put in the value history (@pxref{Value History,
15389 ,Value History}). The expression is evaluated only for its effects.
15391 If the beginning of the argument string of the @code{set} command
15392 appears identical to a @code{set} subcommand, use the @code{set
15393 variable} command instead of just @code{set}. This command is identical
15394 to @code{set} except for its lack of subcommands. For example, if your
15395 program has a variable @code{width}, you get an error if you try to set
15396 a new value with just @samp{set width=13}, because @value{GDBN} has the
15397 command @code{set width}:
15400 (@value{GDBP}) whatis width
15402 (@value{GDBP}) p width
15404 (@value{GDBP}) set width=47
15405 Invalid syntax in expression.
15409 The invalid expression, of course, is @samp{=47}. In
15410 order to actually set the program's variable @code{width}, use
15413 (@value{GDBP}) set var width=47
15416 Because the @code{set} command has many subcommands that can conflict
15417 with the names of program variables, it is a good idea to use the
15418 @code{set variable} command instead of just @code{set}. For example, if
15419 your program has a variable @code{g}, you run into problems if you try
15420 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15421 the command @code{set gnutarget}, abbreviated @code{set g}:
15425 (@value{GDBP}) whatis g
15429 (@value{GDBP}) set g=4
15433 The program being debugged has been started already.
15434 Start it from the beginning? (y or n) y
15435 Starting program: /home/smith/cc_progs/a.out
15436 "/home/smith/cc_progs/a.out": can't open to read symbols:
15437 Invalid bfd target.
15438 (@value{GDBP}) show g
15439 The current BFD target is "=4".
15444 The program variable @code{g} did not change, and you silently set the
15445 @code{gnutarget} to an invalid value. In order to set the variable
15449 (@value{GDBP}) set var g=4
15452 @value{GDBN} allows more implicit conversions in assignments than C; you can
15453 freely store an integer value into a pointer variable or vice versa,
15454 and you can convert any structure to any other structure that is the
15455 same length or shorter.
15456 @comment FIXME: how do structs align/pad in these conversions?
15457 @comment /doc@cygnus.com 18dec1990
15459 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15460 construct to generate a value of specified type at a specified address
15461 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15462 to memory location @code{0x83040} as an integer (which implies a certain size
15463 and representation in memory), and
15466 set @{int@}0x83040 = 4
15470 stores the value 4 into that memory location.
15473 @section Continuing at a Different Address
15475 Ordinarily, when you continue your program, you do so at the place where
15476 it stopped, with the @code{continue} command. You can instead continue at
15477 an address of your own choosing, with the following commands:
15481 @item jump @var{linespec}
15482 @itemx jump @var{location}
15483 Resume execution at line @var{linespec} or at address given by
15484 @var{location}. Execution stops again immediately if there is a
15485 breakpoint there. @xref{Specify Location}, for a description of the
15486 different forms of @var{linespec} and @var{location}. It is common
15487 practice to use the @code{tbreak} command in conjunction with
15488 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15490 The @code{jump} command does not change the current stack frame, or
15491 the stack pointer, or the contents of any memory location or any
15492 register other than the program counter. If line @var{linespec} is in
15493 a different function from the one currently executing, the results may
15494 be bizarre if the two functions expect different patterns of arguments or
15495 of local variables. For this reason, the @code{jump} command requests
15496 confirmation if the specified line is not in the function currently
15497 executing. However, even bizarre results are predictable if you are
15498 well acquainted with the machine-language code of your program.
15501 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15502 On many systems, you can get much the same effect as the @code{jump}
15503 command by storing a new value into the register @code{$pc}. The
15504 difference is that this does not start your program running; it only
15505 changes the address of where it @emph{will} run when you continue. For
15513 makes the next @code{continue} command or stepping command execute at
15514 address @code{0x485}, rather than at the address where your program stopped.
15515 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15517 The most common occasion to use the @code{jump} command is to back
15518 up---perhaps with more breakpoints set---over a portion of a program
15519 that has already executed, in order to examine its execution in more
15524 @section Giving your Program a Signal
15525 @cindex deliver a signal to a program
15529 @item signal @var{signal}
15530 Resume execution where your program stopped, but immediately give it the
15531 signal @var{signal}. @var{signal} can be the name or the number of a
15532 signal. For example, on many systems @code{signal 2} and @code{signal
15533 SIGINT} are both ways of sending an interrupt signal.
15535 Alternatively, if @var{signal} is zero, continue execution without
15536 giving a signal. This is useful when your program stopped on account of
15537 a signal and would ordinary see the signal when resumed with the
15538 @code{continue} command; @samp{signal 0} causes it to resume without a
15541 @code{signal} does not repeat when you press @key{RET} a second time
15542 after executing the command.
15546 Invoking the @code{signal} command is not the same as invoking the
15547 @code{kill} utility from the shell. Sending a signal with @code{kill}
15548 causes @value{GDBN} to decide what to do with the signal depending on
15549 the signal handling tables (@pxref{Signals}). The @code{signal} command
15550 passes the signal directly to your program.
15554 @section Returning from a Function
15557 @cindex returning from a function
15560 @itemx return @var{expression}
15561 You can cancel execution of a function call with the @code{return}
15562 command. If you give an
15563 @var{expression} argument, its value is used as the function's return
15567 When you use @code{return}, @value{GDBN} discards the selected stack frame
15568 (and all frames within it). You can think of this as making the
15569 discarded frame return prematurely. If you wish to specify a value to
15570 be returned, give that value as the argument to @code{return}.
15572 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15573 Frame}), and any other frames inside of it, leaving its caller as the
15574 innermost remaining frame. That frame becomes selected. The
15575 specified value is stored in the registers used for returning values
15578 The @code{return} command does not resume execution; it leaves the
15579 program stopped in the state that would exist if the function had just
15580 returned. In contrast, the @code{finish} command (@pxref{Continuing
15581 and Stepping, ,Continuing and Stepping}) resumes execution until the
15582 selected stack frame returns naturally.
15584 @value{GDBN} needs to know how the @var{expression} argument should be set for
15585 the inferior. The concrete registers assignment depends on the OS ABI and the
15586 type being returned by the selected stack frame. For example it is common for
15587 OS ABI to return floating point values in FPU registers while integer values in
15588 CPU registers. Still some ABIs return even floating point values in CPU
15589 registers. Larger integer widths (such as @code{long long int}) also have
15590 specific placement rules. @value{GDBN} already knows the OS ABI from its
15591 current target so it needs to find out also the type being returned to make the
15592 assignment into the right register(s).
15594 Normally, the selected stack frame has debug info. @value{GDBN} will always
15595 use the debug info instead of the implicit type of @var{expression} when the
15596 debug info is available. For example, if you type @kbd{return -1}, and the
15597 function in the current stack frame is declared to return a @code{long long
15598 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15599 into a @code{long long int}:
15602 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15604 (@value{GDBP}) return -1
15605 Make func return now? (y or n) y
15606 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15607 43 printf ("result=%lld\n", func ());
15611 However, if the selected stack frame does not have a debug info, e.g., if the
15612 function was compiled without debug info, @value{GDBN} has to find out the type
15613 to return from user. Specifying a different type by mistake may set the value
15614 in different inferior registers than the caller code expects. For example,
15615 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15616 of a @code{long long int} result for a debug info less function (on 32-bit
15617 architectures). Therefore the user is required to specify the return type by
15618 an appropriate cast explicitly:
15621 Breakpoint 2, 0x0040050b in func ()
15622 (@value{GDBP}) return -1
15623 Return value type not available for selected stack frame.
15624 Please use an explicit cast of the value to return.
15625 (@value{GDBP}) return (long long int) -1
15626 Make selected stack frame return now? (y or n) y
15627 #0 0x00400526 in main ()
15632 @section Calling Program Functions
15635 @cindex calling functions
15636 @cindex inferior functions, calling
15637 @item print @var{expr}
15638 Evaluate the expression @var{expr} and display the resulting value.
15639 @var{expr} may include calls to functions in the program being
15643 @item call @var{expr}
15644 Evaluate the expression @var{expr} without displaying @code{void}
15647 You can use this variant of the @code{print} command if you want to
15648 execute a function from your program that does not return anything
15649 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15650 with @code{void} returned values that @value{GDBN} will otherwise
15651 print. If the result is not void, it is printed and saved in the
15655 It is possible for the function you call via the @code{print} or
15656 @code{call} command to generate a signal (e.g., if there's a bug in
15657 the function, or if you passed it incorrect arguments). What happens
15658 in that case is controlled by the @code{set unwindonsignal} command.
15660 Similarly, with a C@t{++} program it is possible for the function you
15661 call via the @code{print} or @code{call} command to generate an
15662 exception that is not handled due to the constraints of the dummy
15663 frame. In this case, any exception that is raised in the frame, but has
15664 an out-of-frame exception handler will not be found. GDB builds a
15665 dummy-frame for the inferior function call, and the unwinder cannot
15666 seek for exception handlers outside of this dummy-frame. What happens
15667 in that case is controlled by the
15668 @code{set unwind-on-terminating-exception} command.
15671 @item set unwindonsignal
15672 @kindex set unwindonsignal
15673 @cindex unwind stack in called functions
15674 @cindex call dummy stack unwinding
15675 Set unwinding of the stack if a signal is received while in a function
15676 that @value{GDBN} called in the program being debugged. If set to on,
15677 @value{GDBN} unwinds the stack it created for the call and restores
15678 the context to what it was before the call. If set to off (the
15679 default), @value{GDBN} stops in the frame where the signal was
15682 @item show unwindonsignal
15683 @kindex show unwindonsignal
15684 Show the current setting of stack unwinding in the functions called by
15687 @item set unwind-on-terminating-exception
15688 @kindex set unwind-on-terminating-exception
15689 @cindex unwind stack in called functions with unhandled exceptions
15690 @cindex call dummy stack unwinding on unhandled exception.
15691 Set unwinding of the stack if a C@t{++} exception is raised, but left
15692 unhandled while in a function that @value{GDBN} called in the program being
15693 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15694 it created for the call and restores the context to what it was before
15695 the call. If set to off, @value{GDBN} the exception is delivered to
15696 the default C@t{++} exception handler and the inferior terminated.
15698 @item show unwind-on-terminating-exception
15699 @kindex show unwind-on-terminating-exception
15700 Show the current setting of stack unwinding in the functions called by
15705 @cindex weak alias functions
15706 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15707 for another function. In such case, @value{GDBN} might not pick up
15708 the type information, including the types of the function arguments,
15709 which causes @value{GDBN} to call the inferior function incorrectly.
15710 As a result, the called function will function erroneously and may
15711 even crash. A solution to that is to use the name of the aliased
15715 @section Patching Programs
15717 @cindex patching binaries
15718 @cindex writing into executables
15719 @cindex writing into corefiles
15721 By default, @value{GDBN} opens the file containing your program's
15722 executable code (or the corefile) read-only. This prevents accidental
15723 alterations to machine code; but it also prevents you from intentionally
15724 patching your program's binary.
15726 If you'd like to be able to patch the binary, you can specify that
15727 explicitly with the @code{set write} command. For example, you might
15728 want to turn on internal debugging flags, or even to make emergency
15734 @itemx set write off
15735 If you specify @samp{set write on}, @value{GDBN} opens executable and
15736 core files for both reading and writing; if you specify @kbd{set write
15737 off} (the default), @value{GDBN} opens them read-only.
15739 If you have already loaded a file, you must load it again (using the
15740 @code{exec-file} or @code{core-file} command) after changing @code{set
15741 write}, for your new setting to take effect.
15745 Display whether executable files and core files are opened for writing
15746 as well as reading.
15750 @chapter @value{GDBN} Files
15752 @value{GDBN} needs to know the file name of the program to be debugged,
15753 both in order to read its symbol table and in order to start your
15754 program. To debug a core dump of a previous run, you must also tell
15755 @value{GDBN} the name of the core dump file.
15758 * Files:: Commands to specify files
15759 * Separate Debug Files:: Debugging information in separate files
15760 * Index Files:: Index files speed up GDB
15761 * Symbol Errors:: Errors reading symbol files
15762 * Data Files:: GDB data files
15766 @section Commands to Specify Files
15768 @cindex symbol table
15769 @cindex core dump file
15771 You may want to specify executable and core dump file names. The usual
15772 way to do this is at start-up time, using the arguments to
15773 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15774 Out of @value{GDBN}}).
15776 Occasionally it is necessary to change to a different file during a
15777 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15778 specify a file you want to use. Or you are debugging a remote target
15779 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15780 Program}). In these situations the @value{GDBN} commands to specify
15781 new files are useful.
15784 @cindex executable file
15786 @item file @var{filename}
15787 Use @var{filename} as the program to be debugged. It is read for its
15788 symbols and for the contents of pure memory. It is also the program
15789 executed when you use the @code{run} command. If you do not specify a
15790 directory and the file is not found in the @value{GDBN} working directory,
15791 @value{GDBN} uses the environment variable @code{PATH} as a list of
15792 directories to search, just as the shell does when looking for a program
15793 to run. You can change the value of this variable, for both @value{GDBN}
15794 and your program, using the @code{path} command.
15796 @cindex unlinked object files
15797 @cindex patching object files
15798 You can load unlinked object @file{.o} files into @value{GDBN} using
15799 the @code{file} command. You will not be able to ``run'' an object
15800 file, but you can disassemble functions and inspect variables. Also,
15801 if the underlying BFD functionality supports it, you could use
15802 @kbd{gdb -write} to patch object files using this technique. Note
15803 that @value{GDBN} can neither interpret nor modify relocations in this
15804 case, so branches and some initialized variables will appear to go to
15805 the wrong place. But this feature is still handy from time to time.
15808 @code{file} with no argument makes @value{GDBN} discard any information it
15809 has on both executable file and the symbol table.
15812 @item exec-file @r{[} @var{filename} @r{]}
15813 Specify that the program to be run (but not the symbol table) is found
15814 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15815 if necessary to locate your program. Omitting @var{filename} means to
15816 discard information on the executable file.
15818 @kindex symbol-file
15819 @item symbol-file @r{[} @var{filename} @r{]}
15820 Read symbol table information from file @var{filename}. @code{PATH} is
15821 searched when necessary. Use the @code{file} command to get both symbol
15822 table and program to run from the same file.
15824 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15825 program's symbol table.
15827 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15828 some breakpoints and auto-display expressions. This is because they may
15829 contain pointers to the internal data recording symbols and data types,
15830 which are part of the old symbol table data being discarded inside
15833 @code{symbol-file} does not repeat if you press @key{RET} again after
15836 When @value{GDBN} is configured for a particular environment, it
15837 understands debugging information in whatever format is the standard
15838 generated for that environment; you may use either a @sc{gnu} compiler, or
15839 other compilers that adhere to the local conventions.
15840 Best results are usually obtained from @sc{gnu} compilers; for example,
15841 using @code{@value{NGCC}} you can generate debugging information for
15844 For most kinds of object files, with the exception of old SVR3 systems
15845 using COFF, the @code{symbol-file} command does not normally read the
15846 symbol table in full right away. Instead, it scans the symbol table
15847 quickly to find which source files and which symbols are present. The
15848 details are read later, one source file at a time, as they are needed.
15850 The purpose of this two-stage reading strategy is to make @value{GDBN}
15851 start up faster. For the most part, it is invisible except for
15852 occasional pauses while the symbol table details for a particular source
15853 file are being read. (The @code{set verbose} command can turn these
15854 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15855 Warnings and Messages}.)
15857 We have not implemented the two-stage strategy for COFF yet. When the
15858 symbol table is stored in COFF format, @code{symbol-file} reads the
15859 symbol table data in full right away. Note that ``stabs-in-COFF''
15860 still does the two-stage strategy, since the debug info is actually
15864 @cindex reading symbols immediately
15865 @cindex symbols, reading immediately
15866 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15867 @itemx file @r{[} -readnow @r{]} @var{filename}
15868 You can override the @value{GDBN} two-stage strategy for reading symbol
15869 tables by using the @samp{-readnow} option with any of the commands that
15870 load symbol table information, if you want to be sure @value{GDBN} has the
15871 entire symbol table available.
15873 @c FIXME: for now no mention of directories, since this seems to be in
15874 @c flux. 13mar1992 status is that in theory GDB would look either in
15875 @c current dir or in same dir as myprog; but issues like competing
15876 @c GDB's, or clutter in system dirs, mean that in practice right now
15877 @c only current dir is used. FFish says maybe a special GDB hierarchy
15878 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15882 @item core-file @r{[}@var{filename}@r{]}
15884 Specify the whereabouts of a core dump file to be used as the ``contents
15885 of memory''. Traditionally, core files contain only some parts of the
15886 address space of the process that generated them; @value{GDBN} can access the
15887 executable file itself for other parts.
15889 @code{core-file} with no argument specifies that no core file is
15892 Note that the core file is ignored when your program is actually running
15893 under @value{GDBN}. So, if you have been running your program and you
15894 wish to debug a core file instead, you must kill the subprocess in which
15895 the program is running. To do this, use the @code{kill} command
15896 (@pxref{Kill Process, ,Killing the Child Process}).
15898 @kindex add-symbol-file
15899 @cindex dynamic linking
15900 @item add-symbol-file @var{filename} @var{address}
15901 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15902 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15903 The @code{add-symbol-file} command reads additional symbol table
15904 information from the file @var{filename}. You would use this command
15905 when @var{filename} has been dynamically loaded (by some other means)
15906 into the program that is running. @var{address} should be the memory
15907 address at which the file has been loaded; @value{GDBN} cannot figure
15908 this out for itself. You can additionally specify an arbitrary number
15909 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15910 section name and base address for that section. You can specify any
15911 @var{address} as an expression.
15913 The symbol table of the file @var{filename} is added to the symbol table
15914 originally read with the @code{symbol-file} command. You can use the
15915 @code{add-symbol-file} command any number of times; the new symbol data
15916 thus read keeps adding to the old. To discard all old symbol data
15917 instead, use the @code{symbol-file} command without any arguments.
15919 @cindex relocatable object files, reading symbols from
15920 @cindex object files, relocatable, reading symbols from
15921 @cindex reading symbols from relocatable object files
15922 @cindex symbols, reading from relocatable object files
15923 @cindex @file{.o} files, reading symbols from
15924 Although @var{filename} is typically a shared library file, an
15925 executable file, or some other object file which has been fully
15926 relocated for loading into a process, you can also load symbolic
15927 information from relocatable @file{.o} files, as long as:
15931 the file's symbolic information refers only to linker symbols defined in
15932 that file, not to symbols defined by other object files,
15934 every section the file's symbolic information refers to has actually
15935 been loaded into the inferior, as it appears in the file, and
15937 you can determine the address at which every section was loaded, and
15938 provide these to the @code{add-symbol-file} command.
15942 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15943 relocatable files into an already running program; such systems
15944 typically make the requirements above easy to meet. However, it's
15945 important to recognize that many native systems use complex link
15946 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15947 assembly, for example) that make the requirements difficult to meet. In
15948 general, one cannot assume that using @code{add-symbol-file} to read a
15949 relocatable object file's symbolic information will have the same effect
15950 as linking the relocatable object file into the program in the normal
15953 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15955 @kindex add-symbol-file-from-memory
15956 @cindex @code{syscall DSO}
15957 @cindex load symbols from memory
15958 @item add-symbol-file-from-memory @var{address}
15959 Load symbols from the given @var{address} in a dynamically loaded
15960 object file whose image is mapped directly into the inferior's memory.
15961 For example, the Linux kernel maps a @code{syscall DSO} into each
15962 process's address space; this DSO provides kernel-specific code for
15963 some system calls. The argument can be any expression whose
15964 evaluation yields the address of the file's shared object file header.
15965 For this command to work, you must have used @code{symbol-file} or
15966 @code{exec-file} commands in advance.
15968 @kindex add-shared-symbol-files
15970 @item add-shared-symbol-files @var{library-file}
15971 @itemx assf @var{library-file}
15972 The @code{add-shared-symbol-files} command can currently be used only
15973 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15974 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15975 @value{GDBN} automatically looks for shared libraries, however if
15976 @value{GDBN} does not find yours, you can invoke
15977 @code{add-shared-symbol-files}. It takes one argument: the shared
15978 library's file name. @code{assf} is a shorthand alias for
15979 @code{add-shared-symbol-files}.
15982 @item section @var{section} @var{addr}
15983 The @code{section} command changes the base address of the named
15984 @var{section} of the exec file to @var{addr}. This can be used if the
15985 exec file does not contain section addresses, (such as in the
15986 @code{a.out} format), or when the addresses specified in the file
15987 itself are wrong. Each section must be changed separately. The
15988 @code{info files} command, described below, lists all the sections and
15992 @kindex info target
15995 @code{info files} and @code{info target} are synonymous; both print the
15996 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15997 including the names of the executable and core dump files currently in
15998 use by @value{GDBN}, and the files from which symbols were loaded. The
15999 command @code{help target} lists all possible targets rather than
16002 @kindex maint info sections
16003 @item maint info sections
16004 Another command that can give you extra information about program sections
16005 is @code{maint info sections}. In addition to the section information
16006 displayed by @code{info files}, this command displays the flags and file
16007 offset of each section in the executable and core dump files. In addition,
16008 @code{maint info sections} provides the following command options (which
16009 may be arbitrarily combined):
16013 Display sections for all loaded object files, including shared libraries.
16014 @item @var{sections}
16015 Display info only for named @var{sections}.
16016 @item @var{section-flags}
16017 Display info only for sections for which @var{section-flags} are true.
16018 The section flags that @value{GDBN} currently knows about are:
16021 Section will have space allocated in the process when loaded.
16022 Set for all sections except those containing debug information.
16024 Section will be loaded from the file into the child process memory.
16025 Set for pre-initialized code and data, clear for @code{.bss} sections.
16027 Section needs to be relocated before loading.
16029 Section cannot be modified by the child process.
16031 Section contains executable code only.
16033 Section contains data only (no executable code).
16035 Section will reside in ROM.
16037 Section contains data for constructor/destructor lists.
16039 Section is not empty.
16041 An instruction to the linker to not output the section.
16042 @item COFF_SHARED_LIBRARY
16043 A notification to the linker that the section contains
16044 COFF shared library information.
16046 Section contains common symbols.
16049 @kindex set trust-readonly-sections
16050 @cindex read-only sections
16051 @item set trust-readonly-sections on
16052 Tell @value{GDBN} that readonly sections in your object file
16053 really are read-only (i.e.@: that their contents will not change).
16054 In that case, @value{GDBN} can fetch values from these sections
16055 out of the object file, rather than from the target program.
16056 For some targets (notably embedded ones), this can be a significant
16057 enhancement to debugging performance.
16059 The default is off.
16061 @item set trust-readonly-sections off
16062 Tell @value{GDBN} not to trust readonly sections. This means that
16063 the contents of the section might change while the program is running,
16064 and must therefore be fetched from the target when needed.
16066 @item show trust-readonly-sections
16067 Show the current setting of trusting readonly sections.
16070 All file-specifying commands allow both absolute and relative file names
16071 as arguments. @value{GDBN} always converts the file name to an absolute file
16072 name and remembers it that way.
16074 @cindex shared libraries
16075 @anchor{Shared Libraries}
16076 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16077 and IBM RS/6000 AIX shared libraries.
16079 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16080 shared libraries. @xref{Expat}.
16082 @value{GDBN} automatically loads symbol definitions from shared libraries
16083 when you use the @code{run} command, or when you examine a core file.
16084 (Before you issue the @code{run} command, @value{GDBN} does not understand
16085 references to a function in a shared library, however---unless you are
16086 debugging a core file).
16088 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16089 automatically loads the symbols at the time of the @code{shl_load} call.
16091 @c FIXME: some @value{GDBN} release may permit some refs to undef
16092 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16093 @c FIXME...lib; check this from time to time when updating manual
16095 There are times, however, when you may wish to not automatically load
16096 symbol definitions from shared libraries, such as when they are
16097 particularly large or there are many of them.
16099 To control the automatic loading of shared library symbols, use the
16103 @kindex set auto-solib-add
16104 @item set auto-solib-add @var{mode}
16105 If @var{mode} is @code{on}, symbols from all shared object libraries
16106 will be loaded automatically when the inferior begins execution, you
16107 attach to an independently started inferior, or when the dynamic linker
16108 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16109 is @code{off}, symbols must be loaded manually, using the
16110 @code{sharedlibrary} command. The default value is @code{on}.
16112 @cindex memory used for symbol tables
16113 If your program uses lots of shared libraries with debug info that
16114 takes large amounts of memory, you can decrease the @value{GDBN}
16115 memory footprint by preventing it from automatically loading the
16116 symbols from shared libraries. To that end, type @kbd{set
16117 auto-solib-add off} before running the inferior, then load each
16118 library whose debug symbols you do need with @kbd{sharedlibrary
16119 @var{regexp}}, where @var{regexp} is a regular expression that matches
16120 the libraries whose symbols you want to be loaded.
16122 @kindex show auto-solib-add
16123 @item show auto-solib-add
16124 Display the current autoloading mode.
16127 @cindex load shared library
16128 To explicitly load shared library symbols, use the @code{sharedlibrary}
16132 @kindex info sharedlibrary
16134 @item info share @var{regex}
16135 @itemx info sharedlibrary @var{regex}
16136 Print the names of the shared libraries which are currently loaded
16137 that match @var{regex}. If @var{regex} is omitted then print
16138 all shared libraries that are loaded.
16140 @kindex sharedlibrary
16142 @item sharedlibrary @var{regex}
16143 @itemx share @var{regex}
16144 Load shared object library symbols for files matching a
16145 Unix regular expression.
16146 As with files loaded automatically, it only loads shared libraries
16147 required by your program for a core file or after typing @code{run}. If
16148 @var{regex} is omitted all shared libraries required by your program are
16151 @item nosharedlibrary
16152 @kindex nosharedlibrary
16153 @cindex unload symbols from shared libraries
16154 Unload all shared object library symbols. This discards all symbols
16155 that have been loaded from all shared libraries. Symbols from shared
16156 libraries that were loaded by explicit user requests are not
16160 Sometimes you may wish that @value{GDBN} stops and gives you control
16161 when any of shared library events happen. The best way to do this is
16162 to use @code{catch load} and @code{catch unload} (@pxref{Set
16165 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16166 command for this. This command exists for historical reasons. It is
16167 less useful than setting a catchpoint, because it does not allow for
16168 conditions or commands as a catchpoint does.
16171 @item set stop-on-solib-events
16172 @kindex set stop-on-solib-events
16173 This command controls whether @value{GDBN} should give you control
16174 when the dynamic linker notifies it about some shared library event.
16175 The most common event of interest is loading or unloading of a new
16178 @item show stop-on-solib-events
16179 @kindex show stop-on-solib-events
16180 Show whether @value{GDBN} stops and gives you control when shared
16181 library events happen.
16184 Shared libraries are also supported in many cross or remote debugging
16185 configurations. @value{GDBN} needs to have access to the target's libraries;
16186 this can be accomplished either by providing copies of the libraries
16187 on the host system, or by asking @value{GDBN} to automatically retrieve the
16188 libraries from the target. If copies of the target libraries are
16189 provided, they need to be the same as the target libraries, although the
16190 copies on the target can be stripped as long as the copies on the host are
16193 @cindex where to look for shared libraries
16194 For remote debugging, you need to tell @value{GDBN} where the target
16195 libraries are, so that it can load the correct copies---otherwise, it
16196 may try to load the host's libraries. @value{GDBN} has two variables
16197 to specify the search directories for target libraries.
16200 @cindex prefix for shared library file names
16201 @cindex system root, alternate
16202 @kindex set solib-absolute-prefix
16203 @kindex set sysroot
16204 @item set sysroot @var{path}
16205 Use @var{path} as the system root for the program being debugged. Any
16206 absolute shared library paths will be prefixed with @var{path}; many
16207 runtime loaders store the absolute paths to the shared library in the
16208 target program's memory. If you use @code{set sysroot} to find shared
16209 libraries, they need to be laid out in the same way that they are on
16210 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16213 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16214 retrieve the target libraries from the remote system. This is only
16215 supported when using a remote target that supports the @code{remote get}
16216 command (@pxref{File Transfer,,Sending files to a remote system}).
16217 The part of @var{path} following the initial @file{remote:}
16218 (if present) is used as system root prefix on the remote file system.
16219 @footnote{If you want to specify a local system root using a directory
16220 that happens to be named @file{remote:}, you need to use some equivalent
16221 variant of the name like @file{./remote:}.}
16223 For targets with an MS-DOS based filesystem, such as MS-Windows and
16224 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16225 absolute file name with @var{path}. But first, on Unix hosts,
16226 @value{GDBN} converts all backslash directory separators into forward
16227 slashes, because the backslash is not a directory separator on Unix:
16230 c:\foo\bar.dll @result{} c:/foo/bar.dll
16233 Then, @value{GDBN} attempts prefixing the target file name with
16234 @var{path}, and looks for the resulting file name in the host file
16238 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16241 If that does not find the shared library, @value{GDBN} tries removing
16242 the @samp{:} character from the drive spec, both for convenience, and,
16243 for the case of the host file system not supporting file names with
16247 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16250 This makes it possible to have a system root that mirrors a target
16251 with more than one drive. E.g., you may want to setup your local
16252 copies of the target system shared libraries like so (note @samp{c} vs
16256 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16257 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16258 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16262 and point the system root at @file{/path/to/sysroot}, so that
16263 @value{GDBN} can find the correct copies of both
16264 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16266 If that still does not find the shared library, @value{GDBN} tries
16267 removing the whole drive spec from the target file name:
16270 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16273 This last lookup makes it possible to not care about the drive name,
16274 if you don't want or need to.
16276 The @code{set solib-absolute-prefix} command is an alias for @code{set
16279 @cindex default system root
16280 @cindex @samp{--with-sysroot}
16281 You can set the default system root by using the configure-time
16282 @samp{--with-sysroot} option. If the system root is inside
16283 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16284 @samp{--exec-prefix}), then the default system root will be updated
16285 automatically if the installed @value{GDBN} is moved to a new
16288 @kindex show sysroot
16290 Display the current shared library prefix.
16292 @kindex set solib-search-path
16293 @item set solib-search-path @var{path}
16294 If this variable is set, @var{path} is a colon-separated list of
16295 directories to search for shared libraries. @samp{solib-search-path}
16296 is used after @samp{sysroot} fails to locate the library, or if the
16297 path to the library is relative instead of absolute. If you want to
16298 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16299 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16300 finding your host's libraries. @samp{sysroot} is preferred; setting
16301 it to a nonexistent directory may interfere with automatic loading
16302 of shared library symbols.
16304 @kindex show solib-search-path
16305 @item show solib-search-path
16306 Display the current shared library search path.
16308 @cindex DOS file-name semantics of file names.
16309 @kindex set target-file-system-kind (unix|dos-based|auto)
16310 @kindex show target-file-system-kind
16311 @item set target-file-system-kind @var{kind}
16312 Set assumed file system kind for target reported file names.
16314 Shared library file names as reported by the target system may not
16315 make sense as is on the system @value{GDBN} is running on. For
16316 example, when remote debugging a target that has MS-DOS based file
16317 system semantics, from a Unix host, the target may be reporting to
16318 @value{GDBN} a list of loaded shared libraries with file names such as
16319 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16320 drive letters, so the @samp{c:\} prefix is not normally understood as
16321 indicating an absolute file name, and neither is the backslash
16322 normally considered a directory separator character. In that case,
16323 the native file system would interpret this whole absolute file name
16324 as a relative file name with no directory components. This would make
16325 it impossible to point @value{GDBN} at a copy of the remote target's
16326 shared libraries on the host using @code{set sysroot}, and impractical
16327 with @code{set solib-search-path}. Setting
16328 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16329 to interpret such file names similarly to how the target would, and to
16330 map them to file names valid on @value{GDBN}'s native file system
16331 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16332 to one of the supported file system kinds. In that case, @value{GDBN}
16333 tries to determine the appropriate file system variant based on the
16334 current target's operating system (@pxref{ABI, ,Configuring the
16335 Current ABI}). The supported file system settings are:
16339 Instruct @value{GDBN} to assume the target file system is of Unix
16340 kind. Only file names starting the forward slash (@samp{/}) character
16341 are considered absolute, and the directory separator character is also
16345 Instruct @value{GDBN} to assume the target file system is DOS based.
16346 File names starting with either a forward slash, or a drive letter
16347 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16348 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16349 considered directory separators.
16352 Instruct @value{GDBN} to use the file system kind associated with the
16353 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16354 This is the default.
16358 @cindex file name canonicalization
16359 @cindex base name differences
16360 When processing file names provided by the user, @value{GDBN}
16361 frequently needs to compare them to the file names recorded in the
16362 program's debug info. Normally, @value{GDBN} compares just the
16363 @dfn{base names} of the files as strings, which is reasonably fast
16364 even for very large programs. (The base name of a file is the last
16365 portion of its name, after stripping all the leading directories.)
16366 This shortcut in comparison is based upon the assumption that files
16367 cannot have more than one base name. This is usually true, but
16368 references to files that use symlinks or similar filesystem
16369 facilities violate that assumption. If your program records files
16370 using such facilities, or if you provide file names to @value{GDBN}
16371 using symlinks etc., you can set @code{basenames-may-differ} to
16372 @code{true} to instruct @value{GDBN} to completely canonicalize each
16373 pair of file names it needs to compare. This will make file-name
16374 comparisons accurate, but at a price of a significant slowdown.
16377 @item set basenames-may-differ
16378 @kindex set basenames-may-differ
16379 Set whether a source file may have multiple base names.
16381 @item show basenames-may-differ
16382 @kindex show basenames-may-differ
16383 Show whether a source file may have multiple base names.
16386 @node Separate Debug Files
16387 @section Debugging Information in Separate Files
16388 @cindex separate debugging information files
16389 @cindex debugging information in separate files
16390 @cindex @file{.debug} subdirectories
16391 @cindex debugging information directory, global
16392 @cindex global debugging information directories
16393 @cindex build ID, and separate debugging files
16394 @cindex @file{.build-id} directory
16396 @value{GDBN} allows you to put a program's debugging information in a
16397 file separate from the executable itself, in a way that allows
16398 @value{GDBN} to find and load the debugging information automatically.
16399 Since debugging information can be very large---sometimes larger
16400 than the executable code itself---some systems distribute debugging
16401 information for their executables in separate files, which users can
16402 install only when they need to debug a problem.
16404 @value{GDBN} supports two ways of specifying the separate debug info
16409 The executable contains a @dfn{debug link} that specifies the name of
16410 the separate debug info file. The separate debug file's name is
16411 usually @file{@var{executable}.debug}, where @var{executable} is the
16412 name of the corresponding executable file without leading directories
16413 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16414 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16415 checksum for the debug file, which @value{GDBN} uses to validate that
16416 the executable and the debug file came from the same build.
16419 The executable contains a @dfn{build ID}, a unique bit string that is
16420 also present in the corresponding debug info file. (This is supported
16421 only on some operating systems, notably those which use the ELF format
16422 for binary files and the @sc{gnu} Binutils.) For more details about
16423 this feature, see the description of the @option{--build-id}
16424 command-line option in @ref{Options, , Command Line Options, ld.info,
16425 The GNU Linker}. The debug info file's name is not specified
16426 explicitly by the build ID, but can be computed from the build ID, see
16430 Depending on the way the debug info file is specified, @value{GDBN}
16431 uses two different methods of looking for the debug file:
16435 For the ``debug link'' method, @value{GDBN} looks up the named file in
16436 the directory of the executable file, then in a subdirectory of that
16437 directory named @file{.debug}, and finally under each one of the global debug
16438 directories, in a subdirectory whose name is identical to the leading
16439 directories of the executable's absolute file name.
16442 For the ``build ID'' method, @value{GDBN} looks in the
16443 @file{.build-id} subdirectory of each one of the global debug directories for
16444 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16445 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16446 are the rest of the bit string. (Real build ID strings are 32 or more
16447 hex characters, not 10.)
16450 So, for example, suppose you ask @value{GDBN} to debug
16451 @file{/usr/bin/ls}, which has a debug link that specifies the
16452 file @file{ls.debug}, and a build ID whose value in hex is
16453 @code{abcdef1234}. If the list of the global debug directories includes
16454 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16455 debug information files, in the indicated order:
16459 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16461 @file{/usr/bin/ls.debug}
16463 @file{/usr/bin/.debug/ls.debug}
16465 @file{/usr/lib/debug/usr/bin/ls.debug}.
16468 @anchor{debug-file-directory}
16469 Global debugging info directories default to what is set by @value{GDBN}
16470 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16471 you can also set the global debugging info directories, and view the list
16472 @value{GDBN} is currently using.
16476 @kindex set debug-file-directory
16477 @item set debug-file-directory @var{directories}
16478 Set the directories which @value{GDBN} searches for separate debugging
16479 information files to @var{directory}. Multiple path components can be set
16480 concatenating them by a path separator.
16482 @kindex show debug-file-directory
16483 @item show debug-file-directory
16484 Show the directories @value{GDBN} searches for separate debugging
16489 @cindex @code{.gnu_debuglink} sections
16490 @cindex debug link sections
16491 A debug link is a special section of the executable file named
16492 @code{.gnu_debuglink}. The section must contain:
16496 A filename, with any leading directory components removed, followed by
16499 zero to three bytes of padding, as needed to reach the next four-byte
16500 boundary within the section, and
16502 a four-byte CRC checksum, stored in the same endianness used for the
16503 executable file itself. The checksum is computed on the debugging
16504 information file's full contents by the function given below, passing
16505 zero as the @var{crc} argument.
16508 Any executable file format can carry a debug link, as long as it can
16509 contain a section named @code{.gnu_debuglink} with the contents
16512 @cindex @code{.note.gnu.build-id} sections
16513 @cindex build ID sections
16514 The build ID is a special section in the executable file (and in other
16515 ELF binary files that @value{GDBN} may consider). This section is
16516 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16517 It contains unique identification for the built files---the ID remains
16518 the same across multiple builds of the same build tree. The default
16519 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16520 content for the build ID string. The same section with an identical
16521 value is present in the original built binary with symbols, in its
16522 stripped variant, and in the separate debugging information file.
16524 The debugging information file itself should be an ordinary
16525 executable, containing a full set of linker symbols, sections, and
16526 debugging information. The sections of the debugging information file
16527 should have the same names, addresses, and sizes as the original file,
16528 but they need not contain any data---much like a @code{.bss} section
16529 in an ordinary executable.
16531 The @sc{gnu} binary utilities (Binutils) package includes the
16532 @samp{objcopy} utility that can produce
16533 the separated executable / debugging information file pairs using the
16534 following commands:
16537 @kbd{objcopy --only-keep-debug foo foo.debug}
16542 These commands remove the debugging
16543 information from the executable file @file{foo} and place it in the file
16544 @file{foo.debug}. You can use the first, second or both methods to link the
16549 The debug link method needs the following additional command to also leave
16550 behind a debug link in @file{foo}:
16553 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16556 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16557 a version of the @code{strip} command such that the command @kbd{strip foo -f
16558 foo.debug} has the same functionality as the two @code{objcopy} commands and
16559 the @code{ln -s} command above, together.
16562 Build ID gets embedded into the main executable using @code{ld --build-id} or
16563 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16564 compatibility fixes for debug files separation are present in @sc{gnu} binary
16565 utilities (Binutils) package since version 2.18.
16570 @cindex CRC algorithm definition
16571 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16572 IEEE 802.3 using the polynomial:
16574 @c TexInfo requires naked braces for multi-digit exponents for Tex
16575 @c output, but this causes HTML output to barf. HTML has to be set using
16576 @c raw commands. So we end up having to specify this equation in 2
16581 <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>
16582 + <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
16588 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16589 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16593 The function is computed byte at a time, taking the least
16594 significant bit of each byte first. The initial pattern
16595 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16596 the final result is inverted to ensure trailing zeros also affect the
16599 @emph{Note:} This is the same CRC polynomial as used in handling the
16600 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16601 , @value{GDBN} Remote Serial Protocol}). However in the
16602 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16603 significant bit first, and the result is not inverted, so trailing
16604 zeros have no effect on the CRC value.
16606 To complete the description, we show below the code of the function
16607 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16608 initially supplied @code{crc} argument means that an initial call to
16609 this function passing in zero will start computing the CRC using
16612 @kindex gnu_debuglink_crc32
16615 gnu_debuglink_crc32 (unsigned long crc,
16616 unsigned char *buf, size_t len)
16618 static const unsigned long crc32_table[256] =
16620 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16621 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16622 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16623 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16624 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16625 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16626 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16627 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16628 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16629 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16630 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16631 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16632 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16633 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16634 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16635 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16636 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16637 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16638 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16639 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16640 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16641 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16642 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16643 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16644 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16645 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16646 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16647 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16648 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16649 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16650 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16651 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16652 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16653 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16654 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16655 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16656 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16657 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16658 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16659 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16660 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16661 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16662 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16663 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16664 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16665 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16666 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16667 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16668 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16669 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16670 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16673 unsigned char *end;
16675 crc = ~crc & 0xffffffff;
16676 for (end = buf + len; buf < end; ++buf)
16677 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16678 return ~crc & 0xffffffff;
16683 This computation does not apply to the ``build ID'' method.
16687 @section Index Files Speed Up @value{GDBN}
16688 @cindex index files
16689 @cindex @samp{.gdb_index} section
16691 When @value{GDBN} finds a symbol file, it scans the symbols in the
16692 file in order to construct an internal symbol table. This lets most
16693 @value{GDBN} operations work quickly---at the cost of a delay early
16694 on. For large programs, this delay can be quite lengthy, so
16695 @value{GDBN} provides a way to build an index, which speeds up
16698 The index is stored as a section in the symbol file. @value{GDBN} can
16699 write the index to a file, then you can put it into the symbol file
16700 using @command{objcopy}.
16702 To create an index file, use the @code{save gdb-index} command:
16705 @item save gdb-index @var{directory}
16706 @kindex save gdb-index
16707 Create an index file for each symbol file currently known by
16708 @value{GDBN}. Each file is named after its corresponding symbol file,
16709 with @samp{.gdb-index} appended, and is written into the given
16713 Once you have created an index file you can merge it into your symbol
16714 file, here named @file{symfile}, using @command{objcopy}:
16717 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16718 --set-section-flags .gdb_index=readonly symfile symfile
16721 There are currently some limitation on indices. They only work when
16722 for DWARF debugging information, not stabs. And, they do not
16723 currently work for programs using Ada.
16725 @node Symbol Errors
16726 @section Errors Reading Symbol Files
16728 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16729 such as symbol types it does not recognize, or known bugs in compiler
16730 output. By default, @value{GDBN} does not notify you of such problems, since
16731 they are relatively common and primarily of interest to people
16732 debugging compilers. If you are interested in seeing information
16733 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16734 only one message about each such type of problem, no matter how many
16735 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16736 to see how many times the problems occur, with the @code{set
16737 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16740 The messages currently printed, and their meanings, include:
16743 @item inner block not inside outer block in @var{symbol}
16745 The symbol information shows where symbol scopes begin and end
16746 (such as at the start of a function or a block of statements). This
16747 error indicates that an inner scope block is not fully contained
16748 in its outer scope blocks.
16750 @value{GDBN} circumvents the problem by treating the inner block as if it had
16751 the same scope as the outer block. In the error message, @var{symbol}
16752 may be shown as ``@code{(don't know)}'' if the outer block is not a
16755 @item block at @var{address} out of order
16757 The symbol information for symbol scope blocks should occur in
16758 order of increasing addresses. This error indicates that it does not
16761 @value{GDBN} does not circumvent this problem, and has trouble
16762 locating symbols in the source file whose symbols it is reading. (You
16763 can often determine what source file is affected by specifying
16764 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16767 @item bad block start address patched
16769 The symbol information for a symbol scope block has a start address
16770 smaller than the address of the preceding source line. This is known
16771 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16773 @value{GDBN} circumvents the problem by treating the symbol scope block as
16774 starting on the previous source line.
16776 @item bad string table offset in symbol @var{n}
16779 Symbol number @var{n} contains a pointer into the string table which is
16780 larger than the size of the string table.
16782 @value{GDBN} circumvents the problem by considering the symbol to have the
16783 name @code{foo}, which may cause other problems if many symbols end up
16786 @item unknown symbol type @code{0x@var{nn}}
16788 The symbol information contains new data types that @value{GDBN} does
16789 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16790 uncomprehended information, in hexadecimal.
16792 @value{GDBN} circumvents the error by ignoring this symbol information.
16793 This usually allows you to debug your program, though certain symbols
16794 are not accessible. If you encounter such a problem and feel like
16795 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16796 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16797 and examine @code{*bufp} to see the symbol.
16799 @item stub type has NULL name
16801 @value{GDBN} could not find the full definition for a struct or class.
16803 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16804 The symbol information for a C@t{++} member function is missing some
16805 information that recent versions of the compiler should have output for
16808 @item info mismatch between compiler and debugger
16810 @value{GDBN} could not parse a type specification output by the compiler.
16815 @section GDB Data Files
16817 @cindex prefix for data files
16818 @value{GDBN} will sometimes read an auxiliary data file. These files
16819 are kept in a directory known as the @dfn{data directory}.
16821 You can set the data directory's name, and view the name @value{GDBN}
16822 is currently using.
16825 @kindex set data-directory
16826 @item set data-directory @var{directory}
16827 Set the directory which @value{GDBN} searches for auxiliary data files
16828 to @var{directory}.
16830 @kindex show data-directory
16831 @item show data-directory
16832 Show the directory @value{GDBN} searches for auxiliary data files.
16835 @cindex default data directory
16836 @cindex @samp{--with-gdb-datadir}
16837 You can set the default data directory by using the configure-time
16838 @samp{--with-gdb-datadir} option. If the data directory is inside
16839 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16840 @samp{--exec-prefix}), then the default data directory will be updated
16841 automatically if the installed @value{GDBN} is moved to a new
16844 The data directory may also be specified with the
16845 @code{--data-directory} command line option.
16846 @xref{Mode Options}.
16849 @chapter Specifying a Debugging Target
16851 @cindex debugging target
16852 A @dfn{target} is the execution environment occupied by your program.
16854 Often, @value{GDBN} runs in the same host environment as your program;
16855 in that case, the debugging target is specified as a side effect when
16856 you use the @code{file} or @code{core} commands. When you need more
16857 flexibility---for example, running @value{GDBN} on a physically separate
16858 host, or controlling a standalone system over a serial port or a
16859 realtime system over a TCP/IP connection---you can use the @code{target}
16860 command to specify one of the target types configured for @value{GDBN}
16861 (@pxref{Target Commands, ,Commands for Managing Targets}).
16863 @cindex target architecture
16864 It is possible to build @value{GDBN} for several different @dfn{target
16865 architectures}. When @value{GDBN} is built like that, you can choose
16866 one of the available architectures with the @kbd{set architecture}
16870 @kindex set architecture
16871 @kindex show architecture
16872 @item set architecture @var{arch}
16873 This command sets the current target architecture to @var{arch}. The
16874 value of @var{arch} can be @code{"auto"}, in addition to one of the
16875 supported architectures.
16877 @item show architecture
16878 Show the current target architecture.
16880 @item set processor
16882 @kindex set processor
16883 @kindex show processor
16884 These are alias commands for, respectively, @code{set architecture}
16885 and @code{show architecture}.
16889 * Active Targets:: Active targets
16890 * Target Commands:: Commands for managing targets
16891 * Byte Order:: Choosing target byte order
16894 @node Active Targets
16895 @section Active Targets
16897 @cindex stacking targets
16898 @cindex active targets
16899 @cindex multiple targets
16901 There are multiple classes of targets such as: processes, executable files or
16902 recording sessions. Core files belong to the process class, making core file
16903 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16904 on multiple active targets, one in each class. This allows you to (for
16905 example) start a process and inspect its activity, while still having access to
16906 the executable file after the process finishes. Or if you start process
16907 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16908 presented a virtual layer of the recording target, while the process target
16909 remains stopped at the chronologically last point of the process execution.
16911 Use the @code{core-file} and @code{exec-file} commands to select a new core
16912 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16913 specify as a target a process that is already running, use the @code{attach}
16914 command (@pxref{Attach, ,Debugging an Already-running Process}).
16916 @node Target Commands
16917 @section Commands for Managing Targets
16920 @item target @var{type} @var{parameters}
16921 Connects the @value{GDBN} host environment to a target machine or
16922 process. A target is typically a protocol for talking to debugging
16923 facilities. You use the argument @var{type} to specify the type or
16924 protocol of the target machine.
16926 Further @var{parameters} are interpreted by the target protocol, but
16927 typically include things like device names or host names to connect
16928 with, process numbers, and baud rates.
16930 The @code{target} command does not repeat if you press @key{RET} again
16931 after executing the command.
16933 @kindex help target
16935 Displays the names of all targets available. To display targets
16936 currently selected, use either @code{info target} or @code{info files}
16937 (@pxref{Files, ,Commands to Specify Files}).
16939 @item help target @var{name}
16940 Describe a particular target, including any parameters necessary to
16943 @kindex set gnutarget
16944 @item set gnutarget @var{args}
16945 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16946 knows whether it is reading an @dfn{executable},
16947 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16948 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16949 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16952 @emph{Warning:} To specify a file format with @code{set gnutarget},
16953 you must know the actual BFD name.
16957 @xref{Files, , Commands to Specify Files}.
16959 @kindex show gnutarget
16960 @item show gnutarget
16961 Use the @code{show gnutarget} command to display what file format
16962 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16963 @value{GDBN} will determine the file format for each file automatically,
16964 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16967 @cindex common targets
16968 Here are some common targets (available, or not, depending on the GDB
16973 @item target exec @var{program}
16974 @cindex executable file target
16975 An executable file. @samp{target exec @var{program}} is the same as
16976 @samp{exec-file @var{program}}.
16978 @item target core @var{filename}
16979 @cindex core dump file target
16980 A core dump file. @samp{target core @var{filename}} is the same as
16981 @samp{core-file @var{filename}}.
16983 @item target remote @var{medium}
16984 @cindex remote target
16985 A remote system connected to @value{GDBN} via a serial line or network
16986 connection. This command tells @value{GDBN} to use its own remote
16987 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16989 For example, if you have a board connected to @file{/dev/ttya} on the
16990 machine running @value{GDBN}, you could say:
16993 target remote /dev/ttya
16996 @code{target remote} supports the @code{load} command. This is only
16997 useful if you have some other way of getting the stub to the target
16998 system, and you can put it somewhere in memory where it won't get
16999 clobbered by the download.
17001 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17002 @cindex built-in simulator target
17003 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17011 works; however, you cannot assume that a specific memory map, device
17012 drivers, or even basic I/O is available, although some simulators do
17013 provide these. For info about any processor-specific simulator details,
17014 see the appropriate section in @ref{Embedded Processors, ,Embedded
17019 Some configurations may include these targets as well:
17023 @item target nrom @var{dev}
17024 @cindex NetROM ROM emulator target
17025 NetROM ROM emulator. This target only supports downloading.
17029 Different targets are available on different configurations of @value{GDBN};
17030 your configuration may have more or fewer targets.
17032 Many remote targets require you to download the executable's code once
17033 you've successfully established a connection. You may wish to control
17034 various aspects of this process.
17039 @kindex set hash@r{, for remote monitors}
17040 @cindex hash mark while downloading
17041 This command controls whether a hash mark @samp{#} is displayed while
17042 downloading a file to the remote monitor. If on, a hash mark is
17043 displayed after each S-record is successfully downloaded to the
17047 @kindex show hash@r{, for remote monitors}
17048 Show the current status of displaying the hash mark.
17050 @item set debug monitor
17051 @kindex set debug monitor
17052 @cindex display remote monitor communications
17053 Enable or disable display of communications messages between
17054 @value{GDBN} and the remote monitor.
17056 @item show debug monitor
17057 @kindex show debug monitor
17058 Show the current status of displaying communications between
17059 @value{GDBN} and the remote monitor.
17064 @kindex load @var{filename}
17065 @item load @var{filename}
17067 Depending on what remote debugging facilities are configured into
17068 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17069 is meant to make @var{filename} (an executable) available for debugging
17070 on the remote system---by downloading, or dynamic linking, for example.
17071 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17072 the @code{add-symbol-file} command.
17074 If your @value{GDBN} does not have a @code{load} command, attempting to
17075 execute it gets the error message ``@code{You can't do that when your
17076 target is @dots{}}''
17078 The file is loaded at whatever address is specified in the executable.
17079 For some object file formats, you can specify the load address when you
17080 link the program; for other formats, like a.out, the object file format
17081 specifies a fixed address.
17082 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17084 Depending on the remote side capabilities, @value{GDBN} may be able to
17085 load programs into flash memory.
17087 @code{load} does not repeat if you press @key{RET} again after using it.
17091 @section Choosing Target Byte Order
17093 @cindex choosing target byte order
17094 @cindex target byte order
17096 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17097 offer the ability to run either big-endian or little-endian byte
17098 orders. Usually the executable or symbol will include a bit to
17099 designate the endian-ness, and you will not need to worry about
17100 which to use. However, you may still find it useful to adjust
17101 @value{GDBN}'s idea of processor endian-ness manually.
17105 @item set endian big
17106 Instruct @value{GDBN} to assume the target is big-endian.
17108 @item set endian little
17109 Instruct @value{GDBN} to assume the target is little-endian.
17111 @item set endian auto
17112 Instruct @value{GDBN} to use the byte order associated with the
17116 Display @value{GDBN}'s current idea of the target byte order.
17120 Note that these commands merely adjust interpretation of symbolic
17121 data on the host, and that they have absolutely no effect on the
17125 @node Remote Debugging
17126 @chapter Debugging Remote Programs
17127 @cindex remote debugging
17129 If you are trying to debug a program running on a machine that cannot run
17130 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17131 For example, you might use remote debugging on an operating system kernel,
17132 or on a small system which does not have a general purpose operating system
17133 powerful enough to run a full-featured debugger.
17135 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17136 to make this work with particular debugging targets. In addition,
17137 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17138 but not specific to any particular target system) which you can use if you
17139 write the remote stubs---the code that runs on the remote system to
17140 communicate with @value{GDBN}.
17142 Other remote targets may be available in your
17143 configuration of @value{GDBN}; use @code{help target} to list them.
17146 * Connecting:: Connecting to a remote target
17147 * File Transfer:: Sending files to a remote system
17148 * Server:: Using the gdbserver program
17149 * Remote Configuration:: Remote configuration
17150 * Remote Stub:: Implementing a remote stub
17154 @section Connecting to a Remote Target
17156 On the @value{GDBN} host machine, you will need an unstripped copy of
17157 your program, since @value{GDBN} needs symbol and debugging information.
17158 Start up @value{GDBN} as usual, using the name of the local copy of your
17159 program as the first argument.
17161 @cindex @code{target remote}
17162 @value{GDBN} can communicate with the target over a serial line, or
17163 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17164 each case, @value{GDBN} uses the same protocol for debugging your
17165 program; only the medium carrying the debugging packets varies. The
17166 @code{target remote} command establishes a connection to the target.
17167 Its arguments indicate which medium to use:
17171 @item target remote @var{serial-device}
17172 @cindex serial line, @code{target remote}
17173 Use @var{serial-device} to communicate with the target. For example,
17174 to use a serial line connected to the device named @file{/dev/ttyb}:
17177 target remote /dev/ttyb
17180 If you're using a serial line, you may want to give @value{GDBN} the
17181 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17182 (@pxref{Remote Configuration, set remotebaud}) before the
17183 @code{target} command.
17185 @item target remote @code{@var{host}:@var{port}}
17186 @itemx target remote @code{tcp:@var{host}:@var{port}}
17187 @cindex @acronym{TCP} port, @code{target remote}
17188 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17189 The @var{host} may be either a host name or a numeric @acronym{IP}
17190 address; @var{port} must be a decimal number. The @var{host} could be
17191 the target machine itself, if it is directly connected to the net, or
17192 it might be a terminal server which in turn has a serial line to the
17195 For example, to connect to port 2828 on a terminal server named
17199 target remote manyfarms:2828
17202 If your remote target is actually running on the same machine as your
17203 debugger session (e.g.@: a simulator for your target running on the
17204 same host), you can omit the hostname. For example, to connect to
17205 port 1234 on your local machine:
17208 target remote :1234
17212 Note that the colon is still required here.
17214 @item target remote @code{udp:@var{host}:@var{port}}
17215 @cindex @acronym{UDP} port, @code{target remote}
17216 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17217 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17220 target remote udp:manyfarms:2828
17223 When using a @acronym{UDP} connection for remote debugging, you should
17224 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17225 can silently drop packets on busy or unreliable networks, which will
17226 cause havoc with your debugging session.
17228 @item target remote | @var{command}
17229 @cindex pipe, @code{target remote} to
17230 Run @var{command} in the background and communicate with it using a
17231 pipe. The @var{command} is a shell command, to be parsed and expanded
17232 by the system's command shell, @code{/bin/sh}; it should expect remote
17233 protocol packets on its standard input, and send replies on its
17234 standard output. You could use this to run a stand-alone simulator
17235 that speaks the remote debugging protocol, to make net connections
17236 using programs like @code{ssh}, or for other similar tricks.
17238 If @var{command} closes its standard output (perhaps by exiting),
17239 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17240 program has already exited, this will have no effect.)
17244 Once the connection has been established, you can use all the usual
17245 commands to examine and change data. The remote program is already
17246 running; you can use @kbd{step} and @kbd{continue}, and you do not
17247 need to use @kbd{run}.
17249 @cindex interrupting remote programs
17250 @cindex remote programs, interrupting
17251 Whenever @value{GDBN} is waiting for the remote program, if you type the
17252 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17253 program. This may or may not succeed, depending in part on the hardware
17254 and the serial drivers the remote system uses. If you type the
17255 interrupt character once again, @value{GDBN} displays this prompt:
17258 Interrupted while waiting for the program.
17259 Give up (and stop debugging it)? (y or n)
17262 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17263 (If you decide you want to try again later, you can use @samp{target
17264 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17265 goes back to waiting.
17268 @kindex detach (remote)
17270 When you have finished debugging the remote program, you can use the
17271 @code{detach} command to release it from @value{GDBN} control.
17272 Detaching from the target normally resumes its execution, but the results
17273 will depend on your particular remote stub. After the @code{detach}
17274 command, @value{GDBN} is free to connect to another target.
17278 The @code{disconnect} command behaves like @code{detach}, except that
17279 the target is generally not resumed. It will wait for @value{GDBN}
17280 (this instance or another one) to connect and continue debugging. After
17281 the @code{disconnect} command, @value{GDBN} is again free to connect to
17284 @cindex send command to remote monitor
17285 @cindex extend @value{GDBN} for remote targets
17286 @cindex add new commands for external monitor
17288 @item monitor @var{cmd}
17289 This command allows you to send arbitrary commands directly to the
17290 remote monitor. Since @value{GDBN} doesn't care about the commands it
17291 sends like this, this command is the way to extend @value{GDBN}---you
17292 can add new commands that only the external monitor will understand
17296 @node File Transfer
17297 @section Sending files to a remote system
17298 @cindex remote target, file transfer
17299 @cindex file transfer
17300 @cindex sending files to remote systems
17302 Some remote targets offer the ability to transfer files over the same
17303 connection used to communicate with @value{GDBN}. This is convenient
17304 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17305 running @code{gdbserver} over a network interface. For other targets,
17306 e.g.@: embedded devices with only a single serial port, this may be
17307 the only way to upload or download files.
17309 Not all remote targets support these commands.
17313 @item remote put @var{hostfile} @var{targetfile}
17314 Copy file @var{hostfile} from the host system (the machine running
17315 @value{GDBN}) to @var{targetfile} on the target system.
17318 @item remote get @var{targetfile} @var{hostfile}
17319 Copy file @var{targetfile} from the target system to @var{hostfile}
17320 on the host system.
17322 @kindex remote delete
17323 @item remote delete @var{targetfile}
17324 Delete @var{targetfile} from the target system.
17329 @section Using the @code{gdbserver} Program
17332 @cindex remote connection without stubs
17333 @code{gdbserver} is a control program for Unix-like systems, which
17334 allows you to connect your program with a remote @value{GDBN} via
17335 @code{target remote}---but without linking in the usual debugging stub.
17337 @code{gdbserver} is not a complete replacement for the debugging stubs,
17338 because it requires essentially the same operating-system facilities
17339 that @value{GDBN} itself does. In fact, a system that can run
17340 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17341 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17342 because it is a much smaller program than @value{GDBN} itself. It is
17343 also easier to port than all of @value{GDBN}, so you may be able to get
17344 started more quickly on a new system by using @code{gdbserver}.
17345 Finally, if you develop code for real-time systems, you may find that
17346 the tradeoffs involved in real-time operation make it more convenient to
17347 do as much development work as possible on another system, for example
17348 by cross-compiling. You can use @code{gdbserver} to make a similar
17349 choice for debugging.
17351 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17352 or a TCP connection, using the standard @value{GDBN} remote serial
17356 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17357 Do not run @code{gdbserver} connected to any public network; a
17358 @value{GDBN} connection to @code{gdbserver} provides access to the
17359 target system with the same privileges as the user running
17363 @subsection Running @code{gdbserver}
17364 @cindex arguments, to @code{gdbserver}
17365 @cindex @code{gdbserver}, command-line arguments
17367 Run @code{gdbserver} on the target system. You need a copy of the
17368 program you want to debug, including any libraries it requires.
17369 @code{gdbserver} does not need your program's symbol table, so you can
17370 strip the program if necessary to save space. @value{GDBN} on the host
17371 system does all the symbol handling.
17373 To use the server, you must tell it how to communicate with @value{GDBN};
17374 the name of your program; and the arguments for your program. The usual
17378 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17381 @var{comm} is either a device name (to use a serial line), or a TCP
17382 hostname and portnumber, or @code{-} or @code{stdio} to use
17383 stdin/stdout of @code{gdbserver}.
17384 For example, to debug Emacs with the argument
17385 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17389 target> gdbserver /dev/com1 emacs foo.txt
17392 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17395 To use a TCP connection instead of a serial line:
17398 target> gdbserver host:2345 emacs foo.txt
17401 The only difference from the previous example is the first argument,
17402 specifying that you are communicating with the host @value{GDBN} via
17403 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17404 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17405 (Currently, the @samp{host} part is ignored.) You can choose any number
17406 you want for the port number as long as it does not conflict with any
17407 TCP ports already in use on the target system (for example, @code{23} is
17408 reserved for @code{telnet}).@footnote{If you choose a port number that
17409 conflicts with another service, @code{gdbserver} prints an error message
17410 and exits.} You must use the same port number with the host @value{GDBN}
17411 @code{target remote} command.
17413 The @code{stdio} connection is useful when starting @code{gdbserver}
17417 (gdb) target remote | ssh -T hostname gdbserver - hello
17420 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17421 and we don't want escape-character handling. Ssh does this by default when
17422 a command is provided, the flag is provided to make it explicit.
17423 You could elide it if you want to.
17425 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17426 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17427 display through a pipe connected to gdbserver.
17428 Both @code{stdout} and @code{stderr} use the same pipe.
17430 @subsubsection Attaching to a Running Program
17431 @cindex attach to a program, @code{gdbserver}
17432 @cindex @option{--attach}, @code{gdbserver} option
17434 On some targets, @code{gdbserver} can also attach to running programs.
17435 This is accomplished via the @code{--attach} argument. The syntax is:
17438 target> gdbserver --attach @var{comm} @var{pid}
17441 @var{pid} is the process ID of a currently running process. It isn't necessary
17442 to point @code{gdbserver} at a binary for the running process.
17445 You can debug processes by name instead of process ID if your target has the
17446 @code{pidof} utility:
17449 target> gdbserver --attach @var{comm} `pidof @var{program}`
17452 In case more than one copy of @var{program} is running, or @var{program}
17453 has multiple threads, most versions of @code{pidof} support the
17454 @code{-s} option to only return the first process ID.
17456 @subsubsection Multi-Process Mode for @code{gdbserver}
17457 @cindex @code{gdbserver}, multiple processes
17458 @cindex multiple processes with @code{gdbserver}
17460 When you connect to @code{gdbserver} using @code{target remote},
17461 @code{gdbserver} debugs the specified program only once. When the
17462 program exits, or you detach from it, @value{GDBN} closes the connection
17463 and @code{gdbserver} exits.
17465 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17466 enters multi-process mode. When the debugged program exits, or you
17467 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17468 though no program is running. The @code{run} and @code{attach}
17469 commands instruct @code{gdbserver} to run or attach to a new program.
17470 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17471 remote exec-file}) to select the program to run. Command line
17472 arguments are supported, except for wildcard expansion and I/O
17473 redirection (@pxref{Arguments}).
17475 @cindex @option{--multi}, @code{gdbserver} option
17476 To start @code{gdbserver} without supplying an initial command to run
17477 or process ID to attach, use the @option{--multi} command line option.
17478 Then you can connect using @kbd{target extended-remote} and start
17479 the program you want to debug.
17481 In multi-process mode @code{gdbserver} does not automatically exit unless you
17482 use the option @option{--once}. You can terminate it by using
17483 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17484 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17485 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17486 @option{--multi} option to @code{gdbserver} has no influence on that.
17488 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17490 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17492 @code{gdbserver} normally terminates after all of its debugged processes have
17493 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17494 extended-remote}, @code{gdbserver} stays running even with no processes left.
17495 @value{GDBN} normally terminates the spawned debugged process on its exit,
17496 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17497 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17498 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17499 stays running even in the @kbd{target remote} mode.
17501 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17502 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17503 completeness, at most one @value{GDBN} can be connected at a time.
17505 @cindex @option{--once}, @code{gdbserver} option
17506 By default, @code{gdbserver} keeps the listening TCP port open, so that
17507 additional connections are possible. However, if you start @code{gdbserver}
17508 with the @option{--once} option, it will stop listening for any further
17509 connection attempts after connecting to the first @value{GDBN} session. This
17510 means no further connections to @code{gdbserver} will be possible after the
17511 first one. It also means @code{gdbserver} will terminate after the first
17512 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17513 connections and even in the @kbd{target extended-remote} mode. The
17514 @option{--once} option allows reusing the same port number for connecting to
17515 multiple instances of @code{gdbserver} running on the same host, since each
17516 instance closes its port after the first connection.
17518 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17520 @cindex @option{--debug}, @code{gdbserver} option
17521 The @option{--debug} option tells @code{gdbserver} to display extra
17522 status information about the debugging process.
17523 @cindex @option{--remote-debug}, @code{gdbserver} option
17524 The @option{--remote-debug} option tells @code{gdbserver} to display
17525 remote protocol debug output. These options are intended for
17526 @code{gdbserver} development and for bug reports to the developers.
17528 @cindex @option{--wrapper}, @code{gdbserver} option
17529 The @option{--wrapper} option specifies a wrapper to launch programs
17530 for debugging. The option should be followed by the name of the
17531 wrapper, then any command-line arguments to pass to the wrapper, then
17532 @kbd{--} indicating the end of the wrapper arguments.
17534 @code{gdbserver} runs the specified wrapper program with a combined
17535 command line including the wrapper arguments, then the name of the
17536 program to debug, then any arguments to the program. The wrapper
17537 runs until it executes your program, and then @value{GDBN} gains control.
17539 You can use any program that eventually calls @code{execve} with
17540 its arguments as a wrapper. Several standard Unix utilities do
17541 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17542 with @code{exec "$@@"} will also work.
17544 For example, you can use @code{env} to pass an environment variable to
17545 the debugged program, without setting the variable in @code{gdbserver}'s
17549 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17552 @subsection Connecting to @code{gdbserver}
17554 Run @value{GDBN} on the host system.
17556 First make sure you have the necessary symbol files. Load symbols for
17557 your application using the @code{file} command before you connect. Use
17558 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17559 was compiled with the correct sysroot using @code{--with-sysroot}).
17561 The symbol file and target libraries must exactly match the executable
17562 and libraries on the target, with one exception: the files on the host
17563 system should not be stripped, even if the files on the target system
17564 are. Mismatched or missing files will lead to confusing results
17565 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17566 files may also prevent @code{gdbserver} from debugging multi-threaded
17569 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17570 For TCP connections, you must start up @code{gdbserver} prior to using
17571 the @code{target remote} command. Otherwise you may get an error whose
17572 text depends on the host system, but which usually looks something like
17573 @samp{Connection refused}. Don't use the @code{load}
17574 command in @value{GDBN} when using @code{gdbserver}, since the program is
17575 already on the target.
17577 @subsection Monitor Commands for @code{gdbserver}
17578 @cindex monitor commands, for @code{gdbserver}
17579 @anchor{Monitor Commands for gdbserver}
17581 During a @value{GDBN} session using @code{gdbserver}, you can use the
17582 @code{monitor} command to send special requests to @code{gdbserver}.
17583 Here are the available commands.
17587 List the available monitor commands.
17589 @item monitor set debug 0
17590 @itemx monitor set debug 1
17591 Disable or enable general debugging messages.
17593 @item monitor set remote-debug 0
17594 @itemx monitor set remote-debug 1
17595 Disable or enable specific debugging messages associated with the remote
17596 protocol (@pxref{Remote Protocol}).
17598 @item monitor set libthread-db-search-path [PATH]
17599 @cindex gdbserver, search path for @code{libthread_db}
17600 When this command is issued, @var{path} is a colon-separated list of
17601 directories to search for @code{libthread_db} (@pxref{Threads,,set
17602 libthread-db-search-path}). If you omit @var{path},
17603 @samp{libthread-db-search-path} will be reset to its default value.
17605 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17606 not supported in @code{gdbserver}.
17609 Tell gdbserver to exit immediately. This command should be followed by
17610 @code{disconnect} to close the debugging session. @code{gdbserver} will
17611 detach from any attached processes and kill any processes it created.
17612 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17613 of a multi-process mode debug session.
17617 @subsection Tracepoints support in @code{gdbserver}
17618 @cindex tracepoints support in @code{gdbserver}
17620 On some targets, @code{gdbserver} supports tracepoints, fast
17621 tracepoints and static tracepoints.
17623 For fast or static tracepoints to work, a special library called the
17624 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17625 This library is built and distributed as an integral part of
17626 @code{gdbserver}. In addition, support for static tracepoints
17627 requires building the in-process agent library with static tracepoints
17628 support. At present, the UST (LTTng Userspace Tracer,
17629 @url{http://lttng.org/ust}) tracing engine is supported. This support
17630 is automatically available if UST development headers are found in the
17631 standard include path when @code{gdbserver} is built, or if
17632 @code{gdbserver} was explicitly configured using @option{--with-ust}
17633 to point at such headers. You can explicitly disable the support
17634 using @option{--with-ust=no}.
17636 There are several ways to load the in-process agent in your program:
17639 @item Specifying it as dependency at link time
17641 You can link your program dynamically with the in-process agent
17642 library. On most systems, this is accomplished by adding
17643 @code{-linproctrace} to the link command.
17645 @item Using the system's preloading mechanisms
17647 You can force loading the in-process agent at startup time by using
17648 your system's support for preloading shared libraries. Many Unixes
17649 support the concept of preloading user defined libraries. In most
17650 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17651 in the environment. See also the description of @code{gdbserver}'s
17652 @option{--wrapper} command line option.
17654 @item Using @value{GDBN} to force loading the agent at run time
17656 On some systems, you can force the inferior to load a shared library,
17657 by calling a dynamic loader function in the inferior that takes care
17658 of dynamically looking up and loading a shared library. On most Unix
17659 systems, the function is @code{dlopen}. You'll use the @code{call}
17660 command for that. For example:
17663 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17666 Note that on most Unix systems, for the @code{dlopen} function to be
17667 available, the program needs to be linked with @code{-ldl}.
17670 On systems that have a userspace dynamic loader, like most Unix
17671 systems, when you connect to @code{gdbserver} using @code{target
17672 remote}, you'll find that the program is stopped at the dynamic
17673 loader's entry point, and no shared library has been loaded in the
17674 program's address space yet, including the in-process agent. In that
17675 case, before being able to use any of the fast or static tracepoints
17676 features, you need to let the loader run and load the shared
17677 libraries. The simplest way to do that is to run the program to the
17678 main procedure. E.g., if debugging a C or C@t{++} program, start
17679 @code{gdbserver} like so:
17682 $ gdbserver :9999 myprogram
17685 Start GDB and connect to @code{gdbserver} like so, and run to main:
17689 (@value{GDBP}) target remote myhost:9999
17690 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17691 (@value{GDBP}) b main
17692 (@value{GDBP}) continue
17695 The in-process tracing agent library should now be loaded into the
17696 process; you can confirm it with the @code{info sharedlibrary}
17697 command, which will list @file{libinproctrace.so} as loaded in the
17698 process. You are now ready to install fast tracepoints, list static
17699 tracepoint markers, probe static tracepoints markers, and start
17702 @node Remote Configuration
17703 @section Remote Configuration
17706 @kindex show remote
17707 This section documents the configuration options available when
17708 debugging remote programs. For the options related to the File I/O
17709 extensions of the remote protocol, see @ref{system,
17710 system-call-allowed}.
17713 @item set remoteaddresssize @var{bits}
17714 @cindex address size for remote targets
17715 @cindex bits in remote address
17716 Set the maximum size of address in a memory packet to the specified
17717 number of bits. @value{GDBN} will mask off the address bits above
17718 that number, when it passes addresses to the remote target. The
17719 default value is the number of bits in the target's address.
17721 @item show remoteaddresssize
17722 Show the current value of remote address size in bits.
17724 @item set remotebaud @var{n}
17725 @cindex baud rate for remote targets
17726 Set the baud rate for the remote serial I/O to @var{n} baud. The
17727 value is used to set the speed of the serial port used for debugging
17730 @item show remotebaud
17731 Show the current speed of the remote connection.
17733 @item set remotebreak
17734 @cindex interrupt remote programs
17735 @cindex BREAK signal instead of Ctrl-C
17736 @anchor{set remotebreak}
17737 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17738 when you type @kbd{Ctrl-c} to interrupt the program running
17739 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17740 character instead. The default is off, since most remote systems
17741 expect to see @samp{Ctrl-C} as the interrupt signal.
17743 @item show remotebreak
17744 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17745 interrupt the remote program.
17747 @item set remoteflow on
17748 @itemx set remoteflow off
17749 @kindex set remoteflow
17750 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17751 on the serial port used to communicate to the remote target.
17753 @item show remoteflow
17754 @kindex show remoteflow
17755 Show the current setting of hardware flow control.
17757 @item set remotelogbase @var{base}
17758 Set the base (a.k.a.@: radix) of logging serial protocol
17759 communications to @var{base}. Supported values of @var{base} are:
17760 @code{ascii}, @code{octal}, and @code{hex}. The default is
17763 @item show remotelogbase
17764 Show the current setting of the radix for logging remote serial
17767 @item set remotelogfile @var{file}
17768 @cindex record serial communications on file
17769 Record remote serial communications on the named @var{file}. The
17770 default is not to record at all.
17772 @item show remotelogfile.
17773 Show the current setting of the file name on which to record the
17774 serial communications.
17776 @item set remotetimeout @var{num}
17777 @cindex timeout for serial communications
17778 @cindex remote timeout
17779 Set the timeout limit to wait for the remote target to respond to
17780 @var{num} seconds. The default is 2 seconds.
17782 @item show remotetimeout
17783 Show the current number of seconds to wait for the remote target
17786 @cindex limit hardware breakpoints and watchpoints
17787 @cindex remote target, limit break- and watchpoints
17788 @anchor{set remote hardware-watchpoint-limit}
17789 @anchor{set remote hardware-breakpoint-limit}
17790 @item set remote hardware-watchpoint-limit @var{limit}
17791 @itemx set remote hardware-breakpoint-limit @var{limit}
17792 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17793 watchpoints. A limit of -1, the default, is treated as unlimited.
17795 @cindex limit hardware watchpoints length
17796 @cindex remote target, limit watchpoints length
17797 @anchor{set remote hardware-watchpoint-length-limit}
17798 @item set remote hardware-watchpoint-length-limit @var{limit}
17799 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17800 a remote hardware watchpoint. A limit of -1, the default, is treated
17803 @item show remote hardware-watchpoint-length-limit
17804 Show the current limit (in bytes) of the maximum length of
17805 a remote hardware watchpoint.
17807 @item set remote exec-file @var{filename}
17808 @itemx show remote exec-file
17809 @anchor{set remote exec-file}
17810 @cindex executable file, for remote target
17811 Select the file used for @code{run} with @code{target
17812 extended-remote}. This should be set to a filename valid on the
17813 target system. If it is not set, the target will use a default
17814 filename (e.g.@: the last program run).
17816 @item set remote interrupt-sequence
17817 @cindex interrupt remote programs
17818 @cindex select Ctrl-C, BREAK or BREAK-g
17819 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17820 @samp{BREAK-g} as the
17821 sequence to the remote target in order to interrupt the execution.
17822 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17823 is high level of serial line for some certain time.
17824 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17825 It is @code{BREAK} signal followed by character @code{g}.
17827 @item show interrupt-sequence
17828 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17829 is sent by @value{GDBN} to interrupt the remote program.
17830 @code{BREAK-g} is BREAK signal followed by @code{g} and
17831 also known as Magic SysRq g.
17833 @item set remote interrupt-on-connect
17834 @cindex send interrupt-sequence on start
17835 Specify whether interrupt-sequence is sent to remote target when
17836 @value{GDBN} connects to it. This is mostly needed when you debug
17837 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17838 which is known as Magic SysRq g in order to connect @value{GDBN}.
17840 @item show interrupt-on-connect
17841 Show whether interrupt-sequence is sent
17842 to remote target when @value{GDBN} connects to it.
17846 @item set tcp auto-retry on
17847 @cindex auto-retry, for remote TCP target
17848 Enable auto-retry for remote TCP connections. This is useful if the remote
17849 debugging agent is launched in parallel with @value{GDBN}; there is a race
17850 condition because the agent may not become ready to accept the connection
17851 before @value{GDBN} attempts to connect. When auto-retry is
17852 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17853 to establish the connection using the timeout specified by
17854 @code{set tcp connect-timeout}.
17856 @item set tcp auto-retry off
17857 Do not auto-retry failed TCP connections.
17859 @item show tcp auto-retry
17860 Show the current auto-retry setting.
17862 @item set tcp connect-timeout @var{seconds}
17863 @cindex connection timeout, for remote TCP target
17864 @cindex timeout, for remote target connection
17865 Set the timeout for establishing a TCP connection to the remote target to
17866 @var{seconds}. The timeout affects both polling to retry failed connections
17867 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17868 that are merely slow to complete, and represents an approximate cumulative
17871 @item show tcp connect-timeout
17872 Show the current connection timeout setting.
17875 @cindex remote packets, enabling and disabling
17876 The @value{GDBN} remote protocol autodetects the packets supported by
17877 your debugging stub. If you need to override the autodetection, you
17878 can use these commands to enable or disable individual packets. Each
17879 packet can be set to @samp{on} (the remote target supports this
17880 packet), @samp{off} (the remote target does not support this packet),
17881 or @samp{auto} (detect remote target support for this packet). They
17882 all default to @samp{auto}. For more information about each packet,
17883 see @ref{Remote Protocol}.
17885 During normal use, you should not have to use any of these commands.
17886 If you do, that may be a bug in your remote debugging stub, or a bug
17887 in @value{GDBN}. You may want to report the problem to the
17888 @value{GDBN} developers.
17890 For each packet @var{name}, the command to enable or disable the
17891 packet is @code{set remote @var{name}-packet}. The available settings
17894 @multitable @columnfractions 0.28 0.32 0.25
17897 @tab Related Features
17899 @item @code{fetch-register}
17901 @tab @code{info registers}
17903 @item @code{set-register}
17907 @item @code{binary-download}
17909 @tab @code{load}, @code{set}
17911 @item @code{read-aux-vector}
17912 @tab @code{qXfer:auxv:read}
17913 @tab @code{info auxv}
17915 @item @code{symbol-lookup}
17916 @tab @code{qSymbol}
17917 @tab Detecting multiple threads
17919 @item @code{attach}
17920 @tab @code{vAttach}
17923 @item @code{verbose-resume}
17925 @tab Stepping or resuming multiple threads
17931 @item @code{software-breakpoint}
17935 @item @code{hardware-breakpoint}
17939 @item @code{write-watchpoint}
17943 @item @code{read-watchpoint}
17947 @item @code{access-watchpoint}
17951 @item @code{target-features}
17952 @tab @code{qXfer:features:read}
17953 @tab @code{set architecture}
17955 @item @code{library-info}
17956 @tab @code{qXfer:libraries:read}
17957 @tab @code{info sharedlibrary}
17959 @item @code{memory-map}
17960 @tab @code{qXfer:memory-map:read}
17961 @tab @code{info mem}
17963 @item @code{read-sdata-object}
17964 @tab @code{qXfer:sdata:read}
17965 @tab @code{print $_sdata}
17967 @item @code{read-spu-object}
17968 @tab @code{qXfer:spu:read}
17969 @tab @code{info spu}
17971 @item @code{write-spu-object}
17972 @tab @code{qXfer:spu:write}
17973 @tab @code{info spu}
17975 @item @code{read-siginfo-object}
17976 @tab @code{qXfer:siginfo:read}
17977 @tab @code{print $_siginfo}
17979 @item @code{write-siginfo-object}
17980 @tab @code{qXfer:siginfo:write}
17981 @tab @code{set $_siginfo}
17983 @item @code{threads}
17984 @tab @code{qXfer:threads:read}
17985 @tab @code{info threads}
17987 @item @code{get-thread-local-@*storage-address}
17988 @tab @code{qGetTLSAddr}
17989 @tab Displaying @code{__thread} variables
17991 @item @code{get-thread-information-block-address}
17992 @tab @code{qGetTIBAddr}
17993 @tab Display MS-Windows Thread Information Block.
17995 @item @code{search-memory}
17996 @tab @code{qSearch:memory}
17999 @item @code{supported-packets}
18000 @tab @code{qSupported}
18001 @tab Remote communications parameters
18003 @item @code{pass-signals}
18004 @tab @code{QPassSignals}
18005 @tab @code{handle @var{signal}}
18007 @item @code{program-signals}
18008 @tab @code{QProgramSignals}
18009 @tab @code{handle @var{signal}}
18011 @item @code{hostio-close-packet}
18012 @tab @code{vFile:close}
18013 @tab @code{remote get}, @code{remote put}
18015 @item @code{hostio-open-packet}
18016 @tab @code{vFile:open}
18017 @tab @code{remote get}, @code{remote put}
18019 @item @code{hostio-pread-packet}
18020 @tab @code{vFile:pread}
18021 @tab @code{remote get}, @code{remote put}
18023 @item @code{hostio-pwrite-packet}
18024 @tab @code{vFile:pwrite}
18025 @tab @code{remote get}, @code{remote put}
18027 @item @code{hostio-unlink-packet}
18028 @tab @code{vFile:unlink}
18029 @tab @code{remote delete}
18031 @item @code{hostio-readlink-packet}
18032 @tab @code{vFile:readlink}
18035 @item @code{noack-packet}
18036 @tab @code{QStartNoAckMode}
18037 @tab Packet acknowledgment
18039 @item @code{osdata}
18040 @tab @code{qXfer:osdata:read}
18041 @tab @code{info os}
18043 @item @code{query-attached}
18044 @tab @code{qAttached}
18045 @tab Querying remote process attach state.
18047 @item @code{traceframe-info}
18048 @tab @code{qXfer:traceframe-info:read}
18049 @tab Traceframe info
18051 @item @code{install-in-trace}
18052 @tab @code{InstallInTrace}
18053 @tab Install tracepoint in tracing
18055 @item @code{disable-randomization}
18056 @tab @code{QDisableRandomization}
18057 @tab @code{set disable-randomization}
18059 @item @code{conditional-breakpoints-packet}
18060 @tab @code{Z0 and Z1}
18061 @tab @code{Support for target-side breakpoint condition evaluation}
18065 @section Implementing a Remote Stub
18067 @cindex debugging stub, example
18068 @cindex remote stub, example
18069 @cindex stub example, remote debugging
18070 The stub files provided with @value{GDBN} implement the target side of the
18071 communication protocol, and the @value{GDBN} side is implemented in the
18072 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18073 these subroutines to communicate, and ignore the details. (If you're
18074 implementing your own stub file, you can still ignore the details: start
18075 with one of the existing stub files. @file{sparc-stub.c} is the best
18076 organized, and therefore the easiest to read.)
18078 @cindex remote serial debugging, overview
18079 To debug a program running on another machine (the debugging
18080 @dfn{target} machine), you must first arrange for all the usual
18081 prerequisites for the program to run by itself. For example, for a C
18086 A startup routine to set up the C runtime environment; these usually
18087 have a name like @file{crt0}. The startup routine may be supplied by
18088 your hardware supplier, or you may have to write your own.
18091 A C subroutine library to support your program's
18092 subroutine calls, notably managing input and output.
18095 A way of getting your program to the other machine---for example, a
18096 download program. These are often supplied by the hardware
18097 manufacturer, but you may have to write your own from hardware
18101 The next step is to arrange for your program to use a serial port to
18102 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18103 machine). In general terms, the scheme looks like this:
18107 @value{GDBN} already understands how to use this protocol; when everything
18108 else is set up, you can simply use the @samp{target remote} command
18109 (@pxref{Targets,,Specifying a Debugging Target}).
18111 @item On the target,
18112 you must link with your program a few special-purpose subroutines that
18113 implement the @value{GDBN} remote serial protocol. The file containing these
18114 subroutines is called a @dfn{debugging stub}.
18116 On certain remote targets, you can use an auxiliary program
18117 @code{gdbserver} instead of linking a stub into your program.
18118 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18121 The debugging stub is specific to the architecture of the remote
18122 machine; for example, use @file{sparc-stub.c} to debug programs on
18125 @cindex remote serial stub list
18126 These working remote stubs are distributed with @value{GDBN}:
18131 @cindex @file{i386-stub.c}
18134 For Intel 386 and compatible architectures.
18137 @cindex @file{m68k-stub.c}
18138 @cindex Motorola 680x0
18140 For Motorola 680x0 architectures.
18143 @cindex @file{sh-stub.c}
18146 For Renesas SH architectures.
18149 @cindex @file{sparc-stub.c}
18151 For @sc{sparc} architectures.
18153 @item sparcl-stub.c
18154 @cindex @file{sparcl-stub.c}
18157 For Fujitsu @sc{sparclite} architectures.
18161 The @file{README} file in the @value{GDBN} distribution may list other
18162 recently added stubs.
18165 * Stub Contents:: What the stub can do for you
18166 * Bootstrapping:: What you must do for the stub
18167 * Debug Session:: Putting it all together
18170 @node Stub Contents
18171 @subsection What the Stub Can Do for You
18173 @cindex remote serial stub
18174 The debugging stub for your architecture supplies these three
18178 @item set_debug_traps
18179 @findex set_debug_traps
18180 @cindex remote serial stub, initialization
18181 This routine arranges for @code{handle_exception} to run when your
18182 program stops. You must call this subroutine explicitly in your
18183 program's startup code.
18185 @item handle_exception
18186 @findex handle_exception
18187 @cindex remote serial stub, main routine
18188 This is the central workhorse, but your program never calls it
18189 explicitly---the setup code arranges for @code{handle_exception} to
18190 run when a trap is triggered.
18192 @code{handle_exception} takes control when your program stops during
18193 execution (for example, on a breakpoint), and mediates communications
18194 with @value{GDBN} on the host machine. This is where the communications
18195 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18196 representative on the target machine. It begins by sending summary
18197 information on the state of your program, then continues to execute,
18198 retrieving and transmitting any information @value{GDBN} needs, until you
18199 execute a @value{GDBN} command that makes your program resume; at that point,
18200 @code{handle_exception} returns control to your own code on the target
18204 @cindex @code{breakpoint} subroutine, remote
18205 Use this auxiliary subroutine to make your program contain a
18206 breakpoint. Depending on the particular situation, this may be the only
18207 way for @value{GDBN} to get control. For instance, if your target
18208 machine has some sort of interrupt button, you won't need to call this;
18209 pressing the interrupt button transfers control to
18210 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18211 simply receiving characters on the serial port may also trigger a trap;
18212 again, in that situation, you don't need to call @code{breakpoint} from
18213 your own program---simply running @samp{target remote} from the host
18214 @value{GDBN} session gets control.
18216 Call @code{breakpoint} if none of these is true, or if you simply want
18217 to make certain your program stops at a predetermined point for the
18218 start of your debugging session.
18221 @node Bootstrapping
18222 @subsection What You Must Do for the Stub
18224 @cindex remote stub, support routines
18225 The debugging stubs that come with @value{GDBN} are set up for a particular
18226 chip architecture, but they have no information about the rest of your
18227 debugging target machine.
18229 First of all you need to tell the stub how to communicate with the
18233 @item int getDebugChar()
18234 @findex getDebugChar
18235 Write this subroutine to read a single character from the serial port.
18236 It may be identical to @code{getchar} for your target system; a
18237 different name is used to allow you to distinguish the two if you wish.
18239 @item void putDebugChar(int)
18240 @findex putDebugChar
18241 Write this subroutine to write a single character to the serial port.
18242 It may be identical to @code{putchar} for your target system; a
18243 different name is used to allow you to distinguish the two if you wish.
18246 @cindex control C, and remote debugging
18247 @cindex interrupting remote targets
18248 If you want @value{GDBN} to be able to stop your program while it is
18249 running, you need to use an interrupt-driven serial driver, and arrange
18250 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18251 character). That is the character which @value{GDBN} uses to tell the
18252 remote system to stop.
18254 Getting the debugging target to return the proper status to @value{GDBN}
18255 probably requires changes to the standard stub; one quick and dirty way
18256 is to just execute a breakpoint instruction (the ``dirty'' part is that
18257 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18259 Other routines you need to supply are:
18262 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18263 @findex exceptionHandler
18264 Write this function to install @var{exception_address} in the exception
18265 handling tables. You need to do this because the stub does not have any
18266 way of knowing what the exception handling tables on your target system
18267 are like (for example, the processor's table might be in @sc{rom},
18268 containing entries which point to a table in @sc{ram}).
18269 @var{exception_number} is the exception number which should be changed;
18270 its meaning is architecture-dependent (for example, different numbers
18271 might represent divide by zero, misaligned access, etc). When this
18272 exception occurs, control should be transferred directly to
18273 @var{exception_address}, and the processor state (stack, registers,
18274 and so on) should be just as it is when a processor exception occurs. So if
18275 you want to use a jump instruction to reach @var{exception_address}, it
18276 should be a simple jump, not a jump to subroutine.
18278 For the 386, @var{exception_address} should be installed as an interrupt
18279 gate so that interrupts are masked while the handler runs. The gate
18280 should be at privilege level 0 (the most privileged level). The
18281 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18282 help from @code{exceptionHandler}.
18284 @item void flush_i_cache()
18285 @findex flush_i_cache
18286 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18287 instruction cache, if any, on your target machine. If there is no
18288 instruction cache, this subroutine may be a no-op.
18290 On target machines that have instruction caches, @value{GDBN} requires this
18291 function to make certain that the state of your program is stable.
18295 You must also make sure this library routine is available:
18298 @item void *memset(void *, int, int)
18300 This is the standard library function @code{memset} that sets an area of
18301 memory to a known value. If you have one of the free versions of
18302 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18303 either obtain it from your hardware manufacturer, or write your own.
18306 If you do not use the GNU C compiler, you may need other standard
18307 library subroutines as well; this varies from one stub to another,
18308 but in general the stubs are likely to use any of the common library
18309 subroutines which @code{@value{NGCC}} generates as inline code.
18312 @node Debug Session
18313 @subsection Putting it All Together
18315 @cindex remote serial debugging summary
18316 In summary, when your program is ready to debug, you must follow these
18321 Make sure you have defined the supporting low-level routines
18322 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18324 @code{getDebugChar}, @code{putDebugChar},
18325 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18329 Insert these lines in your program's startup code, before the main
18330 procedure is called:
18337 On some machines, when a breakpoint trap is raised, the hardware
18338 automatically makes the PC point to the instruction after the
18339 breakpoint. If your machine doesn't do that, you may need to adjust
18340 @code{handle_exception} to arrange for it to return to the instruction
18341 after the breakpoint on this first invocation, so that your program
18342 doesn't keep hitting the initial breakpoint instead of making
18346 For the 680x0 stub only, you need to provide a variable called
18347 @code{exceptionHook}. Normally you just use:
18350 void (*exceptionHook)() = 0;
18354 but if before calling @code{set_debug_traps}, you set it to point to a
18355 function in your program, that function is called when
18356 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18357 error). The function indicated by @code{exceptionHook} is called with
18358 one parameter: an @code{int} which is the exception number.
18361 Compile and link together: your program, the @value{GDBN} debugging stub for
18362 your target architecture, and the supporting subroutines.
18365 Make sure you have a serial connection between your target machine and
18366 the @value{GDBN} host, and identify the serial port on the host.
18369 @c The "remote" target now provides a `load' command, so we should
18370 @c document that. FIXME.
18371 Download your program to your target machine (or get it there by
18372 whatever means the manufacturer provides), and start it.
18375 Start @value{GDBN} on the host, and connect to the target
18376 (@pxref{Connecting,,Connecting to a Remote Target}).
18380 @node Configurations
18381 @chapter Configuration-Specific Information
18383 While nearly all @value{GDBN} commands are available for all native and
18384 cross versions of the debugger, there are some exceptions. This chapter
18385 describes things that are only available in certain configurations.
18387 There are three major categories of configurations: native
18388 configurations, where the host and target are the same, embedded
18389 operating system configurations, which are usually the same for several
18390 different processor architectures, and bare embedded processors, which
18391 are quite different from each other.
18396 * Embedded Processors::
18403 This section describes details specific to particular native
18408 * BSD libkvm Interface:: Debugging BSD kernel memory images
18409 * SVR4 Process Information:: SVR4 process information
18410 * DJGPP Native:: Features specific to the DJGPP port
18411 * Cygwin Native:: Features specific to the Cygwin port
18412 * Hurd Native:: Features specific to @sc{gnu} Hurd
18413 * Neutrino:: Features specific to QNX Neutrino
18414 * Darwin:: Features specific to Darwin
18420 On HP-UX systems, if you refer to a function or variable name that
18421 begins with a dollar sign, @value{GDBN} searches for a user or system
18422 name first, before it searches for a convenience variable.
18425 @node BSD libkvm Interface
18426 @subsection BSD libkvm Interface
18429 @cindex kernel memory image
18430 @cindex kernel crash dump
18432 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18433 interface that provides a uniform interface for accessing kernel virtual
18434 memory images, including live systems and crash dumps. @value{GDBN}
18435 uses this interface to allow you to debug live kernels and kernel crash
18436 dumps on many native BSD configurations. This is implemented as a
18437 special @code{kvm} debugging target. For debugging a live system, load
18438 the currently running kernel into @value{GDBN} and connect to the
18442 (@value{GDBP}) @b{target kvm}
18445 For debugging crash dumps, provide the file name of the crash dump as an
18449 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18452 Once connected to the @code{kvm} target, the following commands are
18458 Set current context from the @dfn{Process Control Block} (PCB) address.
18461 Set current context from proc address. This command isn't available on
18462 modern FreeBSD systems.
18465 @node SVR4 Process Information
18466 @subsection SVR4 Process Information
18468 @cindex examine process image
18469 @cindex process info via @file{/proc}
18471 Many versions of SVR4 and compatible systems provide a facility called
18472 @samp{/proc} that can be used to examine the image of a running
18473 process using file-system subroutines. If @value{GDBN} is configured
18474 for an operating system with this facility, the command @code{info
18475 proc} is available to report information about the process running
18476 your program, or about any process running on your system. @code{info
18477 proc} works only on SVR4 systems that include the @code{procfs} code.
18478 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
18479 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
18485 @itemx info proc @var{process-id}
18486 Summarize available information about any running process. If a
18487 process ID is specified by @var{process-id}, display information about
18488 that process; otherwise display information about the program being
18489 debugged. The summary includes the debugged process ID, the command
18490 line used to invoke it, its current working directory, and its
18491 executable file's absolute file name.
18493 On some systems, @var{process-id} can be of the form
18494 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18495 within a process. If the optional @var{pid} part is missing, it means
18496 a thread from the process being debugged (the leading @samp{/} still
18497 needs to be present, or else @value{GDBN} will interpret the number as
18498 a process ID rather than a thread ID).
18500 @item info proc mappings
18501 @cindex memory address space mappings
18502 Report the memory address space ranges accessible in the program, with
18503 information on whether the process has read, write, or execute access
18504 rights to each range. On @sc{gnu}/Linux systems, each memory range
18505 includes the object file which is mapped to that range, instead of the
18506 memory access rights to that range.
18508 @item info proc stat
18509 @itemx info proc status
18510 @cindex process detailed status information
18511 These subcommands are specific to @sc{gnu}/Linux systems. They show
18512 the process-related information, including the user ID and group ID;
18513 how many threads are there in the process; its virtual memory usage;
18514 the signals that are pending, blocked, and ignored; its TTY; its
18515 consumption of system and user time; its stack size; its @samp{nice}
18516 value; etc. For more information, see the @samp{proc} man page
18517 (type @kbd{man 5 proc} from your shell prompt).
18519 @item info proc all
18520 Show all the information about the process described under all of the
18521 above @code{info proc} subcommands.
18524 @comment These sub-options of 'info proc' were not included when
18525 @comment procfs.c was re-written. Keep their descriptions around
18526 @comment against the day when someone finds the time to put them back in.
18527 @kindex info proc times
18528 @item info proc times
18529 Starting time, user CPU time, and system CPU time for your program and
18532 @kindex info proc id
18534 Report on the process IDs related to your program: its own process ID,
18535 the ID of its parent, the process group ID, and the session ID.
18538 @item set procfs-trace
18539 @kindex set procfs-trace
18540 @cindex @code{procfs} API calls
18541 This command enables and disables tracing of @code{procfs} API calls.
18543 @item show procfs-trace
18544 @kindex show procfs-trace
18545 Show the current state of @code{procfs} API call tracing.
18547 @item set procfs-file @var{file}
18548 @kindex set procfs-file
18549 Tell @value{GDBN} to write @code{procfs} API trace to the named
18550 @var{file}. @value{GDBN} appends the trace info to the previous
18551 contents of the file. The default is to display the trace on the
18554 @item show procfs-file
18555 @kindex show procfs-file
18556 Show the file to which @code{procfs} API trace is written.
18558 @item proc-trace-entry
18559 @itemx proc-trace-exit
18560 @itemx proc-untrace-entry
18561 @itemx proc-untrace-exit
18562 @kindex proc-trace-entry
18563 @kindex proc-trace-exit
18564 @kindex proc-untrace-entry
18565 @kindex proc-untrace-exit
18566 These commands enable and disable tracing of entries into and exits
18567 from the @code{syscall} interface.
18570 @kindex info pidlist
18571 @cindex process list, QNX Neutrino
18572 For QNX Neutrino only, this command displays the list of all the
18573 processes and all the threads within each process.
18576 @kindex info meminfo
18577 @cindex mapinfo list, QNX Neutrino
18578 For QNX Neutrino only, this command displays the list of all mapinfos.
18582 @subsection Features for Debugging @sc{djgpp} Programs
18583 @cindex @sc{djgpp} debugging
18584 @cindex native @sc{djgpp} debugging
18585 @cindex MS-DOS-specific commands
18588 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18589 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18590 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18591 top of real-mode DOS systems and their emulations.
18593 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18594 defines a few commands specific to the @sc{djgpp} port. This
18595 subsection describes those commands.
18600 This is a prefix of @sc{djgpp}-specific commands which print
18601 information about the target system and important OS structures.
18604 @cindex MS-DOS system info
18605 @cindex free memory information (MS-DOS)
18606 @item info dos sysinfo
18607 This command displays assorted information about the underlying
18608 platform: the CPU type and features, the OS version and flavor, the
18609 DPMI version, and the available conventional and DPMI memory.
18614 @cindex segment descriptor tables
18615 @cindex descriptor tables display
18617 @itemx info dos ldt
18618 @itemx info dos idt
18619 These 3 commands display entries from, respectively, Global, Local,
18620 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18621 tables are data structures which store a descriptor for each segment
18622 that is currently in use. The segment's selector is an index into a
18623 descriptor table; the table entry for that index holds the
18624 descriptor's base address and limit, and its attributes and access
18627 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18628 segment (used for both data and the stack), and a DOS segment (which
18629 allows access to DOS/BIOS data structures and absolute addresses in
18630 conventional memory). However, the DPMI host will usually define
18631 additional segments in order to support the DPMI environment.
18633 @cindex garbled pointers
18634 These commands allow to display entries from the descriptor tables.
18635 Without an argument, all entries from the specified table are
18636 displayed. An argument, which should be an integer expression, means
18637 display a single entry whose index is given by the argument. For
18638 example, here's a convenient way to display information about the
18639 debugged program's data segment:
18642 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18643 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18647 This comes in handy when you want to see whether a pointer is outside
18648 the data segment's limit (i.e.@: @dfn{garbled}).
18650 @cindex page tables display (MS-DOS)
18652 @itemx info dos pte
18653 These two commands display entries from, respectively, the Page
18654 Directory and the Page Tables. Page Directories and Page Tables are
18655 data structures which control how virtual memory addresses are mapped
18656 into physical addresses. A Page Table includes an entry for every
18657 page of memory that is mapped into the program's address space; there
18658 may be several Page Tables, each one holding up to 4096 entries. A
18659 Page Directory has up to 4096 entries, one each for every Page Table
18660 that is currently in use.
18662 Without an argument, @kbd{info dos pde} displays the entire Page
18663 Directory, and @kbd{info dos pte} displays all the entries in all of
18664 the Page Tables. An argument, an integer expression, given to the
18665 @kbd{info dos pde} command means display only that entry from the Page
18666 Directory table. An argument given to the @kbd{info dos pte} command
18667 means display entries from a single Page Table, the one pointed to by
18668 the specified entry in the Page Directory.
18670 @cindex direct memory access (DMA) on MS-DOS
18671 These commands are useful when your program uses @dfn{DMA} (Direct
18672 Memory Access), which needs physical addresses to program the DMA
18675 These commands are supported only with some DPMI servers.
18677 @cindex physical address from linear address
18678 @item info dos address-pte @var{addr}
18679 This command displays the Page Table entry for a specified linear
18680 address. The argument @var{addr} is a linear address which should
18681 already have the appropriate segment's base address added to it,
18682 because this command accepts addresses which may belong to @emph{any}
18683 segment. For example, here's how to display the Page Table entry for
18684 the page where a variable @code{i} is stored:
18687 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18688 @exdent @code{Page Table entry for address 0x11a00d30:}
18689 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18693 This says that @code{i} is stored at offset @code{0xd30} from the page
18694 whose physical base address is @code{0x02698000}, and shows all the
18695 attributes of that page.
18697 Note that you must cast the addresses of variables to a @code{char *},
18698 since otherwise the value of @code{__djgpp_base_address}, the base
18699 address of all variables and functions in a @sc{djgpp} program, will
18700 be added using the rules of C pointer arithmetics: if @code{i} is
18701 declared an @code{int}, @value{GDBN} will add 4 times the value of
18702 @code{__djgpp_base_address} to the address of @code{i}.
18704 Here's another example, it displays the Page Table entry for the
18708 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18709 @exdent @code{Page Table entry for address 0x29110:}
18710 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18714 (The @code{+ 3} offset is because the transfer buffer's address is the
18715 3rd member of the @code{_go32_info_block} structure.) The output
18716 clearly shows that this DPMI server maps the addresses in conventional
18717 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18718 linear (@code{0x29110}) addresses are identical.
18720 This command is supported only with some DPMI servers.
18723 @cindex DOS serial data link, remote debugging
18724 In addition to native debugging, the DJGPP port supports remote
18725 debugging via a serial data link. The following commands are specific
18726 to remote serial debugging in the DJGPP port of @value{GDBN}.
18729 @kindex set com1base
18730 @kindex set com1irq
18731 @kindex set com2base
18732 @kindex set com2irq
18733 @kindex set com3base
18734 @kindex set com3irq
18735 @kindex set com4base
18736 @kindex set com4irq
18737 @item set com1base @var{addr}
18738 This command sets the base I/O port address of the @file{COM1} serial
18741 @item set com1irq @var{irq}
18742 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18743 for the @file{COM1} serial port.
18745 There are similar commands @samp{set com2base}, @samp{set com3irq},
18746 etc.@: for setting the port address and the @code{IRQ} lines for the
18749 @kindex show com1base
18750 @kindex show com1irq
18751 @kindex show com2base
18752 @kindex show com2irq
18753 @kindex show com3base
18754 @kindex show com3irq
18755 @kindex show com4base
18756 @kindex show com4irq
18757 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18758 display the current settings of the base address and the @code{IRQ}
18759 lines used by the COM ports.
18762 @kindex info serial
18763 @cindex DOS serial port status
18764 This command prints the status of the 4 DOS serial ports. For each
18765 port, it prints whether it's active or not, its I/O base address and
18766 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18767 counts of various errors encountered so far.
18771 @node Cygwin Native
18772 @subsection Features for Debugging MS Windows PE Executables
18773 @cindex MS Windows debugging
18774 @cindex native Cygwin debugging
18775 @cindex Cygwin-specific commands
18777 @value{GDBN} supports native debugging of MS Windows programs, including
18778 DLLs with and without symbolic debugging information.
18780 @cindex Ctrl-BREAK, MS-Windows
18781 @cindex interrupt debuggee on MS-Windows
18782 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18783 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18784 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18785 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18786 sequence, which can be used to interrupt the debuggee even if it
18789 There are various additional Cygwin-specific commands, described in
18790 this section. Working with DLLs that have no debugging symbols is
18791 described in @ref{Non-debug DLL Symbols}.
18796 This is a prefix of MS Windows-specific commands which print
18797 information about the target system and important OS structures.
18799 @item info w32 selector
18800 This command displays information returned by
18801 the Win32 API @code{GetThreadSelectorEntry} function.
18802 It takes an optional argument that is evaluated to
18803 a long value to give the information about this given selector.
18804 Without argument, this command displays information
18805 about the six segment registers.
18807 @item info w32 thread-information-block
18808 This command displays thread specific information stored in the
18809 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18810 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18814 This is a Cygwin-specific alias of @code{info shared}.
18816 @kindex dll-symbols
18818 This command loads symbols from a dll similarly to
18819 add-sym command but without the need to specify a base address.
18821 @kindex set cygwin-exceptions
18822 @cindex debugging the Cygwin DLL
18823 @cindex Cygwin DLL, debugging
18824 @item set cygwin-exceptions @var{mode}
18825 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18826 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18827 @value{GDBN} will delay recognition of exceptions, and may ignore some
18828 exceptions which seem to be caused by internal Cygwin DLL
18829 ``bookkeeping''. This option is meant primarily for debugging the
18830 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18831 @value{GDBN} users with false @code{SIGSEGV} signals.
18833 @kindex show cygwin-exceptions
18834 @item show cygwin-exceptions
18835 Displays whether @value{GDBN} will break on exceptions that happen
18836 inside the Cygwin DLL itself.
18838 @kindex set new-console
18839 @item set new-console @var{mode}
18840 If @var{mode} is @code{on} the debuggee will
18841 be started in a new console on next start.
18842 If @var{mode} is @code{off}, the debuggee will
18843 be started in the same console as the debugger.
18845 @kindex show new-console
18846 @item show new-console
18847 Displays whether a new console is used
18848 when the debuggee is started.
18850 @kindex set new-group
18851 @item set new-group @var{mode}
18852 This boolean value controls whether the debuggee should
18853 start a new group or stay in the same group as the debugger.
18854 This affects the way the Windows OS handles
18857 @kindex show new-group
18858 @item show new-group
18859 Displays current value of new-group boolean.
18861 @kindex set debugevents
18862 @item set debugevents
18863 This boolean value adds debug output concerning kernel events related
18864 to the debuggee seen by the debugger. This includes events that
18865 signal thread and process creation and exit, DLL loading and
18866 unloading, console interrupts, and debugging messages produced by the
18867 Windows @code{OutputDebugString} API call.
18869 @kindex set debugexec
18870 @item set debugexec
18871 This boolean value adds debug output concerning execute events
18872 (such as resume thread) seen by the debugger.
18874 @kindex set debugexceptions
18875 @item set debugexceptions
18876 This boolean value adds debug output concerning exceptions in the
18877 debuggee seen by the debugger.
18879 @kindex set debugmemory
18880 @item set debugmemory
18881 This boolean value adds debug output concerning debuggee memory reads
18882 and writes by the debugger.
18886 This boolean values specifies whether the debuggee is called
18887 via a shell or directly (default value is on).
18891 Displays if the debuggee will be started with a shell.
18896 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18899 @node Non-debug DLL Symbols
18900 @subsubsection Support for DLLs without Debugging Symbols
18901 @cindex DLLs with no debugging symbols
18902 @cindex Minimal symbols and DLLs
18904 Very often on windows, some of the DLLs that your program relies on do
18905 not include symbolic debugging information (for example,
18906 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18907 symbols in a DLL, it relies on the minimal amount of symbolic
18908 information contained in the DLL's export table. This section
18909 describes working with such symbols, known internally to @value{GDBN} as
18910 ``minimal symbols''.
18912 Note that before the debugged program has started execution, no DLLs
18913 will have been loaded. The easiest way around this problem is simply to
18914 start the program --- either by setting a breakpoint or letting the
18915 program run once to completion. It is also possible to force
18916 @value{GDBN} to load a particular DLL before starting the executable ---
18917 see the shared library information in @ref{Files}, or the
18918 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18919 explicitly loading symbols from a DLL with no debugging information will
18920 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18921 which may adversely affect symbol lookup performance.
18923 @subsubsection DLL Name Prefixes
18925 In keeping with the naming conventions used by the Microsoft debugging
18926 tools, DLL export symbols are made available with a prefix based on the
18927 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18928 also entered into the symbol table, so @code{CreateFileA} is often
18929 sufficient. In some cases there will be name clashes within a program
18930 (particularly if the executable itself includes full debugging symbols)
18931 necessitating the use of the fully qualified name when referring to the
18932 contents of the DLL. Use single-quotes around the name to avoid the
18933 exclamation mark (``!'') being interpreted as a language operator.
18935 Note that the internal name of the DLL may be all upper-case, even
18936 though the file name of the DLL is lower-case, or vice-versa. Since
18937 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18938 some confusion. If in doubt, try the @code{info functions} and
18939 @code{info variables} commands or even @code{maint print msymbols}
18940 (@pxref{Symbols}). Here's an example:
18943 (@value{GDBP}) info function CreateFileA
18944 All functions matching regular expression "CreateFileA":
18946 Non-debugging symbols:
18947 0x77e885f4 CreateFileA
18948 0x77e885f4 KERNEL32!CreateFileA
18952 (@value{GDBP}) info function !
18953 All functions matching regular expression "!":
18955 Non-debugging symbols:
18956 0x6100114c cygwin1!__assert
18957 0x61004034 cygwin1!_dll_crt0@@0
18958 0x61004240 cygwin1!dll_crt0(per_process *)
18962 @subsubsection Working with Minimal Symbols
18964 Symbols extracted from a DLL's export table do not contain very much
18965 type information. All that @value{GDBN} can do is guess whether a symbol
18966 refers to a function or variable depending on the linker section that
18967 contains the symbol. Also note that the actual contents of the memory
18968 contained in a DLL are not available unless the program is running. This
18969 means that you cannot examine the contents of a variable or disassemble
18970 a function within a DLL without a running program.
18972 Variables are generally treated as pointers and dereferenced
18973 automatically. For this reason, it is often necessary to prefix a
18974 variable name with the address-of operator (``&'') and provide explicit
18975 type information in the command. Here's an example of the type of
18979 (@value{GDBP}) print 'cygwin1!__argv'
18984 (@value{GDBP}) x 'cygwin1!__argv'
18985 0x10021610: "\230y\""
18988 And two possible solutions:
18991 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18992 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18996 (@value{GDBP}) x/2x &'cygwin1!__argv'
18997 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18998 (@value{GDBP}) x/x 0x10021608
18999 0x10021608: 0x0022fd98
19000 (@value{GDBP}) x/s 0x0022fd98
19001 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19004 Setting a break point within a DLL is possible even before the program
19005 starts execution. However, under these circumstances, @value{GDBN} can't
19006 examine the initial instructions of the function in order to skip the
19007 function's frame set-up code. You can work around this by using ``*&''
19008 to set the breakpoint at a raw memory address:
19011 (@value{GDBP}) break *&'python22!PyOS_Readline'
19012 Breakpoint 1 at 0x1e04eff0
19015 The author of these extensions is not entirely convinced that setting a
19016 break point within a shared DLL like @file{kernel32.dll} is completely
19020 @subsection Commands Specific to @sc{gnu} Hurd Systems
19021 @cindex @sc{gnu} Hurd debugging
19023 This subsection describes @value{GDBN} commands specific to the
19024 @sc{gnu} Hurd native debugging.
19029 @kindex set signals@r{, Hurd command}
19030 @kindex set sigs@r{, Hurd command}
19031 This command toggles the state of inferior signal interception by
19032 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19033 affected by this command. @code{sigs} is a shorthand alias for
19038 @kindex show signals@r{, Hurd command}
19039 @kindex show sigs@r{, Hurd command}
19040 Show the current state of intercepting inferior's signals.
19042 @item set signal-thread
19043 @itemx set sigthread
19044 @kindex set signal-thread
19045 @kindex set sigthread
19046 This command tells @value{GDBN} which thread is the @code{libc} signal
19047 thread. That thread is run when a signal is delivered to a running
19048 process. @code{set sigthread} is the shorthand alias of @code{set
19051 @item show signal-thread
19052 @itemx show sigthread
19053 @kindex show signal-thread
19054 @kindex show sigthread
19055 These two commands show which thread will run when the inferior is
19056 delivered a signal.
19059 @kindex set stopped@r{, Hurd command}
19060 This commands tells @value{GDBN} that the inferior process is stopped,
19061 as with the @code{SIGSTOP} signal. The stopped process can be
19062 continued by delivering a signal to it.
19065 @kindex show stopped@r{, Hurd command}
19066 This command shows whether @value{GDBN} thinks the debuggee is
19069 @item set exceptions
19070 @kindex set exceptions@r{, Hurd command}
19071 Use this command to turn off trapping of exceptions in the inferior.
19072 When exception trapping is off, neither breakpoints nor
19073 single-stepping will work. To restore the default, set exception
19076 @item show exceptions
19077 @kindex show exceptions@r{, Hurd command}
19078 Show the current state of trapping exceptions in the inferior.
19080 @item set task pause
19081 @kindex set task@r{, Hurd commands}
19082 @cindex task attributes (@sc{gnu} Hurd)
19083 @cindex pause current task (@sc{gnu} Hurd)
19084 This command toggles task suspension when @value{GDBN} has control.
19085 Setting it to on takes effect immediately, and the task is suspended
19086 whenever @value{GDBN} gets control. Setting it to off will take
19087 effect the next time the inferior is continued. If this option is set
19088 to off, you can use @code{set thread default pause on} or @code{set
19089 thread pause on} (see below) to pause individual threads.
19091 @item show task pause
19092 @kindex show task@r{, Hurd commands}
19093 Show the current state of task suspension.
19095 @item set task detach-suspend-count
19096 @cindex task suspend count
19097 @cindex detach from task, @sc{gnu} Hurd
19098 This command sets the suspend count the task will be left with when
19099 @value{GDBN} detaches from it.
19101 @item show task detach-suspend-count
19102 Show the suspend count the task will be left with when detaching.
19104 @item set task exception-port
19105 @itemx set task excp
19106 @cindex task exception port, @sc{gnu} Hurd
19107 This command sets the task exception port to which @value{GDBN} will
19108 forward exceptions. The argument should be the value of the @dfn{send
19109 rights} of the task. @code{set task excp} is a shorthand alias.
19111 @item set noninvasive
19112 @cindex noninvasive task options
19113 This command switches @value{GDBN} to a mode that is the least
19114 invasive as far as interfering with the inferior is concerned. This
19115 is the same as using @code{set task pause}, @code{set exceptions}, and
19116 @code{set signals} to values opposite to the defaults.
19118 @item info send-rights
19119 @itemx info receive-rights
19120 @itemx info port-rights
19121 @itemx info port-sets
19122 @itemx info dead-names
19125 @cindex send rights, @sc{gnu} Hurd
19126 @cindex receive rights, @sc{gnu} Hurd
19127 @cindex port rights, @sc{gnu} Hurd
19128 @cindex port sets, @sc{gnu} Hurd
19129 @cindex dead names, @sc{gnu} Hurd
19130 These commands display information about, respectively, send rights,
19131 receive rights, port rights, port sets, and dead names of a task.
19132 There are also shorthand aliases: @code{info ports} for @code{info
19133 port-rights} and @code{info psets} for @code{info port-sets}.
19135 @item set thread pause
19136 @kindex set thread@r{, Hurd command}
19137 @cindex thread properties, @sc{gnu} Hurd
19138 @cindex pause current thread (@sc{gnu} Hurd)
19139 This command toggles current thread suspension when @value{GDBN} has
19140 control. Setting it to on takes effect immediately, and the current
19141 thread is suspended whenever @value{GDBN} gets control. Setting it to
19142 off will take effect the next time the inferior is continued.
19143 Normally, this command has no effect, since when @value{GDBN} has
19144 control, the whole task is suspended. However, if you used @code{set
19145 task pause off} (see above), this command comes in handy to suspend
19146 only the current thread.
19148 @item show thread pause
19149 @kindex show thread@r{, Hurd command}
19150 This command shows the state of current thread suspension.
19152 @item set thread run
19153 This command sets whether the current thread is allowed to run.
19155 @item show thread run
19156 Show whether the current thread is allowed to run.
19158 @item set thread detach-suspend-count
19159 @cindex thread suspend count, @sc{gnu} Hurd
19160 @cindex detach from thread, @sc{gnu} Hurd
19161 This command sets the suspend count @value{GDBN} will leave on a
19162 thread when detaching. This number is relative to the suspend count
19163 found by @value{GDBN} when it notices the thread; use @code{set thread
19164 takeover-suspend-count} to force it to an absolute value.
19166 @item show thread detach-suspend-count
19167 Show the suspend count @value{GDBN} will leave on the thread when
19170 @item set thread exception-port
19171 @itemx set thread excp
19172 Set the thread exception port to which to forward exceptions. This
19173 overrides the port set by @code{set task exception-port} (see above).
19174 @code{set thread excp} is the shorthand alias.
19176 @item set thread takeover-suspend-count
19177 Normally, @value{GDBN}'s thread suspend counts are relative to the
19178 value @value{GDBN} finds when it notices each thread. This command
19179 changes the suspend counts to be absolute instead.
19181 @item set thread default
19182 @itemx show thread default
19183 @cindex thread default settings, @sc{gnu} Hurd
19184 Each of the above @code{set thread} commands has a @code{set thread
19185 default} counterpart (e.g., @code{set thread default pause}, @code{set
19186 thread default exception-port}, etc.). The @code{thread default}
19187 variety of commands sets the default thread properties for all
19188 threads; you can then change the properties of individual threads with
19189 the non-default commands.
19194 @subsection QNX Neutrino
19195 @cindex QNX Neutrino
19197 @value{GDBN} provides the following commands specific to the QNX
19201 @item set debug nto-debug
19202 @kindex set debug nto-debug
19203 When set to on, enables debugging messages specific to the QNX
19206 @item show debug nto-debug
19207 @kindex show debug nto-debug
19208 Show the current state of QNX Neutrino messages.
19215 @value{GDBN} provides the following commands specific to the Darwin target:
19218 @item set debug darwin @var{num}
19219 @kindex set debug darwin
19220 When set to a non zero value, enables debugging messages specific to
19221 the Darwin support. Higher values produce more verbose output.
19223 @item show debug darwin
19224 @kindex show debug darwin
19225 Show the current state of Darwin messages.
19227 @item set debug mach-o @var{num}
19228 @kindex set debug mach-o
19229 When set to a non zero value, enables debugging messages while
19230 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19231 file format used on Darwin for object and executable files.) Higher
19232 values produce more verbose output. This is a command to diagnose
19233 problems internal to @value{GDBN} and should not be needed in normal
19236 @item show debug mach-o
19237 @kindex show debug mach-o
19238 Show the current state of Mach-O file messages.
19240 @item set mach-exceptions on
19241 @itemx set mach-exceptions off
19242 @kindex set mach-exceptions
19243 On Darwin, faults are first reported as a Mach exception and are then
19244 mapped to a Posix signal. Use this command to turn on trapping of
19245 Mach exceptions in the inferior. This might be sometimes useful to
19246 better understand the cause of a fault. The default is off.
19248 @item show mach-exceptions
19249 @kindex show mach-exceptions
19250 Show the current state of exceptions trapping.
19255 @section Embedded Operating Systems
19257 This section describes configurations involving the debugging of
19258 embedded operating systems that are available for several different
19262 * VxWorks:: Using @value{GDBN} with VxWorks
19265 @value{GDBN} includes the ability to debug programs running on
19266 various real-time operating systems.
19269 @subsection Using @value{GDBN} with VxWorks
19275 @kindex target vxworks
19276 @item target vxworks @var{machinename}
19277 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19278 is the target system's machine name or IP address.
19282 On VxWorks, @code{load} links @var{filename} dynamically on the
19283 current target system as well as adding its symbols in @value{GDBN}.
19285 @value{GDBN} enables developers to spawn and debug tasks running on networked
19286 VxWorks targets from a Unix host. Already-running tasks spawned from
19287 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19288 both the Unix host and on the VxWorks target. The program
19289 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19290 installed with the name @code{vxgdb}, to distinguish it from a
19291 @value{GDBN} for debugging programs on the host itself.)
19294 @item VxWorks-timeout @var{args}
19295 @kindex vxworks-timeout
19296 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19297 This option is set by the user, and @var{args} represents the number of
19298 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19299 your VxWorks target is a slow software simulator or is on the far side
19300 of a thin network line.
19303 The following information on connecting to VxWorks was current when
19304 this manual was produced; newer releases of VxWorks may use revised
19307 @findex INCLUDE_RDB
19308 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19309 to include the remote debugging interface routines in the VxWorks
19310 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19311 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19312 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19313 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19314 information on configuring and remaking VxWorks, see the manufacturer's
19316 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19318 Once you have included @file{rdb.a} in your VxWorks system image and set
19319 your Unix execution search path to find @value{GDBN}, you are ready to
19320 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19321 @code{vxgdb}, depending on your installation).
19323 @value{GDBN} comes up showing the prompt:
19330 * VxWorks Connection:: Connecting to VxWorks
19331 * VxWorks Download:: VxWorks download
19332 * VxWorks Attach:: Running tasks
19335 @node VxWorks Connection
19336 @subsubsection Connecting to VxWorks
19338 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19339 network. To connect to a target whose host name is ``@code{tt}'', type:
19342 (vxgdb) target vxworks tt
19346 @value{GDBN} displays messages like these:
19349 Attaching remote machine across net...
19354 @value{GDBN} then attempts to read the symbol tables of any object modules
19355 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19356 these files by searching the directories listed in the command search
19357 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19358 to find an object file, it displays a message such as:
19361 prog.o: No such file or directory.
19364 When this happens, add the appropriate directory to the search path with
19365 the @value{GDBN} command @code{path}, and execute the @code{target}
19368 @node VxWorks Download
19369 @subsubsection VxWorks Download
19371 @cindex download to VxWorks
19372 If you have connected to the VxWorks target and you want to debug an
19373 object that has not yet been loaded, you can use the @value{GDBN}
19374 @code{load} command to download a file from Unix to VxWorks
19375 incrementally. The object file given as an argument to the @code{load}
19376 command is actually opened twice: first by the VxWorks target in order
19377 to download the code, then by @value{GDBN} in order to read the symbol
19378 table. This can lead to problems if the current working directories on
19379 the two systems differ. If both systems have NFS mounted the same
19380 filesystems, you can avoid these problems by using absolute paths.
19381 Otherwise, it is simplest to set the working directory on both systems
19382 to the directory in which the object file resides, and then to reference
19383 the file by its name, without any path. For instance, a program
19384 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19385 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19386 program, type this on VxWorks:
19389 -> cd "@var{vxpath}/vw/demo/rdb"
19393 Then, in @value{GDBN}, type:
19396 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19397 (vxgdb) load prog.o
19400 @value{GDBN} displays a response similar to this:
19403 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19406 You can also use the @code{load} command to reload an object module
19407 after editing and recompiling the corresponding source file. Note that
19408 this makes @value{GDBN} delete all currently-defined breakpoints,
19409 auto-displays, and convenience variables, and to clear the value
19410 history. (This is necessary in order to preserve the integrity of
19411 debugger's data structures that reference the target system's symbol
19414 @node VxWorks Attach
19415 @subsubsection Running Tasks
19417 @cindex running VxWorks tasks
19418 You can also attach to an existing task using the @code{attach} command as
19422 (vxgdb) attach @var{task}
19426 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19427 or suspended when you attach to it. Running tasks are suspended at
19428 the time of attachment.
19430 @node Embedded Processors
19431 @section Embedded Processors
19433 This section goes into details specific to particular embedded
19436 @cindex send command to simulator
19437 Whenever a specific embedded processor has a simulator, @value{GDBN}
19438 allows to send an arbitrary command to the simulator.
19441 @item sim @var{command}
19442 @kindex sim@r{, a command}
19443 Send an arbitrary @var{command} string to the simulator. Consult the
19444 documentation for the specific simulator in use for information about
19445 acceptable commands.
19451 * M32R/D:: Renesas M32R/D
19452 * M68K:: Motorola M68K
19453 * MicroBlaze:: Xilinx MicroBlaze
19454 * MIPS Embedded:: MIPS Embedded
19455 * OpenRISC 1000:: OpenRisc 1000
19456 * PA:: HP PA Embedded
19457 * PowerPC Embedded:: PowerPC Embedded
19458 * Sparclet:: Tsqware Sparclet
19459 * Sparclite:: Fujitsu Sparclite
19460 * Z8000:: Zilog Z8000
19463 * Super-H:: Renesas Super-H
19472 @item target rdi @var{dev}
19473 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19474 use this target to communicate with both boards running the Angel
19475 monitor, or with the EmbeddedICE JTAG debug device.
19478 @item target rdp @var{dev}
19483 @value{GDBN} provides the following ARM-specific commands:
19486 @item set arm disassembler
19488 This commands selects from a list of disassembly styles. The
19489 @code{"std"} style is the standard style.
19491 @item show arm disassembler
19493 Show the current disassembly style.
19495 @item set arm apcs32
19496 @cindex ARM 32-bit mode
19497 This command toggles ARM operation mode between 32-bit and 26-bit.
19499 @item show arm apcs32
19500 Display the current usage of the ARM 32-bit mode.
19502 @item set arm fpu @var{fputype}
19503 This command sets the ARM floating-point unit (FPU) type. The
19504 argument @var{fputype} can be one of these:
19508 Determine the FPU type by querying the OS ABI.
19510 Software FPU, with mixed-endian doubles on little-endian ARM
19513 GCC-compiled FPA co-processor.
19515 Software FPU with pure-endian doubles.
19521 Show the current type of the FPU.
19524 This command forces @value{GDBN} to use the specified ABI.
19527 Show the currently used ABI.
19529 @item set arm fallback-mode (arm|thumb|auto)
19530 @value{GDBN} uses the symbol table, when available, to determine
19531 whether instructions are ARM or Thumb. This command controls
19532 @value{GDBN}'s default behavior when the symbol table is not
19533 available. The default is @samp{auto}, which causes @value{GDBN} to
19534 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19537 @item show arm fallback-mode
19538 Show the current fallback instruction mode.
19540 @item set arm force-mode (arm|thumb|auto)
19541 This command overrides use of the symbol table to determine whether
19542 instructions are ARM or Thumb. The default is @samp{auto}, which
19543 causes @value{GDBN} to use the symbol table and then the setting
19544 of @samp{set arm fallback-mode}.
19546 @item show arm force-mode
19547 Show the current forced instruction mode.
19549 @item set debug arm
19550 Toggle whether to display ARM-specific debugging messages from the ARM
19551 target support subsystem.
19553 @item show debug arm
19554 Show whether ARM-specific debugging messages are enabled.
19557 The following commands are available when an ARM target is debugged
19558 using the RDI interface:
19561 @item rdilogfile @r{[}@var{file}@r{]}
19563 @cindex ADP (Angel Debugger Protocol) logging
19564 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19565 With an argument, sets the log file to the specified @var{file}. With
19566 no argument, show the current log file name. The default log file is
19569 @item rdilogenable @r{[}@var{arg}@r{]}
19570 @kindex rdilogenable
19571 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19572 enables logging, with an argument 0 or @code{"no"} disables it. With
19573 no arguments displays the current setting. When logging is enabled,
19574 ADP packets exchanged between @value{GDBN} and the RDI target device
19575 are logged to a file.
19577 @item set rdiromatzero
19578 @kindex set rdiromatzero
19579 @cindex ROM at zero address, RDI
19580 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19581 vector catching is disabled, so that zero address can be used. If off
19582 (the default), vector catching is enabled. For this command to take
19583 effect, it needs to be invoked prior to the @code{target rdi} command.
19585 @item show rdiromatzero
19586 @kindex show rdiromatzero
19587 Show the current setting of ROM at zero address.
19589 @item set rdiheartbeat
19590 @kindex set rdiheartbeat
19591 @cindex RDI heartbeat
19592 Enable or disable RDI heartbeat packets. It is not recommended to
19593 turn on this option, since it confuses ARM and EPI JTAG interface, as
19594 well as the Angel monitor.
19596 @item show rdiheartbeat
19597 @kindex show rdiheartbeat
19598 Show the setting of RDI heartbeat packets.
19602 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19603 The @value{GDBN} ARM simulator accepts the following optional arguments.
19606 @item --swi-support=@var{type}
19607 Tell the simulator which SWI interfaces to support.
19608 @var{type} may be a comma separated list of the following values.
19609 The default value is @code{all}.
19622 @subsection Renesas M32R/D and M32R/SDI
19625 @kindex target m32r
19626 @item target m32r @var{dev}
19627 Renesas M32R/D ROM monitor.
19629 @kindex target m32rsdi
19630 @item target m32rsdi @var{dev}
19631 Renesas M32R SDI server, connected via parallel port to the board.
19634 The following @value{GDBN} commands are specific to the M32R monitor:
19637 @item set download-path @var{path}
19638 @kindex set download-path
19639 @cindex find downloadable @sc{srec} files (M32R)
19640 Set the default path for finding downloadable @sc{srec} files.
19642 @item show download-path
19643 @kindex show download-path
19644 Show the default path for downloadable @sc{srec} files.
19646 @item set board-address @var{addr}
19647 @kindex set board-address
19648 @cindex M32-EVA target board address
19649 Set the IP address for the M32R-EVA target board.
19651 @item show board-address
19652 @kindex show board-address
19653 Show the current IP address of the target board.
19655 @item set server-address @var{addr}
19656 @kindex set server-address
19657 @cindex download server address (M32R)
19658 Set the IP address for the download server, which is the @value{GDBN}'s
19661 @item show server-address
19662 @kindex show server-address
19663 Display the IP address of the download server.
19665 @item upload @r{[}@var{file}@r{]}
19666 @kindex upload@r{, M32R}
19667 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19668 upload capability. If no @var{file} argument is given, the current
19669 executable file is uploaded.
19671 @item tload @r{[}@var{file}@r{]}
19672 @kindex tload@r{, M32R}
19673 Test the @code{upload} command.
19676 The following commands are available for M32R/SDI:
19681 @cindex reset SDI connection, M32R
19682 This command resets the SDI connection.
19686 This command shows the SDI connection status.
19689 @kindex debug_chaos
19690 @cindex M32R/Chaos debugging
19691 Instructs the remote that M32R/Chaos debugging is to be used.
19693 @item use_debug_dma
19694 @kindex use_debug_dma
19695 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19698 @kindex use_mon_code
19699 Instructs the remote to use the MON_CODE method of accessing memory.
19702 @kindex use_ib_break
19703 Instructs the remote to set breakpoints by IB break.
19705 @item use_dbt_break
19706 @kindex use_dbt_break
19707 Instructs the remote to set breakpoints by DBT.
19713 The Motorola m68k configuration includes ColdFire support, and a
19714 target command for the following ROM monitor.
19718 @kindex target dbug
19719 @item target dbug @var{dev}
19720 dBUG ROM monitor for Motorola ColdFire.
19725 @subsection MicroBlaze
19726 @cindex Xilinx MicroBlaze
19727 @cindex XMD, Xilinx Microprocessor Debugger
19729 The MicroBlaze is a soft-core processor supported on various Xilinx
19730 FPGAs, such as Spartan or Virtex series. Boards with these processors
19731 usually have JTAG ports which connect to a host system running the Xilinx
19732 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19733 This host system is used to download the configuration bitstream to
19734 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19735 communicates with the target board using the JTAG interface and
19736 presents a @code{gdbserver} interface to the board. By default
19737 @code{xmd} uses port @code{1234}. (While it is possible to change
19738 this default port, it requires the use of undocumented @code{xmd}
19739 commands. Contact Xilinx support if you need to do this.)
19741 Use these GDB commands to connect to the MicroBlaze target processor.
19744 @item target remote :1234
19745 Use this command to connect to the target if you are running @value{GDBN}
19746 on the same system as @code{xmd}.
19748 @item target remote @var{xmd-host}:1234
19749 Use this command to connect to the target if it is connected to @code{xmd}
19750 running on a different system named @var{xmd-host}.
19753 Use this command to download a program to the MicroBlaze target.
19755 @item set debug microblaze @var{n}
19756 Enable MicroBlaze-specific debugging messages if non-zero.
19758 @item show debug microblaze @var{n}
19759 Show MicroBlaze-specific debugging level.
19762 @node MIPS Embedded
19763 @subsection @acronym{MIPS} Embedded
19765 @cindex @acronym{MIPS} boards
19766 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
19767 @acronym{MIPS} board attached to a serial line. This is available when
19768 you configure @value{GDBN} with @samp{--target=mips-elf}.
19771 Use these @value{GDBN} commands to specify the connection to your target board:
19774 @item target mips @var{port}
19775 @kindex target mips @var{port}
19776 To run a program on the board, start up @code{@value{GDBP}} with the
19777 name of your program as the argument. To connect to the board, use the
19778 command @samp{target mips @var{port}}, where @var{port} is the name of
19779 the serial port connected to the board. If the program has not already
19780 been downloaded to the board, you may use the @code{load} command to
19781 download it. You can then use all the usual @value{GDBN} commands.
19783 For example, this sequence connects to the target board through a serial
19784 port, and loads and runs a program called @var{prog} through the
19788 host$ @value{GDBP} @var{prog}
19789 @value{GDBN} is free software and @dots{}
19790 (@value{GDBP}) target mips /dev/ttyb
19791 (@value{GDBP}) load @var{prog}
19795 @item target mips @var{hostname}:@var{portnumber}
19796 On some @value{GDBN} host configurations, you can specify a TCP
19797 connection (for instance, to a serial line managed by a terminal
19798 concentrator) instead of a serial port, using the syntax
19799 @samp{@var{hostname}:@var{portnumber}}.
19801 @item target pmon @var{port}
19802 @kindex target pmon @var{port}
19805 @item target ddb @var{port}
19806 @kindex target ddb @var{port}
19807 NEC's DDB variant of PMON for Vr4300.
19809 @item target lsi @var{port}
19810 @kindex target lsi @var{port}
19811 LSI variant of PMON.
19813 @kindex target r3900
19814 @item target r3900 @var{dev}
19815 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19817 @kindex target array
19818 @item target array @var{dev}
19819 Array Tech LSI33K RAID controller board.
19825 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
19828 @item set mipsfpu double
19829 @itemx set mipsfpu single
19830 @itemx set mipsfpu none
19831 @itemx set mipsfpu auto
19832 @itemx show mipsfpu
19833 @kindex set mipsfpu
19834 @kindex show mipsfpu
19835 @cindex @acronym{MIPS} remote floating point
19836 @cindex floating point, @acronym{MIPS} remote
19837 If your target board does not support the @acronym{MIPS} floating point
19838 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19839 need this, you may wish to put the command in your @value{GDBN} init
19840 file). This tells @value{GDBN} how to find the return value of
19841 functions which return floating point values. It also allows
19842 @value{GDBN} to avoid saving the floating point registers when calling
19843 functions on the board. If you are using a floating point coprocessor
19844 with only single precision floating point support, as on the @sc{r4650}
19845 processor, use the command @samp{set mipsfpu single}. The default
19846 double precision floating point coprocessor may be selected using
19847 @samp{set mipsfpu double}.
19849 In previous versions the only choices were double precision or no
19850 floating point, so @samp{set mipsfpu on} will select double precision
19851 and @samp{set mipsfpu off} will select no floating point.
19853 As usual, you can inquire about the @code{mipsfpu} variable with
19854 @samp{show mipsfpu}.
19856 @item set timeout @var{seconds}
19857 @itemx set retransmit-timeout @var{seconds}
19858 @itemx show timeout
19859 @itemx show retransmit-timeout
19860 @cindex @code{timeout}, @acronym{MIPS} protocol
19861 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
19862 @kindex set timeout
19863 @kindex show timeout
19864 @kindex set retransmit-timeout
19865 @kindex show retransmit-timeout
19866 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
19867 remote protocol, with the @code{set timeout @var{seconds}} command. The
19868 default is 5 seconds. Similarly, you can control the timeout used while
19869 waiting for an acknowledgment of a packet with the @code{set
19870 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19871 You can inspect both values with @code{show timeout} and @code{show
19872 retransmit-timeout}. (These commands are @emph{only} available when
19873 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19875 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19876 is waiting for your program to stop. In that case, @value{GDBN} waits
19877 forever because it has no way of knowing how long the program is going
19878 to run before stopping.
19880 @item set syn-garbage-limit @var{num}
19881 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
19882 @cindex synchronize with remote @acronym{MIPS} target
19883 Limit the maximum number of characters @value{GDBN} should ignore when
19884 it tries to synchronize with the remote target. The default is 10
19885 characters. Setting the limit to -1 means there's no limit.
19887 @item show syn-garbage-limit
19888 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
19889 Show the current limit on the number of characters to ignore when
19890 trying to synchronize with the remote system.
19892 @item set monitor-prompt @var{prompt}
19893 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
19894 @cindex remote monitor prompt
19895 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19896 remote monitor. The default depends on the target:
19906 @item show monitor-prompt
19907 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
19908 Show the current strings @value{GDBN} expects as the prompt from the
19911 @item set monitor-warnings
19912 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
19913 Enable or disable monitor warnings about hardware breakpoints. This
19914 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19915 display warning messages whose codes are returned by the @code{lsi}
19916 PMON monitor for breakpoint commands.
19918 @item show monitor-warnings
19919 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
19920 Show the current setting of printing monitor warnings.
19922 @item pmon @var{command}
19923 @kindex pmon@r{, @acronym{MIPS} remote}
19924 @cindex send PMON command
19925 This command allows sending an arbitrary @var{command} string to the
19926 monitor. The monitor must be in debug mode for this to work.
19929 @node OpenRISC 1000
19930 @subsection OpenRISC 1000
19931 @cindex OpenRISC 1000
19933 @cindex or1k boards
19934 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19935 about platform and commands.
19939 @kindex target jtag
19940 @item target jtag jtag://@var{host}:@var{port}
19942 Connects to remote JTAG server.
19943 JTAG remote server can be either an or1ksim or JTAG server,
19944 connected via parallel port to the board.
19946 Example: @code{target jtag jtag://localhost:9999}
19949 @item or1ksim @var{command}
19950 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19951 Simulator, proprietary commands can be executed.
19953 @kindex info or1k spr
19954 @item info or1k spr
19955 Displays spr groups.
19957 @item info or1k spr @var{group}
19958 @itemx info or1k spr @var{groupno}
19959 Displays register names in selected group.
19961 @item info or1k spr @var{group} @var{register}
19962 @itemx info or1k spr @var{register}
19963 @itemx info or1k spr @var{groupno} @var{registerno}
19964 @itemx info or1k spr @var{registerno}
19965 Shows information about specified spr register.
19968 @item spr @var{group} @var{register} @var{value}
19969 @itemx spr @var{register @var{value}}
19970 @itemx spr @var{groupno} @var{registerno @var{value}}
19971 @itemx spr @var{registerno @var{value}}
19972 Writes @var{value} to specified spr register.
19975 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19976 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19977 program execution and is thus much faster. Hardware breakpoints/watchpoint
19978 triggers can be set using:
19981 Load effective address/data
19983 Store effective address/data
19985 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19990 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19991 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19993 @code{htrace} commands:
19994 @cindex OpenRISC 1000 htrace
19997 @item hwatch @var{conditional}
19998 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19999 or Data. For example:
20001 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20003 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20007 Display information about current HW trace configuration.
20009 @item htrace trigger @var{conditional}
20010 Set starting criteria for HW trace.
20012 @item htrace qualifier @var{conditional}
20013 Set acquisition qualifier for HW trace.
20015 @item htrace stop @var{conditional}
20016 Set HW trace stopping criteria.
20018 @item htrace record [@var{data}]*
20019 Selects the data to be recorded, when qualifier is met and HW trace was
20022 @item htrace enable
20023 @itemx htrace disable
20024 Enables/disables the HW trace.
20026 @item htrace rewind [@var{filename}]
20027 Clears currently recorded trace data.
20029 If filename is specified, new trace file is made and any newly collected data
20030 will be written there.
20032 @item htrace print [@var{start} [@var{len}]]
20033 Prints trace buffer, using current record configuration.
20035 @item htrace mode continuous
20036 Set continuous trace mode.
20038 @item htrace mode suspend
20039 Set suspend trace mode.
20043 @node PowerPC Embedded
20044 @subsection PowerPC Embedded
20046 @cindex DVC register
20047 @value{GDBN} supports using the DVC (Data Value Compare) register to
20048 implement in hardware simple hardware watchpoint conditions of the form:
20051 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20052 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20055 The DVC register will be automatically used when @value{GDBN} detects
20056 such pattern in a condition expression, and the created watchpoint uses one
20057 debug register (either the @code{exact-watchpoints} option is on and the
20058 variable is scalar, or the variable has a length of one byte). This feature
20059 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20062 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20063 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20064 in which case watchpoints using only one debug register are created when
20065 watching variables of scalar types.
20067 You can create an artificial array to watch an arbitrary memory
20068 region using one of the following commands (@pxref{Expressions}):
20071 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20072 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20075 PowerPC embedded processors support masked watchpoints. See the discussion
20076 about the @code{mask} argument in @ref{Set Watchpoints}.
20078 @cindex ranged breakpoint
20079 PowerPC embedded processors support hardware accelerated
20080 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20081 the inferior whenever it executes an instruction at any address within
20082 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20083 use the @code{break-range} command.
20085 @value{GDBN} provides the following PowerPC-specific commands:
20088 @kindex break-range
20089 @item break-range @var{start-location}, @var{end-location}
20090 Set a breakpoint for an address range.
20091 @var{start-location} and @var{end-location} can specify a function name,
20092 a line number, an offset of lines from the current line or from the start
20093 location, or an address of an instruction (see @ref{Specify Location},
20094 for a list of all the possible ways to specify a @var{location}.)
20095 The breakpoint will stop execution of the inferior whenever it
20096 executes an instruction at any address within the specified range,
20097 (including @var{start-location} and @var{end-location}.)
20099 @kindex set powerpc
20100 @item set powerpc soft-float
20101 @itemx show powerpc soft-float
20102 Force @value{GDBN} to use (or not use) a software floating point calling
20103 convention. By default, @value{GDBN} selects the calling convention based
20104 on the selected architecture and the provided executable file.
20106 @item set powerpc vector-abi
20107 @itemx show powerpc vector-abi
20108 Force @value{GDBN} to use the specified calling convention for vector
20109 arguments and return values. The valid options are @samp{auto};
20110 @samp{generic}, to avoid vector registers even if they are present;
20111 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20112 registers. By default, @value{GDBN} selects the calling convention
20113 based on the selected architecture and the provided executable file.
20115 @item set powerpc exact-watchpoints
20116 @itemx show powerpc exact-watchpoints
20117 Allow @value{GDBN} to use only one debug register when watching a variable
20118 of scalar type, thus assuming that the variable is accessed through the
20119 address of its first byte.
20121 @kindex target dink32
20122 @item target dink32 @var{dev}
20123 DINK32 ROM monitor.
20125 @kindex target ppcbug
20126 @item target ppcbug @var{dev}
20127 @kindex target ppcbug1
20128 @item target ppcbug1 @var{dev}
20129 PPCBUG ROM monitor for PowerPC.
20132 @item target sds @var{dev}
20133 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20136 @cindex SDS protocol
20137 The following commands specific to the SDS protocol are supported
20141 @item set sdstimeout @var{nsec}
20142 @kindex set sdstimeout
20143 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20144 default is 2 seconds.
20146 @item show sdstimeout
20147 @kindex show sdstimeout
20148 Show the current value of the SDS timeout.
20150 @item sds @var{command}
20151 @kindex sds@r{, a command}
20152 Send the specified @var{command} string to the SDS monitor.
20157 @subsection HP PA Embedded
20161 @kindex target op50n
20162 @item target op50n @var{dev}
20163 OP50N monitor, running on an OKI HPPA board.
20165 @kindex target w89k
20166 @item target w89k @var{dev}
20167 W89K monitor, running on a Winbond HPPA board.
20172 @subsection Tsqware Sparclet
20176 @value{GDBN} enables developers to debug tasks running on
20177 Sparclet targets from a Unix host.
20178 @value{GDBN} uses code that runs on
20179 both the Unix host and on the Sparclet target. The program
20180 @code{@value{GDBP}} is installed and executed on the Unix host.
20183 @item remotetimeout @var{args}
20184 @kindex remotetimeout
20185 @value{GDBN} supports the option @code{remotetimeout}.
20186 This option is set by the user, and @var{args} represents the number of
20187 seconds @value{GDBN} waits for responses.
20190 @cindex compiling, on Sparclet
20191 When compiling for debugging, include the options @samp{-g} to get debug
20192 information and @samp{-Ttext} to relocate the program to where you wish to
20193 load it on the target. You may also want to add the options @samp{-n} or
20194 @samp{-N} in order to reduce the size of the sections. Example:
20197 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20200 You can use @code{objdump} to verify that the addresses are what you intended:
20203 sparclet-aout-objdump --headers --syms prog
20206 @cindex running, on Sparclet
20208 your Unix execution search path to find @value{GDBN}, you are ready to
20209 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20210 (or @code{sparclet-aout-gdb}, depending on your installation).
20212 @value{GDBN} comes up showing the prompt:
20219 * Sparclet File:: Setting the file to debug
20220 * Sparclet Connection:: Connecting to Sparclet
20221 * Sparclet Download:: Sparclet download
20222 * Sparclet Execution:: Running and debugging
20225 @node Sparclet File
20226 @subsubsection Setting File to Debug
20228 The @value{GDBN} command @code{file} lets you choose with program to debug.
20231 (gdbslet) file prog
20235 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20236 @value{GDBN} locates
20237 the file by searching the directories listed in the command search
20239 If the file was compiled with debug information (option @samp{-g}), source
20240 files will be searched as well.
20241 @value{GDBN} locates
20242 the source files by searching the directories listed in the directory search
20243 path (@pxref{Environment, ,Your Program's Environment}).
20245 to find a file, it displays a message such as:
20248 prog: No such file or directory.
20251 When this happens, add the appropriate directories to the search paths with
20252 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20253 @code{target} command again.
20255 @node Sparclet Connection
20256 @subsubsection Connecting to Sparclet
20258 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20259 To connect to a target on serial port ``@code{ttya}'', type:
20262 (gdbslet) target sparclet /dev/ttya
20263 Remote target sparclet connected to /dev/ttya
20264 main () at ../prog.c:3
20268 @value{GDBN} displays messages like these:
20274 @node Sparclet Download
20275 @subsubsection Sparclet Download
20277 @cindex download to Sparclet
20278 Once connected to the Sparclet target,
20279 you can use the @value{GDBN}
20280 @code{load} command to download the file from the host to the target.
20281 The file name and load offset should be given as arguments to the @code{load}
20283 Since the file format is aout, the program must be loaded to the starting
20284 address. You can use @code{objdump} to find out what this value is. The load
20285 offset is an offset which is added to the VMA (virtual memory address)
20286 of each of the file's sections.
20287 For instance, if the program
20288 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20289 and bss at 0x12010170, in @value{GDBN}, type:
20292 (gdbslet) load prog 0x12010000
20293 Loading section .text, size 0xdb0 vma 0x12010000
20296 If the code is loaded at a different address then what the program was linked
20297 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20298 to tell @value{GDBN} where to map the symbol table.
20300 @node Sparclet Execution
20301 @subsubsection Running and Debugging
20303 @cindex running and debugging Sparclet programs
20304 You can now begin debugging the task using @value{GDBN}'s execution control
20305 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20306 manual for the list of commands.
20310 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20312 Starting program: prog
20313 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20314 3 char *symarg = 0;
20316 4 char *execarg = "hello!";
20321 @subsection Fujitsu Sparclite
20325 @kindex target sparclite
20326 @item target sparclite @var{dev}
20327 Fujitsu sparclite boards, used only for the purpose of loading.
20328 You must use an additional command to debug the program.
20329 For example: target remote @var{dev} using @value{GDBN} standard
20335 @subsection Zilog Z8000
20338 @cindex simulator, Z8000
20339 @cindex Zilog Z8000 simulator
20341 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20344 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20345 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20346 segmented variant). The simulator recognizes which architecture is
20347 appropriate by inspecting the object code.
20350 @item target sim @var{args}
20352 @kindex target sim@r{, with Z8000}
20353 Debug programs on a simulated CPU. If the simulator supports setup
20354 options, specify them via @var{args}.
20358 After specifying this target, you can debug programs for the simulated
20359 CPU in the same style as programs for your host computer; use the
20360 @code{file} command to load a new program image, the @code{run} command
20361 to run your program, and so on.
20363 As well as making available all the usual machine registers
20364 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20365 additional items of information as specially named registers:
20370 Counts clock-ticks in the simulator.
20373 Counts instructions run in the simulator.
20376 Execution time in 60ths of a second.
20380 You can refer to these values in @value{GDBN} expressions with the usual
20381 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20382 conditional breakpoint that suspends only after at least 5000
20383 simulated clock ticks.
20386 @subsection Atmel AVR
20389 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20390 following AVR-specific commands:
20393 @item info io_registers
20394 @kindex info io_registers@r{, AVR}
20395 @cindex I/O registers (Atmel AVR)
20396 This command displays information about the AVR I/O registers. For
20397 each register, @value{GDBN} prints its number and value.
20404 When configured for debugging CRIS, @value{GDBN} provides the
20405 following CRIS-specific commands:
20408 @item set cris-version @var{ver}
20409 @cindex CRIS version
20410 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20411 The CRIS version affects register names and sizes. This command is useful in
20412 case autodetection of the CRIS version fails.
20414 @item show cris-version
20415 Show the current CRIS version.
20417 @item set cris-dwarf2-cfi
20418 @cindex DWARF-2 CFI and CRIS
20419 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20420 Change to @samp{off} when using @code{gcc-cris} whose version is below
20423 @item show cris-dwarf2-cfi
20424 Show the current state of using DWARF-2 CFI.
20426 @item set cris-mode @var{mode}
20428 Set the current CRIS mode to @var{mode}. It should only be changed when
20429 debugging in guru mode, in which case it should be set to
20430 @samp{guru} (the default is @samp{normal}).
20432 @item show cris-mode
20433 Show the current CRIS mode.
20437 @subsection Renesas Super-H
20440 For the Renesas Super-H processor, @value{GDBN} provides these
20445 @kindex regs@r{, Super-H}
20446 Show the values of all Super-H registers.
20448 @item set sh calling-convention @var{convention}
20449 @kindex set sh calling-convention
20450 Set the calling-convention used when calling functions from @value{GDBN}.
20451 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20452 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20453 convention. If the DWARF-2 information of the called function specifies
20454 that the function follows the Renesas calling convention, the function
20455 is called using the Renesas calling convention. If the calling convention
20456 is set to @samp{renesas}, the Renesas calling convention is always used,
20457 regardless of the DWARF-2 information. This can be used to override the
20458 default of @samp{gcc} if debug information is missing, or the compiler
20459 does not emit the DWARF-2 calling convention entry for a function.
20461 @item show sh calling-convention
20462 @kindex show sh calling-convention
20463 Show the current calling convention setting.
20468 @node Architectures
20469 @section Architectures
20471 This section describes characteristics of architectures that affect
20472 all uses of @value{GDBN} with the architecture, both native and cross.
20478 * HPPA:: HP PA architecture
20479 * SPU:: Cell Broadband Engine SPU architecture
20484 @subsection x86 Architecture-specific Issues
20487 @item set struct-convention @var{mode}
20488 @kindex set struct-convention
20489 @cindex struct return convention
20490 @cindex struct/union returned in registers
20491 Set the convention used by the inferior to return @code{struct}s and
20492 @code{union}s from functions to @var{mode}. Possible values of
20493 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20494 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20495 are returned on the stack, while @code{"reg"} means that a
20496 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20497 be returned in a register.
20499 @item show struct-convention
20500 @kindex show struct-convention
20501 Show the current setting of the convention to return @code{struct}s
20508 See the following section.
20511 @subsection @acronym{MIPS}
20513 @cindex stack on Alpha
20514 @cindex stack on @acronym{MIPS}
20515 @cindex Alpha stack
20516 @cindex @acronym{MIPS} stack
20517 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20518 sometimes requires @value{GDBN} to search backward in the object code to
20519 find the beginning of a function.
20521 @cindex response time, @acronym{MIPS} debugging
20522 To improve response time (especially for embedded applications, where
20523 @value{GDBN} may be restricted to a slow serial line for this search)
20524 you may want to limit the size of this search, using one of these
20528 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20529 @item set heuristic-fence-post @var{limit}
20530 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20531 search for the beginning of a function. A value of @var{0} (the
20532 default) means there is no limit. However, except for @var{0}, the
20533 larger the limit the more bytes @code{heuristic-fence-post} must search
20534 and therefore the longer it takes to run. You should only need to use
20535 this command when debugging a stripped executable.
20537 @item show heuristic-fence-post
20538 Display the current limit.
20542 These commands are available @emph{only} when @value{GDBN} is configured
20543 for debugging programs on Alpha or @acronym{MIPS} processors.
20545 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20549 @item set mips abi @var{arg}
20550 @kindex set mips abi
20551 @cindex set ABI for @acronym{MIPS}
20552 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20553 values of @var{arg} are:
20557 The default ABI associated with the current binary (this is the
20567 @item show mips abi
20568 @kindex show mips abi
20569 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20571 @item set mips compression @var{arg}
20572 @kindex set mips compression
20573 @cindex code compression, @acronym{MIPS}
20574 Tell @value{GDBN} which @acronym{MIPS} compressed
20575 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20576 inferior. @value{GDBN} uses this for code disassembly and other
20577 internal interpretation purposes. This setting is only referred to
20578 when no executable has been associated with the debugging session or
20579 the executable does not provide information about the encoding it uses.
20580 Otherwise this setting is automatically updated from information
20581 provided by the executable.
20583 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20584 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20585 executables containing @acronym{MIPS16} code frequently are not
20586 identified as such.
20588 This setting is ``sticky''; that is, it retains its value across
20589 debugging sessions until reset either explicitly with this command or
20590 implicitly from an executable.
20592 The compiler and/or assembler typically add symbol table annotations to
20593 identify functions compiled for the @acronym{MIPS16} or
20594 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20595 are present, @value{GDBN} uses them in preference to the global
20596 compressed @acronym{ISA} encoding setting.
20598 @item show mips compression
20599 @kindex show mips compression
20600 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20601 @value{GDBN} to debug the inferior.
20604 @itemx show mipsfpu
20605 @xref{MIPS Embedded, set mipsfpu}.
20607 @item set mips mask-address @var{arg}
20608 @kindex set mips mask-address
20609 @cindex @acronym{MIPS} addresses, masking
20610 This command determines whether the most-significant 32 bits of 64-bit
20611 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20612 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20613 setting, which lets @value{GDBN} determine the correct value.
20615 @item show mips mask-address
20616 @kindex show mips mask-address
20617 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20620 @item set remote-mips64-transfers-32bit-regs
20621 @kindex set remote-mips64-transfers-32bit-regs
20622 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20623 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20624 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20625 and 64 bits for other registers, set this option to @samp{on}.
20627 @item show remote-mips64-transfers-32bit-regs
20628 @kindex show remote-mips64-transfers-32bit-regs
20629 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20631 @item set debug mips
20632 @kindex set debug mips
20633 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20634 target code in @value{GDBN}.
20636 @item show debug mips
20637 @kindex show debug mips
20638 Show the current setting of @acronym{MIPS} debugging messages.
20644 @cindex HPPA support
20646 When @value{GDBN} is debugging the HP PA architecture, it provides the
20647 following special commands:
20650 @item set debug hppa
20651 @kindex set debug hppa
20652 This command determines whether HPPA architecture-specific debugging
20653 messages are to be displayed.
20655 @item show debug hppa
20656 Show whether HPPA debugging messages are displayed.
20658 @item maint print unwind @var{address}
20659 @kindex maint print unwind@r{, HPPA}
20660 This command displays the contents of the unwind table entry at the
20661 given @var{address}.
20667 @subsection Cell Broadband Engine SPU architecture
20668 @cindex Cell Broadband Engine
20671 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20672 it provides the following special commands:
20675 @item info spu event
20677 Display SPU event facility status. Shows current event mask
20678 and pending event status.
20680 @item info spu signal
20681 Display SPU signal notification facility status. Shows pending
20682 signal-control word and signal notification mode of both signal
20683 notification channels.
20685 @item info spu mailbox
20686 Display SPU mailbox facility status. Shows all pending entries,
20687 in order of processing, in each of the SPU Write Outbound,
20688 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20691 Display MFC DMA status. Shows all pending commands in the MFC
20692 DMA queue. For each entry, opcode, tag, class IDs, effective
20693 and local store addresses and transfer size are shown.
20695 @item info spu proxydma
20696 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20697 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20698 and local store addresses and transfer size are shown.
20702 When @value{GDBN} is debugging a combined PowerPC/SPU application
20703 on the Cell Broadband Engine, it provides in addition the following
20707 @item set spu stop-on-load @var{arg}
20709 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20710 will give control to the user when a new SPE thread enters its @code{main}
20711 function. The default is @code{off}.
20713 @item show spu stop-on-load
20715 Show whether to stop for new SPE threads.
20717 @item set spu auto-flush-cache @var{arg}
20718 Set whether to automatically flush the software-managed cache. When set to
20719 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20720 cache to be flushed whenever SPE execution stops. This provides a consistent
20721 view of PowerPC memory that is accessed via the cache. If an application
20722 does not use the software-managed cache, this option has no effect.
20724 @item show spu auto-flush-cache
20725 Show whether to automatically flush the software-managed cache.
20730 @subsection PowerPC
20731 @cindex PowerPC architecture
20733 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20734 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20735 numbers stored in the floating point registers. These values must be stored
20736 in two consecutive registers, always starting at an even register like
20737 @code{f0} or @code{f2}.
20739 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20740 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20741 @code{f2} and @code{f3} for @code{$dl1} and so on.
20743 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20744 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20747 @node Controlling GDB
20748 @chapter Controlling @value{GDBN}
20750 You can alter the way @value{GDBN} interacts with you by using the
20751 @code{set} command. For commands controlling how @value{GDBN} displays
20752 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20757 * Editing:: Command editing
20758 * Command History:: Command history
20759 * Screen Size:: Screen size
20760 * Numbers:: Numbers
20761 * ABI:: Configuring the current ABI
20762 * Auto-loading:: Automatically loading associated files
20763 * Messages/Warnings:: Optional warnings and messages
20764 * Debugging Output:: Optional messages about internal happenings
20765 * Other Misc Settings:: Other Miscellaneous Settings
20773 @value{GDBN} indicates its readiness to read a command by printing a string
20774 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20775 can change the prompt string with the @code{set prompt} command. For
20776 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20777 the prompt in one of the @value{GDBN} sessions so that you can always tell
20778 which one you are talking to.
20780 @emph{Note:} @code{set prompt} does not add a space for you after the
20781 prompt you set. This allows you to set a prompt which ends in a space
20782 or a prompt that does not.
20786 @item set prompt @var{newprompt}
20787 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20789 @kindex show prompt
20791 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20794 Versions of @value{GDBN} that ship with Python scripting enabled have
20795 prompt extensions. The commands for interacting with these extensions
20799 @kindex set extended-prompt
20800 @item set extended-prompt @var{prompt}
20801 Set an extended prompt that allows for substitutions.
20802 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20803 substitution. Any escape sequences specified as part of the prompt
20804 string are replaced with the corresponding strings each time the prompt
20810 set extended-prompt Current working directory: \w (gdb)
20813 Note that when an extended-prompt is set, it takes control of the
20814 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20816 @kindex show extended-prompt
20817 @item show extended-prompt
20818 Prints the extended prompt. Any escape sequences specified as part of
20819 the prompt string with @code{set extended-prompt}, are replaced with the
20820 corresponding strings each time the prompt is displayed.
20824 @section Command Editing
20826 @cindex command line editing
20828 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20829 @sc{gnu} library provides consistent behavior for programs which provide a
20830 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20831 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20832 substitution, and a storage and recall of command history across
20833 debugging sessions.
20835 You may control the behavior of command line editing in @value{GDBN} with the
20836 command @code{set}.
20839 @kindex set editing
20842 @itemx set editing on
20843 Enable command line editing (enabled by default).
20845 @item set editing off
20846 Disable command line editing.
20848 @kindex show editing
20850 Show whether command line editing is enabled.
20853 @ifset SYSTEM_READLINE
20854 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20856 @ifclear SYSTEM_READLINE
20857 @xref{Command Line Editing},
20859 for more details about the Readline
20860 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20861 encouraged to read that chapter.
20863 @node Command History
20864 @section Command History
20865 @cindex command history
20867 @value{GDBN} can keep track of the commands you type during your
20868 debugging sessions, so that you can be certain of precisely what
20869 happened. Use these commands to manage the @value{GDBN} command
20872 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20873 package, to provide the history facility.
20874 @ifset SYSTEM_READLINE
20875 @xref{Using History Interactively, , , history, GNU History Library},
20877 @ifclear SYSTEM_READLINE
20878 @xref{Using History Interactively},
20880 for the detailed description of the History library.
20882 To issue a command to @value{GDBN} without affecting certain aspects of
20883 the state which is seen by users, prefix it with @samp{server }
20884 (@pxref{Server Prefix}). This
20885 means that this command will not affect the command history, nor will it
20886 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20887 pressed on a line by itself.
20889 @cindex @code{server}, command prefix
20890 The server prefix does not affect the recording of values into the value
20891 history; to print a value without recording it into the value history,
20892 use the @code{output} command instead of the @code{print} command.
20894 Here is the description of @value{GDBN} commands related to command
20898 @cindex history substitution
20899 @cindex history file
20900 @kindex set history filename
20901 @cindex @env{GDBHISTFILE}, environment variable
20902 @item set history filename @var{fname}
20903 Set the name of the @value{GDBN} command history file to @var{fname}.
20904 This is the file where @value{GDBN} reads an initial command history
20905 list, and where it writes the command history from this session when it
20906 exits. You can access this list through history expansion or through
20907 the history command editing characters listed below. This file defaults
20908 to the value of the environment variable @code{GDBHISTFILE}, or to
20909 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20912 @cindex save command history
20913 @kindex set history save
20914 @item set history save
20915 @itemx set history save on
20916 Record command history in a file, whose name may be specified with the
20917 @code{set history filename} command. By default, this option is disabled.
20919 @item set history save off
20920 Stop recording command history in a file.
20922 @cindex history size
20923 @kindex set history size
20924 @cindex @env{HISTSIZE}, environment variable
20925 @item set history size @var{size}
20926 Set the number of commands which @value{GDBN} keeps in its history list.
20927 This defaults to the value of the environment variable
20928 @code{HISTSIZE}, or to 256 if this variable is not set.
20931 History expansion assigns special meaning to the character @kbd{!}.
20932 @ifset SYSTEM_READLINE
20933 @xref{Event Designators, , , history, GNU History Library},
20935 @ifclear SYSTEM_READLINE
20936 @xref{Event Designators},
20940 @cindex history expansion, turn on/off
20941 Since @kbd{!} is also the logical not operator in C, history expansion
20942 is off by default. If you decide to enable history expansion with the
20943 @code{set history expansion on} command, you may sometimes need to
20944 follow @kbd{!} (when it is used as logical not, in an expression) with
20945 a space or a tab to prevent it from being expanded. The readline
20946 history facilities do not attempt substitution on the strings
20947 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20949 The commands to control history expansion are:
20952 @item set history expansion on
20953 @itemx set history expansion
20954 @kindex set history expansion
20955 Enable history expansion. History expansion is off by default.
20957 @item set history expansion off
20958 Disable history expansion.
20961 @kindex show history
20963 @itemx show history filename
20964 @itemx show history save
20965 @itemx show history size
20966 @itemx show history expansion
20967 These commands display the state of the @value{GDBN} history parameters.
20968 @code{show history} by itself displays all four states.
20973 @kindex show commands
20974 @cindex show last commands
20975 @cindex display command history
20976 @item show commands
20977 Display the last ten commands in the command history.
20979 @item show commands @var{n}
20980 Print ten commands centered on command number @var{n}.
20982 @item show commands +
20983 Print ten commands just after the commands last printed.
20987 @section Screen Size
20988 @cindex size of screen
20989 @cindex pauses in output
20991 Certain commands to @value{GDBN} may produce large amounts of
20992 information output to the screen. To help you read all of it,
20993 @value{GDBN} pauses and asks you for input at the end of each page of
20994 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20995 to discard the remaining output. Also, the screen width setting
20996 determines when to wrap lines of output. Depending on what is being
20997 printed, @value{GDBN} tries to break the line at a readable place,
20998 rather than simply letting it overflow onto the following line.
21000 Normally @value{GDBN} knows the size of the screen from the terminal
21001 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21002 together with the value of the @code{TERM} environment variable and the
21003 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21004 you can override it with the @code{set height} and @code{set
21011 @kindex show height
21012 @item set height @var{lpp}
21014 @itemx set width @var{cpl}
21016 These @code{set} commands specify a screen height of @var{lpp} lines and
21017 a screen width of @var{cpl} characters. The associated @code{show}
21018 commands display the current settings.
21020 If you specify a height of zero lines, @value{GDBN} does not pause during
21021 output no matter how long the output is. This is useful if output is to a
21022 file or to an editor buffer.
21024 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
21025 from wrapping its output.
21027 @item set pagination on
21028 @itemx set pagination off
21029 @kindex set pagination
21030 Turn the output pagination on or off; the default is on. Turning
21031 pagination off is the alternative to @code{set height 0}. Note that
21032 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21033 Options, -batch}) also automatically disables pagination.
21035 @item show pagination
21036 @kindex show pagination
21037 Show the current pagination mode.
21042 @cindex number representation
21043 @cindex entering numbers
21045 You can always enter numbers in octal, decimal, or hexadecimal in
21046 @value{GDBN} by the usual conventions: octal numbers begin with
21047 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21048 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21049 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21050 10; likewise, the default display for numbers---when no particular
21051 format is specified---is base 10. You can change the default base for
21052 both input and output with the commands described below.
21055 @kindex set input-radix
21056 @item set input-radix @var{base}
21057 Set the default base for numeric input. Supported choices
21058 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21059 specified either unambiguously or using the current input radix; for
21063 set input-radix 012
21064 set input-radix 10.
21065 set input-radix 0xa
21069 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21070 leaves the input radix unchanged, no matter what it was, since
21071 @samp{10}, being without any leading or trailing signs of its base, is
21072 interpreted in the current radix. Thus, if the current radix is 16,
21073 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21076 @kindex set output-radix
21077 @item set output-radix @var{base}
21078 Set the default base for numeric display. Supported choices
21079 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21080 specified either unambiguously or using the current input radix.
21082 @kindex show input-radix
21083 @item show input-radix
21084 Display the current default base for numeric input.
21086 @kindex show output-radix
21087 @item show output-radix
21088 Display the current default base for numeric display.
21090 @item set radix @r{[}@var{base}@r{]}
21094 These commands set and show the default base for both input and output
21095 of numbers. @code{set radix} sets the radix of input and output to
21096 the same base; without an argument, it resets the radix back to its
21097 default value of 10.
21102 @section Configuring the Current ABI
21104 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21105 application automatically. However, sometimes you need to override its
21106 conclusions. Use these commands to manage @value{GDBN}'s view of the
21113 One @value{GDBN} configuration can debug binaries for multiple operating
21114 system targets, either via remote debugging or native emulation.
21115 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21116 but you can override its conclusion using the @code{set osabi} command.
21117 One example where this is useful is in debugging of binaries which use
21118 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21119 not have the same identifying marks that the standard C library for your
21124 Show the OS ABI currently in use.
21127 With no argument, show the list of registered available OS ABI's.
21129 @item set osabi @var{abi}
21130 Set the current OS ABI to @var{abi}.
21133 @cindex float promotion
21135 Generally, the way that an argument of type @code{float} is passed to a
21136 function depends on whether the function is prototyped. For a prototyped
21137 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21138 according to the architecture's convention for @code{float}. For unprototyped
21139 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21140 @code{double} and then passed.
21142 Unfortunately, some forms of debug information do not reliably indicate whether
21143 a function is prototyped. If @value{GDBN} calls a function that is not marked
21144 as prototyped, it consults @kbd{set coerce-float-to-double}.
21147 @kindex set coerce-float-to-double
21148 @item set coerce-float-to-double
21149 @itemx set coerce-float-to-double on
21150 Arguments of type @code{float} will be promoted to @code{double} when passed
21151 to an unprototyped function. This is the default setting.
21153 @item set coerce-float-to-double off
21154 Arguments of type @code{float} will be passed directly to unprototyped
21157 @kindex show coerce-float-to-double
21158 @item show coerce-float-to-double
21159 Show the current setting of promoting @code{float} to @code{double}.
21163 @kindex show cp-abi
21164 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21165 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21166 used to build your application. @value{GDBN} only fully supports
21167 programs with a single C@t{++} ABI; if your program contains code using
21168 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21169 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21170 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21171 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21172 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21173 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21178 Show the C@t{++} ABI currently in use.
21181 With no argument, show the list of supported C@t{++} ABI's.
21183 @item set cp-abi @var{abi}
21184 @itemx set cp-abi auto
21185 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21189 @section Automatically loading associated files
21190 @cindex auto-loading
21192 @value{GDBN} sometimes reads files with commands and settings automatically,
21193 without being explicitly told so by the user. We call this feature
21194 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21195 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21196 results or introduce security risks (e.g., if the file comes from untrusted
21199 Note that loading of these associated files (including the local @file{.gdbinit}
21200 file) requires accordingly configured @code{auto-load safe-path}
21201 (@pxref{Auto-loading safe path}).
21203 For these reasons, @value{GDBN} includes commands and options to let you
21204 control when to auto-load files and which files should be auto-loaded.
21207 @anchor{set auto-load off}
21208 @kindex set auto-load off
21209 @item set auto-load off
21210 Globally disable loading of all auto-loaded files.
21211 You may want to use this command with the @samp{-iex} option
21212 (@pxref{Option -init-eval-command}) such as:
21214 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21217 Be aware that system init file (@pxref{System-wide configuration})
21218 and init files from your home directory (@pxref{Home Directory Init File})
21219 still get read (as they come from generally trusted directories).
21220 To prevent @value{GDBN} from auto-loading even those init files, use the
21221 @option{-nx} option (@pxref{Mode Options}), in addition to
21222 @code{set auto-load no}.
21224 @anchor{show auto-load}
21225 @kindex show auto-load
21226 @item show auto-load
21227 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21231 (gdb) show auto-load
21232 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21233 libthread-db: Auto-loading of inferior specific libthread_db is on.
21234 local-gdbinit: Auto-loading of .gdbinit script from current directory
21236 python-scripts: Auto-loading of Python scripts is on.
21237 safe-path: List of directories from which it is safe to auto-load files
21238 is $debugdir:$datadir/auto-load.
21239 scripts-directory: List of directories from which to load auto-loaded scripts
21240 is $debugdir:$datadir/auto-load.
21243 @anchor{info auto-load}
21244 @kindex info auto-load
21245 @item info auto-load
21246 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21250 (gdb) info auto-load
21253 Yes /home/user/gdb/gdb-gdb.gdb
21254 libthread-db: No auto-loaded libthread-db.
21255 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21259 Yes /home/user/gdb/gdb-gdb.py
21263 These are various kinds of files @value{GDBN} can automatically load:
21267 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21269 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21271 @xref{dotdebug_gdb_scripts section},
21272 controlled by @ref{set auto-load python-scripts}.
21274 @xref{Init File in the Current Directory},
21275 controlled by @ref{set auto-load local-gdbinit}.
21277 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21280 These are @value{GDBN} control commands for the auto-loading:
21282 @multitable @columnfractions .5 .5
21283 @item @xref{set auto-load off}.
21284 @tab Disable auto-loading globally.
21285 @item @xref{show auto-load}.
21286 @tab Show setting of all kinds of files.
21287 @item @xref{info auto-load}.
21288 @tab Show state of all kinds of files.
21289 @item @xref{set auto-load gdb-scripts}.
21290 @tab Control for @value{GDBN} command scripts.
21291 @item @xref{show auto-load gdb-scripts}.
21292 @tab Show setting of @value{GDBN} command scripts.
21293 @item @xref{info auto-load gdb-scripts}.
21294 @tab Show state of @value{GDBN} command scripts.
21295 @item @xref{set auto-load python-scripts}.
21296 @tab Control for @value{GDBN} Python scripts.
21297 @item @xref{show auto-load python-scripts}.
21298 @tab Show setting of @value{GDBN} Python scripts.
21299 @item @xref{info auto-load python-scripts}.
21300 @tab Show state of @value{GDBN} Python scripts.
21301 @item @xref{set auto-load scripts-directory}.
21302 @tab Control for @value{GDBN} auto-loaded scripts location.
21303 @item @xref{show auto-load scripts-directory}.
21304 @tab Show @value{GDBN} auto-loaded scripts location.
21305 @item @xref{set auto-load local-gdbinit}.
21306 @tab Control for init file in the current directory.
21307 @item @xref{show auto-load local-gdbinit}.
21308 @tab Show setting of init file in the current directory.
21309 @item @xref{info auto-load local-gdbinit}.
21310 @tab Show state of init file in the current directory.
21311 @item @xref{set auto-load libthread-db}.
21312 @tab Control for thread debugging library.
21313 @item @xref{show auto-load libthread-db}.
21314 @tab Show setting of thread debugging library.
21315 @item @xref{info auto-load libthread-db}.
21316 @tab Show state of thread debugging library.
21317 @item @xref{set auto-load safe-path}.
21318 @tab Control directories trusted for automatic loading.
21319 @item @xref{show auto-load safe-path}.
21320 @tab Show directories trusted for automatic loading.
21321 @item @xref{add-auto-load-safe-path}.
21322 @tab Add directory trusted for automatic loading.
21326 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21327 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21328 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21329 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21330 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21331 @xref{Python Auto-loading}.
21334 @node Init File in the Current Directory
21335 @subsection Automatically loading init file in the current directory
21336 @cindex auto-loading init file in the current directory
21338 By default, @value{GDBN} reads and executes the canned sequences of commands
21339 from init file (if any) in the current working directory,
21340 see @ref{Init File in the Current Directory during Startup}.
21342 Note that loading of this local @file{.gdbinit} file also requires accordingly
21343 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21346 @anchor{set auto-load local-gdbinit}
21347 @kindex set auto-load local-gdbinit
21348 @item set auto-load local-gdbinit [on|off]
21349 Enable or disable the auto-loading of canned sequences of commands
21350 (@pxref{Sequences}) found in init file in the current directory.
21352 @anchor{show auto-load local-gdbinit}
21353 @kindex show auto-load local-gdbinit
21354 @item show auto-load local-gdbinit
21355 Show whether auto-loading of canned sequences of commands from init file in the
21356 current directory is enabled or disabled.
21358 @anchor{info auto-load local-gdbinit}
21359 @kindex info auto-load local-gdbinit
21360 @item info auto-load local-gdbinit
21361 Print whether canned sequences of commands from init file in the
21362 current directory have been auto-loaded.
21365 @node libthread_db.so.1 file
21366 @subsection Automatically loading thread debugging library
21367 @cindex auto-loading libthread_db.so.1
21369 This feature is currently present only on @sc{gnu}/Linux native hosts.
21371 @value{GDBN} reads in some cases thread debugging library from places specific
21372 to the inferior (@pxref{set libthread-db-search-path}).
21374 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21375 without checking this @samp{set auto-load libthread-db} switch as system
21376 libraries have to be trusted in general. In all other cases of
21377 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21378 auto-load libthread-db} is enabled before trying to open such thread debugging
21381 Note that loading of this debugging library also requires accordingly configured
21382 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21385 @anchor{set auto-load libthread-db}
21386 @kindex set auto-load libthread-db
21387 @item set auto-load libthread-db [on|off]
21388 Enable or disable the auto-loading of inferior specific thread debugging library.
21390 @anchor{show auto-load libthread-db}
21391 @kindex show auto-load libthread-db
21392 @item show auto-load libthread-db
21393 Show whether auto-loading of inferior specific thread debugging library is
21394 enabled or disabled.
21396 @anchor{info auto-load libthread-db}
21397 @kindex info auto-load libthread-db
21398 @item info auto-load libthread-db
21399 Print the list of all loaded inferior specific thread debugging libraries and
21400 for each such library print list of inferior @var{pid}s using it.
21403 @node objfile-gdb.gdb file
21404 @subsection The @file{@var{objfile}-gdb.gdb} file
21405 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21407 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21408 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21409 auto-load gdb-scripts} is set to @samp{on}.
21411 Note that loading of this script file also requires accordingly configured
21412 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21414 For more background refer to the similar Python scripts auto-loading
21415 description (@pxref{objfile-gdb.py file}).
21418 @anchor{set auto-load gdb-scripts}
21419 @kindex set auto-load gdb-scripts
21420 @item set auto-load gdb-scripts [on|off]
21421 Enable or disable the auto-loading of canned sequences of commands scripts.
21423 @anchor{show auto-load gdb-scripts}
21424 @kindex show auto-load gdb-scripts
21425 @item show auto-load gdb-scripts
21426 Show whether auto-loading of canned sequences of commands scripts is enabled or
21429 @anchor{info auto-load gdb-scripts}
21430 @kindex info auto-load gdb-scripts
21431 @cindex print list of auto-loaded canned sequences of commands scripts
21432 @item info auto-load gdb-scripts [@var{regexp}]
21433 Print the list of all canned sequences of commands scripts that @value{GDBN}
21437 If @var{regexp} is supplied only canned sequences of commands scripts with
21438 matching names are printed.
21440 @node Auto-loading safe path
21441 @subsection Security restriction for auto-loading
21442 @cindex auto-loading safe-path
21444 As the files of inferior can come from untrusted source (such as submitted by
21445 an application user) @value{GDBN} does not always load any files automatically.
21446 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21447 directories trusted for loading files not explicitly requested by user.
21449 If the path is not set properly you will see a warning and the file will not
21454 Reading symbols from /home/user/gdb/gdb...done.
21455 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21456 declined by your `auto-load safe-path' set
21457 to "$debugdir:$datadir/auto-load".
21458 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21459 declined by your `auto-load safe-path' set
21460 to "$debugdir:$datadir/auto-load".
21463 The list of trusted directories is controlled by the following commands:
21466 @anchor{set auto-load safe-path}
21467 @kindex set auto-load safe-path
21468 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21469 Set the list of directories (and their subdirectories) trusted for automatic
21470 loading and execution of scripts. You can also enter a specific trusted file.
21471 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21472 its default value as specified during @value{GDBN} compilation.
21474 The list of directories uses path separator (@samp{:} on GNU and Unix
21475 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21476 to the @env{PATH} environment variable.
21478 @anchor{show auto-load safe-path}
21479 @kindex show auto-load safe-path
21480 @item show auto-load safe-path
21481 Show the list of directories trusted for automatic loading and execution of
21484 @anchor{add-auto-load-safe-path}
21485 @kindex add-auto-load-safe-path
21486 @item add-auto-load-safe-path
21487 Add an entry (or list of entries) the list of directories trusted for automatic
21488 loading and execution of scripts. Multiple entries may be delimited by the
21489 host platform path separator in use.
21492 This variable defaults to what @code{--with-auto-load-dir} has been configured
21493 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21494 substitution applies the same as for @ref{set auto-load scripts-directory}.
21495 The default @code{set auto-load safe-path} value can be also overriden by
21496 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21498 Setting this variable to @file{/} disables this security protection,
21499 corresponding @value{GDBN} configuration option is
21500 @option{--without-auto-load-safe-path}.
21501 This variable is supposed to be set to the system directories writable by the
21502 system superuser only. Users can add their source directories in init files in
21503 their home directories (@pxref{Home Directory Init File}). See also deprecated
21504 init file in the current directory
21505 (@pxref{Init File in the Current Directory during Startup}).
21507 To force @value{GDBN} to load the files it declined to load in the previous
21508 example, you could use one of the following ways:
21511 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21512 Specify this trusted directory (or a file) as additional component of the list.
21513 You have to specify also any existing directories displayed by
21514 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21516 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21517 Specify this directory as in the previous case but just for a single
21518 @value{GDBN} session.
21520 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21521 Disable auto-loading safety for a single @value{GDBN} session.
21522 This assumes all the files you debug during this @value{GDBN} session will come
21523 from trusted sources.
21525 @item @kbd{./configure --without-auto-load-safe-path}
21526 During compilation of @value{GDBN} you may disable any auto-loading safety.
21527 This assumes all the files you will ever debug with this @value{GDBN} come from
21531 On the other hand you can also explicitly forbid automatic files loading which
21532 also suppresses any such warning messages:
21535 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21536 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21538 @item @file{~/.gdbinit}: @samp{set auto-load no}
21539 Disable auto-loading globally for the user
21540 (@pxref{Home Directory Init File}). While it is improbable, you could also
21541 use system init file instead (@pxref{System-wide configuration}).
21544 This setting applies to the file names as entered by user. If no entry matches
21545 @value{GDBN} tries as a last resort to also resolve all the file names into
21546 their canonical form (typically resolving symbolic links) and compare the
21547 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21548 own before starting the comparison so a canonical form of directories is
21549 recommended to be entered.
21551 @node Auto-loading verbose mode
21552 @subsection Displaying files tried for auto-load
21553 @cindex auto-loading verbose mode
21555 For better visibility of all the file locations where you can place scripts to
21556 be auto-loaded with inferior --- or to protect yourself against accidental
21557 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21558 all the files attempted to be loaded. Both existing and non-existing files may
21561 For example the list of directories from which it is safe to auto-load files
21562 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21563 may not be too obvious while setting it up.
21566 (gdb) set debug auto-load on
21567 (gdb) file ~/src/t/true
21568 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21569 for objfile "/tmp/true".
21570 auto-load: Updating directories of "/usr:/opt".
21571 auto-load: Using directory "/usr".
21572 auto-load: Using directory "/opt".
21573 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21574 by your `auto-load safe-path' set to "/usr:/opt".
21578 @anchor{set debug auto-load}
21579 @kindex set debug auto-load
21580 @item set debug auto-load [on|off]
21581 Set whether to print the filenames attempted to be auto-loaded.
21583 @anchor{show debug auto-load}
21584 @kindex show debug auto-load
21585 @item show debug auto-load
21586 Show whether printing of the filenames attempted to be auto-loaded is turned
21590 @node Messages/Warnings
21591 @section Optional Warnings and Messages
21593 @cindex verbose operation
21594 @cindex optional warnings
21595 By default, @value{GDBN} is silent about its inner workings. If you are
21596 running on a slow machine, you may want to use the @code{set verbose}
21597 command. This makes @value{GDBN} tell you when it does a lengthy
21598 internal operation, so you will not think it has crashed.
21600 Currently, the messages controlled by @code{set verbose} are those
21601 which announce that the symbol table for a source file is being read;
21602 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21605 @kindex set verbose
21606 @item set verbose on
21607 Enables @value{GDBN} output of certain informational messages.
21609 @item set verbose off
21610 Disables @value{GDBN} output of certain informational messages.
21612 @kindex show verbose
21614 Displays whether @code{set verbose} is on or off.
21617 By default, if @value{GDBN} encounters bugs in the symbol table of an
21618 object file, it is silent; but if you are debugging a compiler, you may
21619 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21624 @kindex set complaints
21625 @item set complaints @var{limit}
21626 Permits @value{GDBN} to output @var{limit} complaints about each type of
21627 unusual symbols before becoming silent about the problem. Set
21628 @var{limit} to zero to suppress all complaints; set it to a large number
21629 to prevent complaints from being suppressed.
21631 @kindex show complaints
21632 @item show complaints
21633 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21637 @anchor{confirmation requests}
21638 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21639 lot of stupid questions to confirm certain commands. For example, if
21640 you try to run a program which is already running:
21644 The program being debugged has been started already.
21645 Start it from the beginning? (y or n)
21648 If you are willing to unflinchingly face the consequences of your own
21649 commands, you can disable this ``feature'':
21653 @kindex set confirm
21655 @cindex confirmation
21656 @cindex stupid questions
21657 @item set confirm off
21658 Disables confirmation requests. Note that running @value{GDBN} with
21659 the @option{--batch} option (@pxref{Mode Options, -batch}) also
21660 automatically disables confirmation requests.
21662 @item set confirm on
21663 Enables confirmation requests (the default).
21665 @kindex show confirm
21667 Displays state of confirmation requests.
21671 @cindex command tracing
21672 If you need to debug user-defined commands or sourced files you may find it
21673 useful to enable @dfn{command tracing}. In this mode each command will be
21674 printed as it is executed, prefixed with one or more @samp{+} symbols, the
21675 quantity denoting the call depth of each command.
21678 @kindex set trace-commands
21679 @cindex command scripts, debugging
21680 @item set trace-commands on
21681 Enable command tracing.
21682 @item set trace-commands off
21683 Disable command tracing.
21684 @item show trace-commands
21685 Display the current state of command tracing.
21688 @node Debugging Output
21689 @section Optional Messages about Internal Happenings
21690 @cindex optional debugging messages
21692 @value{GDBN} has commands that enable optional debugging messages from
21693 various @value{GDBN} subsystems; normally these commands are of
21694 interest to @value{GDBN} maintainers, or when reporting a bug. This
21695 section documents those commands.
21698 @kindex set exec-done-display
21699 @item set exec-done-display
21700 Turns on or off the notification of asynchronous commands'
21701 completion. When on, @value{GDBN} will print a message when an
21702 asynchronous command finishes its execution. The default is off.
21703 @kindex show exec-done-display
21704 @item show exec-done-display
21705 Displays the current setting of asynchronous command completion
21708 @cindex gdbarch debugging info
21709 @cindex architecture debugging info
21710 @item set debug arch
21711 Turns on or off display of gdbarch debugging info. The default is off
21713 @item show debug arch
21714 Displays the current state of displaying gdbarch debugging info.
21715 @item set debug aix-thread
21716 @cindex AIX threads
21717 Display debugging messages about inner workings of the AIX thread
21719 @item show debug aix-thread
21720 Show the current state of AIX thread debugging info display.
21721 @item set debug check-physname
21723 Check the results of the ``physname'' computation. When reading DWARF
21724 debugging information for C@t{++}, @value{GDBN} attempts to compute
21725 each entity's name. @value{GDBN} can do this computation in two
21726 different ways, depending on exactly what information is present.
21727 When enabled, this setting causes @value{GDBN} to compute the names
21728 both ways and display any discrepancies.
21729 @item show debug check-physname
21730 Show the current state of ``physname'' checking.
21731 @item set debug dwarf2-die
21732 @cindex DWARF2 DIEs
21733 Dump DWARF2 DIEs after they are read in.
21734 The value is the number of nesting levels to print.
21735 A value of zero turns off the display.
21736 @item show debug dwarf2-die
21737 Show the current state of DWARF2 DIE debugging.
21738 @item set debug displaced
21739 @cindex displaced stepping debugging info
21740 Turns on or off display of @value{GDBN} debugging info for the
21741 displaced stepping support. The default is off.
21742 @item show debug displaced
21743 Displays the current state of displaying @value{GDBN} debugging info
21744 related to displaced stepping.
21745 @item set debug event
21746 @cindex event debugging info
21747 Turns on or off display of @value{GDBN} event debugging info. The
21749 @item show debug event
21750 Displays the current state of displaying @value{GDBN} event debugging
21752 @item set debug expression
21753 @cindex expression debugging info
21754 Turns on or off display of debugging info about @value{GDBN}
21755 expression parsing. The default is off.
21756 @item show debug expression
21757 Displays the current state of displaying debugging info about
21758 @value{GDBN} expression parsing.
21759 @item set debug frame
21760 @cindex frame debugging info
21761 Turns on or off display of @value{GDBN} frame debugging info. The
21763 @item show debug frame
21764 Displays the current state of displaying @value{GDBN} frame debugging
21766 @item set debug gnu-nat
21767 @cindex @sc{gnu}/Hurd debug messages
21768 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
21769 @item show debug gnu-nat
21770 Show the current state of @sc{gnu}/Hurd debugging messages.
21771 @item set debug infrun
21772 @cindex inferior debugging info
21773 Turns on or off display of @value{GDBN} debugging info for running the inferior.
21774 The default is off. @file{infrun.c} contains GDB's runtime state machine used
21775 for implementing operations such as single-stepping the inferior.
21776 @item show debug infrun
21777 Displays the current state of @value{GDBN} inferior debugging.
21778 @item set debug jit
21779 @cindex just-in-time compilation, debugging messages
21780 Turns on or off debugging messages from JIT debug support.
21781 @item show debug jit
21782 Displays the current state of @value{GDBN} JIT debugging.
21783 @item set debug lin-lwp
21784 @cindex @sc{gnu}/Linux LWP debug messages
21785 @cindex Linux lightweight processes
21786 Turns on or off debugging messages from the Linux LWP debug support.
21787 @item show debug lin-lwp
21788 Show the current state of Linux LWP debugging messages.
21789 @item set debug observer
21790 @cindex observer debugging info
21791 Turns on or off display of @value{GDBN} observer debugging. This
21792 includes info such as the notification of observable events.
21793 @item show debug observer
21794 Displays the current state of observer debugging.
21795 @item set debug overload
21796 @cindex C@t{++} overload debugging info
21797 Turns on or off display of @value{GDBN} C@t{++} overload debugging
21798 info. This includes info such as ranking of functions, etc. The default
21800 @item show debug overload
21801 Displays the current state of displaying @value{GDBN} C@t{++} overload
21803 @cindex expression parser, debugging info
21804 @cindex debug expression parser
21805 @item set debug parser
21806 Turns on or off the display of expression parser debugging output.
21807 Internally, this sets the @code{yydebug} variable in the expression
21808 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
21809 details. The default is off.
21810 @item show debug parser
21811 Show the current state of expression parser debugging.
21812 @cindex packets, reporting on stdout
21813 @cindex serial connections, debugging
21814 @cindex debug remote protocol
21815 @cindex remote protocol debugging
21816 @cindex display remote packets
21817 @item set debug remote
21818 Turns on or off display of reports on all packets sent back and forth across
21819 the serial line to the remote machine. The info is printed on the
21820 @value{GDBN} standard output stream. The default is off.
21821 @item show debug remote
21822 Displays the state of display of remote packets.
21823 @item set debug serial
21824 Turns on or off display of @value{GDBN} serial debugging info. The
21826 @item show debug serial
21827 Displays the current state of displaying @value{GDBN} serial debugging
21829 @item set debug solib-frv
21830 @cindex FR-V shared-library debugging
21831 Turns on or off debugging messages for FR-V shared-library code.
21832 @item show debug solib-frv
21833 Display the current state of FR-V shared-library code debugging
21835 @item set debug target
21836 @cindex target debugging info
21837 Turns on or off display of @value{GDBN} target debugging info. This info
21838 includes what is going on at the target level of GDB, as it happens. The
21839 default is 0. Set it to 1 to track events, and to 2 to also track the
21840 value of large memory transfers. Changes to this flag do not take effect
21841 until the next time you connect to a target or use the @code{run} command.
21842 @item show debug target
21843 Displays the current state of displaying @value{GDBN} target debugging
21845 @item set debug timestamp
21846 @cindex timestampping debugging info
21847 Turns on or off display of timestamps with @value{GDBN} debugging info.
21848 When enabled, seconds and microseconds are displayed before each debugging
21850 @item show debug timestamp
21851 Displays the current state of displaying timestamps with @value{GDBN}
21853 @item set debugvarobj
21854 @cindex variable object debugging info
21855 Turns on or off display of @value{GDBN} variable object debugging
21856 info. The default is off.
21857 @item show debugvarobj
21858 Displays the current state of displaying @value{GDBN} variable object
21860 @item set debug xml
21861 @cindex XML parser debugging
21862 Turns on or off debugging messages for built-in XML parsers.
21863 @item show debug xml
21864 Displays the current state of XML debugging messages.
21867 @node Other Misc Settings
21868 @section Other Miscellaneous Settings
21869 @cindex miscellaneous settings
21872 @kindex set interactive-mode
21873 @item set interactive-mode
21874 If @code{on}, forces @value{GDBN} to assume that GDB was started
21875 in a terminal. In practice, this means that @value{GDBN} should wait
21876 for the user to answer queries generated by commands entered at
21877 the command prompt. If @code{off}, forces @value{GDBN} to operate
21878 in the opposite mode, and it uses the default answers to all queries.
21879 If @code{auto} (the default), @value{GDBN} tries to determine whether
21880 its standard input is a terminal, and works in interactive-mode if it
21881 is, non-interactively otherwise.
21883 In the vast majority of cases, the debugger should be able to guess
21884 correctly which mode should be used. But this setting can be useful
21885 in certain specific cases, such as running a MinGW @value{GDBN}
21886 inside a cygwin window.
21888 @kindex show interactive-mode
21889 @item show interactive-mode
21890 Displays whether the debugger is operating in interactive mode or not.
21893 @node Extending GDB
21894 @chapter Extending @value{GDBN}
21895 @cindex extending GDB
21897 @value{GDBN} provides three mechanisms for extension. The first is based
21898 on composition of @value{GDBN} commands, the second is based on the
21899 Python scripting language, and the third is for defining new aliases of
21902 To facilitate the use of the first two extensions, @value{GDBN} is capable
21903 of evaluating the contents of a file. When doing so, @value{GDBN}
21904 can recognize which scripting language is being used by looking at
21905 the filename extension. Files with an unrecognized filename extension
21906 are always treated as a @value{GDBN} Command Files.
21907 @xref{Command Files,, Command files}.
21909 You can control how @value{GDBN} evaluates these files with the following
21913 @kindex set script-extension
21914 @kindex show script-extension
21915 @item set script-extension off
21916 All scripts are always evaluated as @value{GDBN} Command Files.
21918 @item set script-extension soft
21919 The debugger determines the scripting language based on filename
21920 extension. If this scripting language is supported, @value{GDBN}
21921 evaluates the script using that language. Otherwise, it evaluates
21922 the file as a @value{GDBN} Command File.
21924 @item set script-extension strict
21925 The debugger determines the scripting language based on filename
21926 extension, and evaluates the script using that language. If the
21927 language is not supported, then the evaluation fails.
21929 @item show script-extension
21930 Display the current value of the @code{script-extension} option.
21935 * Sequences:: Canned Sequences of Commands
21936 * Python:: Scripting @value{GDBN} using Python
21937 * Aliases:: Creating new spellings of existing commands
21941 @section Canned Sequences of Commands
21943 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
21944 Command Lists}), @value{GDBN} provides two ways to store sequences of
21945 commands for execution as a unit: user-defined commands and command
21949 * Define:: How to define your own commands
21950 * Hooks:: Hooks for user-defined commands
21951 * Command Files:: How to write scripts of commands to be stored in a file
21952 * Output:: Commands for controlled output
21956 @subsection User-defined Commands
21958 @cindex user-defined command
21959 @cindex arguments, to user-defined commands
21960 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
21961 which you assign a new name as a command. This is done with the
21962 @code{define} command. User commands may accept up to 10 arguments
21963 separated by whitespace. Arguments are accessed within the user command
21964 via @code{$arg0@dots{}$arg9}. A trivial example:
21968 print $arg0 + $arg1 + $arg2
21973 To execute the command use:
21980 This defines the command @code{adder}, which prints the sum of
21981 its three arguments. Note the arguments are text substitutions, so they may
21982 reference variables, use complex expressions, or even perform inferior
21985 @cindex argument count in user-defined commands
21986 @cindex how many arguments (user-defined commands)
21987 In addition, @code{$argc} may be used to find out how many arguments have
21988 been passed. This expands to a number in the range 0@dots{}10.
21993 print $arg0 + $arg1
21996 print $arg0 + $arg1 + $arg2
22004 @item define @var{commandname}
22005 Define a command named @var{commandname}. If there is already a command
22006 by that name, you are asked to confirm that you want to redefine it.
22007 @var{commandname} may be a bare command name consisting of letters,
22008 numbers, dashes, and underscores. It may also start with any predefined
22009 prefix command. For example, @samp{define target my-target} creates
22010 a user-defined @samp{target my-target} command.
22012 The definition of the command is made up of other @value{GDBN} command lines,
22013 which are given following the @code{define} command. The end of these
22014 commands is marked by a line containing @code{end}.
22017 @kindex end@r{ (user-defined commands)}
22018 @item document @var{commandname}
22019 Document the user-defined command @var{commandname}, so that it can be
22020 accessed by @code{help}. The command @var{commandname} must already be
22021 defined. This command reads lines of documentation just as @code{define}
22022 reads the lines of the command definition, ending with @code{end}.
22023 After the @code{document} command is finished, @code{help} on command
22024 @var{commandname} displays the documentation you have written.
22026 You may use the @code{document} command again to change the
22027 documentation of a command. Redefining the command with @code{define}
22028 does not change the documentation.
22030 @kindex dont-repeat
22031 @cindex don't repeat command
22033 Used inside a user-defined command, this tells @value{GDBN} that this
22034 command should not be repeated when the user hits @key{RET}
22035 (@pxref{Command Syntax, repeat last command}).
22037 @kindex help user-defined
22038 @item help user-defined
22039 List all user-defined commands and all python commands defined in class
22040 COMAND_USER. The first line of the documentation or docstring is
22045 @itemx show user @var{commandname}
22046 Display the @value{GDBN} commands used to define @var{commandname} (but
22047 not its documentation). If no @var{commandname} is given, display the
22048 definitions for all user-defined commands.
22049 This does not work for user-defined python commands.
22051 @cindex infinite recursion in user-defined commands
22052 @kindex show max-user-call-depth
22053 @kindex set max-user-call-depth
22054 @item show max-user-call-depth
22055 @itemx set max-user-call-depth
22056 The value of @code{max-user-call-depth} controls how many recursion
22057 levels are allowed in user-defined commands before @value{GDBN} suspects an
22058 infinite recursion and aborts the command.
22059 This does not apply to user-defined python commands.
22062 In addition to the above commands, user-defined commands frequently
22063 use control flow commands, described in @ref{Command Files}.
22065 When user-defined commands are executed, the
22066 commands of the definition are not printed. An error in any command
22067 stops execution of the user-defined command.
22069 If used interactively, commands that would ask for confirmation proceed
22070 without asking when used inside a user-defined command. Many @value{GDBN}
22071 commands that normally print messages to say what they are doing omit the
22072 messages when used in a user-defined command.
22075 @subsection User-defined Command Hooks
22076 @cindex command hooks
22077 @cindex hooks, for commands
22078 @cindex hooks, pre-command
22081 You may define @dfn{hooks}, which are a special kind of user-defined
22082 command. Whenever you run the command @samp{foo}, if the user-defined
22083 command @samp{hook-foo} exists, it is executed (with no arguments)
22084 before that command.
22086 @cindex hooks, post-command
22088 A hook may also be defined which is run after the command you executed.
22089 Whenever you run the command @samp{foo}, if the user-defined command
22090 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22091 that command. Post-execution hooks may exist simultaneously with
22092 pre-execution hooks, for the same command.
22094 It is valid for a hook to call the command which it hooks. If this
22095 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22097 @c It would be nice if hookpost could be passed a parameter indicating
22098 @c if the command it hooks executed properly or not. FIXME!
22100 @kindex stop@r{, a pseudo-command}
22101 In addition, a pseudo-command, @samp{stop} exists. Defining
22102 (@samp{hook-stop}) makes the associated commands execute every time
22103 execution stops in your program: before breakpoint commands are run,
22104 displays are printed, or the stack frame is printed.
22106 For example, to ignore @code{SIGALRM} signals while
22107 single-stepping, but treat them normally during normal execution,
22112 handle SIGALRM nopass
22116 handle SIGALRM pass
22119 define hook-continue
22120 handle SIGALRM pass
22124 As a further example, to hook at the beginning and end of the @code{echo}
22125 command, and to add extra text to the beginning and end of the message,
22133 define hookpost-echo
22137 (@value{GDBP}) echo Hello World
22138 <<<---Hello World--->>>
22143 You can define a hook for any single-word command in @value{GDBN}, but
22144 not for command aliases; you should define a hook for the basic command
22145 name, e.g.@: @code{backtrace} rather than @code{bt}.
22146 @c FIXME! So how does Joe User discover whether a command is an alias
22148 You can hook a multi-word command by adding @code{hook-} or
22149 @code{hookpost-} to the last word of the command, e.g.@:
22150 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22152 If an error occurs during the execution of your hook, execution of
22153 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22154 (before the command that you actually typed had a chance to run).
22156 If you try to define a hook which does not match any known command, you
22157 get a warning from the @code{define} command.
22159 @node Command Files
22160 @subsection Command Files
22162 @cindex command files
22163 @cindex scripting commands
22164 A command file for @value{GDBN} is a text file made of lines that are
22165 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22166 also be included. An empty line in a command file does nothing; it
22167 does not mean to repeat the last command, as it would from the
22170 You can request the execution of a command file with the @code{source}
22171 command. Note that the @code{source} command is also used to evaluate
22172 scripts that are not Command Files. The exact behavior can be configured
22173 using the @code{script-extension} setting.
22174 @xref{Extending GDB,, Extending GDB}.
22178 @cindex execute commands from a file
22179 @item source [-s] [-v] @var{filename}
22180 Execute the command file @var{filename}.
22183 The lines in a command file are generally executed sequentially,
22184 unless the order of execution is changed by one of the
22185 @emph{flow-control commands} described below. The commands are not
22186 printed as they are executed. An error in any command terminates
22187 execution of the command file and control is returned to the console.
22189 @value{GDBN} first searches for @var{filename} in the current directory.
22190 If the file is not found there, and @var{filename} does not specify a
22191 directory, then @value{GDBN} also looks for the file on the source search path
22192 (specified with the @samp{directory} command);
22193 except that @file{$cdir} is not searched because the compilation directory
22194 is not relevant to scripts.
22196 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22197 on the search path even if @var{filename} specifies a directory.
22198 The search is done by appending @var{filename} to each element of the
22199 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22200 and the search path contains @file{/home/user} then @value{GDBN} will
22201 look for the script @file{/home/user/mylib/myscript}.
22202 The search is also done if @var{filename} is an absolute path.
22203 For example, if @var{filename} is @file{/tmp/myscript} and
22204 the search path contains @file{/home/user} then @value{GDBN} will
22205 look for the script @file{/home/user/tmp/myscript}.
22206 For DOS-like systems, if @var{filename} contains a drive specification,
22207 it is stripped before concatenation. For example, if @var{filename} is
22208 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22209 will look for the script @file{c:/tmp/myscript}.
22211 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22212 each command as it is executed. The option must be given before
22213 @var{filename}, and is interpreted as part of the filename anywhere else.
22215 Commands that would ask for confirmation if used interactively proceed
22216 without asking when used in a command file. Many @value{GDBN} commands that
22217 normally print messages to say what they are doing omit the messages
22218 when called from command files.
22220 @value{GDBN} also accepts command input from standard input. In this
22221 mode, normal output goes to standard output and error output goes to
22222 standard error. Errors in a command file supplied on standard input do
22223 not terminate execution of the command file---execution continues with
22227 gdb < cmds > log 2>&1
22230 (The syntax above will vary depending on the shell used.) This example
22231 will execute commands from the file @file{cmds}. All output and errors
22232 would be directed to @file{log}.
22234 Since commands stored on command files tend to be more general than
22235 commands typed interactively, they frequently need to deal with
22236 complicated situations, such as different or unexpected values of
22237 variables and symbols, changes in how the program being debugged is
22238 built, etc. @value{GDBN} provides a set of flow-control commands to
22239 deal with these complexities. Using these commands, you can write
22240 complex scripts that loop over data structures, execute commands
22241 conditionally, etc.
22248 This command allows to include in your script conditionally executed
22249 commands. The @code{if} command takes a single argument, which is an
22250 expression to evaluate. It is followed by a series of commands that
22251 are executed only if the expression is true (its value is nonzero).
22252 There can then optionally be an @code{else} line, followed by a series
22253 of commands that are only executed if the expression was false. The
22254 end of the list is marked by a line containing @code{end}.
22258 This command allows to write loops. Its syntax is similar to
22259 @code{if}: the command takes a single argument, which is an expression
22260 to evaluate, and must be followed by the commands to execute, one per
22261 line, terminated by an @code{end}. These commands are called the
22262 @dfn{body} of the loop. The commands in the body of @code{while} are
22263 executed repeatedly as long as the expression evaluates to true.
22267 This command exits the @code{while} loop in whose body it is included.
22268 Execution of the script continues after that @code{while}s @code{end}
22271 @kindex loop_continue
22272 @item loop_continue
22273 This command skips the execution of the rest of the body of commands
22274 in the @code{while} loop in whose body it is included. Execution
22275 branches to the beginning of the @code{while} loop, where it evaluates
22276 the controlling expression.
22278 @kindex end@r{ (if/else/while commands)}
22280 Terminate the block of commands that are the body of @code{if},
22281 @code{else}, or @code{while} flow-control commands.
22286 @subsection Commands for Controlled Output
22288 During the execution of a command file or a user-defined command, normal
22289 @value{GDBN} output is suppressed; the only output that appears is what is
22290 explicitly printed by the commands in the definition. This section
22291 describes three commands useful for generating exactly the output you
22296 @item echo @var{text}
22297 @c I do not consider backslash-space a standard C escape sequence
22298 @c because it is not in ANSI.
22299 Print @var{text}. Nonprinting characters can be included in
22300 @var{text} using C escape sequences, such as @samp{\n} to print a
22301 newline. @strong{No newline is printed unless you specify one.}
22302 In addition to the standard C escape sequences, a backslash followed
22303 by a space stands for a space. This is useful for displaying a
22304 string with spaces at the beginning or the end, since leading and
22305 trailing spaces are otherwise trimmed from all arguments.
22306 To print @samp{@w{ }and foo =@w{ }}, use the command
22307 @samp{echo \@w{ }and foo = \@w{ }}.
22309 A backslash at the end of @var{text} can be used, as in C, to continue
22310 the command onto subsequent lines. For example,
22313 echo This is some text\n\
22314 which is continued\n\
22315 onto several lines.\n
22318 produces the same output as
22321 echo This is some text\n
22322 echo which is continued\n
22323 echo onto several lines.\n
22327 @item output @var{expression}
22328 Print the value of @var{expression} and nothing but that value: no
22329 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22330 value history either. @xref{Expressions, ,Expressions}, for more information
22333 @item output/@var{fmt} @var{expression}
22334 Print the value of @var{expression} in format @var{fmt}. You can use
22335 the same formats as for @code{print}. @xref{Output Formats,,Output
22336 Formats}, for more information.
22339 @item printf @var{template}, @var{expressions}@dots{}
22340 Print the values of one or more @var{expressions} under the control of
22341 the string @var{template}. To print several values, make
22342 @var{expressions} be a comma-separated list of individual expressions,
22343 which may be either numbers or pointers. Their values are printed as
22344 specified by @var{template}, exactly as a C program would do by
22345 executing the code below:
22348 printf (@var{template}, @var{expressions}@dots{});
22351 As in @code{C} @code{printf}, ordinary characters in @var{template}
22352 are printed verbatim, while @dfn{conversion specification} introduced
22353 by the @samp{%} character cause subsequent @var{expressions} to be
22354 evaluated, their values converted and formatted according to type and
22355 style information encoded in the conversion specifications, and then
22358 For example, you can print two values in hex like this:
22361 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22364 @code{printf} supports all the standard @code{C} conversion
22365 specifications, including the flags and modifiers between the @samp{%}
22366 character and the conversion letter, with the following exceptions:
22370 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22373 The modifier @samp{*} is not supported for specifying precision or
22377 The @samp{'} flag (for separation of digits into groups according to
22378 @code{LC_NUMERIC'}) is not supported.
22381 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22385 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22388 The conversion letters @samp{a} and @samp{A} are not supported.
22392 Note that the @samp{ll} type modifier is supported only if the
22393 underlying @code{C} implementation used to build @value{GDBN} supports
22394 the @code{long long int} type, and the @samp{L} type modifier is
22395 supported only if @code{long double} type is available.
22397 As in @code{C}, @code{printf} supports simple backslash-escape
22398 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22399 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22400 single character. Octal and hexadecimal escape sequences are not
22403 Additionally, @code{printf} supports conversion specifications for DFP
22404 (@dfn{Decimal Floating Point}) types using the following length modifiers
22405 together with a floating point specifier.
22410 @samp{H} for printing @code{Decimal32} types.
22413 @samp{D} for printing @code{Decimal64} types.
22416 @samp{DD} for printing @code{Decimal128} types.
22419 If the underlying @code{C} implementation used to build @value{GDBN} has
22420 support for the three length modifiers for DFP types, other modifiers
22421 such as width and precision will also be available for @value{GDBN} to use.
22423 In case there is no such @code{C} support, no additional modifiers will be
22424 available and the value will be printed in the standard way.
22426 Here's an example of printing DFP types using the above conversion letters:
22428 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22432 @item eval @var{template}, @var{expressions}@dots{}
22433 Convert the values of one or more @var{expressions} under the control of
22434 the string @var{template} to a command line, and call it.
22439 @section Scripting @value{GDBN} using Python
22440 @cindex python scripting
22441 @cindex scripting with python
22443 You can script @value{GDBN} using the @uref{http://www.python.org/,
22444 Python programming language}. This feature is available only if
22445 @value{GDBN} was configured using @option{--with-python}.
22447 @cindex python directory
22448 Python scripts used by @value{GDBN} should be installed in
22449 @file{@var{data-directory}/python}, where @var{data-directory} is
22450 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22451 This directory, known as the @dfn{python directory},
22452 is automatically added to the Python Search Path in order to allow
22453 the Python interpreter to locate all scripts installed at this location.
22455 Additionally, @value{GDBN} commands and convenience functions which
22456 are written in Python and are located in the
22457 @file{@var{data-directory}/python/gdb/command} or
22458 @file{@var{data-directory}/python/gdb/function} directories are
22459 automatically imported when @value{GDBN} starts.
22462 * Python Commands:: Accessing Python from @value{GDBN}.
22463 * Python API:: Accessing @value{GDBN} from Python.
22464 * Python Auto-loading:: Automatically loading Python code.
22465 * Python modules:: Python modules provided by @value{GDBN}.
22468 @node Python Commands
22469 @subsection Python Commands
22470 @cindex python commands
22471 @cindex commands to access python
22473 @value{GDBN} provides one command for accessing the Python interpreter,
22474 and one related setting:
22478 @item python @r{[}@var{code}@r{]}
22479 The @code{python} command can be used to evaluate Python code.
22481 If given an argument, the @code{python} command will evaluate the
22482 argument as a Python command. For example:
22485 (@value{GDBP}) python print 23
22489 If you do not provide an argument to @code{python}, it will act as a
22490 multi-line command, like @code{define}. In this case, the Python
22491 script is made up of subsequent command lines, given after the
22492 @code{python} command. This command list is terminated using a line
22493 containing @code{end}. For example:
22496 (@value{GDBP}) python
22498 End with a line saying just "end".
22504 @kindex set python print-stack
22505 @item set python print-stack
22506 By default, @value{GDBN} will print only the message component of a
22507 Python exception when an error occurs in a Python script. This can be
22508 controlled using @code{set python print-stack}: if @code{full}, then
22509 full Python stack printing is enabled; if @code{none}, then Python stack
22510 and message printing is disabled; if @code{message}, the default, only
22511 the message component of the error is printed.
22514 It is also possible to execute a Python script from the @value{GDBN}
22518 @item source @file{script-name}
22519 The script name must end with @samp{.py} and @value{GDBN} must be configured
22520 to recognize the script language based on filename extension using
22521 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22523 @item python execfile ("script-name")
22524 This method is based on the @code{execfile} Python built-in function,
22525 and thus is always available.
22529 @subsection Python API
22531 @cindex programming in python
22533 @cindex python stdout
22534 @cindex python pagination
22535 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22536 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22537 A Python program which outputs to one of these streams may have its
22538 output interrupted by the user (@pxref{Screen Size}). In this
22539 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22542 * Basic Python:: Basic Python Functions.
22543 * Exception Handling:: How Python exceptions are translated.
22544 * Values From Inferior:: Python representation of values.
22545 * Types In Python:: Python representation of types.
22546 * Pretty Printing API:: Pretty-printing values.
22547 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22548 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22549 * Inferiors In Python:: Python representation of inferiors (processes)
22550 * Events In Python:: Listening for events from @value{GDBN}.
22551 * Threads In Python:: Accessing inferior threads from Python.
22552 * Commands In Python:: Implementing new commands in Python.
22553 * Parameters In Python:: Adding new @value{GDBN} parameters.
22554 * Functions In Python:: Writing new convenience functions.
22555 * Progspaces In Python:: Program spaces.
22556 * Objfiles In Python:: Object files.
22557 * Frames In Python:: Accessing inferior stack frames from Python.
22558 * Blocks In Python:: Accessing frame blocks from Python.
22559 * Symbols In Python:: Python representation of symbols.
22560 * Symbol Tables In Python:: Python representation of symbol tables.
22561 * Lazy Strings In Python:: Python representation of lazy strings.
22562 * Breakpoints In Python:: Manipulating breakpoints using Python.
22563 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22568 @subsubsection Basic Python
22570 @cindex python functions
22571 @cindex python module
22573 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22574 methods and classes added by @value{GDBN} are placed in this module.
22575 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22576 use in all scripts evaluated by the @code{python} command.
22578 @findex gdb.PYTHONDIR
22579 @defvar gdb.PYTHONDIR
22580 A string containing the python directory (@pxref{Python}).
22583 @findex gdb.execute
22584 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
22585 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
22586 If a GDB exception happens while @var{command} runs, it is
22587 translated as described in @ref{Exception Handling,,Exception Handling}.
22589 @var{from_tty} specifies whether @value{GDBN} ought to consider this
22590 command as having originated from the user invoking it interactively.
22591 It must be a boolean value. If omitted, it defaults to @code{False}.
22593 By default, any output produced by @var{command} is sent to
22594 @value{GDBN}'s standard output. If the @var{to_string} parameter is
22595 @code{True}, then output will be collected by @code{gdb.execute} and
22596 returned as a string. The default is @code{False}, in which case the
22597 return value is @code{None}. If @var{to_string} is @code{True}, the
22598 @value{GDBN} virtual terminal will be temporarily set to unlimited width
22599 and height, and its pagination will be disabled; @pxref{Screen Size}.
22602 @findex gdb.breakpoints
22603 @defun gdb.breakpoints ()
22604 Return a sequence holding all of @value{GDBN}'s breakpoints.
22605 @xref{Breakpoints In Python}, for more information.
22608 @findex gdb.parameter
22609 @defun gdb.parameter (parameter)
22610 Return the value of a @value{GDBN} parameter. @var{parameter} is a
22611 string naming the parameter to look up; @var{parameter} may contain
22612 spaces if the parameter has a multi-part name. For example,
22613 @samp{print object} is a valid parameter name.
22615 If the named parameter does not exist, this function throws a
22616 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
22617 parameter's value is converted to a Python value of the appropriate
22618 type, and returned.
22621 @findex gdb.history
22622 @defun gdb.history (number)
22623 Return a value from @value{GDBN}'s value history (@pxref{Value
22624 History}). @var{number} indicates which history element to return.
22625 If @var{number} is negative, then @value{GDBN} will take its absolute value
22626 and count backward from the last element (i.e., the most recent element) to
22627 find the value to return. If @var{number} is zero, then @value{GDBN} will
22628 return the most recent element. If the element specified by @var{number}
22629 doesn't exist in the value history, a @code{gdb.error} exception will be
22632 If no exception is raised, the return value is always an instance of
22633 @code{gdb.Value} (@pxref{Values From Inferior}).
22636 @findex gdb.parse_and_eval
22637 @defun gdb.parse_and_eval (expression)
22638 Parse @var{expression} as an expression in the current language,
22639 evaluate it, and return the result as a @code{gdb.Value}.
22640 @var{expression} must be a string.
22642 This function can be useful when implementing a new command
22643 (@pxref{Commands In Python}), as it provides a way to parse the
22644 command's argument as an expression. It is also useful simply to
22645 compute values, for example, it is the only way to get the value of a
22646 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
22649 @findex gdb.find_pc_line
22650 @defun gdb.find_pc_line (pc)
22651 Return the @code{gdb.Symtab_and_line} object corresponding to the
22652 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
22653 value of @var{pc} is passed as an argument, then the @code{symtab} and
22654 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
22655 will be @code{None} and 0 respectively.
22658 @findex gdb.post_event
22659 @defun gdb.post_event (event)
22660 Put @var{event}, a callable object taking no arguments, into
22661 @value{GDBN}'s internal event queue. This callable will be invoked at
22662 some later point, during @value{GDBN}'s event processing. Events
22663 posted using @code{post_event} will be run in the order in which they
22664 were posted; however, there is no way to know when they will be
22665 processed relative to other events inside @value{GDBN}.
22667 @value{GDBN} is not thread-safe. If your Python program uses multiple
22668 threads, you must be careful to only call @value{GDBN}-specific
22669 functions in the main @value{GDBN} thread. @code{post_event} ensures
22673 (@value{GDBP}) python
22677 > def __init__(self, message):
22678 > self.message = message;
22679 > def __call__(self):
22680 > gdb.write(self.message)
22682 >class MyThread1 (threading.Thread):
22684 > gdb.post_event(Writer("Hello "))
22686 >class MyThread2 (threading.Thread):
22688 > gdb.post_event(Writer("World\n"))
22690 >MyThread1().start()
22691 >MyThread2().start()
22693 (@value{GDBP}) Hello World
22698 @defun gdb.write (string @r{[}, stream{]})
22699 Print a string to @value{GDBN}'s paginated output stream. The
22700 optional @var{stream} determines the stream to print to. The default
22701 stream is @value{GDBN}'s standard output stream. Possible stream
22708 @value{GDBN}'s standard output stream.
22713 @value{GDBN}'s standard error stream.
22718 @value{GDBN}'s log stream (@pxref{Logging Output}).
22721 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
22722 call this function and will automatically direct the output to the
22727 @defun gdb.flush ()
22728 Flush the buffer of a @value{GDBN} paginated stream so that the
22729 contents are displayed immediately. @value{GDBN} will flush the
22730 contents of a stream automatically when it encounters a newline in the
22731 buffer. The optional @var{stream} determines the stream to flush. The
22732 default stream is @value{GDBN}'s standard output stream. Possible
22739 @value{GDBN}'s standard output stream.
22744 @value{GDBN}'s standard error stream.
22749 @value{GDBN}'s log stream (@pxref{Logging Output}).
22753 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
22754 call this function for the relevant stream.
22757 @findex gdb.target_charset
22758 @defun gdb.target_charset ()
22759 Return the name of the current target character set (@pxref{Character
22760 Sets}). This differs from @code{gdb.parameter('target-charset')} in
22761 that @samp{auto} is never returned.
22764 @findex gdb.target_wide_charset
22765 @defun gdb.target_wide_charset ()
22766 Return the name of the current target wide character set
22767 (@pxref{Character Sets}). This differs from
22768 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
22772 @findex gdb.solib_name
22773 @defun gdb.solib_name (address)
22774 Return the name of the shared library holding the given @var{address}
22775 as a string, or @code{None}.
22778 @findex gdb.decode_line
22779 @defun gdb.decode_line @r{[}expression@r{]}
22780 Return locations of the line specified by @var{expression}, or of the
22781 current line if no argument was given. This function returns a Python
22782 tuple containing two elements. The first element contains a string
22783 holding any unparsed section of @var{expression} (or @code{None} if
22784 the expression has been fully parsed). The second element contains
22785 either @code{None} or another tuple that contains all the locations
22786 that match the expression represented as @code{gdb.Symtab_and_line}
22787 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
22788 provided, it is decoded the way that @value{GDBN}'s inbuilt
22789 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
22792 @defun gdb.prompt_hook (current_prompt)
22793 @anchor{prompt_hook}
22795 If @var{prompt_hook} is callable, @value{GDBN} will call the method
22796 assigned to this operation before a prompt is displayed by
22799 The parameter @code{current_prompt} contains the current @value{GDBN}
22800 prompt. This method must return a Python string, or @code{None}. If
22801 a string is returned, the @value{GDBN} prompt will be set to that
22802 string. If @code{None} is returned, @value{GDBN} will continue to use
22803 the current prompt.
22805 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
22806 such as those used by readline for command input, and annotation
22807 related prompts are prohibited from being changed.
22810 @node Exception Handling
22811 @subsubsection Exception Handling
22812 @cindex python exceptions
22813 @cindex exceptions, python
22815 When executing the @code{python} command, Python exceptions
22816 uncaught within the Python code are translated to calls to
22817 @value{GDBN} error-reporting mechanism. If the command that called
22818 @code{python} does not handle the error, @value{GDBN} will
22819 terminate it and print an error message containing the Python
22820 exception name, the associated value, and the Python call stack
22821 backtrace at the point where the exception was raised. Example:
22824 (@value{GDBP}) python print foo
22825 Traceback (most recent call last):
22826 File "<string>", line 1, in <module>
22827 NameError: name 'foo' is not defined
22830 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
22831 Python code are converted to Python exceptions. The type of the
22832 Python exception depends on the error.
22836 This is the base class for most exceptions generated by @value{GDBN}.
22837 It is derived from @code{RuntimeError}, for compatibility with earlier
22838 versions of @value{GDBN}.
22840 If an error occurring in @value{GDBN} does not fit into some more
22841 specific category, then the generated exception will have this type.
22843 @item gdb.MemoryError
22844 This is a subclass of @code{gdb.error} which is thrown when an
22845 operation tried to access invalid memory in the inferior.
22847 @item KeyboardInterrupt
22848 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
22849 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
22852 In all cases, your exception handler will see the @value{GDBN} error
22853 message as its value and the Python call stack backtrace at the Python
22854 statement closest to where the @value{GDBN} error occured as the
22857 @findex gdb.GdbError
22858 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
22859 it is useful to be able to throw an exception that doesn't cause a
22860 traceback to be printed. For example, the user may have invoked the
22861 command incorrectly. Use the @code{gdb.GdbError} exception
22862 to handle this case. Example:
22866 >class HelloWorld (gdb.Command):
22867 > """Greet the whole world."""
22868 > def __init__ (self):
22869 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
22870 > def invoke (self, args, from_tty):
22871 > argv = gdb.string_to_argv (args)
22872 > if len (argv) != 0:
22873 > raise gdb.GdbError ("hello-world takes no arguments")
22874 > print "Hello, World!"
22877 (gdb) hello-world 42
22878 hello-world takes no arguments
22881 @node Values From Inferior
22882 @subsubsection Values From Inferior
22883 @cindex values from inferior, with Python
22884 @cindex python, working with values from inferior
22886 @cindex @code{gdb.Value}
22887 @value{GDBN} provides values it obtains from the inferior program in
22888 an object of type @code{gdb.Value}. @value{GDBN} uses this object
22889 for its internal bookkeeping of the inferior's values, and for
22890 fetching values when necessary.
22892 Inferior values that are simple scalars can be used directly in
22893 Python expressions that are valid for the value's data type. Here's
22894 an example for an integer or floating-point value @code{some_val}:
22901 As result of this, @code{bar} will also be a @code{gdb.Value} object
22902 whose values are of the same type as those of @code{some_val}.
22904 Inferior values that are structures or instances of some class can
22905 be accessed using the Python @dfn{dictionary syntax}. For example, if
22906 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
22907 can access its @code{foo} element with:
22910 bar = some_val['foo']
22913 Again, @code{bar} will also be a @code{gdb.Value} object.
22915 A @code{gdb.Value} that represents a function can be executed via
22916 inferior function call. Any arguments provided to the call must match
22917 the function's prototype, and must be provided in the order specified
22920 For example, @code{some_val} is a @code{gdb.Value} instance
22921 representing a function that takes two integers as arguments. To
22922 execute this function, call it like so:
22925 result = some_val (10,20)
22928 Any values returned from a function call will be stored as a
22931 The following attributes are provided:
22934 @defvar Value.address
22935 If this object is addressable, this read-only attribute holds a
22936 @code{gdb.Value} object representing the address. Otherwise,
22937 this attribute holds @code{None}.
22940 @cindex optimized out value in Python
22941 @defvar Value.is_optimized_out
22942 This read-only boolean attribute is true if the compiler optimized out
22943 this value, thus it is not available for fetching from the inferior.
22947 The type of this @code{gdb.Value}. The value of this attribute is a
22948 @code{gdb.Type} object (@pxref{Types In Python}).
22951 @defvar Value.dynamic_type
22952 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
22953 type information (@acronym{RTTI}) to determine the dynamic type of the
22954 value. If this value is of class type, it will return the class in
22955 which the value is embedded, if any. If this value is of pointer or
22956 reference to a class type, it will compute the dynamic type of the
22957 referenced object, and return a pointer or reference to that type,
22958 respectively. In all other cases, it will return the value's static
22961 Note that this feature will only work when debugging a C@t{++} program
22962 that includes @acronym{RTTI} for the object in question. Otherwise,
22963 it will just return the static type of the value as in @kbd{ptype foo}
22964 (@pxref{Symbols, ptype}).
22967 @defvar Value.is_lazy
22968 The value of this read-only boolean attribute is @code{True} if this
22969 @code{gdb.Value} has not yet been fetched from the inferior.
22970 @value{GDBN} does not fetch values until necessary, for efficiency.
22974 myval = gdb.parse_and_eval ('somevar')
22977 The value of @code{somevar} is not fetched at this time. It will be
22978 fetched when the value is needed, or when the @code{fetch_lazy}
22983 The following methods are provided:
22986 @defun Value.__init__ (@var{val})
22987 Many Python values can be converted directly to a @code{gdb.Value} via
22988 this object initializer. Specifically:
22991 @item Python boolean
22992 A Python boolean is converted to the boolean type from the current
22995 @item Python integer
22996 A Python integer is converted to the C @code{long} type for the
22997 current architecture.
23000 A Python long is converted to the C @code{long long} type for the
23001 current architecture.
23004 A Python float is converted to the C @code{double} type for the
23005 current architecture.
23007 @item Python string
23008 A Python string is converted to a target string, using the current
23011 @item @code{gdb.Value}
23012 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23014 @item @code{gdb.LazyString}
23015 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23016 Python}), then the lazy string's @code{value} method is called, and
23017 its result is used.
23021 @defun Value.cast (type)
23022 Return a new instance of @code{gdb.Value} that is the result of
23023 casting this instance to the type described by @var{type}, which must
23024 be a @code{gdb.Type} object. If the cast cannot be performed for some
23025 reason, this method throws an exception.
23028 @defun Value.dereference ()
23029 For pointer data types, this method returns a new @code{gdb.Value} object
23030 whose contents is the object pointed to by the pointer. For example, if
23031 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23038 then you can use the corresponding @code{gdb.Value} to access what
23039 @code{foo} points to like this:
23042 bar = foo.dereference ()
23045 The result @code{bar} will be a @code{gdb.Value} object holding the
23046 value pointed to by @code{foo}.
23048 A similar function @code{Value.referenced_value} exists which also
23049 returns @code{gdb.Value} objects corresonding to the values pointed to
23050 by pointer values (and additionally, values referenced by reference
23051 values). However, the behavior of @code{Value.dereference}
23052 differs from @code{Value.referenced_value} by the fact that the
23053 behavior of @code{Value.dereference} is identical to applying the C
23054 unary operator @code{*} on a given value. For example, consider a
23055 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23059 typedef int *intptr;
23063 intptr &ptrref = ptr;
23066 Though @code{ptrref} is a reference value, one can apply the method
23067 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23068 to it and obtain a @code{gdb.Value} which is identical to that
23069 corresponding to @code{val}. However, if you apply the method
23070 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23071 object identical to that corresponding to @code{ptr}.
23074 py_ptrref = gdb.parse_and_eval ("ptrref")
23075 py_val = py_ptrref.dereference ()
23076 py_ptr = py_ptrref.referenced_value ()
23079 The @code{gdb.Value} object @code{py_val} is identical to that
23080 corresponding to @code{val}, and @code{py_ptr} is identical to that
23081 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23082 be applied whenever the C unary operator @code{*} can be applied
23083 to the corresponding C value. For those cases where applying both
23084 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23085 the results obtained need not be identical (as we have seen in the above
23086 example). The results are however identical when applied on
23087 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23088 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23091 @defun Value.referenced_value ()
23092 For pointer or reference data types, this method returns a new
23093 @code{gdb.Value} object corresponding to the value referenced by the
23094 pointer/reference value. For pointer data types,
23095 @code{Value.dereference} and @code{Value.referenced_value} produce
23096 identical results. The difference between these methods is that
23097 @code{Value.dereference} cannot get the values referenced by reference
23098 values. For example, consider a reference to an @code{int}, declared
23099 in your C@t{++} program as
23107 then applying @code{Value.dereference} to the @code{gdb.Value} object
23108 corresponding to @code{ref} will result in an error, while applying
23109 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23110 identical to that corresponding to @code{val}.
23113 py_ref = gdb.parse_and_eval ("ref")
23114 er_ref = py_ref.dereference () # Results in error
23115 py_val = py_ref.referenced_value () # Returns the referenced value
23118 The @code{gdb.Value} object @code{py_val} is identical to that
23119 corresponding to @code{val}.
23122 @defun Value.dynamic_cast (type)
23123 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23124 operator were used. Consult a C@t{++} reference for details.
23127 @defun Value.reinterpret_cast (type)
23128 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23129 operator were used. Consult a C@t{++} reference for details.
23132 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23133 If this @code{gdb.Value} represents a string, then this method
23134 converts the contents to a Python string. Otherwise, this method will
23135 throw an exception.
23137 Strings are recognized in a language-specific way; whether a given
23138 @code{gdb.Value} represents a string is determined by the current
23141 For C-like languages, a value is a string if it is a pointer to or an
23142 array of characters or ints. The string is assumed to be terminated
23143 by a zero of the appropriate width. However if the optional length
23144 argument is given, the string will be converted to that given length,
23145 ignoring any embedded zeros that the string may contain.
23147 If the optional @var{encoding} argument is given, it must be a string
23148 naming the encoding of the string in the @code{gdb.Value}, such as
23149 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23150 the same encodings as the corresponding argument to Python's
23151 @code{string.decode} method, and the Python codec machinery will be used
23152 to convert the string. If @var{encoding} is not given, or if
23153 @var{encoding} is the empty string, then either the @code{target-charset}
23154 (@pxref{Character Sets}) will be used, or a language-specific encoding
23155 will be used, if the current language is able to supply one.
23157 The optional @var{errors} argument is the same as the corresponding
23158 argument to Python's @code{string.decode} method.
23160 If the optional @var{length} argument is given, the string will be
23161 fetched and converted to the given length.
23164 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23165 If this @code{gdb.Value} represents a string, then this method
23166 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23167 In Python}). Otherwise, this method will throw an exception.
23169 If the optional @var{encoding} argument is given, it must be a string
23170 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23171 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23172 @var{encoding} argument is an encoding that @value{GDBN} does
23173 recognize, @value{GDBN} will raise an error.
23175 When a lazy string is printed, the @value{GDBN} encoding machinery is
23176 used to convert the string during printing. If the optional
23177 @var{encoding} argument is not provided, or is an empty string,
23178 @value{GDBN} will automatically select the encoding most suitable for
23179 the string type. For further information on encoding in @value{GDBN}
23180 please see @ref{Character Sets}.
23182 If the optional @var{length} argument is given, the string will be
23183 fetched and encoded to the length of characters specified. If
23184 the @var{length} argument is not provided, the string will be fetched
23185 and encoded until a null of appropriate width is found.
23188 @defun Value.fetch_lazy ()
23189 If the @code{gdb.Value} object is currently a lazy value
23190 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23191 fetched from the inferior. Any errors that occur in the process
23192 will produce a Python exception.
23194 If the @code{gdb.Value} object is not a lazy value, this method
23197 This method does not return a value.
23202 @node Types In Python
23203 @subsubsection Types In Python
23204 @cindex types in Python
23205 @cindex Python, working with types
23208 @value{GDBN} represents types from the inferior using the class
23211 The following type-related functions are available in the @code{gdb}
23214 @findex gdb.lookup_type
23215 @defun gdb.lookup_type (name @r{[}, block@r{]})
23216 This function looks up a type by name. @var{name} is the name of the
23217 type to look up. It must be a string.
23219 If @var{block} is given, then @var{name} is looked up in that scope.
23220 Otherwise, it is searched for globally.
23222 Ordinarily, this function will return an instance of @code{gdb.Type}.
23223 If the named type cannot be found, it will throw an exception.
23226 If the type is a structure or class type, or an enum type, the fields
23227 of that type can be accessed using the Python @dfn{dictionary syntax}.
23228 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23229 a structure type, you can access its @code{foo} field with:
23232 bar = some_type['foo']
23235 @code{bar} will be a @code{gdb.Field} object; see below under the
23236 description of the @code{Type.fields} method for a description of the
23237 @code{gdb.Field} class.
23239 An instance of @code{Type} has the following attributes:
23243 The type code for this type. The type code will be one of the
23244 @code{TYPE_CODE_} constants defined below.
23247 @defvar Type.sizeof
23248 The size of this type, in target @code{char} units. Usually, a
23249 target's @code{char} type will be an 8-bit byte. However, on some
23250 unusual platforms, this type may have a different size.
23254 The tag name for this type. The tag name is the name after
23255 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23256 languages have this concept. If this type has no tag name, then
23257 @code{None} is returned.
23261 The following methods are provided:
23264 @defun Type.fields ()
23265 For structure and union types, this method returns the fields. Range
23266 types have two fields, the minimum and maximum values. Enum types
23267 have one field per enum constant. Function and method types have one
23268 field per parameter. The base types of C@t{++} classes are also
23269 represented as fields. If the type has no fields, or does not fit
23270 into one of these categories, an empty sequence will be returned.
23272 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23275 This attribute is not available for @code{static} fields (as in
23276 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23277 position of the field. For @code{enum} fields, the value is the
23278 enumeration member's integer representation.
23281 The name of the field, or @code{None} for anonymous fields.
23284 This is @code{True} if the field is artificial, usually meaning that
23285 it was provided by the compiler and not the user. This attribute is
23286 always provided, and is @code{False} if the field is not artificial.
23288 @item is_base_class
23289 This is @code{True} if the field represents a base class of a C@t{++}
23290 structure. This attribute is always provided, and is @code{False}
23291 if the field is not a base class of the type that is the argument of
23292 @code{fields}, or if that type was not a C@t{++} class.
23295 If the field is packed, or is a bitfield, then this will have a
23296 non-zero value, which is the size of the field in bits. Otherwise,
23297 this will be zero; in this case the field's size is given by its type.
23300 The type of the field. This is usually an instance of @code{Type},
23301 but it can be @code{None} in some situations.
23305 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23306 Return a new @code{gdb.Type} object which represents an array of this
23307 type. If one argument is given, it is the inclusive upper bound of
23308 the array; in this case the lower bound is zero. If two arguments are
23309 given, the first argument is the lower bound of the array, and the
23310 second argument is the upper bound of the array. An array's length
23311 must not be negative, but the bounds can be.
23314 @defun Type.const ()
23315 Return a new @code{gdb.Type} object which represents a
23316 @code{const}-qualified variant of this type.
23319 @defun Type.volatile ()
23320 Return a new @code{gdb.Type} object which represents a
23321 @code{volatile}-qualified variant of this type.
23324 @defun Type.unqualified ()
23325 Return a new @code{gdb.Type} object which represents an unqualified
23326 variant of this type. That is, the result is neither @code{const} nor
23330 @defun Type.range ()
23331 Return a Python @code{Tuple} object that contains two elements: the
23332 low bound of the argument type and the high bound of that type. If
23333 the type does not have a range, @value{GDBN} will raise a
23334 @code{gdb.error} exception (@pxref{Exception Handling}).
23337 @defun Type.reference ()
23338 Return a new @code{gdb.Type} object which represents a reference to this
23342 @defun Type.pointer ()
23343 Return a new @code{gdb.Type} object which represents a pointer to this
23347 @defun Type.strip_typedefs ()
23348 Return a new @code{gdb.Type} that represents the real type,
23349 after removing all layers of typedefs.
23352 @defun Type.target ()
23353 Return a new @code{gdb.Type} object which represents the target type
23356 For a pointer type, the target type is the type of the pointed-to
23357 object. For an array type (meaning C-like arrays), the target type is
23358 the type of the elements of the array. For a function or method type,
23359 the target type is the type of the return value. For a complex type,
23360 the target type is the type of the elements. For a typedef, the
23361 target type is the aliased type.
23363 If the type does not have a target, this method will throw an
23367 @defun Type.template_argument (n @r{[}, block@r{]})
23368 If this @code{gdb.Type} is an instantiation of a template, this will
23369 return a new @code{gdb.Type} which represents the type of the
23370 @var{n}th template argument.
23372 If this @code{gdb.Type} is not a template type, this will throw an
23373 exception. Ordinarily, only C@t{++} code will have template types.
23375 If @var{block} is given, then @var{name} is looked up in that scope.
23376 Otherwise, it is searched for globally.
23381 Each type has a code, which indicates what category this type falls
23382 into. The available type categories are represented by constants
23383 defined in the @code{gdb} module:
23386 @findex TYPE_CODE_PTR
23387 @findex gdb.TYPE_CODE_PTR
23388 @item gdb.TYPE_CODE_PTR
23389 The type is a pointer.
23391 @findex TYPE_CODE_ARRAY
23392 @findex gdb.TYPE_CODE_ARRAY
23393 @item gdb.TYPE_CODE_ARRAY
23394 The type is an array.
23396 @findex TYPE_CODE_STRUCT
23397 @findex gdb.TYPE_CODE_STRUCT
23398 @item gdb.TYPE_CODE_STRUCT
23399 The type is a structure.
23401 @findex TYPE_CODE_UNION
23402 @findex gdb.TYPE_CODE_UNION
23403 @item gdb.TYPE_CODE_UNION
23404 The type is a union.
23406 @findex TYPE_CODE_ENUM
23407 @findex gdb.TYPE_CODE_ENUM
23408 @item gdb.TYPE_CODE_ENUM
23409 The type is an enum.
23411 @findex TYPE_CODE_FLAGS
23412 @findex gdb.TYPE_CODE_FLAGS
23413 @item gdb.TYPE_CODE_FLAGS
23414 A bit flags type, used for things such as status registers.
23416 @findex TYPE_CODE_FUNC
23417 @findex gdb.TYPE_CODE_FUNC
23418 @item gdb.TYPE_CODE_FUNC
23419 The type is a function.
23421 @findex TYPE_CODE_INT
23422 @findex gdb.TYPE_CODE_INT
23423 @item gdb.TYPE_CODE_INT
23424 The type is an integer type.
23426 @findex TYPE_CODE_FLT
23427 @findex gdb.TYPE_CODE_FLT
23428 @item gdb.TYPE_CODE_FLT
23429 A floating point type.
23431 @findex TYPE_CODE_VOID
23432 @findex gdb.TYPE_CODE_VOID
23433 @item gdb.TYPE_CODE_VOID
23434 The special type @code{void}.
23436 @findex TYPE_CODE_SET
23437 @findex gdb.TYPE_CODE_SET
23438 @item gdb.TYPE_CODE_SET
23441 @findex TYPE_CODE_RANGE
23442 @findex gdb.TYPE_CODE_RANGE
23443 @item gdb.TYPE_CODE_RANGE
23444 A range type, that is, an integer type with bounds.
23446 @findex TYPE_CODE_STRING
23447 @findex gdb.TYPE_CODE_STRING
23448 @item gdb.TYPE_CODE_STRING
23449 A string type. Note that this is only used for certain languages with
23450 language-defined string types; C strings are not represented this way.
23452 @findex TYPE_CODE_BITSTRING
23453 @findex gdb.TYPE_CODE_BITSTRING
23454 @item gdb.TYPE_CODE_BITSTRING
23457 @findex TYPE_CODE_ERROR
23458 @findex gdb.TYPE_CODE_ERROR
23459 @item gdb.TYPE_CODE_ERROR
23460 An unknown or erroneous type.
23462 @findex TYPE_CODE_METHOD
23463 @findex gdb.TYPE_CODE_METHOD
23464 @item gdb.TYPE_CODE_METHOD
23465 A method type, as found in C@t{++} or Java.
23467 @findex TYPE_CODE_METHODPTR
23468 @findex gdb.TYPE_CODE_METHODPTR
23469 @item gdb.TYPE_CODE_METHODPTR
23470 A pointer-to-member-function.
23472 @findex TYPE_CODE_MEMBERPTR
23473 @findex gdb.TYPE_CODE_MEMBERPTR
23474 @item gdb.TYPE_CODE_MEMBERPTR
23475 A pointer-to-member.
23477 @findex TYPE_CODE_REF
23478 @findex gdb.TYPE_CODE_REF
23479 @item gdb.TYPE_CODE_REF
23482 @findex TYPE_CODE_CHAR
23483 @findex gdb.TYPE_CODE_CHAR
23484 @item gdb.TYPE_CODE_CHAR
23487 @findex TYPE_CODE_BOOL
23488 @findex gdb.TYPE_CODE_BOOL
23489 @item gdb.TYPE_CODE_BOOL
23492 @findex TYPE_CODE_COMPLEX
23493 @findex gdb.TYPE_CODE_COMPLEX
23494 @item gdb.TYPE_CODE_COMPLEX
23495 A complex float type.
23497 @findex TYPE_CODE_TYPEDEF
23498 @findex gdb.TYPE_CODE_TYPEDEF
23499 @item gdb.TYPE_CODE_TYPEDEF
23500 A typedef to some other type.
23502 @findex TYPE_CODE_NAMESPACE
23503 @findex gdb.TYPE_CODE_NAMESPACE
23504 @item gdb.TYPE_CODE_NAMESPACE
23505 A C@t{++} namespace.
23507 @findex TYPE_CODE_DECFLOAT
23508 @findex gdb.TYPE_CODE_DECFLOAT
23509 @item gdb.TYPE_CODE_DECFLOAT
23510 A decimal floating point type.
23512 @findex TYPE_CODE_INTERNAL_FUNCTION
23513 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23514 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23515 A function internal to @value{GDBN}. This is the type used to represent
23516 convenience functions.
23519 Further support for types is provided in the @code{gdb.types}
23520 Python module (@pxref{gdb.types}).
23522 @node Pretty Printing API
23523 @subsubsection Pretty Printing API
23525 An example output is provided (@pxref{Pretty Printing}).
23527 A pretty-printer is just an object that holds a value and implements a
23528 specific interface, defined here.
23530 @defun pretty_printer.children (self)
23531 @value{GDBN} will call this method on a pretty-printer to compute the
23532 children of the pretty-printer's value.
23534 This method must return an object conforming to the Python iterator
23535 protocol. Each item returned by the iterator must be a tuple holding
23536 two elements. The first element is the ``name'' of the child; the
23537 second element is the child's value. The value can be any Python
23538 object which is convertible to a @value{GDBN} value.
23540 This method is optional. If it does not exist, @value{GDBN} will act
23541 as though the value has no children.
23544 @defun pretty_printer.display_hint (self)
23545 The CLI may call this method and use its result to change the
23546 formatting of a value. The result will also be supplied to an MI
23547 consumer as a @samp{displayhint} attribute of the variable being
23550 This method is optional. If it does exist, this method must return a
23553 Some display hints are predefined by @value{GDBN}:
23557 Indicate that the object being printed is ``array-like''. The CLI
23558 uses this to respect parameters such as @code{set print elements} and
23559 @code{set print array}.
23562 Indicate that the object being printed is ``map-like'', and that the
23563 children of this value can be assumed to alternate between keys and
23567 Indicate that the object being printed is ``string-like''. If the
23568 printer's @code{to_string} method returns a Python string of some
23569 kind, then @value{GDBN} will call its internal language-specific
23570 string-printing function to format the string. For the CLI this means
23571 adding quotation marks, possibly escaping some characters, respecting
23572 @code{set print elements}, and the like.
23576 @defun pretty_printer.to_string (self)
23577 @value{GDBN} will call this method to display the string
23578 representation of the value passed to the object's constructor.
23580 When printing from the CLI, if the @code{to_string} method exists,
23581 then @value{GDBN} will prepend its result to the values returned by
23582 @code{children}. Exactly how this formatting is done is dependent on
23583 the display hint, and may change as more hints are added. Also,
23584 depending on the print settings (@pxref{Print Settings}), the CLI may
23585 print just the result of @code{to_string} in a stack trace, omitting
23586 the result of @code{children}.
23588 If this method returns a string, it is printed verbatim.
23590 Otherwise, if this method returns an instance of @code{gdb.Value},
23591 then @value{GDBN} prints this value. This may result in a call to
23592 another pretty-printer.
23594 If instead the method returns a Python value which is convertible to a
23595 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
23596 the resulting value. Again, this may result in a call to another
23597 pretty-printer. Python scalars (integers, floats, and booleans) and
23598 strings are convertible to @code{gdb.Value}; other types are not.
23600 Finally, if this method returns @code{None} then no further operations
23601 are peformed in this method and nothing is printed.
23603 If the result is not one of these types, an exception is raised.
23606 @value{GDBN} provides a function which can be used to look up the
23607 default pretty-printer for a @code{gdb.Value}:
23609 @findex gdb.default_visualizer
23610 @defun gdb.default_visualizer (value)
23611 This function takes a @code{gdb.Value} object as an argument. If a
23612 pretty-printer for this value exists, then it is returned. If no such
23613 printer exists, then this returns @code{None}.
23616 @node Selecting Pretty-Printers
23617 @subsubsection Selecting Pretty-Printers
23619 The Python list @code{gdb.pretty_printers} contains an array of
23620 functions or callable objects that have been registered via addition
23621 as a pretty-printer. Printers in this list are called @code{global}
23622 printers, they're available when debugging all inferiors.
23623 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
23624 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
23627 Each function on these lists is passed a single @code{gdb.Value}
23628 argument and should return a pretty-printer object conforming to the
23629 interface definition above (@pxref{Pretty Printing API}). If a function
23630 cannot create a pretty-printer for the value, it should return
23633 @value{GDBN} first checks the @code{pretty_printers} attribute of each
23634 @code{gdb.Objfile} in the current program space and iteratively calls
23635 each enabled lookup routine in the list for that @code{gdb.Objfile}
23636 until it receives a pretty-printer object.
23637 If no pretty-printer is found in the objfile lists, @value{GDBN} then
23638 searches the pretty-printer list of the current program space,
23639 calling each enabled function until an object is returned.
23640 After these lists have been exhausted, it tries the global
23641 @code{gdb.pretty_printers} list, again calling each enabled function until an
23642 object is returned.
23644 The order in which the objfiles are searched is not specified. For a
23645 given list, functions are always invoked from the head of the list,
23646 and iterated over sequentially until the end of the list, or a printer
23647 object is returned.
23649 For various reasons a pretty-printer may not work.
23650 For example, the underlying data structure may have changed and
23651 the pretty-printer is out of date.
23653 The consequences of a broken pretty-printer are severe enough that
23654 @value{GDBN} provides support for enabling and disabling individual
23655 printers. For example, if @code{print frame-arguments} is on,
23656 a backtrace can become highly illegible if any argument is printed
23657 with a broken printer.
23659 Pretty-printers are enabled and disabled by attaching an @code{enabled}
23660 attribute to the registered function or callable object. If this attribute
23661 is present and its value is @code{False}, the printer is disabled, otherwise
23662 the printer is enabled.
23664 @node Writing a Pretty-Printer
23665 @subsubsection Writing a Pretty-Printer
23666 @cindex writing a pretty-printer
23668 A pretty-printer consists of two parts: a lookup function to detect
23669 if the type is supported, and the printer itself.
23671 Here is an example showing how a @code{std::string} printer might be
23672 written. @xref{Pretty Printing API}, for details on the API this class
23676 class StdStringPrinter(object):
23677 "Print a std::string"
23679 def __init__(self, val):
23682 def to_string(self):
23683 return self.val['_M_dataplus']['_M_p']
23685 def display_hint(self):
23689 And here is an example showing how a lookup function for the printer
23690 example above might be written.
23693 def str_lookup_function(val):
23694 lookup_tag = val.type.tag
23695 if lookup_tag == None:
23697 regex = re.compile("^std::basic_string<char,.*>$")
23698 if regex.match(lookup_tag):
23699 return StdStringPrinter(val)
23703 The example lookup function extracts the value's type, and attempts to
23704 match it to a type that it can pretty-print. If it is a type the
23705 printer can pretty-print, it will return a printer object. If not, it
23706 returns @code{None}.
23708 We recommend that you put your core pretty-printers into a Python
23709 package. If your pretty-printers are for use with a library, we
23710 further recommend embedding a version number into the package name.
23711 This practice will enable @value{GDBN} to load multiple versions of
23712 your pretty-printers at the same time, because they will have
23715 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
23716 can be evaluated multiple times without changing its meaning. An
23717 ideal auto-load file will consist solely of @code{import}s of your
23718 printer modules, followed by a call to a register pretty-printers with
23719 the current objfile.
23721 Taken as a whole, this approach will scale nicely to multiple
23722 inferiors, each potentially using a different library version.
23723 Embedding a version number in the Python package name will ensure that
23724 @value{GDBN} is able to load both sets of printers simultaneously.
23725 Then, because the search for pretty-printers is done by objfile, and
23726 because your auto-loaded code took care to register your library's
23727 printers with a specific objfile, @value{GDBN} will find the correct
23728 printers for the specific version of the library used by each
23731 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
23732 this code might appear in @code{gdb.libstdcxx.v6}:
23735 def register_printers(objfile):
23736 objfile.pretty_printers.append(str_lookup_function)
23740 And then the corresponding contents of the auto-load file would be:
23743 import gdb.libstdcxx.v6
23744 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
23747 The previous example illustrates a basic pretty-printer.
23748 There are a few things that can be improved on.
23749 The printer doesn't have a name, making it hard to identify in a
23750 list of installed printers. The lookup function has a name, but
23751 lookup functions can have arbitrary, even identical, names.
23753 Second, the printer only handles one type, whereas a library typically has
23754 several types. One could install a lookup function for each desired type
23755 in the library, but one could also have a single lookup function recognize
23756 several types. The latter is the conventional way this is handled.
23757 If a pretty-printer can handle multiple data types, then its
23758 @dfn{subprinters} are the printers for the individual data types.
23760 The @code{gdb.printing} module provides a formal way of solving these
23761 problems (@pxref{gdb.printing}).
23762 Here is another example that handles multiple types.
23764 These are the types we are going to pretty-print:
23767 struct foo @{ int a, b; @};
23768 struct bar @{ struct foo x, y; @};
23771 Here are the printers:
23775 """Print a foo object."""
23777 def __init__(self, val):
23780 def to_string(self):
23781 return ("a=<" + str(self.val["a"]) +
23782 "> b=<" + str(self.val["b"]) + ">")
23785 """Print a bar object."""
23787 def __init__(self, val):
23790 def to_string(self):
23791 return ("x=<" + str(self.val["x"]) +
23792 "> y=<" + str(self.val["y"]) + ">")
23795 This example doesn't need a lookup function, that is handled by the
23796 @code{gdb.printing} module. Instead a function is provided to build up
23797 the object that handles the lookup.
23800 import gdb.printing
23802 def build_pretty_printer():
23803 pp = gdb.printing.RegexpCollectionPrettyPrinter(
23805 pp.add_printer('foo', '^foo$', fooPrinter)
23806 pp.add_printer('bar', '^bar$', barPrinter)
23810 And here is the autoload support:
23813 import gdb.printing
23815 gdb.printing.register_pretty_printer(
23816 gdb.current_objfile(),
23817 my_library.build_pretty_printer())
23820 Finally, when this printer is loaded into @value{GDBN}, here is the
23821 corresponding output of @samp{info pretty-printer}:
23824 (gdb) info pretty-printer
23831 @node Inferiors In Python
23832 @subsubsection Inferiors In Python
23833 @cindex inferiors in Python
23835 @findex gdb.Inferior
23836 Programs which are being run under @value{GDBN} are called inferiors
23837 (@pxref{Inferiors and Programs}). Python scripts can access
23838 information about and manipulate inferiors controlled by @value{GDBN}
23839 via objects of the @code{gdb.Inferior} class.
23841 The following inferior-related functions are available in the @code{gdb}
23844 @defun gdb.inferiors ()
23845 Return a tuple containing all inferior objects.
23848 @defun gdb.selected_inferior ()
23849 Return an object representing the current inferior.
23852 A @code{gdb.Inferior} object has the following attributes:
23855 @defvar Inferior.num
23856 ID of inferior, as assigned by GDB.
23859 @defvar Inferior.pid
23860 Process ID of the inferior, as assigned by the underlying operating
23864 @defvar Inferior.was_attached
23865 Boolean signaling whether the inferior was created using `attach', or
23866 started by @value{GDBN} itself.
23870 A @code{gdb.Inferior} object has the following methods:
23873 @defun Inferior.is_valid ()
23874 Returns @code{True} if the @code{gdb.Inferior} object is valid,
23875 @code{False} if not. A @code{gdb.Inferior} object will become invalid
23876 if the inferior no longer exists within @value{GDBN}. All other
23877 @code{gdb.Inferior} methods will throw an exception if it is invalid
23878 at the time the method is called.
23881 @defun Inferior.threads ()
23882 This method returns a tuple holding all the threads which are valid
23883 when it is called. If there are no valid threads, the method will
23884 return an empty tuple.
23887 @findex gdb.read_memory
23888 @defun Inferior.read_memory (address, length)
23889 Read @var{length} bytes of memory from the inferior, starting at
23890 @var{address}. Returns a buffer object, which behaves much like an array
23891 or a string. It can be modified and given to the @code{gdb.write_memory}
23895 @findex gdb.write_memory
23896 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
23897 Write the contents of @var{buffer} to the inferior, starting at
23898 @var{address}. The @var{buffer} parameter must be a Python object
23899 which supports the buffer protocol, i.e., a string, an array or the
23900 object returned from @code{gdb.read_memory}. If given, @var{length}
23901 determines the number of bytes from @var{buffer} to be written.
23904 @findex gdb.search_memory
23905 @defun Inferior.search_memory (address, length, pattern)
23906 Search a region of the inferior memory starting at @var{address} with
23907 the given @var{length} using the search pattern supplied in
23908 @var{pattern}. The @var{pattern} parameter must be a Python object
23909 which supports the buffer protocol, i.e., a string, an array or the
23910 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
23911 containing the address where the pattern was found, or @code{None} if
23912 the pattern could not be found.
23916 @node Events In Python
23917 @subsubsection Events In Python
23918 @cindex inferior events in Python
23920 @value{GDBN} provides a general event facility so that Python code can be
23921 notified of various state changes, particularly changes that occur in
23924 An @dfn{event} is just an object that describes some state change. The
23925 type of the object and its attributes will vary depending on the details
23926 of the change. All the existing events are described below.
23928 In order to be notified of an event, you must register an event handler
23929 with an @dfn{event registry}. An event registry is an object in the
23930 @code{gdb.events} module which dispatches particular events. A registry
23931 provides methods to register and unregister event handlers:
23934 @defun EventRegistry.connect (object)
23935 Add the given callable @var{object} to the registry. This object will be
23936 called when an event corresponding to this registry occurs.
23939 @defun EventRegistry.disconnect (object)
23940 Remove the given @var{object} from the registry. Once removed, the object
23941 will no longer receive notifications of events.
23945 Here is an example:
23948 def exit_handler (event):
23949 print "event type: exit"
23950 print "exit code: %d" % (event.exit_code)
23952 gdb.events.exited.connect (exit_handler)
23955 In the above example we connect our handler @code{exit_handler} to the
23956 registry @code{events.exited}. Once connected, @code{exit_handler} gets
23957 called when the inferior exits. The argument @dfn{event} in this example is
23958 of type @code{gdb.ExitedEvent}. As you can see in the example the
23959 @code{ExitedEvent} object has an attribute which indicates the exit code of
23962 The following is a listing of the event registries that are available and
23963 details of the events they emit:
23968 Emits @code{gdb.ThreadEvent}.
23970 Some events can be thread specific when @value{GDBN} is running in non-stop
23971 mode. When represented in Python, these events all extend
23972 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
23973 events which are emitted by this or other modules might extend this event.
23974 Examples of these events are @code{gdb.BreakpointEvent} and
23975 @code{gdb.ContinueEvent}.
23978 @defvar ThreadEvent.inferior_thread
23979 In non-stop mode this attribute will be set to the specific thread which was
23980 involved in the emitted event. Otherwise, it will be set to @code{None}.
23984 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
23986 This event indicates that the inferior has been continued after a stop. For
23987 inherited attribute refer to @code{gdb.ThreadEvent} above.
23989 @item events.exited
23990 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
23991 @code{events.ExitedEvent} has two attributes:
23993 @defvar ExitedEvent.exit_code
23994 An integer representing the exit code, if available, which the inferior
23995 has returned. (The exit code could be unavailable if, for example,
23996 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
23997 the attribute does not exist.
23999 @defvar ExitedEvent inferior
24000 A reference to the inferior which triggered the @code{exited} event.
24005 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24007 Indicates that the inferior has stopped. All events emitted by this registry
24008 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24009 will indicate the stopped thread when @value{GDBN} is running in non-stop
24010 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24012 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24014 This event indicates that the inferior or one of its threads has received as
24015 signal. @code{gdb.SignalEvent} has the following attributes:
24018 @defvar SignalEvent.stop_signal
24019 A string representing the signal received by the inferior. A list of possible
24020 signal values can be obtained by running the command @code{info signals} in
24021 the @value{GDBN} command prompt.
24025 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24027 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24028 been hit, and has the following attributes:
24031 @defvar BreakpointEvent.breakpoints
24032 A sequence containing references to all the breakpoints (type
24033 @code{gdb.Breakpoint}) that were hit.
24034 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24036 @defvar BreakpointEvent.breakpoint
24037 A reference to the first breakpoint that was hit.
24038 This function is maintained for backward compatibility and is now deprecated
24039 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24043 @item events.new_objfile
24044 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24045 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24048 @defvar NewObjFileEvent.new_objfile
24049 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24050 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24056 @node Threads In Python
24057 @subsubsection Threads In Python
24058 @cindex threads in python
24060 @findex gdb.InferiorThread
24061 Python scripts can access information about, and manipulate inferior threads
24062 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24064 The following thread-related functions are available in the @code{gdb}
24067 @findex gdb.selected_thread
24068 @defun gdb.selected_thread ()
24069 This function returns the thread object for the selected thread. If there
24070 is no selected thread, this will return @code{None}.
24073 A @code{gdb.InferiorThread} object has the following attributes:
24076 @defvar InferiorThread.name
24077 The name of the thread. If the user specified a name using
24078 @code{thread name}, then this returns that name. Otherwise, if an
24079 OS-supplied name is available, then it is returned. Otherwise, this
24080 returns @code{None}.
24082 This attribute can be assigned to. The new value must be a string
24083 object, which sets the new name, or @code{None}, which removes any
24084 user-specified thread name.
24087 @defvar InferiorThread.num
24088 ID of the thread, as assigned by GDB.
24091 @defvar InferiorThread.ptid
24092 ID of the thread, as assigned by the operating system. This attribute is a
24093 tuple containing three integers. The first is the Process ID (PID); the second
24094 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24095 Either the LWPID or TID may be 0, which indicates that the operating system
24096 does not use that identifier.
24100 A @code{gdb.InferiorThread} object has the following methods:
24103 @defun InferiorThread.is_valid ()
24104 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24105 @code{False} if not. A @code{gdb.InferiorThread} object will become
24106 invalid if the thread exits, or the inferior that the thread belongs
24107 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24108 exception if it is invalid at the time the method is called.
24111 @defun InferiorThread.switch ()
24112 This changes @value{GDBN}'s currently selected thread to the one represented
24116 @defun InferiorThread.is_stopped ()
24117 Return a Boolean indicating whether the thread is stopped.
24120 @defun InferiorThread.is_running ()
24121 Return a Boolean indicating whether the thread is running.
24124 @defun InferiorThread.is_exited ()
24125 Return a Boolean indicating whether the thread is exited.
24129 @node Commands In Python
24130 @subsubsection Commands In Python
24132 @cindex commands in python
24133 @cindex python commands
24134 You can implement new @value{GDBN} CLI commands in Python. A CLI
24135 command is implemented using an instance of the @code{gdb.Command}
24136 class, most commonly using a subclass.
24138 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24139 The object initializer for @code{Command} registers the new command
24140 with @value{GDBN}. This initializer is normally invoked from the
24141 subclass' own @code{__init__} method.
24143 @var{name} is the name of the command. If @var{name} consists of
24144 multiple words, then the initial words are looked for as prefix
24145 commands. In this case, if one of the prefix commands does not exist,
24146 an exception is raised.
24148 There is no support for multi-line commands.
24150 @var{command_class} should be one of the @samp{COMMAND_} constants
24151 defined below. This argument tells @value{GDBN} how to categorize the
24152 new command in the help system.
24154 @var{completer_class} is an optional argument. If given, it should be
24155 one of the @samp{COMPLETE_} constants defined below. This argument
24156 tells @value{GDBN} how to perform completion for this command. If not
24157 given, @value{GDBN} will attempt to complete using the object's
24158 @code{complete} method (see below); if no such method is found, an
24159 error will occur when completion is attempted.
24161 @var{prefix} is an optional argument. If @code{True}, then the new
24162 command is a prefix command; sub-commands of this command may be
24165 The help text for the new command is taken from the Python
24166 documentation string for the command's class, if there is one. If no
24167 documentation string is provided, the default value ``This command is
24168 not documented.'' is used.
24171 @cindex don't repeat Python command
24172 @defun Command.dont_repeat ()
24173 By default, a @value{GDBN} command is repeated when the user enters a
24174 blank line at the command prompt. A command can suppress this
24175 behavior by invoking the @code{dont_repeat} method. This is similar
24176 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24179 @defun Command.invoke (argument, from_tty)
24180 This method is called by @value{GDBN} when this command is invoked.
24182 @var{argument} is a string. It is the argument to the command, after
24183 leading and trailing whitespace has been stripped.
24185 @var{from_tty} is a boolean argument. When true, this means that the
24186 command was entered by the user at the terminal; when false it means
24187 that the command came from elsewhere.
24189 If this method throws an exception, it is turned into a @value{GDBN}
24190 @code{error} call. Otherwise, the return value is ignored.
24192 @findex gdb.string_to_argv
24193 To break @var{argument} up into an argv-like string use
24194 @code{gdb.string_to_argv}. This function behaves identically to
24195 @value{GDBN}'s internal argument lexer @code{buildargv}.
24196 It is recommended to use this for consistency.
24197 Arguments are separated by spaces and may be quoted.
24201 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24202 ['1', '2 "3', '4 "5', "6 '7"]
24207 @cindex completion of Python commands
24208 @defun Command.complete (text, word)
24209 This method is called by @value{GDBN} when the user attempts
24210 completion on this command. All forms of completion are handled by
24211 this method, that is, the @key{TAB} and @key{M-?} key bindings
24212 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24215 The arguments @var{text} and @var{word} are both strings. @var{text}
24216 holds the complete command line up to the cursor's location.
24217 @var{word} holds the last word of the command line; this is computed
24218 using a word-breaking heuristic.
24220 The @code{complete} method can return several values:
24223 If the return value is a sequence, the contents of the sequence are
24224 used as the completions. It is up to @code{complete} to ensure that the
24225 contents actually do complete the word. A zero-length sequence is
24226 allowed, it means that there were no completions available. Only
24227 string elements of the sequence are used; other elements in the
24228 sequence are ignored.
24231 If the return value is one of the @samp{COMPLETE_} constants defined
24232 below, then the corresponding @value{GDBN}-internal completion
24233 function is invoked, and its result is used.
24236 All other results are treated as though there were no available
24241 When a new command is registered, it must be declared as a member of
24242 some general class of commands. This is used to classify top-level
24243 commands in the on-line help system; note that prefix commands are not
24244 listed under their own category but rather that of their top-level
24245 command. The available classifications are represented by constants
24246 defined in the @code{gdb} module:
24249 @findex COMMAND_NONE
24250 @findex gdb.COMMAND_NONE
24251 @item gdb.COMMAND_NONE
24252 The command does not belong to any particular class. A command in
24253 this category will not be displayed in any of the help categories.
24255 @findex COMMAND_RUNNING
24256 @findex gdb.COMMAND_RUNNING
24257 @item gdb.COMMAND_RUNNING
24258 The command is related to running the inferior. For example,
24259 @code{start}, @code{step}, and @code{continue} are in this category.
24260 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24261 commands in this category.
24263 @findex COMMAND_DATA
24264 @findex gdb.COMMAND_DATA
24265 @item gdb.COMMAND_DATA
24266 The command is related to data or variables. For example,
24267 @code{call}, @code{find}, and @code{print} are in this category. Type
24268 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24271 @findex COMMAND_STACK
24272 @findex gdb.COMMAND_STACK
24273 @item gdb.COMMAND_STACK
24274 The command has to do with manipulation of the stack. For example,
24275 @code{backtrace}, @code{frame}, and @code{return} are in this
24276 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24277 list of commands in this category.
24279 @findex COMMAND_FILES
24280 @findex gdb.COMMAND_FILES
24281 @item gdb.COMMAND_FILES
24282 This class is used for file-related commands. For example,
24283 @code{file}, @code{list} and @code{section} are in this category.
24284 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24285 commands in this category.
24287 @findex COMMAND_SUPPORT
24288 @findex gdb.COMMAND_SUPPORT
24289 @item gdb.COMMAND_SUPPORT
24290 This should be used for ``support facilities'', generally meaning
24291 things that are useful to the user when interacting with @value{GDBN},
24292 but not related to the state of the inferior. For example,
24293 @code{help}, @code{make}, and @code{shell} are in this category. Type
24294 @kbd{help support} at the @value{GDBN} prompt to see a list of
24295 commands in this category.
24297 @findex COMMAND_STATUS
24298 @findex gdb.COMMAND_STATUS
24299 @item gdb.COMMAND_STATUS
24300 The command is an @samp{info}-related command, that is, related to the
24301 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24302 and @code{show} are in this category. Type @kbd{help status} at the
24303 @value{GDBN} prompt to see a list of commands in this category.
24305 @findex COMMAND_BREAKPOINTS
24306 @findex gdb.COMMAND_BREAKPOINTS
24307 @item gdb.COMMAND_BREAKPOINTS
24308 The command has to do with breakpoints. For example, @code{break},
24309 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24310 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24313 @findex COMMAND_TRACEPOINTS
24314 @findex gdb.COMMAND_TRACEPOINTS
24315 @item gdb.COMMAND_TRACEPOINTS
24316 The command has to do with tracepoints. For example, @code{trace},
24317 @code{actions}, and @code{tfind} are in this category. Type
24318 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24319 commands in this category.
24321 @findex COMMAND_USER
24322 @findex gdb.COMMAND_USER
24323 @item gdb.COMMAND_USER
24324 The command is a general purpose command for the user, and typically
24325 does not fit in one of the other categories.
24326 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24327 a list of commands in this category, as well as the list of gdb macros
24328 (@pxref{Sequences}).
24330 @findex COMMAND_OBSCURE
24331 @findex gdb.COMMAND_OBSCURE
24332 @item gdb.COMMAND_OBSCURE
24333 The command is only used in unusual circumstances, or is not of
24334 general interest to users. For example, @code{checkpoint},
24335 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24336 obscure} at the @value{GDBN} prompt to see a list of commands in this
24339 @findex COMMAND_MAINTENANCE
24340 @findex gdb.COMMAND_MAINTENANCE
24341 @item gdb.COMMAND_MAINTENANCE
24342 The command is only useful to @value{GDBN} maintainers. The
24343 @code{maintenance} and @code{flushregs} commands are in this category.
24344 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24345 commands in this category.
24348 A new command can use a predefined completion function, either by
24349 specifying it via an argument at initialization, or by returning it
24350 from the @code{complete} method. These predefined completion
24351 constants are all defined in the @code{gdb} module:
24354 @findex COMPLETE_NONE
24355 @findex gdb.COMPLETE_NONE
24356 @item gdb.COMPLETE_NONE
24357 This constant means that no completion should be done.
24359 @findex COMPLETE_FILENAME
24360 @findex gdb.COMPLETE_FILENAME
24361 @item gdb.COMPLETE_FILENAME
24362 This constant means that filename completion should be performed.
24364 @findex COMPLETE_LOCATION
24365 @findex gdb.COMPLETE_LOCATION
24366 @item gdb.COMPLETE_LOCATION
24367 This constant means that location completion should be done.
24368 @xref{Specify Location}.
24370 @findex COMPLETE_COMMAND
24371 @findex gdb.COMPLETE_COMMAND
24372 @item gdb.COMPLETE_COMMAND
24373 This constant means that completion should examine @value{GDBN}
24376 @findex COMPLETE_SYMBOL
24377 @findex gdb.COMPLETE_SYMBOL
24378 @item gdb.COMPLETE_SYMBOL
24379 This constant means that completion should be done using symbol names
24383 The following code snippet shows how a trivial CLI command can be
24384 implemented in Python:
24387 class HelloWorld (gdb.Command):
24388 """Greet the whole world."""
24390 def __init__ (self):
24391 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24393 def invoke (self, arg, from_tty):
24394 print "Hello, World!"
24399 The last line instantiates the class, and is necessary to trigger the
24400 registration of the command with @value{GDBN}. Depending on how the
24401 Python code is read into @value{GDBN}, you may need to import the
24402 @code{gdb} module explicitly.
24404 @node Parameters In Python
24405 @subsubsection Parameters In Python
24407 @cindex parameters in python
24408 @cindex python parameters
24409 @tindex gdb.Parameter
24411 You can implement new @value{GDBN} parameters using Python. A new
24412 parameter is implemented as an instance of the @code{gdb.Parameter}
24415 Parameters are exposed to the user via the @code{set} and
24416 @code{show} commands. @xref{Help}.
24418 There are many parameters that already exist and can be set in
24419 @value{GDBN}. Two examples are: @code{set follow fork} and
24420 @code{set charset}. Setting these parameters influences certain
24421 behavior in @value{GDBN}. Similarly, you can define parameters that
24422 can be used to influence behavior in custom Python scripts and commands.
24424 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24425 The object initializer for @code{Parameter} registers the new
24426 parameter with @value{GDBN}. This initializer is normally invoked
24427 from the subclass' own @code{__init__} method.
24429 @var{name} is the name of the new parameter. If @var{name} consists
24430 of multiple words, then the initial words are looked for as prefix
24431 parameters. An example of this can be illustrated with the
24432 @code{set print} set of parameters. If @var{name} is
24433 @code{print foo}, then @code{print} will be searched as the prefix
24434 parameter. In this case the parameter can subsequently be accessed in
24435 @value{GDBN} as @code{set print foo}.
24437 If @var{name} consists of multiple words, and no prefix parameter group
24438 can be found, an exception is raised.
24440 @var{command-class} should be one of the @samp{COMMAND_} constants
24441 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24442 categorize the new parameter in the help system.
24444 @var{parameter-class} should be one of the @samp{PARAM_} constants
24445 defined below. This argument tells @value{GDBN} the type of the new
24446 parameter; this information is used for input validation and
24449 If @var{parameter-class} is @code{PARAM_ENUM}, then
24450 @var{enum-sequence} must be a sequence of strings. These strings
24451 represent the possible values for the parameter.
24453 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24454 of a fourth argument will cause an exception to be thrown.
24456 The help text for the new parameter is taken from the Python
24457 documentation string for the parameter's class, if there is one. If
24458 there is no documentation string, a default value is used.
24461 @defvar Parameter.set_doc
24462 If this attribute exists, and is a string, then its value is used as
24463 the help text for this parameter's @code{set} command. The value is
24464 examined when @code{Parameter.__init__} is invoked; subsequent changes
24468 @defvar Parameter.show_doc
24469 If this attribute exists, and is a string, then its value is used as
24470 the help text for this parameter's @code{show} command. The value is
24471 examined when @code{Parameter.__init__} is invoked; subsequent changes
24475 @defvar Parameter.value
24476 The @code{value} attribute holds the underlying value of the
24477 parameter. It can be read and assigned to just as any other
24478 attribute. @value{GDBN} does validation when assignments are made.
24481 There are two methods that should be implemented in any
24482 @code{Parameter} class. These are:
24484 @defun Parameter.get_set_string (self)
24485 @value{GDBN} will call this method when a @var{parameter}'s value has
24486 been changed via the @code{set} API (for example, @kbd{set foo off}).
24487 The @code{value} attribute has already been populated with the new
24488 value and may be used in output. This method must return a string.
24491 @defun Parameter.get_show_string (self, svalue)
24492 @value{GDBN} will call this method when a @var{parameter}'s
24493 @code{show} API has been invoked (for example, @kbd{show foo}). The
24494 argument @code{svalue} receives the string representation of the
24495 current value. This method must return a string.
24498 When a new parameter is defined, its type must be specified. The
24499 available types are represented by constants defined in the @code{gdb}
24503 @findex PARAM_BOOLEAN
24504 @findex gdb.PARAM_BOOLEAN
24505 @item gdb.PARAM_BOOLEAN
24506 The value is a plain boolean. The Python boolean values, @code{True}
24507 and @code{False} are the only valid values.
24509 @findex PARAM_AUTO_BOOLEAN
24510 @findex gdb.PARAM_AUTO_BOOLEAN
24511 @item gdb.PARAM_AUTO_BOOLEAN
24512 The value has three possible states: true, false, and @samp{auto}. In
24513 Python, true and false are represented using boolean constants, and
24514 @samp{auto} is represented using @code{None}.
24516 @findex PARAM_UINTEGER
24517 @findex gdb.PARAM_UINTEGER
24518 @item gdb.PARAM_UINTEGER
24519 The value is an unsigned integer. The value of 0 should be
24520 interpreted to mean ``unlimited''.
24522 @findex PARAM_INTEGER
24523 @findex gdb.PARAM_INTEGER
24524 @item gdb.PARAM_INTEGER
24525 The value is a signed integer. The value of 0 should be interpreted
24526 to mean ``unlimited''.
24528 @findex PARAM_STRING
24529 @findex gdb.PARAM_STRING
24530 @item gdb.PARAM_STRING
24531 The value is a string. When the user modifies the string, any escape
24532 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
24533 translated into corresponding characters and encoded into the current
24536 @findex PARAM_STRING_NOESCAPE
24537 @findex gdb.PARAM_STRING_NOESCAPE
24538 @item gdb.PARAM_STRING_NOESCAPE
24539 The value is a string. When the user modifies the string, escapes are
24540 passed through untranslated.
24542 @findex PARAM_OPTIONAL_FILENAME
24543 @findex gdb.PARAM_OPTIONAL_FILENAME
24544 @item gdb.PARAM_OPTIONAL_FILENAME
24545 The value is a either a filename (a string), or @code{None}.
24547 @findex PARAM_FILENAME
24548 @findex gdb.PARAM_FILENAME
24549 @item gdb.PARAM_FILENAME
24550 The value is a filename. This is just like
24551 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
24553 @findex PARAM_ZINTEGER
24554 @findex gdb.PARAM_ZINTEGER
24555 @item gdb.PARAM_ZINTEGER
24556 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
24557 is interpreted as itself.
24560 @findex gdb.PARAM_ENUM
24561 @item gdb.PARAM_ENUM
24562 The value is a string, which must be one of a collection string
24563 constants provided when the parameter is created.
24566 @node Functions In Python
24567 @subsubsection Writing new convenience functions
24569 @cindex writing convenience functions
24570 @cindex convenience functions in python
24571 @cindex python convenience functions
24572 @tindex gdb.Function
24574 You can implement new convenience functions (@pxref{Convenience Vars})
24575 in Python. A convenience function is an instance of a subclass of the
24576 class @code{gdb.Function}.
24578 @defun Function.__init__ (name)
24579 The initializer for @code{Function} registers the new function with
24580 @value{GDBN}. The argument @var{name} is the name of the function,
24581 a string. The function will be visible to the user as a convenience
24582 variable of type @code{internal function}, whose name is the same as
24583 the given @var{name}.
24585 The documentation for the new function is taken from the documentation
24586 string for the new class.
24589 @defun Function.invoke (@var{*args})
24590 When a convenience function is evaluated, its arguments are converted
24591 to instances of @code{gdb.Value}, and then the function's
24592 @code{invoke} method is called. Note that @value{GDBN} does not
24593 predetermine the arity of convenience functions. Instead, all
24594 available arguments are passed to @code{invoke}, following the
24595 standard Python calling convention. In particular, a convenience
24596 function can have default values for parameters without ill effect.
24598 The return value of this method is used as its value in the enclosing
24599 expression. If an ordinary Python value is returned, it is converted
24600 to a @code{gdb.Value} following the usual rules.
24603 The following code snippet shows how a trivial convenience function can
24604 be implemented in Python:
24607 class Greet (gdb.Function):
24608 """Return string to greet someone.
24609 Takes a name as argument."""
24611 def __init__ (self):
24612 super (Greet, self).__init__ ("greet")
24614 def invoke (self, name):
24615 return "Hello, %s!" % name.string ()
24620 The last line instantiates the class, and is necessary to trigger the
24621 registration of the function with @value{GDBN}. Depending on how the
24622 Python code is read into @value{GDBN}, you may need to import the
24623 @code{gdb} module explicitly.
24625 @node Progspaces In Python
24626 @subsubsection Program Spaces In Python
24628 @cindex progspaces in python
24629 @tindex gdb.Progspace
24631 A program space, or @dfn{progspace}, represents a symbolic view
24632 of an address space.
24633 It consists of all of the objfiles of the program.
24634 @xref{Objfiles In Python}.
24635 @xref{Inferiors and Programs, program spaces}, for more details
24636 about program spaces.
24638 The following progspace-related functions are available in the
24641 @findex gdb.current_progspace
24642 @defun gdb.current_progspace ()
24643 This function returns the program space of the currently selected inferior.
24644 @xref{Inferiors and Programs}.
24647 @findex gdb.progspaces
24648 @defun gdb.progspaces ()
24649 Return a sequence of all the progspaces currently known to @value{GDBN}.
24652 Each progspace is represented by an instance of the @code{gdb.Progspace}
24655 @defvar Progspace.filename
24656 The file name of the progspace as a string.
24659 @defvar Progspace.pretty_printers
24660 The @code{pretty_printers} attribute is a list of functions. It is
24661 used to look up pretty-printers. A @code{Value} is passed to each
24662 function in order; if the function returns @code{None}, then the
24663 search continues. Otherwise, the return value should be an object
24664 which is used to format the value. @xref{Pretty Printing API}, for more
24668 @node Objfiles In Python
24669 @subsubsection Objfiles In Python
24671 @cindex objfiles in python
24672 @tindex gdb.Objfile
24674 @value{GDBN} loads symbols for an inferior from various
24675 symbol-containing files (@pxref{Files}). These include the primary
24676 executable file, any shared libraries used by the inferior, and any
24677 separate debug info files (@pxref{Separate Debug Files}).
24678 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
24680 The following objfile-related functions are available in the
24683 @findex gdb.current_objfile
24684 @defun gdb.current_objfile ()
24685 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
24686 sets the ``current objfile'' to the corresponding objfile. This
24687 function returns the current objfile. If there is no current objfile,
24688 this function returns @code{None}.
24691 @findex gdb.objfiles
24692 @defun gdb.objfiles ()
24693 Return a sequence of all the objfiles current known to @value{GDBN}.
24694 @xref{Objfiles In Python}.
24697 Each objfile is represented by an instance of the @code{gdb.Objfile}
24700 @defvar Objfile.filename
24701 The file name of the objfile as a string.
24704 @defvar Objfile.pretty_printers
24705 The @code{pretty_printers} attribute is a list of functions. It is
24706 used to look up pretty-printers. A @code{Value} is passed to each
24707 function in order; if the function returns @code{None}, then the
24708 search continues. Otherwise, the return value should be an object
24709 which is used to format the value. @xref{Pretty Printing API}, for more
24713 A @code{gdb.Objfile} object has the following methods:
24715 @defun Objfile.is_valid ()
24716 Returns @code{True} if the @code{gdb.Objfile} object is valid,
24717 @code{False} if not. A @code{gdb.Objfile} object can become invalid
24718 if the object file it refers to is not loaded in @value{GDBN} any
24719 longer. All other @code{gdb.Objfile} methods will throw an exception
24720 if it is invalid at the time the method is called.
24723 @node Frames In Python
24724 @subsubsection Accessing inferior stack frames from Python.
24726 @cindex frames in python
24727 When the debugged program stops, @value{GDBN} is able to analyze its call
24728 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
24729 represents a frame in the stack. A @code{gdb.Frame} object is only valid
24730 while its corresponding frame exists in the inferior's stack. If you try
24731 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
24732 exception (@pxref{Exception Handling}).
24734 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
24738 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
24742 The following frame-related functions are available in the @code{gdb} module:
24744 @findex gdb.selected_frame
24745 @defun gdb.selected_frame ()
24746 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
24749 @findex gdb.newest_frame
24750 @defun gdb.newest_frame ()
24751 Return the newest frame object for the selected thread.
24754 @defun gdb.frame_stop_reason_string (reason)
24755 Return a string explaining the reason why @value{GDBN} stopped unwinding
24756 frames, as expressed by the given @var{reason} code (an integer, see the
24757 @code{unwind_stop_reason} method further down in this section).
24760 A @code{gdb.Frame} object has the following methods:
24763 @defun Frame.is_valid ()
24764 Returns true if the @code{gdb.Frame} object is valid, false if not.
24765 A frame object can become invalid if the frame it refers to doesn't
24766 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
24767 an exception if it is invalid at the time the method is called.
24770 @defun Frame.name ()
24771 Returns the function name of the frame, or @code{None} if it can't be
24775 @defun Frame.type ()
24776 Returns the type of the frame. The value can be one of:
24778 @item gdb.NORMAL_FRAME
24779 An ordinary stack frame.
24781 @item gdb.DUMMY_FRAME
24782 A fake stack frame that was created by @value{GDBN} when performing an
24783 inferior function call.
24785 @item gdb.INLINE_FRAME
24786 A frame representing an inlined function. The function was inlined
24787 into a @code{gdb.NORMAL_FRAME} that is older than this one.
24789 @item gdb.TAILCALL_FRAME
24790 A frame representing a tail call. @xref{Tail Call Frames}.
24792 @item gdb.SIGTRAMP_FRAME
24793 A signal trampoline frame. This is the frame created by the OS when
24794 it calls into a signal handler.
24796 @item gdb.ARCH_FRAME
24797 A fake stack frame representing a cross-architecture call.
24799 @item gdb.SENTINEL_FRAME
24800 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
24805 @defun Frame.unwind_stop_reason ()
24806 Return an integer representing the reason why it's not possible to find
24807 more frames toward the outermost frame. Use
24808 @code{gdb.frame_stop_reason_string} to convert the value returned by this
24809 function to a string. The value can be one of:
24812 @item gdb.FRAME_UNWIND_NO_REASON
24813 No particular reason (older frames should be available).
24815 @item gdb.FRAME_UNWIND_NULL_ID
24816 The previous frame's analyzer returns an invalid result.
24818 @item gdb.FRAME_UNWIND_OUTERMOST
24819 This frame is the outermost.
24821 @item gdb.FRAME_UNWIND_UNAVAILABLE
24822 Cannot unwind further, because that would require knowing the
24823 values of registers or memory that have not been collected.
24825 @item gdb.FRAME_UNWIND_INNER_ID
24826 This frame ID looks like it ought to belong to a NEXT frame,
24827 but we got it for a PREV frame. Normally, this is a sign of
24828 unwinder failure. It could also indicate stack corruption.
24830 @item gdb.FRAME_UNWIND_SAME_ID
24831 This frame has the same ID as the previous one. That means
24832 that unwinding further would almost certainly give us another
24833 frame with exactly the same ID, so break the chain. Normally,
24834 this is a sign of unwinder failure. It could also indicate
24837 @item gdb.FRAME_UNWIND_NO_SAVED_PC
24838 The frame unwinder did not find any saved PC, but we needed
24839 one to unwind further.
24841 @item gdb.FRAME_UNWIND_FIRST_ERROR
24842 Any stop reason greater or equal to this value indicates some kind
24843 of error. This special value facilitates writing code that tests
24844 for errors in unwinding in a way that will work correctly even if
24845 the list of the other values is modified in future @value{GDBN}
24846 versions. Using it, you could write:
24848 reason = gdb.selected_frame().unwind_stop_reason ()
24849 reason_str = gdb.frame_stop_reason_string (reason)
24850 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
24851 print "An error occured: %s" % reason_str
24858 Returns the frame's resume address.
24861 @defun Frame.block ()
24862 Return the frame's code block. @xref{Blocks In Python}.
24865 @defun Frame.function ()
24866 Return the symbol for the function corresponding to this frame.
24867 @xref{Symbols In Python}.
24870 @defun Frame.older ()
24871 Return the frame that called this frame.
24874 @defun Frame.newer ()
24875 Return the frame called by this frame.
24878 @defun Frame.find_sal ()
24879 Return the frame's symtab and line object.
24880 @xref{Symbol Tables In Python}.
24883 @defun Frame.read_var (variable @r{[}, block@r{]})
24884 Return the value of @var{variable} in this frame. If the optional
24885 argument @var{block} is provided, search for the variable from that
24886 block; otherwise start at the frame's current block (which is
24887 determined by the frame's current program counter). @var{variable}
24888 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
24889 @code{gdb.Block} object.
24892 @defun Frame.select ()
24893 Set this frame to be the selected frame. @xref{Stack, ,Examining the
24898 @node Blocks In Python
24899 @subsubsection Accessing frame blocks from Python.
24901 @cindex blocks in python
24904 Within each frame, @value{GDBN} maintains information on each block
24905 stored in that frame. These blocks are organized hierarchically, and
24906 are represented individually in Python as a @code{gdb.Block}.
24907 Please see @ref{Frames In Python}, for a more in-depth discussion on
24908 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
24909 detailed technical information on @value{GDBN}'s book-keeping of the
24912 A @code{gdb.Block} is iterable. The iterator returns the symbols
24913 (@pxref{Symbols In Python}) local to the block. Python programs
24914 should not assume that a specific block object will always contain a
24915 given symbol, since changes in @value{GDBN} features and
24916 infrastructure may cause symbols move across blocks in a symbol
24919 The following block-related functions are available in the @code{gdb}
24922 @findex gdb.block_for_pc
24923 @defun gdb.block_for_pc (pc)
24924 Return the @code{gdb.Block} containing the given @var{pc} value. If the
24925 block cannot be found for the @var{pc} value specified, the function
24926 will return @code{None}.
24929 A @code{gdb.Block} object has the following methods:
24932 @defun Block.is_valid ()
24933 Returns @code{True} if the @code{gdb.Block} object is valid,
24934 @code{False} if not. A block object can become invalid if the block it
24935 refers to doesn't exist anymore in the inferior. All other
24936 @code{gdb.Block} methods will throw an exception if it is invalid at
24937 the time the method is called. The block's validity is also checked
24938 during iteration over symbols of the block.
24942 A @code{gdb.Block} object has the following attributes:
24945 @defvar Block.start
24946 The start address of the block. This attribute is not writable.
24950 The end address of the block. This attribute is not writable.
24953 @defvar Block.function
24954 The name of the block represented as a @code{gdb.Symbol}. If the
24955 block is not named, then this attribute holds @code{None}. This
24956 attribute is not writable.
24959 @defvar Block.superblock
24960 The block containing this block. If this parent block does not exist,
24961 this attribute holds @code{None}. This attribute is not writable.
24964 @defvar Block.global_block
24965 The global block associated with this block. This attribute is not
24969 @defvar Block.static_block
24970 The static block associated with this block. This attribute is not
24974 @defvar Block.is_global
24975 @code{True} if the @code{gdb.Block} object is a global block,
24976 @code{False} if not. This attribute is not
24980 @defvar Block.is_static
24981 @code{True} if the @code{gdb.Block} object is a static block,
24982 @code{False} if not. This attribute is not writable.
24986 @node Symbols In Python
24987 @subsubsection Python representation of Symbols.
24989 @cindex symbols in python
24992 @value{GDBN} represents every variable, function and type as an
24993 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
24994 Similarly, Python represents these symbols in @value{GDBN} with the
24995 @code{gdb.Symbol} object.
24997 The following symbol-related functions are available in the @code{gdb}
25000 @findex gdb.lookup_symbol
25001 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25002 This function searches for a symbol by name. The search scope can be
25003 restricted to the parameters defined in the optional domain and block
25006 @var{name} is the name of the symbol. It must be a string. The
25007 optional @var{block} argument restricts the search to symbols visible
25008 in that @var{block}. The @var{block} argument must be a
25009 @code{gdb.Block} object. If omitted, the block for the current frame
25010 is used. The optional @var{domain} argument restricts
25011 the search to the domain type. The @var{domain} argument must be a
25012 domain constant defined in the @code{gdb} module and described later
25015 The result is a tuple of two elements.
25016 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25018 If the symbol is found, the second element is @code{True} if the symbol
25019 is a field of a method's object (e.g., @code{this} in C@t{++}),
25020 otherwise it is @code{False}.
25021 If the symbol is not found, the second element is @code{False}.
25024 @findex gdb.lookup_global_symbol
25025 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25026 This function searches for a global symbol by name.
25027 The search scope can be restricted to by the domain argument.
25029 @var{name} is the name of the symbol. It must be a string.
25030 The optional @var{domain} argument restricts the search to the domain type.
25031 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25032 module and described later in this chapter.
25034 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25038 A @code{gdb.Symbol} object has the following attributes:
25041 @defvar Symbol.type
25042 The type of the symbol or @code{None} if no type is recorded.
25043 This attribute is represented as a @code{gdb.Type} object.
25044 @xref{Types In Python}. This attribute is not writable.
25047 @defvar Symbol.symtab
25048 The symbol table in which the symbol appears. This attribute is
25049 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25050 Python}. This attribute is not writable.
25053 @defvar Symbol.line
25054 The line number in the source code at which the symbol was defined.
25055 This is an integer.
25058 @defvar Symbol.name
25059 The name of the symbol as a string. This attribute is not writable.
25062 @defvar Symbol.linkage_name
25063 The name of the symbol, as used by the linker (i.e., may be mangled).
25064 This attribute is not writable.
25067 @defvar Symbol.print_name
25068 The name of the symbol in a form suitable for output. This is either
25069 @code{name} or @code{linkage_name}, depending on whether the user
25070 asked @value{GDBN} to display demangled or mangled names.
25073 @defvar Symbol.addr_class
25074 The address class of the symbol. This classifies how to find the value
25075 of a symbol. Each address class is a constant defined in the
25076 @code{gdb} module and described later in this chapter.
25079 @defvar Symbol.needs_frame
25080 This is @code{True} if evaluating this symbol's value requires a frame
25081 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25082 local variables will require a frame, but other symbols will not.
25085 @defvar Symbol.is_argument
25086 @code{True} if the symbol is an argument of a function.
25089 @defvar Symbol.is_constant
25090 @code{True} if the symbol is a constant.
25093 @defvar Symbol.is_function
25094 @code{True} if the symbol is a function or a method.
25097 @defvar Symbol.is_variable
25098 @code{True} if the symbol is a variable.
25102 A @code{gdb.Symbol} object has the following methods:
25105 @defun Symbol.is_valid ()
25106 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25107 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25108 the symbol it refers to does not exist in @value{GDBN} any longer.
25109 All other @code{gdb.Symbol} methods will throw an exception if it is
25110 invalid at the time the method is called.
25113 @defun Symbol.value (@r{[}frame@r{]})
25114 Compute the value of the symbol, as a @code{gdb.Value}. For
25115 functions, this computes the address of the function, cast to the
25116 appropriate type. If the symbol requires a frame in order to compute
25117 its value, then @var{frame} must be given. If @var{frame} is not
25118 given, or if @var{frame} is invalid, then this method will throw an
25123 The available domain categories in @code{gdb.Symbol} are represented
25124 as constants in the @code{gdb} module:
25127 @findex SYMBOL_UNDEF_DOMAIN
25128 @findex gdb.SYMBOL_UNDEF_DOMAIN
25129 @item gdb.SYMBOL_UNDEF_DOMAIN
25130 This is used when a domain has not been discovered or none of the
25131 following domains apply. This usually indicates an error either
25132 in the symbol information or in @value{GDBN}'s handling of symbols.
25133 @findex SYMBOL_VAR_DOMAIN
25134 @findex gdb.SYMBOL_VAR_DOMAIN
25135 @item gdb.SYMBOL_VAR_DOMAIN
25136 This domain contains variables, function names, typedef names and enum
25138 @findex SYMBOL_STRUCT_DOMAIN
25139 @findex gdb.SYMBOL_STRUCT_DOMAIN
25140 @item gdb.SYMBOL_STRUCT_DOMAIN
25141 This domain holds struct, union and enum type names.
25142 @findex SYMBOL_LABEL_DOMAIN
25143 @findex gdb.SYMBOL_LABEL_DOMAIN
25144 @item gdb.SYMBOL_LABEL_DOMAIN
25145 This domain contains names of labels (for gotos).
25146 @findex SYMBOL_VARIABLES_DOMAIN
25147 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25148 @item gdb.SYMBOL_VARIABLES_DOMAIN
25149 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25150 contains everything minus functions and types.
25151 @findex SYMBOL_FUNCTIONS_DOMAIN
25152 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25153 @item gdb.SYMBOL_FUNCTION_DOMAIN
25154 This domain contains all functions.
25155 @findex SYMBOL_TYPES_DOMAIN
25156 @findex gdb.SYMBOL_TYPES_DOMAIN
25157 @item gdb.SYMBOL_TYPES_DOMAIN
25158 This domain contains all types.
25161 The available address class categories in @code{gdb.Symbol} are represented
25162 as constants in the @code{gdb} module:
25165 @findex SYMBOL_LOC_UNDEF
25166 @findex gdb.SYMBOL_LOC_UNDEF
25167 @item gdb.SYMBOL_LOC_UNDEF
25168 If this is returned by address class, it indicates an error either in
25169 the symbol information or in @value{GDBN}'s handling of symbols.
25170 @findex SYMBOL_LOC_CONST
25171 @findex gdb.SYMBOL_LOC_CONST
25172 @item gdb.SYMBOL_LOC_CONST
25173 Value is constant int.
25174 @findex SYMBOL_LOC_STATIC
25175 @findex gdb.SYMBOL_LOC_STATIC
25176 @item gdb.SYMBOL_LOC_STATIC
25177 Value is at a fixed address.
25178 @findex SYMBOL_LOC_REGISTER
25179 @findex gdb.SYMBOL_LOC_REGISTER
25180 @item gdb.SYMBOL_LOC_REGISTER
25181 Value is in a register.
25182 @findex SYMBOL_LOC_ARG
25183 @findex gdb.SYMBOL_LOC_ARG
25184 @item gdb.SYMBOL_LOC_ARG
25185 Value is an argument. This value is at the offset stored within the
25186 symbol inside the frame's argument list.
25187 @findex SYMBOL_LOC_REF_ARG
25188 @findex gdb.SYMBOL_LOC_REF_ARG
25189 @item gdb.SYMBOL_LOC_REF_ARG
25190 Value address is stored in the frame's argument list. Just like
25191 @code{LOC_ARG} except that the value's address is stored at the
25192 offset, not the value itself.
25193 @findex SYMBOL_LOC_REGPARM_ADDR
25194 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25195 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25196 Value is a specified register. Just like @code{LOC_REGISTER} except
25197 the register holds the address of the argument instead of the argument
25199 @findex SYMBOL_LOC_LOCAL
25200 @findex gdb.SYMBOL_LOC_LOCAL
25201 @item gdb.SYMBOL_LOC_LOCAL
25202 Value is a local variable.
25203 @findex SYMBOL_LOC_TYPEDEF
25204 @findex gdb.SYMBOL_LOC_TYPEDEF
25205 @item gdb.SYMBOL_LOC_TYPEDEF
25206 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25208 @findex SYMBOL_LOC_BLOCK
25209 @findex gdb.SYMBOL_LOC_BLOCK
25210 @item gdb.SYMBOL_LOC_BLOCK
25212 @findex SYMBOL_LOC_CONST_BYTES
25213 @findex gdb.SYMBOL_LOC_CONST_BYTES
25214 @item gdb.SYMBOL_LOC_CONST_BYTES
25215 Value is a byte-sequence.
25216 @findex SYMBOL_LOC_UNRESOLVED
25217 @findex gdb.SYMBOL_LOC_UNRESOLVED
25218 @item gdb.SYMBOL_LOC_UNRESOLVED
25219 Value is at a fixed address, but the address of the variable has to be
25220 determined from the minimal symbol table whenever the variable is
25222 @findex SYMBOL_LOC_OPTIMIZED_OUT
25223 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25224 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25225 The value does not actually exist in the program.
25226 @findex SYMBOL_LOC_COMPUTED
25227 @findex gdb.SYMBOL_LOC_COMPUTED
25228 @item gdb.SYMBOL_LOC_COMPUTED
25229 The value's address is a computed location.
25232 @node Symbol Tables In Python
25233 @subsubsection Symbol table representation in Python.
25235 @cindex symbol tables in python
25237 @tindex gdb.Symtab_and_line
25239 Access to symbol table data maintained by @value{GDBN} on the inferior
25240 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25241 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25242 from the @code{find_sal} method in @code{gdb.Frame} object.
25243 @xref{Frames In Python}.
25245 For more information on @value{GDBN}'s symbol table management, see
25246 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25248 A @code{gdb.Symtab_and_line} object has the following attributes:
25251 @defvar Symtab_and_line.symtab
25252 The symbol table object (@code{gdb.Symtab}) for this frame.
25253 This attribute is not writable.
25256 @defvar Symtab_and_line.pc
25257 Indicates the current program counter address. This attribute is not
25261 @defvar Symtab_and_line.line
25262 Indicates the current line number for this object. This
25263 attribute is not writable.
25267 A @code{gdb.Symtab_and_line} object has the following methods:
25270 @defun Symtab_and_line.is_valid ()
25271 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25272 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25273 invalid if the Symbol table and line object it refers to does not
25274 exist in @value{GDBN} any longer. All other
25275 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25276 invalid at the time the method is called.
25280 A @code{gdb.Symtab} object has the following attributes:
25283 @defvar Symtab.filename
25284 The symbol table's source filename. This attribute is not writable.
25287 @defvar Symtab.objfile
25288 The symbol table's backing object file. @xref{Objfiles In Python}.
25289 This attribute is not writable.
25293 A @code{gdb.Symtab} object has the following methods:
25296 @defun Symtab.is_valid ()
25297 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25298 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25299 the symbol table it refers to does not exist in @value{GDBN} any
25300 longer. All other @code{gdb.Symtab} methods will throw an exception
25301 if it is invalid at the time the method is called.
25304 @defun Symtab.fullname ()
25305 Return the symbol table's source absolute file name.
25308 @defun Symtab.global_block ()
25309 Return the global block of the underlying symbol table.
25310 @xref{Blocks In Python}.
25313 @defun Symtab.static_block ()
25314 Return the static block of the underlying symbol table.
25315 @xref{Blocks In Python}.
25319 @node Breakpoints In Python
25320 @subsubsection Manipulating breakpoints using Python
25322 @cindex breakpoints in python
25323 @tindex gdb.Breakpoint
25325 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25328 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25329 Create a new breakpoint. @var{spec} is a string naming the
25330 location of the breakpoint, or an expression that defines a
25331 watchpoint. The contents can be any location recognized by the
25332 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25333 command. The optional @var{type} denotes the breakpoint to create
25334 from the types defined later in this chapter. This argument can be
25335 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25336 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25337 allows the breakpoint to become invisible to the user. The breakpoint
25338 will neither be reported when created, nor will it be listed in the
25339 output from @code{info breakpoints} (but will be listed with the
25340 @code{maint info breakpoints} command). The optional @var{wp_class}
25341 argument defines the class of watchpoint to create, if @var{type} is
25342 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25343 assumed to be a @code{gdb.WP_WRITE} class.
25346 @defun Breakpoint.stop (self)
25347 The @code{gdb.Breakpoint} class can be sub-classed and, in
25348 particular, you may choose to implement the @code{stop} method.
25349 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25350 it will be called when the inferior reaches any location of a
25351 breakpoint which instantiates that sub-class. If the method returns
25352 @code{True}, the inferior will be stopped at the location of the
25353 breakpoint, otherwise the inferior will continue.
25355 If there are multiple breakpoints at the same location with a
25356 @code{stop} method, each one will be called regardless of the
25357 return status of the previous. This ensures that all @code{stop}
25358 methods have a chance to execute at that location. In this scenario
25359 if one of the methods returns @code{True} but the others return
25360 @code{False}, the inferior will still be stopped.
25362 You should not alter the execution state of the inferior (i.e.@:, step,
25363 next, etc.), alter the current frame context (i.e.@:, change the current
25364 active frame), or alter, add or delete any breakpoint. As a general
25365 rule, you should not alter any data within @value{GDBN} or the inferior
25368 Example @code{stop} implementation:
25371 class MyBreakpoint (gdb.Breakpoint):
25373 inf_val = gdb.parse_and_eval("foo")
25380 The available watchpoint types represented by constants are defined in the
25385 @findex gdb.WP_READ
25387 Read only watchpoint.
25390 @findex gdb.WP_WRITE
25392 Write only watchpoint.
25395 @findex gdb.WP_ACCESS
25396 @item gdb.WP_ACCESS
25397 Read/Write watchpoint.
25400 @defun Breakpoint.is_valid ()
25401 Return @code{True} if this @code{Breakpoint} object is valid,
25402 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25403 if the user deletes the breakpoint. In this case, the object still
25404 exists, but the underlying breakpoint does not. In the cases of
25405 watchpoint scope, the watchpoint remains valid even if execution of the
25406 inferior leaves the scope of that watchpoint.
25409 @defun Breakpoint.delete
25410 Permanently deletes the @value{GDBN} breakpoint. This also
25411 invalidates the Python @code{Breakpoint} object. Any further access
25412 to this object's attributes or methods will raise an error.
25415 @defvar Breakpoint.enabled
25416 This attribute is @code{True} if the breakpoint is enabled, and
25417 @code{False} otherwise. This attribute is writable.
25420 @defvar Breakpoint.silent
25421 This attribute is @code{True} if the breakpoint is silent, and
25422 @code{False} otherwise. This attribute is writable.
25424 Note that a breakpoint can also be silent if it has commands and the
25425 first command is @code{silent}. This is not reported by the
25426 @code{silent} attribute.
25429 @defvar Breakpoint.thread
25430 If the breakpoint is thread-specific, this attribute holds the thread
25431 id. If the breakpoint is not thread-specific, this attribute is
25432 @code{None}. This attribute is writable.
25435 @defvar Breakpoint.task
25436 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25437 id. If the breakpoint is not task-specific (or the underlying
25438 language is not Ada), this attribute is @code{None}. This attribute
25442 @defvar Breakpoint.ignore_count
25443 This attribute holds the ignore count for the breakpoint, an integer.
25444 This attribute is writable.
25447 @defvar Breakpoint.number
25448 This attribute holds the breakpoint's number --- the identifier used by
25449 the user to manipulate the breakpoint. This attribute is not writable.
25452 @defvar Breakpoint.type
25453 This attribute holds the breakpoint's type --- the identifier used to
25454 determine the actual breakpoint type or use-case. This attribute is not
25458 @defvar Breakpoint.visible
25459 This attribute tells whether the breakpoint is visible to the user
25460 when set, or when the @samp{info breakpoints} command is run. This
25461 attribute is not writable.
25464 The available types are represented by constants defined in the @code{gdb}
25468 @findex BP_BREAKPOINT
25469 @findex gdb.BP_BREAKPOINT
25470 @item gdb.BP_BREAKPOINT
25471 Normal code breakpoint.
25473 @findex BP_WATCHPOINT
25474 @findex gdb.BP_WATCHPOINT
25475 @item gdb.BP_WATCHPOINT
25476 Watchpoint breakpoint.
25478 @findex BP_HARDWARE_WATCHPOINT
25479 @findex gdb.BP_HARDWARE_WATCHPOINT
25480 @item gdb.BP_HARDWARE_WATCHPOINT
25481 Hardware assisted watchpoint.
25483 @findex BP_READ_WATCHPOINT
25484 @findex gdb.BP_READ_WATCHPOINT
25485 @item gdb.BP_READ_WATCHPOINT
25486 Hardware assisted read watchpoint.
25488 @findex BP_ACCESS_WATCHPOINT
25489 @findex gdb.BP_ACCESS_WATCHPOINT
25490 @item gdb.BP_ACCESS_WATCHPOINT
25491 Hardware assisted access watchpoint.
25494 @defvar Breakpoint.hit_count
25495 This attribute holds the hit count for the breakpoint, an integer.
25496 This attribute is writable, but currently it can only be set to zero.
25499 @defvar Breakpoint.location
25500 This attribute holds the location of the breakpoint, as specified by
25501 the user. It is a string. If the breakpoint does not have a location
25502 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25503 attribute is not writable.
25506 @defvar Breakpoint.expression
25507 This attribute holds a breakpoint expression, as specified by
25508 the user. It is a string. If the breakpoint does not have an
25509 expression (the breakpoint is not a watchpoint) the attribute's value
25510 is @code{None}. This attribute is not writable.
25513 @defvar Breakpoint.condition
25514 This attribute holds the condition of the breakpoint, as specified by
25515 the user. It is a string. If there is no condition, this attribute's
25516 value is @code{None}. This attribute is writable.
25519 @defvar Breakpoint.commands
25520 This attribute holds the commands attached to the breakpoint. If
25521 there are commands, this attribute's value is a string holding all the
25522 commands, separated by newlines. If there are no commands, this
25523 attribute is @code{None}. This attribute is not writable.
25526 @node Finish Breakpoints in Python
25527 @subsubsection Finish Breakpoints
25529 @cindex python finish breakpoints
25530 @tindex gdb.FinishBreakpoint
25532 A finish breakpoint is a temporary breakpoint set at the return address of
25533 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
25534 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
25535 and deleted when the execution will run out of the breakpoint scope (i.e.@:
25536 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
25537 Finish breakpoints are thread specific and must be create with the right
25540 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
25541 Create a finish breakpoint at the return address of the @code{gdb.Frame}
25542 object @var{frame}. If @var{frame} is not provided, this defaults to the
25543 newest frame. The optional @var{internal} argument allows the breakpoint to
25544 become invisible to the user. @xref{Breakpoints In Python}, for further
25545 details about this argument.
25548 @defun FinishBreakpoint.out_of_scope (self)
25549 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
25550 @code{return} command, @dots{}), a function may not properly terminate, and
25551 thus never hit the finish breakpoint. When @value{GDBN} notices such a
25552 situation, the @code{out_of_scope} callback will be triggered.
25554 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
25558 class MyFinishBreakpoint (gdb.FinishBreakpoint)
25560 print "normal finish"
25563 def out_of_scope ():
25564 print "abnormal finish"
25568 @defvar FinishBreakpoint.return_value
25569 When @value{GDBN} is stopped at a finish breakpoint and the frame
25570 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
25571 attribute will contain a @code{gdb.Value} object corresponding to the return
25572 value of the function. The value will be @code{None} if the function return
25573 type is @code{void} or if the return value was not computable. This attribute
25577 @node Lazy Strings In Python
25578 @subsubsection Python representation of lazy strings.
25580 @cindex lazy strings in python
25581 @tindex gdb.LazyString
25583 A @dfn{lazy string} is a string whose contents is not retrieved or
25584 encoded until it is needed.
25586 A @code{gdb.LazyString} is represented in @value{GDBN} as an
25587 @code{address} that points to a region of memory, an @code{encoding}
25588 that will be used to encode that region of memory, and a @code{length}
25589 to delimit the region of memory that represents the string. The
25590 difference between a @code{gdb.LazyString} and a string wrapped within
25591 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
25592 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
25593 retrieved and encoded during printing, while a @code{gdb.Value}
25594 wrapping a string is immediately retrieved and encoded on creation.
25596 A @code{gdb.LazyString} object has the following functions:
25598 @defun LazyString.value ()
25599 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
25600 will point to the string in memory, but will lose all the delayed
25601 retrieval, encoding and handling that @value{GDBN} applies to a
25602 @code{gdb.LazyString}.
25605 @defvar LazyString.address
25606 This attribute holds the address of the string. This attribute is not
25610 @defvar LazyString.length
25611 This attribute holds the length of the string in characters. If the
25612 length is -1, then the string will be fetched and encoded up to the
25613 first null of appropriate width. This attribute is not writable.
25616 @defvar LazyString.encoding
25617 This attribute holds the encoding that will be applied to the string
25618 when the string is printed by @value{GDBN}. If the encoding is not
25619 set, or contains an empty string, then @value{GDBN} will select the
25620 most appropriate encoding when the string is printed. This attribute
25624 @defvar LazyString.type
25625 This attribute holds the type that is represented by the lazy string's
25626 type. For a lazy string this will always be a pointer type. To
25627 resolve this to the lazy string's character type, use the type's
25628 @code{target} method. @xref{Types In Python}. This attribute is not
25632 @node Python Auto-loading
25633 @subsection Python Auto-loading
25634 @cindex Python auto-loading
25636 When a new object file is read (for example, due to the @code{file}
25637 command, or because the inferior has loaded a shared library),
25638 @value{GDBN} will look for Python support scripts in several ways:
25639 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
25640 and @code{.debug_gdb_scripts} section
25641 (@pxref{dotdebug_gdb_scripts section}).
25643 The auto-loading feature is useful for supplying application-specific
25644 debugging commands and scripts.
25646 Auto-loading can be enabled or disabled,
25647 and the list of auto-loaded scripts can be printed.
25650 @anchor{set auto-load python-scripts}
25651 @kindex set auto-load python-scripts
25652 @item set auto-load python-scripts [on|off]
25653 Enable or disable the auto-loading of Python scripts.
25655 @anchor{show auto-load python-scripts}
25656 @kindex show auto-load python-scripts
25657 @item show auto-load python-scripts
25658 Show whether auto-loading of Python scripts is enabled or disabled.
25660 @anchor{info auto-load python-scripts}
25661 @kindex info auto-load python-scripts
25662 @cindex print list of auto-loaded Python scripts
25663 @item info auto-load python-scripts [@var{regexp}]
25664 Print the list of all Python scripts that @value{GDBN} auto-loaded.
25666 Also printed is the list of Python scripts that were mentioned in
25667 the @code{.debug_gdb_scripts} section and were not found
25668 (@pxref{dotdebug_gdb_scripts section}).
25669 This is useful because their names are not printed when @value{GDBN}
25670 tries to load them and fails. There may be many of them, and printing
25671 an error message for each one is problematic.
25673 If @var{regexp} is supplied only Python scripts with matching names are printed.
25678 (gdb) info auto-load python-scripts
25680 Yes py-section-script.py
25681 full name: /tmp/py-section-script.py
25682 No my-foo-pretty-printers.py
25686 When reading an auto-loaded file, @value{GDBN} sets the
25687 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
25688 function (@pxref{Objfiles In Python}). This can be useful for
25689 registering objfile-specific pretty-printers.
25692 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
25693 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
25694 * Which flavor to choose?::
25697 @node objfile-gdb.py file
25698 @subsubsection The @file{@var{objfile}-gdb.py} file
25699 @cindex @file{@var{objfile}-gdb.py}
25701 When a new object file is read, @value{GDBN} looks for
25702 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
25703 where @var{objfile} is the object file's real name, formed by ensuring
25704 that the file name is absolute, following all symlinks, and resolving
25705 @code{.} and @code{..} components. If this file exists and is
25706 readable, @value{GDBN} will evaluate it as a Python script.
25708 If this file does not exist, then @value{GDBN} will look for
25709 @var{script-name} file in all of the directories as specified below.
25711 Note that loading of this script file also requires accordingly configured
25712 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25715 @anchor{set auto-load scripts-directory}
25716 @kindex set auto-load scripts-directory
25717 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25718 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25719 may be delimited by the host platform path separator in use
25720 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25722 Each entry here needs to be covered also by the security setting
25723 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25725 @anchor{with-auto-load-dir}
25726 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25727 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25728 configuration option @option{--with-auto-load-dir}.
25730 Any reference to @file{$debugdir} will get replaced by
25731 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25732 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25733 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25734 @file{$datadir} must be placed as a directory component --- either alone or
25735 delimited by @file{/} or @file{\} directory separators, depending on the host
25738 The list of directories uses path separator (@samp{:} on GNU and Unix
25739 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25740 to the @env{PATH} environment variable.
25742 @anchor{show auto-load scripts-directory}
25743 @kindex show auto-load scripts-directory
25744 @item show auto-load scripts-directory
25745 Show @value{GDBN} auto-loaded scripts location.
25748 @value{GDBN} does not track which files it has already auto-loaded this way.
25749 @value{GDBN} will load the associated script every time the corresponding
25750 @var{objfile} is opened.
25751 So your @file{-gdb.py} file should be careful to avoid errors if it
25752 is evaluated more than once.
25754 @node dotdebug_gdb_scripts section
25755 @subsubsection The @code{.debug_gdb_scripts} section
25756 @cindex @code{.debug_gdb_scripts} section
25758 For systems using file formats like ELF and COFF,
25759 when @value{GDBN} loads a new object file
25760 it will look for a special section named @samp{.debug_gdb_scripts}.
25761 If this section exists, its contents is a list of names of scripts to load.
25763 @value{GDBN} will look for each specified script file first in the
25764 current directory and then along the source search path
25765 (@pxref{Source Path, ,Specifying Source Directories}),
25766 except that @file{$cdir} is not searched, since the compilation
25767 directory is not relevant to scripts.
25769 Entries can be placed in section @code{.debug_gdb_scripts} with,
25770 for example, this GCC macro:
25773 /* Note: The "MS" section flags are to remove duplicates. */
25774 #define DEFINE_GDB_SCRIPT(script_name) \
25776 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25778 .asciz \"" script_name "\"\n\
25784 Then one can reference the macro in a header or source file like this:
25787 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
25790 The script name may include directories if desired.
25792 Note that loading of this script file also requires accordingly configured
25793 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25795 If the macro is put in a header, any application or library
25796 using this header will get a reference to the specified script.
25798 @node Which flavor to choose?
25799 @subsubsection Which flavor to choose?
25801 Given the multiple ways of auto-loading Python scripts, it might not always
25802 be clear which one to choose. This section provides some guidance.
25804 Benefits of the @file{-gdb.py} way:
25808 Can be used with file formats that don't support multiple sections.
25811 Ease of finding scripts for public libraries.
25813 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25814 in the source search path.
25815 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25816 isn't a source directory in which to find the script.
25819 Doesn't require source code additions.
25822 Benefits of the @code{.debug_gdb_scripts} way:
25826 Works with static linking.
25828 Scripts for libraries done the @file{-gdb.py} way require an objfile to
25829 trigger their loading. When an application is statically linked the only
25830 objfile available is the executable, and it is cumbersome to attach all the
25831 scripts from all the input libraries to the executable's @file{-gdb.py} script.
25834 Works with classes that are entirely inlined.
25836 Some classes can be entirely inlined, and thus there may not be an associated
25837 shared library to attach a @file{-gdb.py} script to.
25840 Scripts needn't be copied out of the source tree.
25842 In some circumstances, apps can be built out of large collections of internal
25843 libraries, and the build infrastructure necessary to install the
25844 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
25845 cumbersome. It may be easier to specify the scripts in the
25846 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25847 top of the source tree to the source search path.
25850 @node Python modules
25851 @subsection Python modules
25852 @cindex python modules
25854 @value{GDBN} comes with several modules to assist writing Python code.
25857 * gdb.printing:: Building and registering pretty-printers.
25858 * gdb.types:: Utilities for working with types.
25859 * gdb.prompt:: Utilities for prompt value substitution.
25863 @subsubsection gdb.printing
25864 @cindex gdb.printing
25866 This module provides a collection of utilities for working with
25870 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
25871 This class specifies the API that makes @samp{info pretty-printer},
25872 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
25873 Pretty-printers should generally inherit from this class.
25875 @item SubPrettyPrinter (@var{name})
25876 For printers that handle multiple types, this class specifies the
25877 corresponding API for the subprinters.
25879 @item RegexpCollectionPrettyPrinter (@var{name})
25880 Utility class for handling multiple printers, all recognized via
25881 regular expressions.
25882 @xref{Writing a Pretty-Printer}, for an example.
25884 @item FlagEnumerationPrinter (@var{name})
25885 A pretty-printer which handles printing of @code{enum} values. Unlike
25886 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
25887 work properly when there is some overlap between the enumeration
25888 constants. @var{name} is the name of the printer and also the name of
25889 the @code{enum} type to look up.
25891 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
25892 Register @var{printer} with the pretty-printer list of @var{obj}.
25893 If @var{replace} is @code{True} then any existing copy of the printer
25894 is replaced. Otherwise a @code{RuntimeError} exception is raised
25895 if a printer with the same name already exists.
25899 @subsubsection gdb.types
25902 This module provides a collection of utilities for working with
25903 @code{gdb.Types} objects.
25906 @item get_basic_type (@var{type})
25907 Return @var{type} with const and volatile qualifiers stripped,
25908 and with typedefs and C@t{++} references converted to the underlying type.
25913 typedef const int const_int;
25915 const_int& foo_ref (foo);
25916 int main () @{ return 0; @}
25923 (gdb) python import gdb.types
25924 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
25925 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
25929 @item has_field (@var{type}, @var{field})
25930 Return @code{True} if @var{type}, assumed to be a type with fields
25931 (e.g., a structure or union), has field @var{field}.
25933 @item make_enum_dict (@var{enum_type})
25934 Return a Python @code{dictionary} type produced from @var{enum_type}.
25936 @item deep_items (@var{type})
25937 Returns a Python iterator similar to the standard
25938 @code{gdb.Type.iteritems} method, except that the iterator returned
25939 by @code{deep_items} will recursively traverse anonymous struct or
25940 union fields. For example:
25954 Then in @value{GDBN}:
25956 (@value{GDBP}) python import gdb.types
25957 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
25958 (@value{GDBP}) python print struct_a.keys ()
25960 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
25961 @{['a', 'b0', 'b1']@}
25967 @subsubsection gdb.prompt
25970 This module provides a method for prompt value-substitution.
25973 @item substitute_prompt (@var{string})
25974 Return @var{string} with escape sequences substituted by values. Some
25975 escape sequences take arguments. You can specify arguments inside
25976 ``@{@}'' immediately following the escape sequence.
25978 The escape sequences you can pass to this function are:
25982 Substitute a backslash.
25984 Substitute an ESC character.
25986 Substitute the selected frame; an argument names a frame parameter.
25988 Substitute a newline.
25990 Substitute a parameter's value; the argument names the parameter.
25992 Substitute a carriage return.
25994 Substitute the selected thread; an argument names a thread parameter.
25996 Substitute the version of GDB.
25998 Substitute the current working directory.
26000 Begin a sequence of non-printing characters. These sequences are
26001 typically used with the ESC character, and are not counted in the string
26002 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26003 blue-colored ``(gdb)'' prompt where the length is five.
26005 End a sequence of non-printing characters.
26011 substitute_prompt (``frame: \f,
26012 print arguments: \p@{print frame-arguments@}'')
26015 @exdent will return the string:
26018 "frame: main, print arguments: scalars"
26023 @section Creating new spellings of existing commands
26024 @cindex aliases for commands
26026 It is often useful to define alternate spellings of existing commands.
26027 For example, if a new @value{GDBN} command defined in Python has
26028 a long name to type, it is handy to have an abbreviated version of it
26029 that involves less typing.
26031 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26032 of the @samp{step} command even though it is otherwise an ambiguous
26033 abbreviation of other commands like @samp{set} and @samp{show}.
26035 Aliases are also used to provide shortened or more common versions
26036 of multi-word commands. For example, @value{GDBN} provides the
26037 @samp{tty} alias of the @samp{set inferior-tty} command.
26039 You can define a new alias with the @samp{alias} command.
26044 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26048 @var{ALIAS} specifies the name of the new alias.
26049 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26052 @var{COMMAND} specifies the name of an existing command
26053 that is being aliased.
26055 The @samp{-a} option specifies that the new alias is an abbreviation
26056 of the command. Abbreviations are not shown in command
26057 lists displayed by the @samp{help} command.
26059 The @samp{--} option specifies the end of options,
26060 and is useful when @var{ALIAS} begins with a dash.
26062 Here is a simple example showing how to make an abbreviation
26063 of a command so that there is less to type.
26064 Suppose you were tired of typing @samp{disas}, the current
26065 shortest unambiguous abbreviation of the @samp{disassemble} command
26066 and you wanted an even shorter version named @samp{di}.
26067 The following will accomplish this.
26070 (gdb) alias -a di = disas
26073 Note that aliases are different from user-defined commands.
26074 With a user-defined command, you also need to write documentation
26075 for it with the @samp{document} command.
26076 An alias automatically picks up the documentation of the existing command.
26078 Here is an example where we make @samp{elms} an abbreviation of
26079 @samp{elements} in the @samp{set print elements} command.
26080 This is to show that you can make an abbreviation of any part
26084 (gdb) alias -a set print elms = set print elements
26085 (gdb) alias -a show print elms = show print elements
26086 (gdb) set p elms 20
26088 Limit on string chars or array elements to print is 200.
26091 Note that if you are defining an alias of a @samp{set} command,
26092 and you want to have an alias for the corresponding @samp{show}
26093 command, then you need to define the latter separately.
26095 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26096 @var{ALIAS}, just as they are normally.
26099 (gdb) alias -a set pr elms = set p ele
26102 Finally, here is an example showing the creation of a one word
26103 alias for a more complex command.
26104 This creates alias @samp{spe} of the command @samp{set print elements}.
26107 (gdb) alias spe = set print elements
26112 @chapter Command Interpreters
26113 @cindex command interpreters
26115 @value{GDBN} supports multiple command interpreters, and some command
26116 infrastructure to allow users or user interface writers to switch
26117 between interpreters or run commands in other interpreters.
26119 @value{GDBN} currently supports two command interpreters, the console
26120 interpreter (sometimes called the command-line interpreter or @sc{cli})
26121 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26122 describes both of these interfaces in great detail.
26124 By default, @value{GDBN} will start with the console interpreter.
26125 However, the user may choose to start @value{GDBN} with another
26126 interpreter by specifying the @option{-i} or @option{--interpreter}
26127 startup options. Defined interpreters include:
26131 @cindex console interpreter
26132 The traditional console or command-line interpreter. This is the most often
26133 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26134 @value{GDBN} will use this interpreter.
26137 @cindex mi interpreter
26138 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26139 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26140 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26144 @cindex mi2 interpreter
26145 The current @sc{gdb/mi} interface.
26148 @cindex mi1 interpreter
26149 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26153 @cindex invoke another interpreter
26154 The interpreter being used by @value{GDBN} may not be dynamically
26155 switched at runtime. Although possible, this could lead to a very
26156 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26157 enters the command "interpreter-set console" in a console view,
26158 @value{GDBN} would switch to using the console interpreter, rendering
26159 the IDE inoperable!
26161 @kindex interpreter-exec
26162 Although you may only choose a single interpreter at startup, you may execute
26163 commands in any interpreter from the current interpreter using the appropriate
26164 command. If you are running the console interpreter, simply use the
26165 @code{interpreter-exec} command:
26168 interpreter-exec mi "-data-list-register-names"
26171 @sc{gdb/mi} has a similar command, although it is only available in versions of
26172 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26175 @chapter @value{GDBN} Text User Interface
26177 @cindex Text User Interface
26180 * TUI Overview:: TUI overview
26181 * TUI Keys:: TUI key bindings
26182 * TUI Single Key Mode:: TUI single key mode
26183 * TUI Commands:: TUI-specific commands
26184 * TUI Configuration:: TUI configuration variables
26187 The @value{GDBN} Text User Interface (TUI) is a terminal
26188 interface which uses the @code{curses} library to show the source
26189 file, the assembly output, the program registers and @value{GDBN}
26190 commands in separate text windows. The TUI mode is supported only
26191 on platforms where a suitable version of the @code{curses} library
26194 The TUI mode is enabled by default when you invoke @value{GDBN} as
26195 @samp{@value{GDBP} -tui}.
26196 You can also switch in and out of TUI mode while @value{GDBN} runs by
26197 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26198 @xref{TUI Keys, ,TUI Key Bindings}.
26201 @section TUI Overview
26203 In TUI mode, @value{GDBN} can display several text windows:
26207 This window is the @value{GDBN} command window with the @value{GDBN}
26208 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26209 managed using readline.
26212 The source window shows the source file of the program. The current
26213 line and active breakpoints are displayed in this window.
26216 The assembly window shows the disassembly output of the program.
26219 This window shows the processor registers. Registers are highlighted
26220 when their values change.
26223 The source and assembly windows show the current program position
26224 by highlighting the current line and marking it with a @samp{>} marker.
26225 Breakpoints are indicated with two markers. The first marker
26226 indicates the breakpoint type:
26230 Breakpoint which was hit at least once.
26233 Breakpoint which was never hit.
26236 Hardware breakpoint which was hit at least once.
26239 Hardware breakpoint which was never hit.
26242 The second marker indicates whether the breakpoint is enabled or not:
26246 Breakpoint is enabled.
26249 Breakpoint is disabled.
26252 The source, assembly and register windows are updated when the current
26253 thread changes, when the frame changes, or when the program counter
26256 These windows are not all visible at the same time. The command
26257 window is always visible. The others can be arranged in several
26268 source and assembly,
26271 source and registers, or
26274 assembly and registers.
26277 A status line above the command window shows the following information:
26281 Indicates the current @value{GDBN} target.
26282 (@pxref{Targets, ,Specifying a Debugging Target}).
26285 Gives the current process or thread number.
26286 When no process is being debugged, this field is set to @code{No process}.
26289 Gives the current function name for the selected frame.
26290 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26291 When there is no symbol corresponding to the current program counter,
26292 the string @code{??} is displayed.
26295 Indicates the current line number for the selected frame.
26296 When the current line number is not known, the string @code{??} is displayed.
26299 Indicates the current program counter address.
26303 @section TUI Key Bindings
26304 @cindex TUI key bindings
26306 The TUI installs several key bindings in the readline keymaps
26307 @ifset SYSTEM_READLINE
26308 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26310 @ifclear SYSTEM_READLINE
26311 (@pxref{Command Line Editing}).
26313 The following key bindings are installed for both TUI mode and the
26314 @value{GDBN} standard mode.
26323 Enter or leave the TUI mode. When leaving the TUI mode,
26324 the curses window management stops and @value{GDBN} operates using
26325 its standard mode, writing on the terminal directly. When reentering
26326 the TUI mode, control is given back to the curses windows.
26327 The screen is then refreshed.
26331 Use a TUI layout with only one window. The layout will
26332 either be @samp{source} or @samp{assembly}. When the TUI mode
26333 is not active, it will switch to the TUI mode.
26335 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26339 Use a TUI layout with at least two windows. When the current
26340 layout already has two windows, the next layout with two windows is used.
26341 When a new layout is chosen, one window will always be common to the
26342 previous layout and the new one.
26344 Think of it as the Emacs @kbd{C-x 2} binding.
26348 Change the active window. The TUI associates several key bindings
26349 (like scrolling and arrow keys) with the active window. This command
26350 gives the focus to the next TUI window.
26352 Think of it as the Emacs @kbd{C-x o} binding.
26356 Switch in and out of the TUI SingleKey mode that binds single
26357 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26360 The following key bindings only work in the TUI mode:
26365 Scroll the active window one page up.
26369 Scroll the active window one page down.
26373 Scroll the active window one line up.
26377 Scroll the active window one line down.
26381 Scroll the active window one column left.
26385 Scroll the active window one column right.
26389 Refresh the screen.
26392 Because the arrow keys scroll the active window in the TUI mode, they
26393 are not available for their normal use by readline unless the command
26394 window has the focus. When another window is active, you must use
26395 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26396 and @kbd{C-f} to control the command window.
26398 @node TUI Single Key Mode
26399 @section TUI Single Key Mode
26400 @cindex TUI single key mode
26402 The TUI also provides a @dfn{SingleKey} mode, which binds several
26403 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26404 switch into this mode, where the following key bindings are used:
26407 @kindex c @r{(SingleKey TUI key)}
26411 @kindex d @r{(SingleKey TUI key)}
26415 @kindex f @r{(SingleKey TUI key)}
26419 @kindex n @r{(SingleKey TUI key)}
26423 @kindex q @r{(SingleKey TUI key)}
26425 exit the SingleKey mode.
26427 @kindex r @r{(SingleKey TUI key)}
26431 @kindex s @r{(SingleKey TUI key)}
26435 @kindex u @r{(SingleKey TUI key)}
26439 @kindex v @r{(SingleKey TUI key)}
26443 @kindex w @r{(SingleKey TUI key)}
26448 Other keys temporarily switch to the @value{GDBN} command prompt.
26449 The key that was pressed is inserted in the editing buffer so that
26450 it is possible to type most @value{GDBN} commands without interaction
26451 with the TUI SingleKey mode. Once the command is entered the TUI
26452 SingleKey mode is restored. The only way to permanently leave
26453 this mode is by typing @kbd{q} or @kbd{C-x s}.
26457 @section TUI-specific Commands
26458 @cindex TUI commands
26460 The TUI has specific commands to control the text windows.
26461 These commands are always available, even when @value{GDBN} is not in
26462 the TUI mode. When @value{GDBN} is in the standard mode, most
26463 of these commands will automatically switch to the TUI mode.
26465 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26466 terminal, or @value{GDBN} has been started with the machine interface
26467 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26468 these commands will fail with an error, because it would not be
26469 possible or desirable to enable curses window management.
26474 List and give the size of all displayed windows.
26478 Display the next layout.
26481 Display the previous layout.
26484 Display the source window only.
26487 Display the assembly window only.
26490 Display the source and assembly window.
26493 Display the register window together with the source or assembly window.
26497 Make the next window active for scrolling.
26500 Make the previous window active for scrolling.
26503 Make the source window active for scrolling.
26506 Make the assembly window active for scrolling.
26509 Make the register window active for scrolling.
26512 Make the command window active for scrolling.
26516 Refresh the screen. This is similar to typing @kbd{C-L}.
26518 @item tui reg float
26520 Show the floating point registers in the register window.
26522 @item tui reg general
26523 Show the general registers in the register window.
26526 Show the next register group. The list of register groups as well as
26527 their order is target specific. The predefined register groups are the
26528 following: @code{general}, @code{float}, @code{system}, @code{vector},
26529 @code{all}, @code{save}, @code{restore}.
26531 @item tui reg system
26532 Show the system registers in the register window.
26536 Update the source window and the current execution point.
26538 @item winheight @var{name} +@var{count}
26539 @itemx winheight @var{name} -@var{count}
26541 Change the height of the window @var{name} by @var{count}
26542 lines. Positive counts increase the height, while negative counts
26545 @item tabset @var{nchars}
26547 Set the width of tab stops to be @var{nchars} characters.
26550 @node TUI Configuration
26551 @section TUI Configuration Variables
26552 @cindex TUI configuration variables
26554 Several configuration variables control the appearance of TUI windows.
26557 @item set tui border-kind @var{kind}
26558 @kindex set tui border-kind
26559 Select the border appearance for the source, assembly and register windows.
26560 The possible values are the following:
26563 Use a space character to draw the border.
26566 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26569 Use the Alternate Character Set to draw the border. The border is
26570 drawn using character line graphics if the terminal supports them.
26573 @item set tui border-mode @var{mode}
26574 @kindex set tui border-mode
26575 @itemx set tui active-border-mode @var{mode}
26576 @kindex set tui active-border-mode
26577 Select the display attributes for the borders of the inactive windows
26578 or the active window. The @var{mode} can be one of the following:
26581 Use normal attributes to display the border.
26587 Use reverse video mode.
26590 Use half bright mode.
26592 @item half-standout
26593 Use half bright and standout mode.
26596 Use extra bright or bold mode.
26598 @item bold-standout
26599 Use extra bright or bold and standout mode.
26604 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26607 @cindex @sc{gnu} Emacs
26608 A special interface allows you to use @sc{gnu} Emacs to view (and
26609 edit) the source files for the program you are debugging with
26612 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26613 executable file you want to debug as an argument. This command starts
26614 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26615 created Emacs buffer.
26616 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26618 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26623 All ``terminal'' input and output goes through an Emacs buffer, called
26626 This applies both to @value{GDBN} commands and their output, and to the input
26627 and output done by the program you are debugging.
26629 This is useful because it means that you can copy the text of previous
26630 commands and input them again; you can even use parts of the output
26633 All the facilities of Emacs' Shell mode are available for interacting
26634 with your program. In particular, you can send signals the usual
26635 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26639 @value{GDBN} displays source code through Emacs.
26641 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26642 source file for that frame and puts an arrow (@samp{=>}) at the
26643 left margin of the current line. Emacs uses a separate buffer for
26644 source display, and splits the screen to show both your @value{GDBN} session
26647 Explicit @value{GDBN} @code{list} or search commands still produce output as
26648 usual, but you probably have no reason to use them from Emacs.
26651 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26652 a graphical mode, enabled by default, which provides further buffers
26653 that can control the execution and describe the state of your program.
26654 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26656 If you specify an absolute file name when prompted for the @kbd{M-x
26657 gdb} argument, then Emacs sets your current working directory to where
26658 your program resides. If you only specify the file name, then Emacs
26659 sets your current working directory to the directory associated
26660 with the previous buffer. In this case, @value{GDBN} may find your
26661 program by searching your environment's @code{PATH} variable, but on
26662 some operating systems it might not find the source. So, although the
26663 @value{GDBN} input and output session proceeds normally, the auxiliary
26664 buffer does not display the current source and line of execution.
26666 The initial working directory of @value{GDBN} is printed on the top
26667 line of the GUD buffer and this serves as a default for the commands
26668 that specify files for @value{GDBN} to operate on. @xref{Files,
26669 ,Commands to Specify Files}.
26671 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26672 need to call @value{GDBN} by a different name (for example, if you
26673 keep several configurations around, with different names) you can
26674 customize the Emacs variable @code{gud-gdb-command-name} to run the
26677 In the GUD buffer, you can use these special Emacs commands in
26678 addition to the standard Shell mode commands:
26682 Describe the features of Emacs' GUD Mode.
26685 Execute to another source line, like the @value{GDBN} @code{step} command; also
26686 update the display window to show the current file and location.
26689 Execute to next source line in this function, skipping all function
26690 calls, like the @value{GDBN} @code{next} command. Then update the display window
26691 to show the current file and location.
26694 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26695 display window accordingly.
26698 Execute until exit from the selected stack frame, like the @value{GDBN}
26699 @code{finish} command.
26702 Continue execution of your program, like the @value{GDBN} @code{continue}
26706 Go up the number of frames indicated by the numeric argument
26707 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26708 like the @value{GDBN} @code{up} command.
26711 Go down the number of frames indicated by the numeric argument, like the
26712 @value{GDBN} @code{down} command.
26715 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26716 tells @value{GDBN} to set a breakpoint on the source line point is on.
26718 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26719 separate frame which shows a backtrace when the GUD buffer is current.
26720 Move point to any frame in the stack and type @key{RET} to make it
26721 become the current frame and display the associated source in the
26722 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26723 selected frame become the current one. In graphical mode, the
26724 speedbar displays watch expressions.
26726 If you accidentally delete the source-display buffer, an easy way to get
26727 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26728 request a frame display; when you run under Emacs, this recreates
26729 the source buffer if necessary to show you the context of the current
26732 The source files displayed in Emacs are in ordinary Emacs buffers
26733 which are visiting the source files in the usual way. You can edit
26734 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26735 communicates with Emacs in terms of line numbers. If you add or
26736 delete lines from the text, the line numbers that @value{GDBN} knows cease
26737 to correspond properly with the code.
26739 A more detailed description of Emacs' interaction with @value{GDBN} is
26740 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26743 @c The following dropped because Epoch is nonstandard. Reactivate
26744 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
26746 @kindex Emacs Epoch environment
26750 Version 18 of @sc{gnu} Emacs has a built-in window system
26751 called the @code{epoch}
26752 environment. Users of this environment can use a new command,
26753 @code{inspect} which performs identically to @code{print} except that
26754 each value is printed in its own window.
26759 @chapter The @sc{gdb/mi} Interface
26761 @unnumberedsec Function and Purpose
26763 @cindex @sc{gdb/mi}, its purpose
26764 @sc{gdb/mi} is a line based machine oriented text interface to
26765 @value{GDBN} and is activated by specifying using the
26766 @option{--interpreter} command line option (@pxref{Mode Options}). It
26767 is specifically intended to support the development of systems which
26768 use the debugger as just one small component of a larger system.
26770 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26771 in the form of a reference manual.
26773 Note that @sc{gdb/mi} is still under construction, so some of the
26774 features described below are incomplete and subject to change
26775 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26777 @unnumberedsec Notation and Terminology
26779 @cindex notational conventions, for @sc{gdb/mi}
26780 This chapter uses the following notation:
26784 @code{|} separates two alternatives.
26787 @code{[ @var{something} ]} indicates that @var{something} is optional:
26788 it may or may not be given.
26791 @code{( @var{group} )*} means that @var{group} inside the parentheses
26792 may repeat zero or more times.
26795 @code{( @var{group} )+} means that @var{group} inside the parentheses
26796 may repeat one or more times.
26799 @code{"@var{string}"} means a literal @var{string}.
26803 @heading Dependencies
26807 * GDB/MI General Design::
26808 * GDB/MI Command Syntax::
26809 * GDB/MI Compatibility with CLI::
26810 * GDB/MI Development and Front Ends::
26811 * GDB/MI Output Records::
26812 * GDB/MI Simple Examples::
26813 * GDB/MI Command Description Format::
26814 * GDB/MI Breakpoint Commands::
26815 * GDB/MI Program Context::
26816 * GDB/MI Thread Commands::
26817 * GDB/MI Ada Tasking Commands::
26818 * GDB/MI Program Execution::
26819 * GDB/MI Stack Manipulation::
26820 * GDB/MI Variable Objects::
26821 * GDB/MI Data Manipulation::
26822 * GDB/MI Tracepoint Commands::
26823 * GDB/MI Symbol Query::
26824 * GDB/MI File Commands::
26826 * GDB/MI Kod Commands::
26827 * GDB/MI Memory Overlay Commands::
26828 * GDB/MI Signal Handling Commands::
26830 * GDB/MI Target Manipulation::
26831 * GDB/MI File Transfer Commands::
26832 * GDB/MI Miscellaneous Commands::
26835 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26836 @node GDB/MI General Design
26837 @section @sc{gdb/mi} General Design
26838 @cindex GDB/MI General Design
26840 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26841 parts---commands sent to @value{GDBN}, responses to those commands
26842 and notifications. Each command results in exactly one response,
26843 indicating either successful completion of the command, or an error.
26844 For the commands that do not resume the target, the response contains the
26845 requested information. For the commands that resume the target, the
26846 response only indicates whether the target was successfully resumed.
26847 Notifications is the mechanism for reporting changes in the state of the
26848 target, or in @value{GDBN} state, that cannot conveniently be associated with
26849 a command and reported as part of that command response.
26851 The important examples of notifications are:
26855 Exec notifications. These are used to report changes in
26856 target state---when a target is resumed, or stopped. It would not
26857 be feasible to include this information in response of resuming
26858 commands, because one resume commands can result in multiple events in
26859 different threads. Also, quite some time may pass before any event
26860 happens in the target, while a frontend needs to know whether the resuming
26861 command itself was successfully executed.
26864 Console output, and status notifications. Console output
26865 notifications are used to report output of CLI commands, as well as
26866 diagnostics for other commands. Status notifications are used to
26867 report the progress of a long-running operation. Naturally, including
26868 this information in command response would mean no output is produced
26869 until the command is finished, which is undesirable.
26872 General notifications. Commands may have various side effects on
26873 the @value{GDBN} or target state beyond their official purpose. For example,
26874 a command may change the selected thread. Although such changes can
26875 be included in command response, using notification allows for more
26876 orthogonal frontend design.
26880 There's no guarantee that whenever an MI command reports an error,
26881 @value{GDBN} or the target are in any specific state, and especially,
26882 the state is not reverted to the state before the MI command was
26883 processed. Therefore, whenever an MI command results in an error,
26884 we recommend that the frontend refreshes all the information shown in
26885 the user interface.
26889 * Context management::
26890 * Asynchronous and non-stop modes::
26894 @node Context management
26895 @subsection Context management
26897 In most cases when @value{GDBN} accesses the target, this access is
26898 done in context of a specific thread and frame (@pxref{Frames}).
26899 Often, even when accessing global data, the target requires that a thread
26900 be specified. The CLI interface maintains the selected thread and frame,
26901 and supplies them to target on each command. This is convenient,
26902 because a command line user would not want to specify that information
26903 explicitly on each command, and because user interacts with
26904 @value{GDBN} via a single terminal, so no confusion is possible as
26905 to what thread and frame are the current ones.
26907 In the case of MI, the concept of selected thread and frame is less
26908 useful. First, a frontend can easily remember this information
26909 itself. Second, a graphical frontend can have more than one window,
26910 each one used for debugging a different thread, and the frontend might
26911 want to access additional threads for internal purposes. This
26912 increases the risk that by relying on implicitly selected thread, the
26913 frontend may be operating on a wrong one. Therefore, each MI command
26914 should explicitly specify which thread and frame to operate on. To
26915 make it possible, each MI command accepts the @samp{--thread} and
26916 @samp{--frame} options, the value to each is @value{GDBN} identifier
26917 for thread and frame to operate on.
26919 Usually, each top-level window in a frontend allows the user to select
26920 a thread and a frame, and remembers the user selection for further
26921 operations. However, in some cases @value{GDBN} may suggest that the
26922 current thread be changed. For example, when stopping on a breakpoint
26923 it is reasonable to switch to the thread where breakpoint is hit. For
26924 another example, if the user issues the CLI @samp{thread} command via
26925 the frontend, it is desirable to change the frontend's selected thread to the
26926 one specified by user. @value{GDBN} communicates the suggestion to
26927 change current thread using the @samp{=thread-selected} notification.
26928 No such notification is available for the selected frame at the moment.
26930 Note that historically, MI shares the selected thread with CLI, so
26931 frontends used the @code{-thread-select} to execute commands in the
26932 right context. However, getting this to work right is cumbersome. The
26933 simplest way is for frontend to emit @code{-thread-select} command
26934 before every command. This doubles the number of commands that need
26935 to be sent. The alternative approach is to suppress @code{-thread-select}
26936 if the selected thread in @value{GDBN} is supposed to be identical to the
26937 thread the frontend wants to operate on. However, getting this
26938 optimization right can be tricky. In particular, if the frontend
26939 sends several commands to @value{GDBN}, and one of the commands changes the
26940 selected thread, then the behaviour of subsequent commands will
26941 change. So, a frontend should either wait for response from such
26942 problematic commands, or explicitly add @code{-thread-select} for
26943 all subsequent commands. No frontend is known to do this exactly
26944 right, so it is suggested to just always pass the @samp{--thread} and
26945 @samp{--frame} options.
26947 @node Asynchronous and non-stop modes
26948 @subsection Asynchronous command execution and non-stop mode
26950 On some targets, @value{GDBN} is capable of processing MI commands
26951 even while the target is running. This is called @dfn{asynchronous
26952 command execution} (@pxref{Background Execution}). The frontend may
26953 specify a preferrence for asynchronous execution using the
26954 @code{-gdb-set target-async 1} command, which should be emitted before
26955 either running the executable or attaching to the target. After the
26956 frontend has started the executable or attached to the target, it can
26957 find if asynchronous execution is enabled using the
26958 @code{-list-target-features} command.
26960 Even if @value{GDBN} can accept a command while target is running,
26961 many commands that access the target do not work when the target is
26962 running. Therefore, asynchronous command execution is most useful
26963 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26964 it is possible to examine the state of one thread, while other threads
26967 When a given thread is running, MI commands that try to access the
26968 target in the context of that thread may not work, or may work only on
26969 some targets. In particular, commands that try to operate on thread's
26970 stack will not work, on any target. Commands that read memory, or
26971 modify breakpoints, may work or not work, depending on the target. Note
26972 that even commands that operate on global state, such as @code{print},
26973 @code{set}, and breakpoint commands, still access the target in the
26974 context of a specific thread, so frontend should try to find a
26975 stopped thread and perform the operation on that thread (using the
26976 @samp{--thread} option).
26978 Which commands will work in the context of a running thread is
26979 highly target dependent. However, the two commands
26980 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26981 to find the state of a thread, will always work.
26983 @node Thread groups
26984 @subsection Thread groups
26985 @value{GDBN} may be used to debug several processes at the same time.
26986 On some platfroms, @value{GDBN} may support debugging of several
26987 hardware systems, each one having several cores with several different
26988 processes running on each core. This section describes the MI
26989 mechanism to support such debugging scenarios.
26991 The key observation is that regardless of the structure of the
26992 target, MI can have a global list of threads, because most commands that
26993 accept the @samp{--thread} option do not need to know what process that
26994 thread belongs to. Therefore, it is not necessary to introduce
26995 neither additional @samp{--process} option, nor an notion of the
26996 current process in the MI interface. The only strictly new feature
26997 that is required is the ability to find how the threads are grouped
27000 To allow the user to discover such grouping, and to support arbitrary
27001 hierarchy of machines/cores/processes, MI introduces the concept of a
27002 @dfn{thread group}. Thread group is a collection of threads and other
27003 thread groups. A thread group always has a string identifier, a type,
27004 and may have additional attributes specific to the type. A new
27005 command, @code{-list-thread-groups}, returns the list of top-level
27006 thread groups, which correspond to processes that @value{GDBN} is
27007 debugging at the moment. By passing an identifier of a thread group
27008 to the @code{-list-thread-groups} command, it is possible to obtain
27009 the members of specific thread group.
27011 To allow the user to easily discover processes, and other objects, he
27012 wishes to debug, a concept of @dfn{available thread group} is
27013 introduced. Available thread group is an thread group that
27014 @value{GDBN} is not debugging, but that can be attached to, using the
27015 @code{-target-attach} command. The list of available top-level thread
27016 groups can be obtained using @samp{-list-thread-groups --available}.
27017 In general, the content of a thread group may be only retrieved only
27018 after attaching to that thread group.
27020 Thread groups are related to inferiors (@pxref{Inferiors and
27021 Programs}). Each inferior corresponds to a thread group of a special
27022 type @samp{process}, and some additional operations are permitted on
27023 such thread groups.
27025 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27026 @node GDB/MI Command Syntax
27027 @section @sc{gdb/mi} Command Syntax
27030 * GDB/MI Input Syntax::
27031 * GDB/MI Output Syntax::
27034 @node GDB/MI Input Syntax
27035 @subsection @sc{gdb/mi} Input Syntax
27037 @cindex input syntax for @sc{gdb/mi}
27038 @cindex @sc{gdb/mi}, input syntax
27040 @item @var{command} @expansion{}
27041 @code{@var{cli-command} | @var{mi-command}}
27043 @item @var{cli-command} @expansion{}
27044 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27045 @var{cli-command} is any existing @value{GDBN} CLI command.
27047 @item @var{mi-command} @expansion{}
27048 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27049 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27051 @item @var{token} @expansion{}
27052 "any sequence of digits"
27054 @item @var{option} @expansion{}
27055 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27057 @item @var{parameter} @expansion{}
27058 @code{@var{non-blank-sequence} | @var{c-string}}
27060 @item @var{operation} @expansion{}
27061 @emph{any of the operations described in this chapter}
27063 @item @var{non-blank-sequence} @expansion{}
27064 @emph{anything, provided it doesn't contain special characters such as
27065 "-", @var{nl}, """ and of course " "}
27067 @item @var{c-string} @expansion{}
27068 @code{""" @var{seven-bit-iso-c-string-content} """}
27070 @item @var{nl} @expansion{}
27079 The CLI commands are still handled by the @sc{mi} interpreter; their
27080 output is described below.
27083 The @code{@var{token}}, when present, is passed back when the command
27087 Some @sc{mi} commands accept optional arguments as part of the parameter
27088 list. Each option is identified by a leading @samp{-} (dash) and may be
27089 followed by an optional argument parameter. Options occur first in the
27090 parameter list and can be delimited from normal parameters using
27091 @samp{--} (this is useful when some parameters begin with a dash).
27098 We want easy access to the existing CLI syntax (for debugging).
27101 We want it to be easy to spot a @sc{mi} operation.
27104 @node GDB/MI Output Syntax
27105 @subsection @sc{gdb/mi} Output Syntax
27107 @cindex output syntax of @sc{gdb/mi}
27108 @cindex @sc{gdb/mi}, output syntax
27109 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27110 followed, optionally, by a single result record. This result record
27111 is for the most recent command. The sequence of output records is
27112 terminated by @samp{(gdb)}.
27114 If an input command was prefixed with a @code{@var{token}} then the
27115 corresponding output for that command will also be prefixed by that same
27119 @item @var{output} @expansion{}
27120 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27122 @item @var{result-record} @expansion{}
27123 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27125 @item @var{out-of-band-record} @expansion{}
27126 @code{@var{async-record} | @var{stream-record}}
27128 @item @var{async-record} @expansion{}
27129 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27131 @item @var{exec-async-output} @expansion{}
27132 @code{[ @var{token} ] "*" @var{async-output}}
27134 @item @var{status-async-output} @expansion{}
27135 @code{[ @var{token} ] "+" @var{async-output}}
27137 @item @var{notify-async-output} @expansion{}
27138 @code{[ @var{token} ] "=" @var{async-output}}
27140 @item @var{async-output} @expansion{}
27141 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27143 @item @var{result-class} @expansion{}
27144 @code{"done" | "running" | "connected" | "error" | "exit"}
27146 @item @var{async-class} @expansion{}
27147 @code{"stopped" | @var{others}} (where @var{others} will be added
27148 depending on the needs---this is still in development).
27150 @item @var{result} @expansion{}
27151 @code{ @var{variable} "=" @var{value}}
27153 @item @var{variable} @expansion{}
27154 @code{ @var{string} }
27156 @item @var{value} @expansion{}
27157 @code{ @var{const} | @var{tuple} | @var{list} }
27159 @item @var{const} @expansion{}
27160 @code{@var{c-string}}
27162 @item @var{tuple} @expansion{}
27163 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27165 @item @var{list} @expansion{}
27166 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27167 @var{result} ( "," @var{result} )* "]" }
27169 @item @var{stream-record} @expansion{}
27170 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27172 @item @var{console-stream-output} @expansion{}
27173 @code{"~" @var{c-string}}
27175 @item @var{target-stream-output} @expansion{}
27176 @code{"@@" @var{c-string}}
27178 @item @var{log-stream-output} @expansion{}
27179 @code{"&" @var{c-string}}
27181 @item @var{nl} @expansion{}
27184 @item @var{token} @expansion{}
27185 @emph{any sequence of digits}.
27193 All output sequences end in a single line containing a period.
27196 The @code{@var{token}} is from the corresponding request. Note that
27197 for all async output, while the token is allowed by the grammar and
27198 may be output by future versions of @value{GDBN} for select async
27199 output messages, it is generally omitted. Frontends should treat
27200 all async output as reporting general changes in the state of the
27201 target and there should be no need to associate async output to any
27205 @cindex status output in @sc{gdb/mi}
27206 @var{status-async-output} contains on-going status information about the
27207 progress of a slow operation. It can be discarded. All status output is
27208 prefixed by @samp{+}.
27211 @cindex async output in @sc{gdb/mi}
27212 @var{exec-async-output} contains asynchronous state change on the target
27213 (stopped, started, disappeared). All async output is prefixed by
27217 @cindex notify output in @sc{gdb/mi}
27218 @var{notify-async-output} contains supplementary information that the
27219 client should handle (e.g., a new breakpoint information). All notify
27220 output is prefixed by @samp{=}.
27223 @cindex console output in @sc{gdb/mi}
27224 @var{console-stream-output} is output that should be displayed as is in the
27225 console. It is the textual response to a CLI command. All the console
27226 output is prefixed by @samp{~}.
27229 @cindex target output in @sc{gdb/mi}
27230 @var{target-stream-output} is the output produced by the target program.
27231 All the target output is prefixed by @samp{@@}.
27234 @cindex log output in @sc{gdb/mi}
27235 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27236 instance messages that should be displayed as part of an error log. All
27237 the log output is prefixed by @samp{&}.
27240 @cindex list output in @sc{gdb/mi}
27241 New @sc{gdb/mi} commands should only output @var{lists} containing
27247 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27248 details about the various output records.
27250 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27251 @node GDB/MI Compatibility with CLI
27252 @section @sc{gdb/mi} Compatibility with CLI
27254 @cindex compatibility, @sc{gdb/mi} and CLI
27255 @cindex @sc{gdb/mi}, compatibility with CLI
27257 For the developers convenience CLI commands can be entered directly,
27258 but there may be some unexpected behaviour. For example, commands
27259 that query the user will behave as if the user replied yes, breakpoint
27260 command lists are not executed and some CLI commands, such as
27261 @code{if}, @code{when} and @code{define}, prompt for further input with
27262 @samp{>}, which is not valid MI output.
27264 This feature may be removed at some stage in the future and it is
27265 recommended that front ends use the @code{-interpreter-exec} command
27266 (@pxref{-interpreter-exec}).
27268 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27269 @node GDB/MI Development and Front Ends
27270 @section @sc{gdb/mi} Development and Front Ends
27271 @cindex @sc{gdb/mi} development
27273 The application which takes the MI output and presents the state of the
27274 program being debugged to the user is called a @dfn{front end}.
27276 Although @sc{gdb/mi} is still incomplete, it is currently being used
27277 by a variety of front ends to @value{GDBN}. This makes it difficult
27278 to introduce new functionality without breaking existing usage. This
27279 section tries to minimize the problems by describing how the protocol
27282 Some changes in MI need not break a carefully designed front end, and
27283 for these the MI version will remain unchanged. The following is a
27284 list of changes that may occur within one level, so front ends should
27285 parse MI output in a way that can handle them:
27289 New MI commands may be added.
27292 New fields may be added to the output of any MI command.
27295 The range of values for fields with specified values, e.g.,
27296 @code{in_scope} (@pxref{-var-update}) may be extended.
27298 @c The format of field's content e.g type prefix, may change so parse it
27299 @c at your own risk. Yes, in general?
27301 @c The order of fields may change? Shouldn't really matter but it might
27302 @c resolve inconsistencies.
27305 If the changes are likely to break front ends, the MI version level
27306 will be increased by one. This will allow the front end to parse the
27307 output according to the MI version. Apart from mi0, new versions of
27308 @value{GDBN} will not support old versions of MI and it will be the
27309 responsibility of the front end to work with the new one.
27311 @c Starting with mi3, add a new command -mi-version that prints the MI
27314 The best way to avoid unexpected changes in MI that might break your front
27315 end is to make your project known to @value{GDBN} developers and
27316 follow development on @email{gdb@@sourceware.org} and
27317 @email{gdb-patches@@sourceware.org}.
27318 @cindex mailing lists
27320 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27321 @node GDB/MI Output Records
27322 @section @sc{gdb/mi} Output Records
27325 * GDB/MI Result Records::
27326 * GDB/MI Stream Records::
27327 * GDB/MI Async Records::
27328 * GDB/MI Frame Information::
27329 * GDB/MI Thread Information::
27330 * GDB/MI Ada Exception Information::
27333 @node GDB/MI Result Records
27334 @subsection @sc{gdb/mi} Result Records
27336 @cindex result records in @sc{gdb/mi}
27337 @cindex @sc{gdb/mi}, result records
27338 In addition to a number of out-of-band notifications, the response to a
27339 @sc{gdb/mi} command includes one of the following result indications:
27343 @item "^done" [ "," @var{results} ]
27344 The synchronous operation was successful, @code{@var{results}} are the return
27349 This result record is equivalent to @samp{^done}. Historically, it
27350 was output instead of @samp{^done} if the command has resumed the
27351 target. This behaviour is maintained for backward compatibility, but
27352 all frontends should treat @samp{^done} and @samp{^running}
27353 identically and rely on the @samp{*running} output record to determine
27354 which threads are resumed.
27358 @value{GDBN} has connected to a remote target.
27360 @item "^error" "," @var{c-string}
27362 The operation failed. The @code{@var{c-string}} contains the corresponding
27367 @value{GDBN} has terminated.
27371 @node GDB/MI Stream Records
27372 @subsection @sc{gdb/mi} Stream Records
27374 @cindex @sc{gdb/mi}, stream records
27375 @cindex stream records in @sc{gdb/mi}
27376 @value{GDBN} internally maintains a number of output streams: the console, the
27377 target, and the log. The output intended for each of these streams is
27378 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27380 Each stream record begins with a unique @dfn{prefix character} which
27381 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27382 Syntax}). In addition to the prefix, each stream record contains a
27383 @code{@var{string-output}}. This is either raw text (with an implicit new
27384 line) or a quoted C string (which does not contain an implicit newline).
27387 @item "~" @var{string-output}
27388 The console output stream contains text that should be displayed in the
27389 CLI console window. It contains the textual responses to CLI commands.
27391 @item "@@" @var{string-output}
27392 The target output stream contains any textual output from the running
27393 target. This is only present when GDB's event loop is truly
27394 asynchronous, which is currently only the case for remote targets.
27396 @item "&" @var{string-output}
27397 The log stream contains debugging messages being produced by @value{GDBN}'s
27401 @node GDB/MI Async Records
27402 @subsection @sc{gdb/mi} Async Records
27404 @cindex async records in @sc{gdb/mi}
27405 @cindex @sc{gdb/mi}, async records
27406 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27407 additional changes that have occurred. Those changes can either be a
27408 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27409 target activity (e.g., target stopped).
27411 The following is the list of possible async records:
27415 @item *running,thread-id="@var{thread}"
27416 The target is now running. The @var{thread} field tells which
27417 specific thread is now running, and can be @samp{all} if all threads
27418 are running. The frontend should assume that no interaction with a
27419 running thread is possible after this notification is produced.
27420 The frontend should not assume that this notification is output
27421 only once for any command. @value{GDBN} may emit this notification
27422 several times, either for different threads, because it cannot resume
27423 all threads together, or even for a single thread, if the thread must
27424 be stepped though some code before letting it run freely.
27426 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27427 The target has stopped. The @var{reason} field can have one of the
27431 @item breakpoint-hit
27432 A breakpoint was reached.
27433 @item watchpoint-trigger
27434 A watchpoint was triggered.
27435 @item read-watchpoint-trigger
27436 A read watchpoint was triggered.
27437 @item access-watchpoint-trigger
27438 An access watchpoint was triggered.
27439 @item function-finished
27440 An -exec-finish or similar CLI command was accomplished.
27441 @item location-reached
27442 An -exec-until or similar CLI command was accomplished.
27443 @item watchpoint-scope
27444 A watchpoint has gone out of scope.
27445 @item end-stepping-range
27446 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27447 similar CLI command was accomplished.
27448 @item exited-signalled
27449 The inferior exited because of a signal.
27451 The inferior exited.
27452 @item exited-normally
27453 The inferior exited normally.
27454 @item signal-received
27455 A signal was received by the inferior.
27457 The inferior has stopped due to a library being loaded or unloaded.
27458 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27459 set or when a @code{catch load} or @code{catch unload} catchpoint is
27460 in use (@pxref{Set Catchpoints}).
27462 The inferior has forked. This is reported when @code{catch fork}
27463 (@pxref{Set Catchpoints}) has been used.
27465 The inferior has vforked. This is reported in when @code{catch vfork}
27466 (@pxref{Set Catchpoints}) has been used.
27467 @item syscall-entry
27468 The inferior entered a system call. This is reported when @code{catch
27469 syscall} (@pxref{Set Catchpoints}) has been used.
27470 @item syscall-entry
27471 The inferior returned from a system call. This is reported when
27472 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27474 The inferior called @code{exec}. This is reported when @code{catch exec}
27475 (@pxref{Set Catchpoints}) has been used.
27478 The @var{id} field identifies the thread that directly caused the stop
27479 -- for example by hitting a breakpoint. Depending on whether all-stop
27480 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27481 stop all threads, or only the thread that directly triggered the stop.
27482 If all threads are stopped, the @var{stopped} field will have the
27483 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27484 field will be a list of thread identifiers. Presently, this list will
27485 always include a single thread, but frontend should be prepared to see
27486 several threads in the list. The @var{core} field reports the
27487 processor core on which the stop event has happened. This field may be absent
27488 if such information is not available.
27490 @item =thread-group-added,id="@var{id}"
27491 @itemx =thread-group-removed,id="@var{id}"
27492 A thread group was either added or removed. The @var{id} field
27493 contains the @value{GDBN} identifier of the thread group. When a thread
27494 group is added, it generally might not be associated with a running
27495 process. When a thread group is removed, its id becomes invalid and
27496 cannot be used in any way.
27498 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27499 A thread group became associated with a running program,
27500 either because the program was just started or the thread group
27501 was attached to a program. The @var{id} field contains the
27502 @value{GDBN} identifier of the thread group. The @var{pid} field
27503 contains process identifier, specific to the operating system.
27505 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27506 A thread group is no longer associated with a running program,
27507 either because the program has exited, or because it was detached
27508 from. The @var{id} field contains the @value{GDBN} identifier of the
27509 thread group. @var{code} is the exit code of the inferior; it exists
27510 only when the inferior exited with some code.
27512 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27513 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27514 A thread either was created, or has exited. The @var{id} field
27515 contains the @value{GDBN} identifier of the thread. The @var{gid}
27516 field identifies the thread group this thread belongs to.
27518 @item =thread-selected,id="@var{id}"
27519 Informs that the selected thread was changed as result of the last
27520 command. This notification is not emitted as result of @code{-thread-select}
27521 command but is emitted whenever an MI command that is not documented
27522 to change the selected thread actually changes it. In particular,
27523 invoking, directly or indirectly (via user-defined command), the CLI
27524 @code{thread} command, will generate this notification.
27526 We suggest that in response to this notification, front ends
27527 highlight the selected thread and cause subsequent commands to apply to
27530 @item =library-loaded,...
27531 Reports that a new library file was loaded by the program. This
27532 notification has 4 fields---@var{id}, @var{target-name},
27533 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
27534 opaque identifier of the library. For remote debugging case,
27535 @var{target-name} and @var{host-name} fields give the name of the
27536 library file on the target, and on the host respectively. For native
27537 debugging, both those fields have the same value. The
27538 @var{symbols-loaded} field is emitted only for backward compatibility
27539 and should not be relied on to convey any useful information. The
27540 @var{thread-group} field, if present, specifies the id of the thread
27541 group in whose context the library was loaded. If the field is
27542 absent, it means the library was loaded in the context of all present
27545 @item =library-unloaded,...
27546 Reports that a library was unloaded by the program. This notification
27547 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27548 the same meaning as for the @code{=library-loaded} notification.
27549 The @var{thread-group} field, if present, specifies the id of the
27550 thread group in whose context the library was unloaded. If the field is
27551 absent, it means the library was unloaded in the context of all present
27554 @item =breakpoint-created,bkpt=@{...@}
27555 @itemx =breakpoint-modified,bkpt=@{...@}
27556 @itemx =breakpoint-deleted,bkpt=@{...@}
27557 Reports that a breakpoint was created, modified, or deleted,
27558 respectively. Only user-visible breakpoints are reported to the MI
27561 The @var{bkpt} argument is of the same form as returned by the various
27562 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
27564 Note that if a breakpoint is emitted in the result record of a
27565 command, then it will not also be emitted in an async record.
27569 @node GDB/MI Frame Information
27570 @subsection @sc{gdb/mi} Frame Information
27572 Response from many MI commands includes an information about stack
27573 frame. This information is a tuple that may have the following
27578 The level of the stack frame. The innermost frame has the level of
27579 zero. This field is always present.
27582 The name of the function corresponding to the frame. This field may
27583 be absent if @value{GDBN} is unable to determine the function name.
27586 The code address for the frame. This field is always present.
27589 The name of the source files that correspond to the frame's code
27590 address. This field may be absent.
27593 The source line corresponding to the frames' code address. This field
27597 The name of the binary file (either executable or shared library) the
27598 corresponds to the frame's code address. This field may be absent.
27602 @node GDB/MI Thread Information
27603 @subsection @sc{gdb/mi} Thread Information
27605 Whenever @value{GDBN} has to report an information about a thread, it
27606 uses a tuple with the following fields:
27610 The numeric id assigned to the thread by @value{GDBN}. This field is
27614 Target-specific string identifying the thread. This field is always present.
27617 Additional information about the thread provided by the target.
27618 It is supposed to be human-readable and not interpreted by the
27619 frontend. This field is optional.
27622 Either @samp{stopped} or @samp{running}, depending on whether the
27623 thread is presently running. This field is always present.
27626 The value of this field is an integer number of the processor core the
27627 thread was last seen on. This field is optional.
27630 @node GDB/MI Ada Exception Information
27631 @subsection @sc{gdb/mi} Ada Exception Information
27633 Whenever a @code{*stopped} record is emitted because the program
27634 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27635 @value{GDBN} provides the name of the exception that was raised via
27636 the @code{exception-name} field.
27638 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27639 @node GDB/MI Simple Examples
27640 @section Simple Examples of @sc{gdb/mi} Interaction
27641 @cindex @sc{gdb/mi}, simple examples
27643 This subsection presents several simple examples of interaction using
27644 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27645 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27646 the output received from @sc{gdb/mi}.
27648 Note the line breaks shown in the examples are here only for
27649 readability, they don't appear in the real output.
27651 @subheading Setting a Breakpoint
27653 Setting a breakpoint generates synchronous output which contains detailed
27654 information of the breakpoint.
27657 -> -break-insert main
27658 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27659 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27660 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
27664 @subheading Program Execution
27666 Program execution generates asynchronous records and MI gives the
27667 reason that execution stopped.
27673 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27674 frame=@{addr="0x08048564",func="main",
27675 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27676 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27681 <- *stopped,reason="exited-normally"
27685 @subheading Quitting @value{GDBN}
27687 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27695 Please note that @samp{^exit} is printed immediately, but it might
27696 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27697 performs necessary cleanups, including killing programs being debugged
27698 or disconnecting from debug hardware, so the frontend should wait till
27699 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27700 fails to exit in reasonable time.
27702 @subheading A Bad Command
27704 Here's what happens if you pass a non-existent command:
27708 <- ^error,msg="Undefined MI command: rubbish"
27713 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27714 @node GDB/MI Command Description Format
27715 @section @sc{gdb/mi} Command Description Format
27717 The remaining sections describe blocks of commands. Each block of
27718 commands is laid out in a fashion similar to this section.
27720 @subheading Motivation
27722 The motivation for this collection of commands.
27724 @subheading Introduction
27726 A brief introduction to this collection of commands as a whole.
27728 @subheading Commands
27730 For each command in the block, the following is described:
27732 @subsubheading Synopsis
27735 -command @var{args}@dots{}
27738 @subsubheading Result
27740 @subsubheading @value{GDBN} Command
27742 The corresponding @value{GDBN} CLI command(s), if any.
27744 @subsubheading Example
27746 Example(s) formatted for readability. Some of the described commands have
27747 not been implemented yet and these are labeled N.A.@: (not available).
27750 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27751 @node GDB/MI Breakpoint Commands
27752 @section @sc{gdb/mi} Breakpoint Commands
27754 @cindex breakpoint commands for @sc{gdb/mi}
27755 @cindex @sc{gdb/mi}, breakpoint commands
27756 This section documents @sc{gdb/mi} commands for manipulating
27759 @subheading The @code{-break-after} Command
27760 @findex -break-after
27762 @subsubheading Synopsis
27765 -break-after @var{number} @var{count}
27768 The breakpoint number @var{number} is not in effect until it has been
27769 hit @var{count} times. To see how this is reflected in the output of
27770 the @samp{-break-list} command, see the description of the
27771 @samp{-break-list} command below.
27773 @subsubheading @value{GDBN} Command
27775 The corresponding @value{GDBN} command is @samp{ignore}.
27777 @subsubheading Example
27782 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27783 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27784 fullname="/home/foo/hello.c",line="5",times="0"@}
27791 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27792 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27793 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27794 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27795 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27796 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27797 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27798 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27799 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27800 line="5",times="0",ignore="3"@}]@}
27805 @subheading The @code{-break-catch} Command
27806 @findex -break-catch
27809 @subheading The @code{-break-commands} Command
27810 @findex -break-commands
27812 @subsubheading Synopsis
27815 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27818 Specifies the CLI commands that should be executed when breakpoint
27819 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27820 are the commands. If no command is specified, any previously-set
27821 commands are cleared. @xref{Break Commands}. Typical use of this
27822 functionality is tracing a program, that is, printing of values of
27823 some variables whenever breakpoint is hit and then continuing.
27825 @subsubheading @value{GDBN} Command
27827 The corresponding @value{GDBN} command is @samp{commands}.
27829 @subsubheading Example
27834 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27835 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27836 fullname="/home/foo/hello.c",line="5",times="0"@}
27838 -break-commands 1 "print v" "continue"
27843 @subheading The @code{-break-condition} Command
27844 @findex -break-condition
27846 @subsubheading Synopsis
27849 -break-condition @var{number} @var{expr}
27852 Breakpoint @var{number} will stop the program only if the condition in
27853 @var{expr} is true. The condition becomes part of the
27854 @samp{-break-list} output (see the description of the @samp{-break-list}
27857 @subsubheading @value{GDBN} Command
27859 The corresponding @value{GDBN} command is @samp{condition}.
27861 @subsubheading Example
27865 -break-condition 1 1
27869 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27870 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27871 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27872 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27873 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27874 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27875 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27876 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27877 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27878 line="5",cond="1",times="0",ignore="3"@}]@}
27882 @subheading The @code{-break-delete} Command
27883 @findex -break-delete
27885 @subsubheading Synopsis
27888 -break-delete ( @var{breakpoint} )+
27891 Delete the breakpoint(s) whose number(s) are specified in the argument
27892 list. This is obviously reflected in the breakpoint list.
27894 @subsubheading @value{GDBN} Command
27896 The corresponding @value{GDBN} command is @samp{delete}.
27898 @subsubheading Example
27906 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27907 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27908 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27909 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27910 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27911 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27912 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27917 @subheading The @code{-break-disable} Command
27918 @findex -break-disable
27920 @subsubheading Synopsis
27923 -break-disable ( @var{breakpoint} )+
27926 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27927 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27929 @subsubheading @value{GDBN} Command
27931 The corresponding @value{GDBN} command is @samp{disable}.
27933 @subsubheading Example
27941 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27942 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27943 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27944 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27945 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27946 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27947 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27948 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27949 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27950 line="5",times="0"@}]@}
27954 @subheading The @code{-break-enable} Command
27955 @findex -break-enable
27957 @subsubheading Synopsis
27960 -break-enable ( @var{breakpoint} )+
27963 Enable (previously disabled) @var{breakpoint}(s).
27965 @subsubheading @value{GDBN} Command
27967 The corresponding @value{GDBN} command is @samp{enable}.
27969 @subsubheading Example
27977 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27978 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27979 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27980 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27981 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27982 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27983 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27984 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27985 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27986 line="5",times="0"@}]@}
27990 @subheading The @code{-break-info} Command
27991 @findex -break-info
27993 @subsubheading Synopsis
27996 -break-info @var{breakpoint}
28000 Get information about a single breakpoint.
28002 @subsubheading @value{GDBN} Command
28004 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28006 @subsubheading Example
28009 @subheading The @code{-break-insert} Command
28010 @findex -break-insert
28012 @subsubheading Synopsis
28015 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28016 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28017 [ -p @var{thread} ] [ @var{location} ]
28021 If specified, @var{location}, can be one of:
28028 @item filename:linenum
28029 @item filename:function
28033 The possible optional parameters of this command are:
28037 Insert a temporary breakpoint.
28039 Insert a hardware breakpoint.
28040 @item -c @var{condition}
28041 Make the breakpoint conditional on @var{condition}.
28042 @item -i @var{ignore-count}
28043 Initialize the @var{ignore-count}.
28045 If @var{location} cannot be parsed (for example if it
28046 refers to unknown files or functions), create a pending
28047 breakpoint. Without this flag, @value{GDBN} will report
28048 an error, and won't create a breakpoint, if @var{location}
28051 Create a disabled breakpoint.
28053 Create a tracepoint. @xref{Tracepoints}. When this parameter
28054 is used together with @samp{-h}, a fast tracepoint is created.
28057 @subsubheading Result
28059 The result is in the form:
28062 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
28063 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
28064 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
28065 times="@var{times}"@}
28069 where @var{number} is the @value{GDBN} number for this breakpoint,
28070 @var{funcname} is the name of the function where the breakpoint was
28071 inserted, @var{filename} is the name of the source file which contains
28072 this function, @var{lineno} is the source line number within that file
28073 and @var{times} the number of times that the breakpoint has been hit
28074 (always 0 for -break-insert but may be greater for -break-info or -break-list
28075 which use the same output).
28077 Note: this format is open to change.
28078 @c An out-of-band breakpoint instead of part of the result?
28080 @subsubheading @value{GDBN} Command
28082 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28083 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
28085 @subsubheading Example
28090 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28091 fullname="/home/foo/recursive2.c,line="4",times="0"@}
28093 -break-insert -t foo
28094 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28095 fullname="/home/foo/recursive2.c,line="11",times="0"@}
28098 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28099 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28100 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28101 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28102 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28103 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28104 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28105 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28106 addr="0x0001072c", func="main",file="recursive2.c",
28107 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
28108 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28109 addr="0x00010774",func="foo",file="recursive2.c",
28110 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
28112 -break-insert -r foo.*
28113 ~int foo(int, int);
28114 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28115 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
28119 @subheading The @code{-break-list} Command
28120 @findex -break-list
28122 @subsubheading Synopsis
28128 Displays the list of inserted breakpoints, showing the following fields:
28132 number of the breakpoint
28134 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28136 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28139 is the breakpoint enabled or no: @samp{y} or @samp{n}
28141 memory location at which the breakpoint is set
28143 logical location of the breakpoint, expressed by function name, file
28146 number of times the breakpoint has been hit
28149 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28150 @code{body} field is an empty list.
28152 @subsubheading @value{GDBN} Command
28154 The corresponding @value{GDBN} command is @samp{info break}.
28156 @subsubheading Example
28161 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28162 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28163 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28164 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28165 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28166 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28167 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28168 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28169 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
28170 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28171 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28172 line="13",times="0"@}]@}
28176 Here's an example of the result when there are no breakpoints:
28181 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28182 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28183 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28184 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28185 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28186 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28187 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28192 @subheading The @code{-break-passcount} Command
28193 @findex -break-passcount
28195 @subsubheading Synopsis
28198 -break-passcount @var{tracepoint-number} @var{passcount}
28201 Set the passcount for tracepoint @var{tracepoint-number} to
28202 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28203 is not a tracepoint, error is emitted. This corresponds to CLI
28204 command @samp{passcount}.
28206 @subheading The @code{-break-watch} Command
28207 @findex -break-watch
28209 @subsubheading Synopsis
28212 -break-watch [ -a | -r ]
28215 Create a watchpoint. With the @samp{-a} option it will create an
28216 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28217 read from or on a write to the memory location. With the @samp{-r}
28218 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28219 trigger only when the memory location is accessed for reading. Without
28220 either of the options, the watchpoint created is a regular watchpoint,
28221 i.e., it will trigger when the memory location is accessed for writing.
28222 @xref{Set Watchpoints, , Setting Watchpoints}.
28224 Note that @samp{-break-list} will report a single list of watchpoints and
28225 breakpoints inserted.
28227 @subsubheading @value{GDBN} Command
28229 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28232 @subsubheading Example
28234 Setting a watchpoint on a variable in the @code{main} function:
28239 ^done,wpt=@{number="2",exp="x"@}
28244 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28245 value=@{old="-268439212",new="55"@},
28246 frame=@{func="main",args=[],file="recursive2.c",
28247 fullname="/home/foo/bar/recursive2.c",line="5"@}
28251 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28252 the program execution twice: first for the variable changing value, then
28253 for the watchpoint going out of scope.
28258 ^done,wpt=@{number="5",exp="C"@}
28263 *stopped,reason="watchpoint-trigger",
28264 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28265 frame=@{func="callee4",args=[],
28266 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28267 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28272 *stopped,reason="watchpoint-scope",wpnum="5",
28273 frame=@{func="callee3",args=[@{name="strarg",
28274 value="0x11940 \"A string argument.\""@}],
28275 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28276 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28280 Listing breakpoints and watchpoints, at different points in the program
28281 execution. Note that once the watchpoint goes out of scope, it is
28287 ^done,wpt=@{number="2",exp="C"@}
28290 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28291 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28292 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28293 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28294 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28295 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28296 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28297 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28298 addr="0x00010734",func="callee4",
28299 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28300 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
28301 bkpt=@{number="2",type="watchpoint",disp="keep",
28302 enabled="y",addr="",what="C",times="0"@}]@}
28307 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28308 value=@{old="-276895068",new="3"@},
28309 frame=@{func="callee4",args=[],
28310 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28311 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28314 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28315 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28316 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28317 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28318 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28319 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28320 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28321 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28322 addr="0x00010734",func="callee4",
28323 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28324 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
28325 bkpt=@{number="2",type="watchpoint",disp="keep",
28326 enabled="y",addr="",what="C",times="-5"@}]@}
28330 ^done,reason="watchpoint-scope",wpnum="2",
28331 frame=@{func="callee3",args=[@{name="strarg",
28332 value="0x11940 \"A string argument.\""@}],
28333 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28334 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28337 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28338 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28339 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28340 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28341 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28342 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28343 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28344 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28345 addr="0x00010734",func="callee4",
28346 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28347 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28352 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28353 @node GDB/MI Program Context
28354 @section @sc{gdb/mi} Program Context
28356 @subheading The @code{-exec-arguments} Command
28357 @findex -exec-arguments
28360 @subsubheading Synopsis
28363 -exec-arguments @var{args}
28366 Set the inferior program arguments, to be used in the next
28369 @subsubheading @value{GDBN} Command
28371 The corresponding @value{GDBN} command is @samp{set args}.
28373 @subsubheading Example
28377 -exec-arguments -v word
28384 @subheading The @code{-exec-show-arguments} Command
28385 @findex -exec-show-arguments
28387 @subsubheading Synopsis
28390 -exec-show-arguments
28393 Print the arguments of the program.
28395 @subsubheading @value{GDBN} Command
28397 The corresponding @value{GDBN} command is @samp{show args}.
28399 @subsubheading Example
28404 @subheading The @code{-environment-cd} Command
28405 @findex -environment-cd
28407 @subsubheading Synopsis
28410 -environment-cd @var{pathdir}
28413 Set @value{GDBN}'s working directory.
28415 @subsubheading @value{GDBN} Command
28417 The corresponding @value{GDBN} command is @samp{cd}.
28419 @subsubheading Example
28423 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28429 @subheading The @code{-environment-directory} Command
28430 @findex -environment-directory
28432 @subsubheading Synopsis
28435 -environment-directory [ -r ] [ @var{pathdir} ]+
28438 Add directories @var{pathdir} to beginning of search path for source files.
28439 If the @samp{-r} option is used, the search path is reset to the default
28440 search path. If directories @var{pathdir} are supplied in addition to the
28441 @samp{-r} option, the search path is first reset and then addition
28443 Multiple directories may be specified, separated by blanks. Specifying
28444 multiple directories in a single command
28445 results in the directories added to the beginning of the
28446 search path in the same order they were presented in the command.
28447 If blanks are needed as
28448 part of a directory name, double-quotes should be used around
28449 the name. In the command output, the path will show up separated
28450 by the system directory-separator character. The directory-separator
28451 character must not be used
28452 in any directory name.
28453 If no directories are specified, the current search path is displayed.
28455 @subsubheading @value{GDBN} Command
28457 The corresponding @value{GDBN} command is @samp{dir}.
28459 @subsubheading Example
28463 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28464 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28466 -environment-directory ""
28467 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28469 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28470 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28472 -environment-directory -r
28473 ^done,source-path="$cdir:$cwd"
28478 @subheading The @code{-environment-path} Command
28479 @findex -environment-path
28481 @subsubheading Synopsis
28484 -environment-path [ -r ] [ @var{pathdir} ]+
28487 Add directories @var{pathdir} to beginning of search path for object files.
28488 If the @samp{-r} option is used, the search path is reset to the original
28489 search path that existed at gdb start-up. If directories @var{pathdir} are
28490 supplied in addition to the
28491 @samp{-r} option, the search path is first reset and then addition
28493 Multiple directories may be specified, separated by blanks. Specifying
28494 multiple directories in a single command
28495 results in the directories added to the beginning of the
28496 search path in the same order they were presented in the command.
28497 If blanks are needed as
28498 part of a directory name, double-quotes should be used around
28499 the name. In the command output, the path will show up separated
28500 by the system directory-separator character. The directory-separator
28501 character must not be used
28502 in any directory name.
28503 If no directories are specified, the current path is displayed.
28506 @subsubheading @value{GDBN} Command
28508 The corresponding @value{GDBN} command is @samp{path}.
28510 @subsubheading Example
28515 ^done,path="/usr/bin"
28517 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28518 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28520 -environment-path -r /usr/local/bin
28521 ^done,path="/usr/local/bin:/usr/bin"
28526 @subheading The @code{-environment-pwd} Command
28527 @findex -environment-pwd
28529 @subsubheading Synopsis
28535 Show the current working directory.
28537 @subsubheading @value{GDBN} Command
28539 The corresponding @value{GDBN} command is @samp{pwd}.
28541 @subsubheading Example
28546 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28550 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28551 @node GDB/MI Thread Commands
28552 @section @sc{gdb/mi} Thread Commands
28555 @subheading The @code{-thread-info} Command
28556 @findex -thread-info
28558 @subsubheading Synopsis
28561 -thread-info [ @var{thread-id} ]
28564 Reports information about either a specific thread, if
28565 the @var{thread-id} parameter is present, or about all
28566 threads. When printing information about all threads,
28567 also reports the current thread.
28569 @subsubheading @value{GDBN} Command
28571 The @samp{info thread} command prints the same information
28574 @subsubheading Result
28576 The result is a list of threads. The following attributes are
28577 defined for a given thread:
28581 This field exists only for the current thread. It has the value @samp{*}.
28584 The identifier that @value{GDBN} uses to refer to the thread.
28587 The identifier that the target uses to refer to the thread.
28590 Extra information about the thread, in a target-specific format. This
28594 The name of the thread. If the user specified a name using the
28595 @code{thread name} command, then this name is given. Otherwise, if
28596 @value{GDBN} can extract the thread name from the target, then that
28597 name is given. If @value{GDBN} cannot find the thread name, then this
28601 The stack frame currently executing in the thread.
28604 The thread's state. The @samp{state} field may have the following
28609 The thread is stopped. Frame information is available for stopped
28613 The thread is running. There's no frame information for running
28619 If @value{GDBN} can find the CPU core on which this thread is running,
28620 then this field is the core identifier. This field is optional.
28624 @subsubheading Example
28629 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28630 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28631 args=[]@},state="running"@},
28632 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28633 frame=@{level="0",addr="0x0804891f",func="foo",
28634 args=[@{name="i",value="10"@}],
28635 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28636 state="running"@}],
28637 current-thread-id="1"
28641 @subheading The @code{-thread-list-ids} Command
28642 @findex -thread-list-ids
28644 @subsubheading Synopsis
28650 Produces a list of the currently known @value{GDBN} thread ids. At the
28651 end of the list it also prints the total number of such threads.
28653 This command is retained for historical reasons, the
28654 @code{-thread-info} command should be used instead.
28656 @subsubheading @value{GDBN} Command
28658 Part of @samp{info threads} supplies the same information.
28660 @subsubheading Example
28665 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28666 current-thread-id="1",number-of-threads="3"
28671 @subheading The @code{-thread-select} Command
28672 @findex -thread-select
28674 @subsubheading Synopsis
28677 -thread-select @var{threadnum}
28680 Make @var{threadnum} the current thread. It prints the number of the new
28681 current thread, and the topmost frame for that thread.
28683 This command is deprecated in favor of explicitly using the
28684 @samp{--thread} option to each command.
28686 @subsubheading @value{GDBN} Command
28688 The corresponding @value{GDBN} command is @samp{thread}.
28690 @subsubheading Example
28697 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28698 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28702 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28703 number-of-threads="3"
28706 ^done,new-thread-id="3",
28707 frame=@{level="0",func="vprintf",
28708 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28709 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28713 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28714 @node GDB/MI Ada Tasking Commands
28715 @section @sc{gdb/mi} Ada Tasking Commands
28717 @subheading The @code{-ada-task-info} Command
28718 @findex -ada-task-info
28720 @subsubheading Synopsis
28723 -ada-task-info [ @var{task-id} ]
28726 Reports information about either a specific Ada task, if the
28727 @var{task-id} parameter is present, or about all Ada tasks.
28729 @subsubheading @value{GDBN} Command
28731 The @samp{info tasks} command prints the same information
28732 about all Ada tasks (@pxref{Ada Tasks}).
28734 @subsubheading Result
28736 The result is a table of Ada tasks. The following columns are
28737 defined for each Ada task:
28741 This field exists only for the current thread. It has the value @samp{*}.
28744 The identifier that @value{GDBN} uses to refer to the Ada task.
28747 The identifier that the target uses to refer to the Ada task.
28750 The identifier of the thread corresponding to the Ada task.
28752 This field should always exist, as Ada tasks are always implemented
28753 on top of a thread. But if @value{GDBN} cannot find this corresponding
28754 thread for any reason, the field is omitted.
28757 This field exists only when the task was created by another task.
28758 In this case, it provides the ID of the parent task.
28761 The base priority of the task.
28764 The current state of the task. For a detailed description of the
28765 possible states, see @ref{Ada Tasks}.
28768 The name of the task.
28772 @subsubheading Example
28776 ^done,tasks=@{nr_rows="3",nr_cols="8",
28777 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28778 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28779 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28780 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28781 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28782 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28783 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28784 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28785 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28786 state="Child Termination Wait",name="main_task"@}]@}
28790 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28791 @node GDB/MI Program Execution
28792 @section @sc{gdb/mi} Program Execution
28794 These are the asynchronous commands which generate the out-of-band
28795 record @samp{*stopped}. Currently @value{GDBN} only really executes
28796 asynchronously with remote targets and this interaction is mimicked in
28799 @subheading The @code{-exec-continue} Command
28800 @findex -exec-continue
28802 @subsubheading Synopsis
28805 -exec-continue [--reverse] [--all|--thread-group N]
28808 Resumes the execution of the inferior program, which will continue
28809 to execute until it reaches a debugger stop event. If the
28810 @samp{--reverse} option is specified, execution resumes in reverse until
28811 it reaches a stop event. Stop events may include
28814 breakpoints or watchpoints
28816 signals or exceptions
28818 the end of the process (or its beginning under @samp{--reverse})
28820 the end or beginning of a replay log if one is being used.
28822 In all-stop mode (@pxref{All-Stop
28823 Mode}), may resume only one thread, or all threads, depending on the
28824 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28825 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28826 ignored in all-stop mode. If the @samp{--thread-group} options is
28827 specified, then all threads in that thread group are resumed.
28829 @subsubheading @value{GDBN} Command
28831 The corresponding @value{GDBN} corresponding is @samp{continue}.
28833 @subsubheading Example
28840 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28841 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28847 @subheading The @code{-exec-finish} Command
28848 @findex -exec-finish
28850 @subsubheading Synopsis
28853 -exec-finish [--reverse]
28856 Resumes the execution of the inferior program until the current
28857 function is exited. Displays the results returned by the function.
28858 If the @samp{--reverse} option is specified, resumes the reverse
28859 execution of the inferior program until the point where current
28860 function was called.
28862 @subsubheading @value{GDBN} Command
28864 The corresponding @value{GDBN} command is @samp{finish}.
28866 @subsubheading Example
28868 Function returning @code{void}.
28875 *stopped,reason="function-finished",frame=@{func="main",args=[],
28876 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28880 Function returning other than @code{void}. The name of the internal
28881 @value{GDBN} variable storing the result is printed, together with the
28888 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28889 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28890 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28891 gdb-result-var="$1",return-value="0"
28896 @subheading The @code{-exec-interrupt} Command
28897 @findex -exec-interrupt
28899 @subsubheading Synopsis
28902 -exec-interrupt [--all|--thread-group N]
28905 Interrupts the background execution of the target. Note how the token
28906 associated with the stop message is the one for the execution command
28907 that has been interrupted. The token for the interrupt itself only
28908 appears in the @samp{^done} output. If the user is trying to
28909 interrupt a non-running program, an error message will be printed.
28911 Note that when asynchronous execution is enabled, this command is
28912 asynchronous just like other execution commands. That is, first the
28913 @samp{^done} response will be printed, and the target stop will be
28914 reported after that using the @samp{*stopped} notification.
28916 In non-stop mode, only the context thread is interrupted by default.
28917 All threads (in all inferiors) will be interrupted if the
28918 @samp{--all} option is specified. If the @samp{--thread-group}
28919 option is specified, all threads in that group will be interrupted.
28921 @subsubheading @value{GDBN} Command
28923 The corresponding @value{GDBN} command is @samp{interrupt}.
28925 @subsubheading Example
28936 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28937 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28938 fullname="/home/foo/bar/try.c",line="13"@}
28943 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28947 @subheading The @code{-exec-jump} Command
28950 @subsubheading Synopsis
28953 -exec-jump @var{location}
28956 Resumes execution of the inferior program at the location specified by
28957 parameter. @xref{Specify Location}, for a description of the
28958 different forms of @var{location}.
28960 @subsubheading @value{GDBN} Command
28962 The corresponding @value{GDBN} command is @samp{jump}.
28964 @subsubheading Example
28967 -exec-jump foo.c:10
28968 *running,thread-id="all"
28973 @subheading The @code{-exec-next} Command
28976 @subsubheading Synopsis
28979 -exec-next [--reverse]
28982 Resumes execution of the inferior program, stopping when the beginning
28983 of the next source line is reached.
28985 If the @samp{--reverse} option is specified, resumes reverse execution
28986 of the inferior program, stopping at the beginning of the previous
28987 source line. If you issue this command on the first line of a
28988 function, it will take you back to the caller of that function, to the
28989 source line where the function was called.
28992 @subsubheading @value{GDBN} Command
28994 The corresponding @value{GDBN} command is @samp{next}.
28996 @subsubheading Example
29002 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29007 @subheading The @code{-exec-next-instruction} Command
29008 @findex -exec-next-instruction
29010 @subsubheading Synopsis
29013 -exec-next-instruction [--reverse]
29016 Executes one machine instruction. If the instruction is a function
29017 call, continues until the function returns. If the program stops at an
29018 instruction in the middle of a source line, the address will be
29021 If the @samp{--reverse} option is specified, resumes reverse execution
29022 of the inferior program, stopping at the previous instruction. If the
29023 previously executed instruction was a return from another function,
29024 it will continue to execute in reverse until the call to that function
29025 (from the current stack frame) is reached.
29027 @subsubheading @value{GDBN} Command
29029 The corresponding @value{GDBN} command is @samp{nexti}.
29031 @subsubheading Example
29035 -exec-next-instruction
29039 *stopped,reason="end-stepping-range",
29040 addr="0x000100d4",line="5",file="hello.c"
29045 @subheading The @code{-exec-return} Command
29046 @findex -exec-return
29048 @subsubheading Synopsis
29054 Makes current function return immediately. Doesn't execute the inferior.
29055 Displays the new current frame.
29057 @subsubheading @value{GDBN} Command
29059 The corresponding @value{GDBN} command is @samp{return}.
29061 @subsubheading Example
29065 200-break-insert callee4
29066 200^done,bkpt=@{number="1",addr="0x00010734",
29067 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29072 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29073 frame=@{func="callee4",args=[],
29074 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29075 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29081 111^done,frame=@{level="0",func="callee3",
29082 args=[@{name="strarg",
29083 value="0x11940 \"A string argument.\""@}],
29084 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29085 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29090 @subheading The @code{-exec-run} Command
29093 @subsubheading Synopsis
29096 -exec-run [--all | --thread-group N]
29099 Starts execution of the inferior from the beginning. The inferior
29100 executes until either a breakpoint is encountered or the program
29101 exits. In the latter case the output will include an exit code, if
29102 the program has exited exceptionally.
29104 When no option is specified, the current inferior is started. If the
29105 @samp{--thread-group} option is specified, it should refer to a thread
29106 group of type @samp{process}, and that thread group will be started.
29107 If the @samp{--all} option is specified, then all inferiors will be started.
29109 @subsubheading @value{GDBN} Command
29111 The corresponding @value{GDBN} command is @samp{run}.
29113 @subsubheading Examples
29118 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29123 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29124 frame=@{func="main",args=[],file="recursive2.c",
29125 fullname="/home/foo/bar/recursive2.c",line="4"@}
29130 Program exited normally:
29138 *stopped,reason="exited-normally"
29143 Program exited exceptionally:
29151 *stopped,reason="exited",exit-code="01"
29155 Another way the program can terminate is if it receives a signal such as
29156 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29160 *stopped,reason="exited-signalled",signal-name="SIGINT",
29161 signal-meaning="Interrupt"
29165 @c @subheading -exec-signal
29168 @subheading The @code{-exec-step} Command
29171 @subsubheading Synopsis
29174 -exec-step [--reverse]
29177 Resumes execution of the inferior program, stopping when the beginning
29178 of the next source line is reached, if the next source line is not a
29179 function call. If it is, stop at the first instruction of the called
29180 function. If the @samp{--reverse} option is specified, resumes reverse
29181 execution of the inferior program, stopping at the beginning of the
29182 previously executed source line.
29184 @subsubheading @value{GDBN} Command
29186 The corresponding @value{GDBN} command is @samp{step}.
29188 @subsubheading Example
29190 Stepping into a function:
29196 *stopped,reason="end-stepping-range",
29197 frame=@{func="foo",args=[@{name="a",value="10"@},
29198 @{name="b",value="0"@}],file="recursive2.c",
29199 fullname="/home/foo/bar/recursive2.c",line="11"@}
29209 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29214 @subheading The @code{-exec-step-instruction} Command
29215 @findex -exec-step-instruction
29217 @subsubheading Synopsis
29220 -exec-step-instruction [--reverse]
29223 Resumes the inferior which executes one machine instruction. If the
29224 @samp{--reverse} option is specified, resumes reverse execution of the
29225 inferior program, stopping at the previously executed instruction.
29226 The output, once @value{GDBN} has stopped, will vary depending on
29227 whether we have stopped in the middle of a source line or not. In the
29228 former case, the address at which the program stopped will be printed
29231 @subsubheading @value{GDBN} Command
29233 The corresponding @value{GDBN} command is @samp{stepi}.
29235 @subsubheading Example
29239 -exec-step-instruction
29243 *stopped,reason="end-stepping-range",
29244 frame=@{func="foo",args=[],file="try.c",
29245 fullname="/home/foo/bar/try.c",line="10"@}
29247 -exec-step-instruction
29251 *stopped,reason="end-stepping-range",
29252 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29253 fullname="/home/foo/bar/try.c",line="10"@}
29258 @subheading The @code{-exec-until} Command
29259 @findex -exec-until
29261 @subsubheading Synopsis
29264 -exec-until [ @var{location} ]
29267 Executes the inferior until the @var{location} specified in the
29268 argument is reached. If there is no argument, the inferior executes
29269 until a source line greater than the current one is reached. The
29270 reason for stopping in this case will be @samp{location-reached}.
29272 @subsubheading @value{GDBN} Command
29274 The corresponding @value{GDBN} command is @samp{until}.
29276 @subsubheading Example
29280 -exec-until recursive2.c:6
29284 *stopped,reason="location-reached",frame=@{func="main",args=[],
29285 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29290 @subheading -file-clear
29291 Is this going away????
29294 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29295 @node GDB/MI Stack Manipulation
29296 @section @sc{gdb/mi} Stack Manipulation Commands
29299 @subheading The @code{-stack-info-frame} Command
29300 @findex -stack-info-frame
29302 @subsubheading Synopsis
29308 Get info on the selected frame.
29310 @subsubheading @value{GDBN} Command
29312 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29313 (without arguments).
29315 @subsubheading Example
29320 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29321 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29322 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29326 @subheading The @code{-stack-info-depth} Command
29327 @findex -stack-info-depth
29329 @subsubheading Synopsis
29332 -stack-info-depth [ @var{max-depth} ]
29335 Return the depth of the stack. If the integer argument @var{max-depth}
29336 is specified, do not count beyond @var{max-depth} frames.
29338 @subsubheading @value{GDBN} Command
29340 There's no equivalent @value{GDBN} command.
29342 @subsubheading Example
29344 For a stack with frame levels 0 through 11:
29351 -stack-info-depth 4
29354 -stack-info-depth 12
29357 -stack-info-depth 11
29360 -stack-info-depth 13
29365 @subheading The @code{-stack-list-arguments} Command
29366 @findex -stack-list-arguments
29368 @subsubheading Synopsis
29371 -stack-list-arguments @var{print-values}
29372 [ @var{low-frame} @var{high-frame} ]
29375 Display a list of the arguments for the frames between @var{low-frame}
29376 and @var{high-frame} (inclusive). If @var{low-frame} and
29377 @var{high-frame} are not provided, list the arguments for the whole
29378 call stack. If the two arguments are equal, show the single frame
29379 at the corresponding level. It is an error if @var{low-frame} is
29380 larger than the actual number of frames. On the other hand,
29381 @var{high-frame} may be larger than the actual number of frames, in
29382 which case only existing frames will be returned.
29384 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29385 the variables; if it is 1 or @code{--all-values}, print also their
29386 values; and if it is 2 or @code{--simple-values}, print the name,
29387 type and value for simple data types, and the name and type for arrays,
29388 structures and unions.
29390 Use of this command to obtain arguments in a single frame is
29391 deprecated in favor of the @samp{-stack-list-variables} command.
29393 @subsubheading @value{GDBN} Command
29395 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29396 @samp{gdb_get_args} command which partially overlaps with the
29397 functionality of @samp{-stack-list-arguments}.
29399 @subsubheading Example
29406 frame=@{level="0",addr="0x00010734",func="callee4",
29407 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29408 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29409 frame=@{level="1",addr="0x0001076c",func="callee3",
29410 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29411 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29412 frame=@{level="2",addr="0x0001078c",func="callee2",
29413 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29414 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29415 frame=@{level="3",addr="0x000107b4",func="callee1",
29416 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29417 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29418 frame=@{level="4",addr="0x000107e0",func="main",
29419 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29420 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29422 -stack-list-arguments 0
29425 frame=@{level="0",args=[]@},
29426 frame=@{level="1",args=[name="strarg"]@},
29427 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29428 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29429 frame=@{level="4",args=[]@}]
29431 -stack-list-arguments 1
29434 frame=@{level="0",args=[]@},
29436 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29437 frame=@{level="2",args=[
29438 @{name="intarg",value="2"@},
29439 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29440 @{frame=@{level="3",args=[
29441 @{name="intarg",value="2"@},
29442 @{name="strarg",value="0x11940 \"A string argument.\""@},
29443 @{name="fltarg",value="3.5"@}]@},
29444 frame=@{level="4",args=[]@}]
29446 -stack-list-arguments 0 2 2
29447 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29449 -stack-list-arguments 1 2 2
29450 ^done,stack-args=[frame=@{level="2",
29451 args=[@{name="intarg",value="2"@},
29452 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29456 @c @subheading -stack-list-exception-handlers
29459 @subheading The @code{-stack-list-frames} Command
29460 @findex -stack-list-frames
29462 @subsubheading Synopsis
29465 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
29468 List the frames currently on the stack. For each frame it displays the
29473 The frame number, 0 being the topmost frame, i.e., the innermost function.
29475 The @code{$pc} value for that frame.
29479 File name of the source file where the function lives.
29480 @item @var{fullname}
29481 The full file name of the source file where the function lives.
29483 Line number corresponding to the @code{$pc}.
29485 The shared library where this function is defined. This is only given
29486 if the frame's function is not known.
29489 If invoked without arguments, this command prints a backtrace for the
29490 whole stack. If given two integer arguments, it shows the frames whose
29491 levels are between the two arguments (inclusive). If the two arguments
29492 are equal, it shows the single frame at the corresponding level. It is
29493 an error if @var{low-frame} is larger than the actual number of
29494 frames. On the other hand, @var{high-frame} may be larger than the
29495 actual number of frames, in which case only existing frames will be returned.
29497 @subsubheading @value{GDBN} Command
29499 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29501 @subsubheading Example
29503 Full stack backtrace:
29509 [frame=@{level="0",addr="0x0001076c",func="foo",
29510 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29511 frame=@{level="1",addr="0x000107a4",func="foo",
29512 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29513 frame=@{level="2",addr="0x000107a4",func="foo",
29514 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29515 frame=@{level="3",addr="0x000107a4",func="foo",
29516 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29517 frame=@{level="4",addr="0x000107a4",func="foo",
29518 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29519 frame=@{level="5",addr="0x000107a4",func="foo",
29520 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29521 frame=@{level="6",addr="0x000107a4",func="foo",
29522 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29523 frame=@{level="7",addr="0x000107a4",func="foo",
29524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29525 frame=@{level="8",addr="0x000107a4",func="foo",
29526 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29527 frame=@{level="9",addr="0x000107a4",func="foo",
29528 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29529 frame=@{level="10",addr="0x000107a4",func="foo",
29530 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29531 frame=@{level="11",addr="0x00010738",func="main",
29532 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29536 Show frames between @var{low_frame} and @var{high_frame}:
29540 -stack-list-frames 3 5
29542 [frame=@{level="3",addr="0x000107a4",func="foo",
29543 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29544 frame=@{level="4",addr="0x000107a4",func="foo",
29545 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29546 frame=@{level="5",addr="0x000107a4",func="foo",
29547 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29551 Show a single frame:
29555 -stack-list-frames 3 3
29557 [frame=@{level="3",addr="0x000107a4",func="foo",
29558 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29563 @subheading The @code{-stack-list-locals} Command
29564 @findex -stack-list-locals
29566 @subsubheading Synopsis
29569 -stack-list-locals @var{print-values}
29572 Display the local variable names for the selected frame. If
29573 @var{print-values} is 0 or @code{--no-values}, print only the names of
29574 the variables; if it is 1 or @code{--all-values}, print also their
29575 values; and if it is 2 or @code{--simple-values}, print the name,
29576 type and value for simple data types, and the name and type for arrays,
29577 structures and unions. In this last case, a frontend can immediately
29578 display the value of simple data types and create variable objects for
29579 other data types when the user wishes to explore their values in
29582 This command is deprecated in favor of the
29583 @samp{-stack-list-variables} command.
29585 @subsubheading @value{GDBN} Command
29587 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29589 @subsubheading Example
29593 -stack-list-locals 0
29594 ^done,locals=[name="A",name="B",name="C"]
29596 -stack-list-locals --all-values
29597 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29598 @{name="C",value="@{1, 2, 3@}"@}]
29599 -stack-list-locals --simple-values
29600 ^done,locals=[@{name="A",type="int",value="1"@},
29601 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29605 @subheading The @code{-stack-list-variables} Command
29606 @findex -stack-list-variables
29608 @subsubheading Synopsis
29611 -stack-list-variables @var{print-values}
29614 Display the names of local variables and function arguments for the selected frame. If
29615 @var{print-values} is 0 or @code{--no-values}, print only the names of
29616 the variables; if it is 1 or @code{--all-values}, print also their
29617 values; and if it is 2 or @code{--simple-values}, print the name,
29618 type and value for simple data types, and the name and type for arrays,
29619 structures and unions.
29621 @subsubheading Example
29625 -stack-list-variables --thread 1 --frame 0 --all-values
29626 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29631 @subheading The @code{-stack-select-frame} Command
29632 @findex -stack-select-frame
29634 @subsubheading Synopsis
29637 -stack-select-frame @var{framenum}
29640 Change the selected frame. Select a different frame @var{framenum} on
29643 This command in deprecated in favor of passing the @samp{--frame}
29644 option to every command.
29646 @subsubheading @value{GDBN} Command
29648 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29649 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29651 @subsubheading Example
29655 -stack-select-frame 2
29660 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29661 @node GDB/MI Variable Objects
29662 @section @sc{gdb/mi} Variable Objects
29666 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29668 For the implementation of a variable debugger window (locals, watched
29669 expressions, etc.), we are proposing the adaptation of the existing code
29670 used by @code{Insight}.
29672 The two main reasons for that are:
29676 It has been proven in practice (it is already on its second generation).
29679 It will shorten development time (needless to say how important it is
29683 The original interface was designed to be used by Tcl code, so it was
29684 slightly changed so it could be used through @sc{gdb/mi}. This section
29685 describes the @sc{gdb/mi} operations that will be available and gives some
29686 hints about their use.
29688 @emph{Note}: In addition to the set of operations described here, we
29689 expect the @sc{gui} implementation of a variable window to require, at
29690 least, the following operations:
29693 @item @code{-gdb-show} @code{output-radix}
29694 @item @code{-stack-list-arguments}
29695 @item @code{-stack-list-locals}
29696 @item @code{-stack-select-frame}
29701 @subheading Introduction to Variable Objects
29703 @cindex variable objects in @sc{gdb/mi}
29705 Variable objects are "object-oriented" MI interface for examining and
29706 changing values of expressions. Unlike some other MI interfaces that
29707 work with expressions, variable objects are specifically designed for
29708 simple and efficient presentation in the frontend. A variable object
29709 is identified by string name. When a variable object is created, the
29710 frontend specifies the expression for that variable object. The
29711 expression can be a simple variable, or it can be an arbitrary complex
29712 expression, and can even involve CPU registers. After creating a
29713 variable object, the frontend can invoke other variable object
29714 operations---for example to obtain or change the value of a variable
29715 object, or to change display format.
29717 Variable objects have hierarchical tree structure. Any variable object
29718 that corresponds to a composite type, such as structure in C, has
29719 a number of child variable objects, for example corresponding to each
29720 element of a structure. A child variable object can itself have
29721 children, recursively. Recursion ends when we reach
29722 leaf variable objects, which always have built-in types. Child variable
29723 objects are created only by explicit request, so if a frontend
29724 is not interested in the children of a particular variable object, no
29725 child will be created.
29727 For a leaf variable object it is possible to obtain its value as a
29728 string, or set the value from a string. String value can be also
29729 obtained for a non-leaf variable object, but it's generally a string
29730 that only indicates the type of the object, and does not list its
29731 contents. Assignment to a non-leaf variable object is not allowed.
29733 A frontend does not need to read the values of all variable objects each time
29734 the program stops. Instead, MI provides an update command that lists all
29735 variable objects whose values has changed since the last update
29736 operation. This considerably reduces the amount of data that must
29737 be transferred to the frontend. As noted above, children variable
29738 objects are created on demand, and only leaf variable objects have a
29739 real value. As result, gdb will read target memory only for leaf
29740 variables that frontend has created.
29742 The automatic update is not always desirable. For example, a frontend
29743 might want to keep a value of some expression for future reference,
29744 and never update it. For another example, fetching memory is
29745 relatively slow for embedded targets, so a frontend might want
29746 to disable automatic update for the variables that are either not
29747 visible on the screen, or ``closed''. This is possible using so
29748 called ``frozen variable objects''. Such variable objects are never
29749 implicitly updated.
29751 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29752 fixed variable object, the expression is parsed when the variable
29753 object is created, including associating identifiers to specific
29754 variables. The meaning of expression never changes. For a floating
29755 variable object the values of variables whose names appear in the
29756 expressions are re-evaluated every time in the context of the current
29757 frame. Consider this example:
29762 struct work_state state;
29769 If a fixed variable object for the @code{state} variable is created in
29770 this function, and we enter the recursive call, the variable
29771 object will report the value of @code{state} in the top-level
29772 @code{do_work} invocation. On the other hand, a floating variable
29773 object will report the value of @code{state} in the current frame.
29775 If an expression specified when creating a fixed variable object
29776 refers to a local variable, the variable object becomes bound to the
29777 thread and frame in which the variable object is created. When such
29778 variable object is updated, @value{GDBN} makes sure that the
29779 thread/frame combination the variable object is bound to still exists,
29780 and re-evaluates the variable object in context of that thread/frame.
29782 The following is the complete set of @sc{gdb/mi} operations defined to
29783 access this functionality:
29785 @multitable @columnfractions .4 .6
29786 @item @strong{Operation}
29787 @tab @strong{Description}
29789 @item @code{-enable-pretty-printing}
29790 @tab enable Python-based pretty-printing
29791 @item @code{-var-create}
29792 @tab create a variable object
29793 @item @code{-var-delete}
29794 @tab delete the variable object and/or its children
29795 @item @code{-var-set-format}
29796 @tab set the display format of this variable
29797 @item @code{-var-show-format}
29798 @tab show the display format of this variable
29799 @item @code{-var-info-num-children}
29800 @tab tells how many children this object has
29801 @item @code{-var-list-children}
29802 @tab return a list of the object's children
29803 @item @code{-var-info-type}
29804 @tab show the type of this variable object
29805 @item @code{-var-info-expression}
29806 @tab print parent-relative expression that this variable object represents
29807 @item @code{-var-info-path-expression}
29808 @tab print full expression that this variable object represents
29809 @item @code{-var-show-attributes}
29810 @tab is this variable editable? does it exist here?
29811 @item @code{-var-evaluate-expression}
29812 @tab get the value of this variable
29813 @item @code{-var-assign}
29814 @tab set the value of this variable
29815 @item @code{-var-update}
29816 @tab update the variable and its children
29817 @item @code{-var-set-frozen}
29818 @tab set frozeness attribute
29819 @item @code{-var-set-update-range}
29820 @tab set range of children to display on update
29823 In the next subsection we describe each operation in detail and suggest
29824 how it can be used.
29826 @subheading Description And Use of Operations on Variable Objects
29828 @subheading The @code{-enable-pretty-printing} Command
29829 @findex -enable-pretty-printing
29832 -enable-pretty-printing
29835 @value{GDBN} allows Python-based visualizers to affect the output of the
29836 MI variable object commands. However, because there was no way to
29837 implement this in a fully backward-compatible way, a front end must
29838 request that this functionality be enabled.
29840 Once enabled, this feature cannot be disabled.
29842 Note that if Python support has not been compiled into @value{GDBN},
29843 this command will still succeed (and do nothing).
29845 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29846 may work differently in future versions of @value{GDBN}.
29848 @subheading The @code{-var-create} Command
29849 @findex -var-create
29851 @subsubheading Synopsis
29854 -var-create @{@var{name} | "-"@}
29855 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29858 This operation creates a variable object, which allows the monitoring of
29859 a variable, the result of an expression, a memory cell or a CPU
29862 The @var{name} parameter is the string by which the object can be
29863 referenced. It must be unique. If @samp{-} is specified, the varobj
29864 system will generate a string ``varNNNNNN'' automatically. It will be
29865 unique provided that one does not specify @var{name} of that format.
29866 The command fails if a duplicate name is found.
29868 The frame under which the expression should be evaluated can be
29869 specified by @var{frame-addr}. A @samp{*} indicates that the current
29870 frame should be used. A @samp{@@} indicates that a floating variable
29871 object must be created.
29873 @var{expression} is any expression valid on the current language set (must not
29874 begin with a @samp{*}), or one of the following:
29878 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29881 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29884 @samp{$@var{regname}} --- a CPU register name
29887 @cindex dynamic varobj
29888 A varobj's contents may be provided by a Python-based pretty-printer. In this
29889 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29890 have slightly different semantics in some cases. If the
29891 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29892 will never create a dynamic varobj. This ensures backward
29893 compatibility for existing clients.
29895 @subsubheading Result
29897 This operation returns attributes of the newly-created varobj. These
29902 The name of the varobj.
29905 The number of children of the varobj. This number is not necessarily
29906 reliable for a dynamic varobj. Instead, you must examine the
29907 @samp{has_more} attribute.
29910 The varobj's scalar value. For a varobj whose type is some sort of
29911 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29912 will not be interesting.
29915 The varobj's type. This is a string representation of the type, as
29916 would be printed by the @value{GDBN} CLI. If @samp{print object}
29917 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29918 @emph{actual} (derived) type of the object is shown rather than the
29919 @emph{declared} one.
29922 If a variable object is bound to a specific thread, then this is the
29923 thread's identifier.
29926 For a dynamic varobj, this indicates whether there appear to be any
29927 children available. For a non-dynamic varobj, this will be 0.
29930 This attribute will be present and have the value @samp{1} if the
29931 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29932 then this attribute will not be present.
29935 A dynamic varobj can supply a display hint to the front end. The
29936 value comes directly from the Python pretty-printer object's
29937 @code{display_hint} method. @xref{Pretty Printing API}.
29940 Typical output will look like this:
29943 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29944 has_more="@var{has_more}"
29948 @subheading The @code{-var-delete} Command
29949 @findex -var-delete
29951 @subsubheading Synopsis
29954 -var-delete [ -c ] @var{name}
29957 Deletes a previously created variable object and all of its children.
29958 With the @samp{-c} option, just deletes the children.
29960 Returns an error if the object @var{name} is not found.
29963 @subheading The @code{-var-set-format} Command
29964 @findex -var-set-format
29966 @subsubheading Synopsis
29969 -var-set-format @var{name} @var{format-spec}
29972 Sets the output format for the value of the object @var{name} to be
29975 @anchor{-var-set-format}
29976 The syntax for the @var{format-spec} is as follows:
29979 @var{format-spec} @expansion{}
29980 @{binary | decimal | hexadecimal | octal | natural@}
29983 The natural format is the default format choosen automatically
29984 based on the variable type (like decimal for an @code{int}, hex
29985 for pointers, etc.).
29987 For a variable with children, the format is set only on the
29988 variable itself, and the children are not affected.
29990 @subheading The @code{-var-show-format} Command
29991 @findex -var-show-format
29993 @subsubheading Synopsis
29996 -var-show-format @var{name}
29999 Returns the format used to display the value of the object @var{name}.
30002 @var{format} @expansion{}
30007 @subheading The @code{-var-info-num-children} Command
30008 @findex -var-info-num-children
30010 @subsubheading Synopsis
30013 -var-info-num-children @var{name}
30016 Returns the number of children of a variable object @var{name}:
30022 Note that this number is not completely reliable for a dynamic varobj.
30023 It will return the current number of children, but more children may
30027 @subheading The @code{-var-list-children} Command
30028 @findex -var-list-children
30030 @subsubheading Synopsis
30033 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30035 @anchor{-var-list-children}
30037 Return a list of the children of the specified variable object and
30038 create variable objects for them, if they do not already exist. With
30039 a single argument or if @var{print-values} has a value of 0 or
30040 @code{--no-values}, print only the names of the variables; if
30041 @var{print-values} is 1 or @code{--all-values}, also print their
30042 values; and if it is 2 or @code{--simple-values} print the name and
30043 value for simple data types and just the name for arrays, structures
30046 @var{from} and @var{to}, if specified, indicate the range of children
30047 to report. If @var{from} or @var{to} is less than zero, the range is
30048 reset and all children will be reported. Otherwise, children starting
30049 at @var{from} (zero-based) and up to and excluding @var{to} will be
30052 If a child range is requested, it will only affect the current call to
30053 @code{-var-list-children}, but not future calls to @code{-var-update}.
30054 For this, you must instead use @code{-var-set-update-range}. The
30055 intent of this approach is to enable a front end to implement any
30056 update approach it likes; for example, scrolling a view may cause the
30057 front end to request more children with @code{-var-list-children}, and
30058 then the front end could call @code{-var-set-update-range} with a
30059 different range to ensure that future updates are restricted to just
30062 For each child the following results are returned:
30067 Name of the variable object created for this child.
30070 The expression to be shown to the user by the front end to designate this child.
30071 For example this may be the name of a structure member.
30073 For a dynamic varobj, this value cannot be used to form an
30074 expression. There is no way to do this at all with a dynamic varobj.
30076 For C/C@t{++} structures there are several pseudo children returned to
30077 designate access qualifiers. For these pseudo children @var{exp} is
30078 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30079 type and value are not present.
30081 A dynamic varobj will not report the access qualifying
30082 pseudo-children, regardless of the language. This information is not
30083 available at all with a dynamic varobj.
30086 Number of children this child has. For a dynamic varobj, this will be
30090 The type of the child. If @samp{print object}
30091 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30092 @emph{actual} (derived) type of the object is shown rather than the
30093 @emph{declared} one.
30096 If values were requested, this is the value.
30099 If this variable object is associated with a thread, this is the thread id.
30100 Otherwise this result is not present.
30103 If the variable object is frozen, this variable will be present with a value of 1.
30106 The result may have its own attributes:
30110 A dynamic varobj can supply a display hint to the front end. The
30111 value comes directly from the Python pretty-printer object's
30112 @code{display_hint} method. @xref{Pretty Printing API}.
30115 This is an integer attribute which is nonzero if there are children
30116 remaining after the end of the selected range.
30119 @subsubheading Example
30123 -var-list-children n
30124 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30125 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30127 -var-list-children --all-values n
30128 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30129 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30133 @subheading The @code{-var-info-type} Command
30134 @findex -var-info-type
30136 @subsubheading Synopsis
30139 -var-info-type @var{name}
30142 Returns the type of the specified variable @var{name}. The type is
30143 returned as a string in the same format as it is output by the
30147 type=@var{typename}
30151 @subheading The @code{-var-info-expression} Command
30152 @findex -var-info-expression
30154 @subsubheading Synopsis
30157 -var-info-expression @var{name}
30160 Returns a string that is suitable for presenting this
30161 variable object in user interface. The string is generally
30162 not valid expression in the current language, and cannot be evaluated.
30164 For example, if @code{a} is an array, and variable object
30165 @code{A} was created for @code{a}, then we'll get this output:
30168 (gdb) -var-info-expression A.1
30169 ^done,lang="C",exp="1"
30173 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30175 Note that the output of the @code{-var-list-children} command also
30176 includes those expressions, so the @code{-var-info-expression} command
30179 @subheading The @code{-var-info-path-expression} Command
30180 @findex -var-info-path-expression
30182 @subsubheading Synopsis
30185 -var-info-path-expression @var{name}
30188 Returns an expression that can be evaluated in the current
30189 context and will yield the same value that a variable object has.
30190 Compare this with the @code{-var-info-expression} command, which
30191 result can be used only for UI presentation. Typical use of
30192 the @code{-var-info-path-expression} command is creating a
30193 watchpoint from a variable object.
30195 This command is currently not valid for children of a dynamic varobj,
30196 and will give an error when invoked on one.
30198 For example, suppose @code{C} is a C@t{++} class, derived from class
30199 @code{Base}, and that the @code{Base} class has a member called
30200 @code{m_size}. Assume a variable @code{c} is has the type of
30201 @code{C} and a variable object @code{C} was created for variable
30202 @code{c}. Then, we'll get this output:
30204 (gdb) -var-info-path-expression C.Base.public.m_size
30205 ^done,path_expr=((Base)c).m_size)
30208 @subheading The @code{-var-show-attributes} Command
30209 @findex -var-show-attributes
30211 @subsubheading Synopsis
30214 -var-show-attributes @var{name}
30217 List attributes of the specified variable object @var{name}:
30220 status=@var{attr} [ ( ,@var{attr} )* ]
30224 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30226 @subheading The @code{-var-evaluate-expression} Command
30227 @findex -var-evaluate-expression
30229 @subsubheading Synopsis
30232 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30235 Evaluates the expression that is represented by the specified variable
30236 object and returns its value as a string. The format of the string
30237 can be specified with the @samp{-f} option. The possible values of
30238 this option are the same as for @code{-var-set-format}
30239 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30240 the current display format will be used. The current display format
30241 can be changed using the @code{-var-set-format} command.
30247 Note that one must invoke @code{-var-list-children} for a variable
30248 before the value of a child variable can be evaluated.
30250 @subheading The @code{-var-assign} Command
30251 @findex -var-assign
30253 @subsubheading Synopsis
30256 -var-assign @var{name} @var{expression}
30259 Assigns the value of @var{expression} to the variable object specified
30260 by @var{name}. The object must be @samp{editable}. If the variable's
30261 value is altered by the assign, the variable will show up in any
30262 subsequent @code{-var-update} list.
30264 @subsubheading Example
30272 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30276 @subheading The @code{-var-update} Command
30277 @findex -var-update
30279 @subsubheading Synopsis
30282 -var-update [@var{print-values}] @{@var{name} | "*"@}
30285 Reevaluate the expressions corresponding to the variable object
30286 @var{name} and all its direct and indirect children, and return the
30287 list of variable objects whose values have changed; @var{name} must
30288 be a root variable object. Here, ``changed'' means that the result of
30289 @code{-var-evaluate-expression} before and after the
30290 @code{-var-update} is different. If @samp{*} is used as the variable
30291 object names, all existing variable objects are updated, except
30292 for frozen ones (@pxref{-var-set-frozen}). The option
30293 @var{print-values} determines whether both names and values, or just
30294 names are printed. The possible values of this option are the same
30295 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30296 recommended to use the @samp{--all-values} option, to reduce the
30297 number of MI commands needed on each program stop.
30299 With the @samp{*} parameter, if a variable object is bound to a
30300 currently running thread, it will not be updated, without any
30303 If @code{-var-set-update-range} was previously used on a varobj, then
30304 only the selected range of children will be reported.
30306 @code{-var-update} reports all the changed varobjs in a tuple named
30309 Each item in the change list is itself a tuple holding:
30313 The name of the varobj.
30316 If values were requested for this update, then this field will be
30317 present and will hold the value of the varobj.
30320 @anchor{-var-update}
30321 This field is a string which may take one of three values:
30325 The variable object's current value is valid.
30328 The variable object does not currently hold a valid value but it may
30329 hold one in the future if its associated expression comes back into
30333 The variable object no longer holds a valid value.
30334 This can occur when the executable file being debugged has changed,
30335 either through recompilation or by using the @value{GDBN} @code{file}
30336 command. The front end should normally choose to delete these variable
30340 In the future new values may be added to this list so the front should
30341 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30344 This is only present if the varobj is still valid. If the type
30345 changed, then this will be the string @samp{true}; otherwise it will
30348 When a varobj's type changes, its children are also likely to have
30349 become incorrect. Therefore, the varobj's children are automatically
30350 deleted when this attribute is @samp{true}. Also, the varobj's update
30351 range, when set using the @code{-var-set-update-range} command, is
30355 If the varobj's type changed, then this field will be present and will
30358 @item new_num_children
30359 For a dynamic varobj, if the number of children changed, or if the
30360 type changed, this will be the new number of children.
30362 The @samp{numchild} field in other varobj responses is generally not
30363 valid for a dynamic varobj -- it will show the number of children that
30364 @value{GDBN} knows about, but because dynamic varobjs lazily
30365 instantiate their children, this will not reflect the number of
30366 children which may be available.
30368 The @samp{new_num_children} attribute only reports changes to the
30369 number of children known by @value{GDBN}. This is the only way to
30370 detect whether an update has removed children (which necessarily can
30371 only happen at the end of the update range).
30374 The display hint, if any.
30377 This is an integer value, which will be 1 if there are more children
30378 available outside the varobj's update range.
30381 This attribute will be present and have the value @samp{1} if the
30382 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30383 then this attribute will not be present.
30386 If new children were added to a dynamic varobj within the selected
30387 update range (as set by @code{-var-set-update-range}), then they will
30388 be listed in this attribute.
30391 @subsubheading Example
30398 -var-update --all-values var1
30399 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30400 type_changed="false"@}]
30404 @subheading The @code{-var-set-frozen} Command
30405 @findex -var-set-frozen
30406 @anchor{-var-set-frozen}
30408 @subsubheading Synopsis
30411 -var-set-frozen @var{name} @var{flag}
30414 Set the frozenness flag on the variable object @var{name}. The
30415 @var{flag} parameter should be either @samp{1} to make the variable
30416 frozen or @samp{0} to make it unfrozen. If a variable object is
30417 frozen, then neither itself, nor any of its children, are
30418 implicitly updated by @code{-var-update} of
30419 a parent variable or by @code{-var-update *}. Only
30420 @code{-var-update} of the variable itself will update its value and
30421 values of its children. After a variable object is unfrozen, it is
30422 implicitly updated by all subsequent @code{-var-update} operations.
30423 Unfreezing a variable does not update it, only subsequent
30424 @code{-var-update} does.
30426 @subsubheading Example
30430 -var-set-frozen V 1
30435 @subheading The @code{-var-set-update-range} command
30436 @findex -var-set-update-range
30437 @anchor{-var-set-update-range}
30439 @subsubheading Synopsis
30442 -var-set-update-range @var{name} @var{from} @var{to}
30445 Set the range of children to be returned by future invocations of
30446 @code{-var-update}.
30448 @var{from} and @var{to} indicate the range of children to report. If
30449 @var{from} or @var{to} is less than zero, the range is reset and all
30450 children will be reported. Otherwise, children starting at @var{from}
30451 (zero-based) and up to and excluding @var{to} will be reported.
30453 @subsubheading Example
30457 -var-set-update-range V 1 2
30461 @subheading The @code{-var-set-visualizer} command
30462 @findex -var-set-visualizer
30463 @anchor{-var-set-visualizer}
30465 @subsubheading Synopsis
30468 -var-set-visualizer @var{name} @var{visualizer}
30471 Set a visualizer for the variable object @var{name}.
30473 @var{visualizer} is the visualizer to use. The special value
30474 @samp{None} means to disable any visualizer in use.
30476 If not @samp{None}, @var{visualizer} must be a Python expression.
30477 This expression must evaluate to a callable object which accepts a
30478 single argument. @value{GDBN} will call this object with the value of
30479 the varobj @var{name} as an argument (this is done so that the same
30480 Python pretty-printing code can be used for both the CLI and MI).
30481 When called, this object must return an object which conforms to the
30482 pretty-printing interface (@pxref{Pretty Printing API}).
30484 The pre-defined function @code{gdb.default_visualizer} may be used to
30485 select a visualizer by following the built-in process
30486 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30487 a varobj is created, and so ordinarily is not needed.
30489 This feature is only available if Python support is enabled. The MI
30490 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
30491 can be used to check this.
30493 @subsubheading Example
30495 Resetting the visualizer:
30499 -var-set-visualizer V None
30503 Reselecting the default (type-based) visualizer:
30507 -var-set-visualizer V gdb.default_visualizer
30511 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30512 can be used to instantiate this class for a varobj:
30516 -var-set-visualizer V "lambda val: SomeClass()"
30520 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30521 @node GDB/MI Data Manipulation
30522 @section @sc{gdb/mi} Data Manipulation
30524 @cindex data manipulation, in @sc{gdb/mi}
30525 @cindex @sc{gdb/mi}, data manipulation
30526 This section describes the @sc{gdb/mi} commands that manipulate data:
30527 examine memory and registers, evaluate expressions, etc.
30529 @c REMOVED FROM THE INTERFACE.
30530 @c @subheading -data-assign
30531 @c Change the value of a program variable. Plenty of side effects.
30532 @c @subsubheading GDB Command
30534 @c @subsubheading Example
30537 @subheading The @code{-data-disassemble} Command
30538 @findex -data-disassemble
30540 @subsubheading Synopsis
30544 [ -s @var{start-addr} -e @var{end-addr} ]
30545 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30553 @item @var{start-addr}
30554 is the beginning address (or @code{$pc})
30555 @item @var{end-addr}
30557 @item @var{filename}
30558 is the name of the file to disassemble
30559 @item @var{linenum}
30560 is the line number to disassemble around
30562 is the number of disassembly lines to be produced. If it is -1,
30563 the whole function will be disassembled, in case no @var{end-addr} is
30564 specified. If @var{end-addr} is specified as a non-zero value, and
30565 @var{lines} is lower than the number of disassembly lines between
30566 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30567 displayed; if @var{lines} is higher than the number of lines between
30568 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30571 is either 0 (meaning only disassembly), 1 (meaning mixed source and
30572 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
30573 mixed source and disassembly with raw opcodes).
30576 @subsubheading Result
30578 The output for each instruction is composed of four fields:
30587 Note that whatever included in the instruction field, is not manipulated
30588 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
30590 @subsubheading @value{GDBN} Command
30592 There's no direct mapping from this command to the CLI.
30594 @subsubheading Example
30596 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30600 -data-disassemble -s $pc -e "$pc + 20" -- 0
30603 @{address="0x000107c0",func-name="main",offset="4",
30604 inst="mov 2, %o0"@},
30605 @{address="0x000107c4",func-name="main",offset="8",
30606 inst="sethi %hi(0x11800), %o2"@},
30607 @{address="0x000107c8",func-name="main",offset="12",
30608 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30609 @{address="0x000107cc",func-name="main",offset="16",
30610 inst="sethi %hi(0x11800), %o2"@},
30611 @{address="0x000107d0",func-name="main",offset="20",
30612 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30616 Disassemble the whole @code{main} function. Line 32 is part of
30620 -data-disassemble -f basics.c -l 32 -- 0
30622 @{address="0x000107bc",func-name="main",offset="0",
30623 inst="save %sp, -112, %sp"@},
30624 @{address="0x000107c0",func-name="main",offset="4",
30625 inst="mov 2, %o0"@},
30626 @{address="0x000107c4",func-name="main",offset="8",
30627 inst="sethi %hi(0x11800), %o2"@},
30629 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30630 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30634 Disassemble 3 instructions from the start of @code{main}:
30638 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30640 @{address="0x000107bc",func-name="main",offset="0",
30641 inst="save %sp, -112, %sp"@},
30642 @{address="0x000107c0",func-name="main",offset="4",
30643 inst="mov 2, %o0"@},
30644 @{address="0x000107c4",func-name="main",offset="8",
30645 inst="sethi %hi(0x11800), %o2"@}]
30649 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30653 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30655 src_and_asm_line=@{line="31",
30656 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30657 testsuite/gdb.mi/basics.c",line_asm_insn=[
30658 @{address="0x000107bc",func-name="main",offset="0",
30659 inst="save %sp, -112, %sp"@}]@},
30660 src_and_asm_line=@{line="32",
30661 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
30662 testsuite/gdb.mi/basics.c",line_asm_insn=[
30663 @{address="0x000107c0",func-name="main",offset="4",
30664 inst="mov 2, %o0"@},
30665 @{address="0x000107c4",func-name="main",offset="8",
30666 inst="sethi %hi(0x11800), %o2"@}]@}]
30671 @subheading The @code{-data-evaluate-expression} Command
30672 @findex -data-evaluate-expression
30674 @subsubheading Synopsis
30677 -data-evaluate-expression @var{expr}
30680 Evaluate @var{expr} as an expression. The expression could contain an
30681 inferior function call. The function call will execute synchronously.
30682 If the expression contains spaces, it must be enclosed in double quotes.
30684 @subsubheading @value{GDBN} Command
30686 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30687 @samp{call}. In @code{gdbtk} only, there's a corresponding
30688 @samp{gdb_eval} command.
30690 @subsubheading Example
30692 In the following example, the numbers that precede the commands are the
30693 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30694 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30698 211-data-evaluate-expression A
30701 311-data-evaluate-expression &A
30702 311^done,value="0xefffeb7c"
30704 411-data-evaluate-expression A+3
30707 511-data-evaluate-expression "A + 3"
30713 @subheading The @code{-data-list-changed-registers} Command
30714 @findex -data-list-changed-registers
30716 @subsubheading Synopsis
30719 -data-list-changed-registers
30722 Display a list of the registers that have changed.
30724 @subsubheading @value{GDBN} Command
30726 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30727 has the corresponding command @samp{gdb_changed_register_list}.
30729 @subsubheading Example
30731 On a PPC MBX board:
30739 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30740 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30743 -data-list-changed-registers
30744 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30745 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30746 "24","25","26","27","28","30","31","64","65","66","67","69"]
30751 @subheading The @code{-data-list-register-names} Command
30752 @findex -data-list-register-names
30754 @subsubheading Synopsis
30757 -data-list-register-names [ ( @var{regno} )+ ]
30760 Show a list of register names for the current target. If no arguments
30761 are given, it shows a list of the names of all the registers. If
30762 integer numbers are given as arguments, it will print a list of the
30763 names of the registers corresponding to the arguments. To ensure
30764 consistency between a register name and its number, the output list may
30765 include empty register names.
30767 @subsubheading @value{GDBN} Command
30769 @value{GDBN} does not have a command which corresponds to
30770 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30771 corresponding command @samp{gdb_regnames}.
30773 @subsubheading Example
30775 For the PPC MBX board:
30778 -data-list-register-names
30779 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30780 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30781 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30782 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30783 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30784 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30785 "", "pc","ps","cr","lr","ctr","xer"]
30787 -data-list-register-names 1 2 3
30788 ^done,register-names=["r1","r2","r3"]
30792 @subheading The @code{-data-list-register-values} Command
30793 @findex -data-list-register-values
30795 @subsubheading Synopsis
30798 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
30801 Display the registers' contents. @var{fmt} is the format according to
30802 which the registers' contents are to be returned, followed by an optional
30803 list of numbers specifying the registers to display. A missing list of
30804 numbers indicates that the contents of all the registers must be returned.
30806 Allowed formats for @var{fmt} are:
30823 @subsubheading @value{GDBN} Command
30825 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30826 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30828 @subsubheading Example
30830 For a PPC MBX board (note: line breaks are for readability only, they
30831 don't appear in the actual output):
30835 -data-list-register-values r 64 65
30836 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30837 @{number="65",value="0x00029002"@}]
30839 -data-list-register-values x
30840 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30841 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30842 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30843 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30844 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30845 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30846 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30847 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30848 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30849 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30850 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30851 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30852 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30853 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30854 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30855 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30856 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30857 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30858 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30859 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30860 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30861 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30862 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30863 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30864 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30865 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30866 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30867 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30868 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30869 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30870 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30871 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30872 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30873 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30874 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30875 @{number="69",value="0x20002b03"@}]
30880 @subheading The @code{-data-read-memory} Command
30881 @findex -data-read-memory
30883 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30885 @subsubheading Synopsis
30888 -data-read-memory [ -o @var{byte-offset} ]
30889 @var{address} @var{word-format} @var{word-size}
30890 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30897 @item @var{address}
30898 An expression specifying the address of the first memory word to be
30899 read. Complex expressions containing embedded white space should be
30900 quoted using the C convention.
30902 @item @var{word-format}
30903 The format to be used to print the memory words. The notation is the
30904 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30907 @item @var{word-size}
30908 The size of each memory word in bytes.
30910 @item @var{nr-rows}
30911 The number of rows in the output table.
30913 @item @var{nr-cols}
30914 The number of columns in the output table.
30917 If present, indicates that each row should include an @sc{ascii} dump. The
30918 value of @var{aschar} is used as a padding character when a byte is not a
30919 member of the printable @sc{ascii} character set (printable @sc{ascii}
30920 characters are those whose code is between 32 and 126, inclusively).
30922 @item @var{byte-offset}
30923 An offset to add to the @var{address} before fetching memory.
30926 This command displays memory contents as a table of @var{nr-rows} by
30927 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30928 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30929 (returned as @samp{total-bytes}). Should less than the requested number
30930 of bytes be returned by the target, the missing words are identified
30931 using @samp{N/A}. The number of bytes read from the target is returned
30932 in @samp{nr-bytes} and the starting address used to read memory in
30935 The address of the next/previous row or page is available in
30936 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30939 @subsubheading @value{GDBN} Command
30941 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30942 @samp{gdb_get_mem} memory read command.
30944 @subsubheading Example
30946 Read six bytes of memory starting at @code{bytes+6} but then offset by
30947 @code{-6} bytes. Format as three rows of two columns. One byte per
30948 word. Display each word in hex.
30952 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30953 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30954 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30955 prev-page="0x0000138a",memory=[
30956 @{addr="0x00001390",data=["0x00","0x01"]@},
30957 @{addr="0x00001392",data=["0x02","0x03"]@},
30958 @{addr="0x00001394",data=["0x04","0x05"]@}]
30962 Read two bytes of memory starting at address @code{shorts + 64} and
30963 display as a single word formatted in decimal.
30967 5-data-read-memory shorts+64 d 2 1 1
30968 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30969 next-row="0x00001512",prev-row="0x0000150e",
30970 next-page="0x00001512",prev-page="0x0000150e",memory=[
30971 @{addr="0x00001510",data=["128"]@}]
30975 Read thirty two bytes of memory starting at @code{bytes+16} and format
30976 as eight rows of four columns. Include a string encoding with @samp{x}
30977 used as the non-printable character.
30981 4-data-read-memory bytes+16 x 1 8 4 x
30982 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30983 next-row="0x000013c0",prev-row="0x0000139c",
30984 next-page="0x000013c0",prev-page="0x00001380",memory=[
30985 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30986 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30987 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30988 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30989 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30990 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30991 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30992 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30996 @subheading The @code{-data-read-memory-bytes} Command
30997 @findex -data-read-memory-bytes
30999 @subsubheading Synopsis
31002 -data-read-memory-bytes [ -o @var{byte-offset} ]
31003 @var{address} @var{count}
31010 @item @var{address}
31011 An expression specifying the address of the first memory word to be
31012 read. Complex expressions containing embedded white space should be
31013 quoted using the C convention.
31016 The number of bytes to read. This should be an integer literal.
31018 @item @var{byte-offset}
31019 The offsets in bytes relative to @var{address} at which to start
31020 reading. This should be an integer literal. This option is provided
31021 so that a frontend is not required to first evaluate address and then
31022 perform address arithmetics itself.
31026 This command attempts to read all accessible memory regions in the
31027 specified range. First, all regions marked as unreadable in the memory
31028 map (if one is defined) will be skipped. @xref{Memory Region
31029 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31030 regions. For each one, if reading full region results in an errors,
31031 @value{GDBN} will try to read a subset of the region.
31033 In general, every single byte in the region may be readable or not,
31034 and the only way to read every readable byte is to try a read at
31035 every address, which is not practical. Therefore, @value{GDBN} will
31036 attempt to read all accessible bytes at either beginning or the end
31037 of the region, using a binary division scheme. This heuristic works
31038 well for reading accross a memory map boundary. Note that if a region
31039 has a readable range that is neither at the beginning or the end,
31040 @value{GDBN} will not read it.
31042 The result record (@pxref{GDB/MI Result Records}) that is output of
31043 the command includes a field named @samp{memory} whose content is a
31044 list of tuples. Each tuple represent a successfully read memory block
31045 and has the following fields:
31049 The start address of the memory block, as hexadecimal literal.
31052 The end address of the memory block, as hexadecimal literal.
31055 The offset of the memory block, as hexadecimal literal, relative to
31056 the start address passed to @code{-data-read-memory-bytes}.
31059 The contents of the memory block, in hex.
31065 @subsubheading @value{GDBN} Command
31067 The corresponding @value{GDBN} command is @samp{x}.
31069 @subsubheading Example
31073 -data-read-memory-bytes &a 10
31074 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31076 contents="01000000020000000300"@}]
31081 @subheading The @code{-data-write-memory-bytes} Command
31082 @findex -data-write-memory-bytes
31084 @subsubheading Synopsis
31087 -data-write-memory-bytes @var{address} @var{contents}
31094 @item @var{address}
31095 An expression specifying the address of the first memory word to be
31096 read. Complex expressions containing embedded white space should be
31097 quoted using the C convention.
31099 @item @var{contents}
31100 The hex-encoded bytes to write.
31104 @subsubheading @value{GDBN} Command
31106 There's no corresponding @value{GDBN} command.
31108 @subsubheading Example
31112 -data-write-memory-bytes &a "aabbccdd"
31118 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31119 @node GDB/MI Tracepoint Commands
31120 @section @sc{gdb/mi} Tracepoint Commands
31122 The commands defined in this section implement MI support for
31123 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31125 @subheading The @code{-trace-find} Command
31126 @findex -trace-find
31128 @subsubheading Synopsis
31131 -trace-find @var{mode} [@var{parameters}@dots{}]
31134 Find a trace frame using criteria defined by @var{mode} and
31135 @var{parameters}. The following table lists permissible
31136 modes and their parameters. For details of operation, see @ref{tfind}.
31141 No parameters are required. Stops examining trace frames.
31144 An integer is required as parameter. Selects tracepoint frame with
31147 @item tracepoint-number
31148 An integer is required as parameter. Finds next
31149 trace frame that corresponds to tracepoint with the specified number.
31152 An address is required as parameter. Finds
31153 next trace frame that corresponds to any tracepoint at the specified
31156 @item pc-inside-range
31157 Two addresses are required as parameters. Finds next trace
31158 frame that corresponds to a tracepoint at an address inside the
31159 specified range. Both bounds are considered to be inside the range.
31161 @item pc-outside-range
31162 Two addresses are required as parameters. Finds
31163 next trace frame that corresponds to a tracepoint at an address outside
31164 the specified range. Both bounds are considered to be inside the range.
31167 Line specification is required as parameter. @xref{Specify Location}.
31168 Finds next trace frame that corresponds to a tracepoint at
31169 the specified location.
31173 If @samp{none} was passed as @var{mode}, the response does not
31174 have fields. Otherwise, the response may have the following fields:
31178 This field has either @samp{0} or @samp{1} as the value, depending
31179 on whether a matching tracepoint was found.
31182 The index of the found traceframe. This field is present iff
31183 the @samp{found} field has value of @samp{1}.
31186 The index of the found tracepoint. This field is present iff
31187 the @samp{found} field has value of @samp{1}.
31190 The information about the frame corresponding to the found trace
31191 frame. This field is present only if a trace frame was found.
31192 @xref{GDB/MI Frame Information}, for description of this field.
31196 @subsubheading @value{GDBN} Command
31198 The corresponding @value{GDBN} command is @samp{tfind}.
31200 @subheading -trace-define-variable
31201 @findex -trace-define-variable
31203 @subsubheading Synopsis
31206 -trace-define-variable @var{name} [ @var{value} ]
31209 Create trace variable @var{name} if it does not exist. If
31210 @var{value} is specified, sets the initial value of the specified
31211 trace variable to that value. Note that the @var{name} should start
31212 with the @samp{$} character.
31214 @subsubheading @value{GDBN} Command
31216 The corresponding @value{GDBN} command is @samp{tvariable}.
31218 @subheading -trace-list-variables
31219 @findex -trace-list-variables
31221 @subsubheading Synopsis
31224 -trace-list-variables
31227 Return a table of all defined trace variables. Each element of the
31228 table has the following fields:
31232 The name of the trace variable. This field is always present.
31235 The initial value. This is a 64-bit signed integer. This
31236 field is always present.
31239 The value the trace variable has at the moment. This is a 64-bit
31240 signed integer. This field is absent iff current value is
31241 not defined, for example if the trace was never run, or is
31246 @subsubheading @value{GDBN} Command
31248 The corresponding @value{GDBN} command is @samp{tvariables}.
31250 @subsubheading Example
31254 -trace-list-variables
31255 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31256 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31257 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31258 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31259 body=[variable=@{name="$trace_timestamp",initial="0"@}
31260 variable=@{name="$foo",initial="10",current="15"@}]@}
31264 @subheading -trace-save
31265 @findex -trace-save
31267 @subsubheading Synopsis
31270 -trace-save [-r ] @var{filename}
31273 Saves the collected trace data to @var{filename}. Without the
31274 @samp{-r} option, the data is downloaded from the target and saved
31275 in a local file. With the @samp{-r} option the target is asked
31276 to perform the save.
31278 @subsubheading @value{GDBN} Command
31280 The corresponding @value{GDBN} command is @samp{tsave}.
31283 @subheading -trace-start
31284 @findex -trace-start
31286 @subsubheading Synopsis
31292 Starts a tracing experiments. The result of this command does not
31295 @subsubheading @value{GDBN} Command
31297 The corresponding @value{GDBN} command is @samp{tstart}.
31299 @subheading -trace-status
31300 @findex -trace-status
31302 @subsubheading Synopsis
31308 Obtains the status of a tracing experiment. The result may include
31309 the following fields:
31314 May have a value of either @samp{0}, when no tracing operations are
31315 supported, @samp{1}, when all tracing operations are supported, or
31316 @samp{file} when examining trace file. In the latter case, examining
31317 of trace frame is possible but new tracing experiement cannot be
31318 started. This field is always present.
31321 May have a value of either @samp{0} or @samp{1} depending on whether
31322 tracing experiement is in progress on target. This field is present
31323 if @samp{supported} field is not @samp{0}.
31326 Report the reason why the tracing was stopped last time. This field
31327 may be absent iff tracing was never stopped on target yet. The
31328 value of @samp{request} means the tracing was stopped as result of
31329 the @code{-trace-stop} command. The value of @samp{overflow} means
31330 the tracing buffer is full. The value of @samp{disconnection} means
31331 tracing was automatically stopped when @value{GDBN} has disconnected.
31332 The value of @samp{passcount} means tracing was stopped when a
31333 tracepoint was passed a maximal number of times for that tracepoint.
31334 This field is present if @samp{supported} field is not @samp{0}.
31336 @item stopping-tracepoint
31337 The number of tracepoint whose passcount as exceeded. This field is
31338 present iff the @samp{stop-reason} field has the value of
31342 @itemx frames-created
31343 The @samp{frames} field is a count of the total number of trace frames
31344 in the trace buffer, while @samp{frames-created} is the total created
31345 during the run, including ones that were discarded, such as when a
31346 circular trace buffer filled up. Both fields are optional.
31350 These fields tell the current size of the tracing buffer and the
31351 remaining space. These fields are optional.
31354 The value of the circular trace buffer flag. @code{1} means that the
31355 trace buffer is circular and old trace frames will be discarded if
31356 necessary to make room, @code{0} means that the trace buffer is linear
31360 The value of the disconnected tracing flag. @code{1} means that
31361 tracing will continue after @value{GDBN} disconnects, @code{0} means
31362 that the trace run will stop.
31366 @subsubheading @value{GDBN} Command
31368 The corresponding @value{GDBN} command is @samp{tstatus}.
31370 @subheading -trace-stop
31371 @findex -trace-stop
31373 @subsubheading Synopsis
31379 Stops a tracing experiment. The result of this command has the same
31380 fields as @code{-trace-status}, except that the @samp{supported} and
31381 @samp{running} fields are not output.
31383 @subsubheading @value{GDBN} Command
31385 The corresponding @value{GDBN} command is @samp{tstop}.
31388 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31389 @node GDB/MI Symbol Query
31390 @section @sc{gdb/mi} Symbol Query Commands
31394 @subheading The @code{-symbol-info-address} Command
31395 @findex -symbol-info-address
31397 @subsubheading Synopsis
31400 -symbol-info-address @var{symbol}
31403 Describe where @var{symbol} is stored.
31405 @subsubheading @value{GDBN} Command
31407 The corresponding @value{GDBN} command is @samp{info address}.
31409 @subsubheading Example
31413 @subheading The @code{-symbol-info-file} Command
31414 @findex -symbol-info-file
31416 @subsubheading Synopsis
31422 Show the file for the symbol.
31424 @subsubheading @value{GDBN} Command
31426 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31427 @samp{gdb_find_file}.
31429 @subsubheading Example
31433 @subheading The @code{-symbol-info-function} Command
31434 @findex -symbol-info-function
31436 @subsubheading Synopsis
31439 -symbol-info-function
31442 Show which function the symbol lives in.
31444 @subsubheading @value{GDBN} Command
31446 @samp{gdb_get_function} in @code{gdbtk}.
31448 @subsubheading Example
31452 @subheading The @code{-symbol-info-line} Command
31453 @findex -symbol-info-line
31455 @subsubheading Synopsis
31461 Show the core addresses of the code for a source line.
31463 @subsubheading @value{GDBN} Command
31465 The corresponding @value{GDBN} command is @samp{info line}.
31466 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31468 @subsubheading Example
31472 @subheading The @code{-symbol-info-symbol} Command
31473 @findex -symbol-info-symbol
31475 @subsubheading Synopsis
31478 -symbol-info-symbol @var{addr}
31481 Describe what symbol is at location @var{addr}.
31483 @subsubheading @value{GDBN} Command
31485 The corresponding @value{GDBN} command is @samp{info symbol}.
31487 @subsubheading Example
31491 @subheading The @code{-symbol-list-functions} Command
31492 @findex -symbol-list-functions
31494 @subsubheading Synopsis
31497 -symbol-list-functions
31500 List the functions in the executable.
31502 @subsubheading @value{GDBN} Command
31504 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31505 @samp{gdb_search} in @code{gdbtk}.
31507 @subsubheading Example
31512 @subheading The @code{-symbol-list-lines} Command
31513 @findex -symbol-list-lines
31515 @subsubheading Synopsis
31518 -symbol-list-lines @var{filename}
31521 Print the list of lines that contain code and their associated program
31522 addresses for the given source filename. The entries are sorted in
31523 ascending PC order.
31525 @subsubheading @value{GDBN} Command
31527 There is no corresponding @value{GDBN} command.
31529 @subsubheading Example
31532 -symbol-list-lines basics.c
31533 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31539 @subheading The @code{-symbol-list-types} Command
31540 @findex -symbol-list-types
31542 @subsubheading Synopsis
31548 List all the type names.
31550 @subsubheading @value{GDBN} Command
31552 The corresponding commands are @samp{info types} in @value{GDBN},
31553 @samp{gdb_search} in @code{gdbtk}.
31555 @subsubheading Example
31559 @subheading The @code{-symbol-list-variables} Command
31560 @findex -symbol-list-variables
31562 @subsubheading Synopsis
31565 -symbol-list-variables
31568 List all the global and static variable names.
31570 @subsubheading @value{GDBN} Command
31572 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31574 @subsubheading Example
31578 @subheading The @code{-symbol-locate} Command
31579 @findex -symbol-locate
31581 @subsubheading Synopsis
31587 @subsubheading @value{GDBN} Command
31589 @samp{gdb_loc} in @code{gdbtk}.
31591 @subsubheading Example
31595 @subheading The @code{-symbol-type} Command
31596 @findex -symbol-type
31598 @subsubheading Synopsis
31601 -symbol-type @var{variable}
31604 Show type of @var{variable}.
31606 @subsubheading @value{GDBN} Command
31608 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31609 @samp{gdb_obj_variable}.
31611 @subsubheading Example
31616 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31617 @node GDB/MI File Commands
31618 @section @sc{gdb/mi} File Commands
31620 This section describes the GDB/MI commands to specify executable file names
31621 and to read in and obtain symbol table information.
31623 @subheading The @code{-file-exec-and-symbols} Command
31624 @findex -file-exec-and-symbols
31626 @subsubheading Synopsis
31629 -file-exec-and-symbols @var{file}
31632 Specify the executable file to be debugged. This file is the one from
31633 which the symbol table is also read. If no file is specified, the
31634 command clears the executable and symbol information. If breakpoints
31635 are set when using this command with no arguments, @value{GDBN} will produce
31636 error messages. Otherwise, no output is produced, except a completion
31639 @subsubheading @value{GDBN} Command
31641 The corresponding @value{GDBN} command is @samp{file}.
31643 @subsubheading Example
31647 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31653 @subheading The @code{-file-exec-file} Command
31654 @findex -file-exec-file
31656 @subsubheading Synopsis
31659 -file-exec-file @var{file}
31662 Specify the executable file to be debugged. Unlike
31663 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31664 from this file. If used without argument, @value{GDBN} clears the information
31665 about the executable file. No output is produced, except a completion
31668 @subsubheading @value{GDBN} Command
31670 The corresponding @value{GDBN} command is @samp{exec-file}.
31672 @subsubheading Example
31676 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31683 @subheading The @code{-file-list-exec-sections} Command
31684 @findex -file-list-exec-sections
31686 @subsubheading Synopsis
31689 -file-list-exec-sections
31692 List the sections of the current executable file.
31694 @subsubheading @value{GDBN} Command
31696 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31697 information as this command. @code{gdbtk} has a corresponding command
31698 @samp{gdb_load_info}.
31700 @subsubheading Example
31705 @subheading The @code{-file-list-exec-source-file} Command
31706 @findex -file-list-exec-source-file
31708 @subsubheading Synopsis
31711 -file-list-exec-source-file
31714 List the line number, the current source file, and the absolute path
31715 to the current source file for the current executable. The macro
31716 information field has a value of @samp{1} or @samp{0} depending on
31717 whether or not the file includes preprocessor macro information.
31719 @subsubheading @value{GDBN} Command
31721 The @value{GDBN} equivalent is @samp{info source}
31723 @subsubheading Example
31727 123-file-list-exec-source-file
31728 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31733 @subheading The @code{-file-list-exec-source-files} Command
31734 @findex -file-list-exec-source-files
31736 @subsubheading Synopsis
31739 -file-list-exec-source-files
31742 List the source files for the current executable.
31744 It will always output the filename, but only when @value{GDBN} can find
31745 the absolute file name of a source file, will it output the fullname.
31747 @subsubheading @value{GDBN} Command
31749 The @value{GDBN} equivalent is @samp{info sources}.
31750 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31752 @subsubheading Example
31755 -file-list-exec-source-files
31757 @{file=foo.c,fullname=/home/foo.c@},
31758 @{file=/home/bar.c,fullname=/home/bar.c@},
31759 @{file=gdb_could_not_find_fullpath.c@}]
31764 @subheading The @code{-file-list-shared-libraries} Command
31765 @findex -file-list-shared-libraries
31767 @subsubheading Synopsis
31770 -file-list-shared-libraries
31773 List the shared libraries in the program.
31775 @subsubheading @value{GDBN} Command
31777 The corresponding @value{GDBN} command is @samp{info shared}.
31779 @subsubheading Example
31783 @subheading The @code{-file-list-symbol-files} Command
31784 @findex -file-list-symbol-files
31786 @subsubheading Synopsis
31789 -file-list-symbol-files
31794 @subsubheading @value{GDBN} Command
31796 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31798 @subsubheading Example
31803 @subheading The @code{-file-symbol-file} Command
31804 @findex -file-symbol-file
31806 @subsubheading Synopsis
31809 -file-symbol-file @var{file}
31812 Read symbol table info from the specified @var{file} argument. When
31813 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31814 produced, except for a completion notification.
31816 @subsubheading @value{GDBN} Command
31818 The corresponding @value{GDBN} command is @samp{symbol-file}.
31820 @subsubheading Example
31824 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31830 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31831 @node GDB/MI Memory Overlay Commands
31832 @section @sc{gdb/mi} Memory Overlay Commands
31834 The memory overlay commands are not implemented.
31836 @c @subheading -overlay-auto
31838 @c @subheading -overlay-list-mapping-state
31840 @c @subheading -overlay-list-overlays
31842 @c @subheading -overlay-map
31844 @c @subheading -overlay-off
31846 @c @subheading -overlay-on
31848 @c @subheading -overlay-unmap
31850 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31851 @node GDB/MI Signal Handling Commands
31852 @section @sc{gdb/mi} Signal Handling Commands
31854 Signal handling commands are not implemented.
31856 @c @subheading -signal-handle
31858 @c @subheading -signal-list-handle-actions
31860 @c @subheading -signal-list-signal-types
31864 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31865 @node GDB/MI Target Manipulation
31866 @section @sc{gdb/mi} Target Manipulation Commands
31869 @subheading The @code{-target-attach} Command
31870 @findex -target-attach
31872 @subsubheading Synopsis
31875 -target-attach @var{pid} | @var{gid} | @var{file}
31878 Attach to a process @var{pid} or a file @var{file} outside of
31879 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31880 group, the id previously returned by
31881 @samp{-list-thread-groups --available} must be used.
31883 @subsubheading @value{GDBN} Command
31885 The corresponding @value{GDBN} command is @samp{attach}.
31887 @subsubheading Example
31891 =thread-created,id="1"
31892 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31898 @subheading The @code{-target-compare-sections} Command
31899 @findex -target-compare-sections
31901 @subsubheading Synopsis
31904 -target-compare-sections [ @var{section} ]
31907 Compare data of section @var{section} on target to the exec file.
31908 Without the argument, all sections are compared.
31910 @subsubheading @value{GDBN} Command
31912 The @value{GDBN} equivalent is @samp{compare-sections}.
31914 @subsubheading Example
31919 @subheading The @code{-target-detach} Command
31920 @findex -target-detach
31922 @subsubheading Synopsis
31925 -target-detach [ @var{pid} | @var{gid} ]
31928 Detach from the remote target which normally resumes its execution.
31929 If either @var{pid} or @var{gid} is specified, detaches from either
31930 the specified process, or specified thread group. There's no output.
31932 @subsubheading @value{GDBN} Command
31934 The corresponding @value{GDBN} command is @samp{detach}.
31936 @subsubheading Example
31946 @subheading The @code{-target-disconnect} Command
31947 @findex -target-disconnect
31949 @subsubheading Synopsis
31955 Disconnect from the remote target. There's no output and the target is
31956 generally not resumed.
31958 @subsubheading @value{GDBN} Command
31960 The corresponding @value{GDBN} command is @samp{disconnect}.
31962 @subsubheading Example
31972 @subheading The @code{-target-download} Command
31973 @findex -target-download
31975 @subsubheading Synopsis
31981 Loads the executable onto the remote target.
31982 It prints out an update message every half second, which includes the fields:
31986 The name of the section.
31988 The size of what has been sent so far for that section.
31990 The size of the section.
31992 The total size of what was sent so far (the current and the previous sections).
31994 The size of the overall executable to download.
31998 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31999 @sc{gdb/mi} Output Syntax}).
32001 In addition, it prints the name and size of the sections, as they are
32002 downloaded. These messages include the following fields:
32006 The name of the section.
32008 The size of the section.
32010 The size of the overall executable to download.
32014 At the end, a summary is printed.
32016 @subsubheading @value{GDBN} Command
32018 The corresponding @value{GDBN} command is @samp{load}.
32020 @subsubheading Example
32022 Note: each status message appears on a single line. Here the messages
32023 have been broken down so that they can fit onto a page.
32028 +download,@{section=".text",section-size="6668",total-size="9880"@}
32029 +download,@{section=".text",section-sent="512",section-size="6668",
32030 total-sent="512",total-size="9880"@}
32031 +download,@{section=".text",section-sent="1024",section-size="6668",
32032 total-sent="1024",total-size="9880"@}
32033 +download,@{section=".text",section-sent="1536",section-size="6668",
32034 total-sent="1536",total-size="9880"@}
32035 +download,@{section=".text",section-sent="2048",section-size="6668",
32036 total-sent="2048",total-size="9880"@}
32037 +download,@{section=".text",section-sent="2560",section-size="6668",
32038 total-sent="2560",total-size="9880"@}
32039 +download,@{section=".text",section-sent="3072",section-size="6668",
32040 total-sent="3072",total-size="9880"@}
32041 +download,@{section=".text",section-sent="3584",section-size="6668",
32042 total-sent="3584",total-size="9880"@}
32043 +download,@{section=".text",section-sent="4096",section-size="6668",
32044 total-sent="4096",total-size="9880"@}
32045 +download,@{section=".text",section-sent="4608",section-size="6668",
32046 total-sent="4608",total-size="9880"@}
32047 +download,@{section=".text",section-sent="5120",section-size="6668",
32048 total-sent="5120",total-size="9880"@}
32049 +download,@{section=".text",section-sent="5632",section-size="6668",
32050 total-sent="5632",total-size="9880"@}
32051 +download,@{section=".text",section-sent="6144",section-size="6668",
32052 total-sent="6144",total-size="9880"@}
32053 +download,@{section=".text",section-sent="6656",section-size="6668",
32054 total-sent="6656",total-size="9880"@}
32055 +download,@{section=".init",section-size="28",total-size="9880"@}
32056 +download,@{section=".fini",section-size="28",total-size="9880"@}
32057 +download,@{section=".data",section-size="3156",total-size="9880"@}
32058 +download,@{section=".data",section-sent="512",section-size="3156",
32059 total-sent="7236",total-size="9880"@}
32060 +download,@{section=".data",section-sent="1024",section-size="3156",
32061 total-sent="7748",total-size="9880"@}
32062 +download,@{section=".data",section-sent="1536",section-size="3156",
32063 total-sent="8260",total-size="9880"@}
32064 +download,@{section=".data",section-sent="2048",section-size="3156",
32065 total-sent="8772",total-size="9880"@}
32066 +download,@{section=".data",section-sent="2560",section-size="3156",
32067 total-sent="9284",total-size="9880"@}
32068 +download,@{section=".data",section-sent="3072",section-size="3156",
32069 total-sent="9796",total-size="9880"@}
32070 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32077 @subheading The @code{-target-exec-status} Command
32078 @findex -target-exec-status
32080 @subsubheading Synopsis
32083 -target-exec-status
32086 Provide information on the state of the target (whether it is running or
32087 not, for instance).
32089 @subsubheading @value{GDBN} Command
32091 There's no equivalent @value{GDBN} command.
32093 @subsubheading Example
32097 @subheading The @code{-target-list-available-targets} Command
32098 @findex -target-list-available-targets
32100 @subsubheading Synopsis
32103 -target-list-available-targets
32106 List the possible targets to connect to.
32108 @subsubheading @value{GDBN} Command
32110 The corresponding @value{GDBN} command is @samp{help target}.
32112 @subsubheading Example
32116 @subheading The @code{-target-list-current-targets} Command
32117 @findex -target-list-current-targets
32119 @subsubheading Synopsis
32122 -target-list-current-targets
32125 Describe the current target.
32127 @subsubheading @value{GDBN} Command
32129 The corresponding information is printed by @samp{info file} (among
32132 @subsubheading Example
32136 @subheading The @code{-target-list-parameters} Command
32137 @findex -target-list-parameters
32139 @subsubheading Synopsis
32142 -target-list-parameters
32148 @subsubheading @value{GDBN} Command
32152 @subsubheading Example
32156 @subheading The @code{-target-select} Command
32157 @findex -target-select
32159 @subsubheading Synopsis
32162 -target-select @var{type} @var{parameters @dots{}}
32165 Connect @value{GDBN} to the remote target. This command takes two args:
32169 The type of target, for instance @samp{remote}, etc.
32170 @item @var{parameters}
32171 Device names, host names and the like. @xref{Target Commands, ,
32172 Commands for Managing Targets}, for more details.
32175 The output is a connection notification, followed by the address at
32176 which the target program is, in the following form:
32179 ^connected,addr="@var{address}",func="@var{function name}",
32180 args=[@var{arg list}]
32183 @subsubheading @value{GDBN} Command
32185 The corresponding @value{GDBN} command is @samp{target}.
32187 @subsubheading Example
32191 -target-select remote /dev/ttya
32192 ^connected,addr="0xfe00a300",func="??",args=[]
32196 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32197 @node GDB/MI File Transfer Commands
32198 @section @sc{gdb/mi} File Transfer Commands
32201 @subheading The @code{-target-file-put} Command
32202 @findex -target-file-put
32204 @subsubheading Synopsis
32207 -target-file-put @var{hostfile} @var{targetfile}
32210 Copy file @var{hostfile} from the host system (the machine running
32211 @value{GDBN}) to @var{targetfile} on the target system.
32213 @subsubheading @value{GDBN} Command
32215 The corresponding @value{GDBN} command is @samp{remote put}.
32217 @subsubheading Example
32221 -target-file-put localfile remotefile
32227 @subheading The @code{-target-file-get} Command
32228 @findex -target-file-get
32230 @subsubheading Synopsis
32233 -target-file-get @var{targetfile} @var{hostfile}
32236 Copy file @var{targetfile} from the target system to @var{hostfile}
32237 on the host system.
32239 @subsubheading @value{GDBN} Command
32241 The corresponding @value{GDBN} command is @samp{remote get}.
32243 @subsubheading Example
32247 -target-file-get remotefile localfile
32253 @subheading The @code{-target-file-delete} Command
32254 @findex -target-file-delete
32256 @subsubheading Synopsis
32259 -target-file-delete @var{targetfile}
32262 Delete @var{targetfile} from the target system.
32264 @subsubheading @value{GDBN} Command
32266 The corresponding @value{GDBN} command is @samp{remote delete}.
32268 @subsubheading Example
32272 -target-file-delete remotefile
32278 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32279 @node GDB/MI Miscellaneous Commands
32280 @section Miscellaneous @sc{gdb/mi} Commands
32282 @c @subheading -gdb-complete
32284 @subheading The @code{-gdb-exit} Command
32287 @subsubheading Synopsis
32293 Exit @value{GDBN} immediately.
32295 @subsubheading @value{GDBN} Command
32297 Approximately corresponds to @samp{quit}.
32299 @subsubheading Example
32309 @subheading The @code{-exec-abort} Command
32310 @findex -exec-abort
32312 @subsubheading Synopsis
32318 Kill the inferior running program.
32320 @subsubheading @value{GDBN} Command
32322 The corresponding @value{GDBN} command is @samp{kill}.
32324 @subsubheading Example
32329 @subheading The @code{-gdb-set} Command
32332 @subsubheading Synopsis
32338 Set an internal @value{GDBN} variable.
32339 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32341 @subsubheading @value{GDBN} Command
32343 The corresponding @value{GDBN} command is @samp{set}.
32345 @subsubheading Example
32355 @subheading The @code{-gdb-show} Command
32358 @subsubheading Synopsis
32364 Show the current value of a @value{GDBN} variable.
32366 @subsubheading @value{GDBN} Command
32368 The corresponding @value{GDBN} command is @samp{show}.
32370 @subsubheading Example
32379 @c @subheading -gdb-source
32382 @subheading The @code{-gdb-version} Command
32383 @findex -gdb-version
32385 @subsubheading Synopsis
32391 Show version information for @value{GDBN}. Used mostly in testing.
32393 @subsubheading @value{GDBN} Command
32395 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32396 default shows this information when you start an interactive session.
32398 @subsubheading Example
32400 @c This example modifies the actual output from GDB to avoid overfull
32406 ~Copyright 2000 Free Software Foundation, Inc.
32407 ~GDB is free software, covered by the GNU General Public License, and
32408 ~you are welcome to change it and/or distribute copies of it under
32409 ~ certain conditions.
32410 ~Type "show copying" to see the conditions.
32411 ~There is absolutely no warranty for GDB. Type "show warranty" for
32413 ~This GDB was configured as
32414 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32419 @subheading The @code{-list-features} Command
32420 @findex -list-features
32422 Returns a list of particular features of the MI protocol that
32423 this version of gdb implements. A feature can be a command,
32424 or a new field in an output of some command, or even an
32425 important bugfix. While a frontend can sometimes detect presence
32426 of a feature at runtime, it is easier to perform detection at debugger
32429 The command returns a list of strings, with each string naming an
32430 available feature. Each returned string is just a name, it does not
32431 have any internal structure. The list of possible feature names
32437 (gdb) -list-features
32438 ^done,result=["feature1","feature2"]
32441 The current list of features is:
32444 @item frozen-varobjs
32445 Indicates support for the @code{-var-set-frozen} command, as well
32446 as possible presense of the @code{frozen} field in the output
32447 of @code{-varobj-create}.
32448 @item pending-breakpoints
32449 Indicates support for the @option{-f} option to the @code{-break-insert}
32452 Indicates Python scripting support, Python-based
32453 pretty-printing commands, and possible presence of the
32454 @samp{display_hint} field in the output of @code{-var-list-children}
32456 Indicates support for the @code{-thread-info} command.
32457 @item data-read-memory-bytes
32458 Indicates support for the @code{-data-read-memory-bytes} and the
32459 @code{-data-write-memory-bytes} commands.
32460 @item breakpoint-notifications
32461 Indicates that changes to breakpoints and breakpoints created via the
32462 CLI will be announced via async records.
32463 @item ada-task-info
32464 Indicates support for the @code{-ada-task-info} command.
32467 @subheading The @code{-list-target-features} Command
32468 @findex -list-target-features
32470 Returns a list of particular features that are supported by the
32471 target. Those features affect the permitted MI commands, but
32472 unlike the features reported by the @code{-list-features} command, the
32473 features depend on which target GDB is using at the moment. Whenever
32474 a target can change, due to commands such as @code{-target-select},
32475 @code{-target-attach} or @code{-exec-run}, the list of target features
32476 may change, and the frontend should obtain it again.
32480 (gdb) -list-features
32481 ^done,result=["async"]
32484 The current list of features is:
32488 Indicates that the target is capable of asynchronous command
32489 execution, which means that @value{GDBN} will accept further commands
32490 while the target is running.
32493 Indicates that the target is capable of reverse execution.
32494 @xref{Reverse Execution}, for more information.
32498 @subheading The @code{-list-thread-groups} Command
32499 @findex -list-thread-groups
32501 @subheading Synopsis
32504 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32507 Lists thread groups (@pxref{Thread groups}). When a single thread
32508 group is passed as the argument, lists the children of that group.
32509 When several thread group are passed, lists information about those
32510 thread groups. Without any parameters, lists information about all
32511 top-level thread groups.
32513 Normally, thread groups that are being debugged are reported.
32514 With the @samp{--available} option, @value{GDBN} reports thread groups
32515 available on the target.
32517 The output of this command may have either a @samp{threads} result or
32518 a @samp{groups} result. The @samp{thread} result has a list of tuples
32519 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32520 Information}). The @samp{groups} result has a list of tuples as value,
32521 each tuple describing a thread group. If top-level groups are
32522 requested (that is, no parameter is passed), or when several groups
32523 are passed, the output always has a @samp{groups} result. The format
32524 of the @samp{group} result is described below.
32526 To reduce the number of roundtrips it's possible to list thread groups
32527 together with their children, by passing the @samp{--recurse} option
32528 and the recursion depth. Presently, only recursion depth of 1 is
32529 permitted. If this option is present, then every reported thread group
32530 will also include its children, either as @samp{group} or
32531 @samp{threads} field.
32533 In general, any combination of option and parameters is permitted, with
32534 the following caveats:
32538 When a single thread group is passed, the output will typically
32539 be the @samp{threads} result. Because threads may not contain
32540 anything, the @samp{recurse} option will be ignored.
32543 When the @samp{--available} option is passed, limited information may
32544 be available. In particular, the list of threads of a process might
32545 be inaccessible. Further, specifying specific thread groups might
32546 not give any performance advantage over listing all thread groups.
32547 The frontend should assume that @samp{-list-thread-groups --available}
32548 is always an expensive operation and cache the results.
32552 The @samp{groups} result is a list of tuples, where each tuple may
32553 have the following fields:
32557 Identifier of the thread group. This field is always present.
32558 The identifier is an opaque string; frontends should not try to
32559 convert it to an integer, even though it might look like one.
32562 The type of the thread group. At present, only @samp{process} is a
32566 The target-specific process identifier. This field is only present
32567 for thread groups of type @samp{process} and only if the process exists.
32570 The number of children this thread group has. This field may be
32571 absent for an available thread group.
32574 This field has a list of tuples as value, each tuple describing a
32575 thread. It may be present if the @samp{--recurse} option is
32576 specified, and it's actually possible to obtain the threads.
32579 This field is a list of integers, each identifying a core that one
32580 thread of the group is running on. This field may be absent if
32581 such information is not available.
32584 The name of the executable file that corresponds to this thread group.
32585 The field is only present for thread groups of type @samp{process},
32586 and only if there is a corresponding executable file.
32590 @subheading Example
32594 -list-thread-groups
32595 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32596 -list-thread-groups 17
32597 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32598 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32599 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32600 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32601 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32602 -list-thread-groups --available
32603 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32604 -list-thread-groups --available --recurse 1
32605 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32606 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32607 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32608 -list-thread-groups --available --recurse 1 17 18
32609 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32610 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32611 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32615 @subheading The @code{-add-inferior} Command
32616 @findex -add-inferior
32618 @subheading Synopsis
32624 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32625 inferior is not associated with any executable. Such association may
32626 be established with the @samp{-file-exec-and-symbols} command
32627 (@pxref{GDB/MI File Commands}). The command response has a single
32628 field, @samp{thread-group}, whose value is the identifier of the
32629 thread group corresponding to the new inferior.
32631 @subheading Example
32636 ^done,thread-group="i3"
32639 @subheading The @code{-interpreter-exec} Command
32640 @findex -interpreter-exec
32642 @subheading Synopsis
32645 -interpreter-exec @var{interpreter} @var{command}
32647 @anchor{-interpreter-exec}
32649 Execute the specified @var{command} in the given @var{interpreter}.
32651 @subheading @value{GDBN} Command
32653 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32655 @subheading Example
32659 -interpreter-exec console "break main"
32660 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32661 &"During symbol reading, bad structure-type format.\n"
32662 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32667 @subheading The @code{-inferior-tty-set} Command
32668 @findex -inferior-tty-set
32670 @subheading Synopsis
32673 -inferior-tty-set /dev/pts/1
32676 Set terminal for future runs of the program being debugged.
32678 @subheading @value{GDBN} Command
32680 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32682 @subheading Example
32686 -inferior-tty-set /dev/pts/1
32691 @subheading The @code{-inferior-tty-show} Command
32692 @findex -inferior-tty-show
32694 @subheading Synopsis
32700 Show terminal for future runs of program being debugged.
32702 @subheading @value{GDBN} Command
32704 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32706 @subheading Example
32710 -inferior-tty-set /dev/pts/1
32714 ^done,inferior_tty_terminal="/dev/pts/1"
32718 @subheading The @code{-enable-timings} Command
32719 @findex -enable-timings
32721 @subheading Synopsis
32724 -enable-timings [yes | no]
32727 Toggle the printing of the wallclock, user and system times for an MI
32728 command as a field in its output. This command is to help frontend
32729 developers optimize the performance of their code. No argument is
32730 equivalent to @samp{yes}.
32732 @subheading @value{GDBN} Command
32736 @subheading Example
32744 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32745 addr="0x080484ed",func="main",file="myprog.c",
32746 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
32747 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32755 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32756 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32757 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32758 fullname="/home/nickrob/myprog.c",line="73"@}
32763 @chapter @value{GDBN} Annotations
32765 This chapter describes annotations in @value{GDBN}. Annotations were
32766 designed to interface @value{GDBN} to graphical user interfaces or other
32767 similar programs which want to interact with @value{GDBN} at a
32768 relatively high level.
32770 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32774 This is Edition @value{EDITION}, @value{DATE}.
32778 * Annotations Overview:: What annotations are; the general syntax.
32779 * Server Prefix:: Issuing a command without affecting user state.
32780 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32781 * Errors:: Annotations for error messages.
32782 * Invalidation:: Some annotations describe things now invalid.
32783 * Annotations for Running::
32784 Whether the program is running, how it stopped, etc.
32785 * Source Annotations:: Annotations describing source code.
32788 @node Annotations Overview
32789 @section What is an Annotation?
32790 @cindex annotations
32792 Annotations start with a newline character, two @samp{control-z}
32793 characters, and the name of the annotation. If there is no additional
32794 information associated with this annotation, the name of the annotation
32795 is followed immediately by a newline. If there is additional
32796 information, the name of the annotation is followed by a space, the
32797 additional information, and a newline. The additional information
32798 cannot contain newline characters.
32800 Any output not beginning with a newline and two @samp{control-z}
32801 characters denotes literal output from @value{GDBN}. Currently there is
32802 no need for @value{GDBN} to output a newline followed by two
32803 @samp{control-z} characters, but if there was such a need, the
32804 annotations could be extended with an @samp{escape} annotation which
32805 means those three characters as output.
32807 The annotation @var{level}, which is specified using the
32808 @option{--annotate} command line option (@pxref{Mode Options}), controls
32809 how much information @value{GDBN} prints together with its prompt,
32810 values of expressions, source lines, and other types of output. Level 0
32811 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32812 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32813 for programs that control @value{GDBN}, and level 2 annotations have
32814 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32815 Interface, annotate, GDB's Obsolete Annotations}).
32818 @kindex set annotate
32819 @item set annotate @var{level}
32820 The @value{GDBN} command @code{set annotate} sets the level of
32821 annotations to the specified @var{level}.
32823 @item show annotate
32824 @kindex show annotate
32825 Show the current annotation level.
32828 This chapter describes level 3 annotations.
32830 A simple example of starting up @value{GDBN} with annotations is:
32833 $ @kbd{gdb --annotate=3}
32835 Copyright 2003 Free Software Foundation, Inc.
32836 GDB is free software, covered by the GNU General Public License,
32837 and you are welcome to change it and/or distribute copies of it
32838 under certain conditions.
32839 Type "show copying" to see the conditions.
32840 There is absolutely no warranty for GDB. Type "show warranty"
32842 This GDB was configured as "i386-pc-linux-gnu"
32853 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32854 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32855 denotes a @samp{control-z} character) are annotations; the rest is
32856 output from @value{GDBN}.
32858 @node Server Prefix
32859 @section The Server Prefix
32860 @cindex server prefix
32862 If you prefix a command with @samp{server } then it will not affect
32863 the command history, nor will it affect @value{GDBN}'s notion of which
32864 command to repeat if @key{RET} is pressed on a line by itself. This
32865 means that commands can be run behind a user's back by a front-end in
32866 a transparent manner.
32868 The @code{server } prefix does not affect the recording of values into
32869 the value history; to print a value without recording it into the
32870 value history, use the @code{output} command instead of the
32871 @code{print} command.
32873 Using this prefix also disables confirmation requests
32874 (@pxref{confirmation requests}).
32877 @section Annotation for @value{GDBN} Input
32879 @cindex annotations for prompts
32880 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32881 to know when to send output, when the output from a given command is
32884 Different kinds of input each have a different @dfn{input type}. Each
32885 input type has three annotations: a @code{pre-} annotation, which
32886 denotes the beginning of any prompt which is being output, a plain
32887 annotation, which denotes the end of the prompt, and then a @code{post-}
32888 annotation which denotes the end of any echo which may (or may not) be
32889 associated with the input. For example, the @code{prompt} input type
32890 features the following annotations:
32898 The input types are
32901 @findex pre-prompt annotation
32902 @findex prompt annotation
32903 @findex post-prompt annotation
32905 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32907 @findex pre-commands annotation
32908 @findex commands annotation
32909 @findex post-commands annotation
32911 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32912 command. The annotations are repeated for each command which is input.
32914 @findex pre-overload-choice annotation
32915 @findex overload-choice annotation
32916 @findex post-overload-choice annotation
32917 @item overload-choice
32918 When @value{GDBN} wants the user to select between various overloaded functions.
32920 @findex pre-query annotation
32921 @findex query annotation
32922 @findex post-query annotation
32924 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32926 @findex pre-prompt-for-continue annotation
32927 @findex prompt-for-continue annotation
32928 @findex post-prompt-for-continue annotation
32929 @item prompt-for-continue
32930 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32931 expect this to work well; instead use @code{set height 0} to disable
32932 prompting. This is because the counting of lines is buggy in the
32933 presence of annotations.
32938 @cindex annotations for errors, warnings and interrupts
32940 @findex quit annotation
32945 This annotation occurs right before @value{GDBN} responds to an interrupt.
32947 @findex error annotation
32952 This annotation occurs right before @value{GDBN} responds to an error.
32954 Quit and error annotations indicate that any annotations which @value{GDBN} was
32955 in the middle of may end abruptly. For example, if a
32956 @code{value-history-begin} annotation is followed by a @code{error}, one
32957 cannot expect to receive the matching @code{value-history-end}. One
32958 cannot expect not to receive it either, however; an error annotation
32959 does not necessarily mean that @value{GDBN} is immediately returning all the way
32962 @findex error-begin annotation
32963 A quit or error annotation may be preceded by
32969 Any output between that and the quit or error annotation is the error
32972 Warning messages are not yet annotated.
32973 @c If we want to change that, need to fix warning(), type_error(),
32974 @c range_error(), and possibly other places.
32977 @section Invalidation Notices
32979 @cindex annotations for invalidation messages
32980 The following annotations say that certain pieces of state may have
32984 @findex frames-invalid annotation
32985 @item ^Z^Zframes-invalid
32987 The frames (for example, output from the @code{backtrace} command) may
32990 @findex breakpoints-invalid annotation
32991 @item ^Z^Zbreakpoints-invalid
32993 The breakpoints may have changed. For example, the user just added or
32994 deleted a breakpoint.
32997 @node Annotations for Running
32998 @section Running the Program
32999 @cindex annotations for running programs
33001 @findex starting annotation
33002 @findex stopping annotation
33003 When the program starts executing due to a @value{GDBN} command such as
33004 @code{step} or @code{continue},
33010 is output. When the program stops,
33016 is output. Before the @code{stopped} annotation, a variety of
33017 annotations describe how the program stopped.
33020 @findex exited annotation
33021 @item ^Z^Zexited @var{exit-status}
33022 The program exited, and @var{exit-status} is the exit status (zero for
33023 successful exit, otherwise nonzero).
33025 @findex signalled annotation
33026 @findex signal-name annotation
33027 @findex signal-name-end annotation
33028 @findex signal-string annotation
33029 @findex signal-string-end annotation
33030 @item ^Z^Zsignalled
33031 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33032 annotation continues:
33038 ^Z^Zsignal-name-end
33042 ^Z^Zsignal-string-end
33047 where @var{name} is the name of the signal, such as @code{SIGILL} or
33048 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33049 as @code{Illegal Instruction} or @code{Segmentation fault}.
33050 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33051 user's benefit and have no particular format.
33053 @findex signal annotation
33055 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33056 just saying that the program received the signal, not that it was
33057 terminated with it.
33059 @findex breakpoint annotation
33060 @item ^Z^Zbreakpoint @var{number}
33061 The program hit breakpoint number @var{number}.
33063 @findex watchpoint annotation
33064 @item ^Z^Zwatchpoint @var{number}
33065 The program hit watchpoint number @var{number}.
33068 @node Source Annotations
33069 @section Displaying Source
33070 @cindex annotations for source display
33072 @findex source annotation
33073 The following annotation is used instead of displaying source code:
33076 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33079 where @var{filename} is an absolute file name indicating which source
33080 file, @var{line} is the line number within that file (where 1 is the
33081 first line in the file), @var{character} is the character position
33082 within the file (where 0 is the first character in the file) (for most
33083 debug formats this will necessarily point to the beginning of a line),
33084 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33085 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33086 @var{addr} is the address in the target program associated with the
33087 source which is being displayed. @var{addr} is in the form @samp{0x}
33088 followed by one or more lowercase hex digits (note that this does not
33089 depend on the language).
33091 @node JIT Interface
33092 @chapter JIT Compilation Interface
33093 @cindex just-in-time compilation
33094 @cindex JIT compilation interface
33096 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33097 interface. A JIT compiler is a program or library that generates native
33098 executable code at runtime and executes it, usually in order to achieve good
33099 performance while maintaining platform independence.
33101 Programs that use JIT compilation are normally difficult to debug because
33102 portions of their code are generated at runtime, instead of being loaded from
33103 object files, which is where @value{GDBN} normally finds the program's symbols
33104 and debug information. In order to debug programs that use JIT compilation,
33105 @value{GDBN} has an interface that allows the program to register in-memory
33106 symbol files with @value{GDBN} at runtime.
33108 If you are using @value{GDBN} to debug a program that uses this interface, then
33109 it should work transparently so long as you have not stripped the binary. If
33110 you are developing a JIT compiler, then the interface is documented in the rest
33111 of this chapter. At this time, the only known client of this interface is the
33114 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33115 JIT compiler communicates with @value{GDBN} by writing data into a global
33116 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33117 attaches, it reads a linked list of symbol files from the global variable to
33118 find existing code, and puts a breakpoint in the function so that it can find
33119 out about additional code.
33122 * Declarations:: Relevant C struct declarations
33123 * Registering Code:: Steps to register code
33124 * Unregistering Code:: Steps to unregister code
33125 * Custom Debug Info:: Emit debug information in a custom format
33129 @section JIT Declarations
33131 These are the relevant struct declarations that a C program should include to
33132 implement the interface:
33142 struct jit_code_entry
33144 struct jit_code_entry *next_entry;
33145 struct jit_code_entry *prev_entry;
33146 const char *symfile_addr;
33147 uint64_t symfile_size;
33150 struct jit_descriptor
33153 /* This type should be jit_actions_t, but we use uint32_t
33154 to be explicit about the bitwidth. */
33155 uint32_t action_flag;
33156 struct jit_code_entry *relevant_entry;
33157 struct jit_code_entry *first_entry;
33160 /* GDB puts a breakpoint in this function. */
33161 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33163 /* Make sure to specify the version statically, because the
33164 debugger may check the version before we can set it. */
33165 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33168 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33169 modifications to this global data properly, which can easily be done by putting
33170 a global mutex around modifications to these structures.
33172 @node Registering Code
33173 @section Registering Code
33175 To register code with @value{GDBN}, the JIT should follow this protocol:
33179 Generate an object file in memory with symbols and other desired debug
33180 information. The file must include the virtual addresses of the sections.
33183 Create a code entry for the file, which gives the start and size of the symbol
33187 Add it to the linked list in the JIT descriptor.
33190 Point the relevant_entry field of the descriptor at the entry.
33193 Set @code{action_flag} to @code{JIT_REGISTER} and call
33194 @code{__jit_debug_register_code}.
33197 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33198 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33199 new code. However, the linked list must still be maintained in order to allow
33200 @value{GDBN} to attach to a running process and still find the symbol files.
33202 @node Unregistering Code
33203 @section Unregistering Code
33205 If code is freed, then the JIT should use the following protocol:
33209 Remove the code entry corresponding to the code from the linked list.
33212 Point the @code{relevant_entry} field of the descriptor at the code entry.
33215 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33216 @code{__jit_debug_register_code}.
33219 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33220 and the JIT will leak the memory used for the associated symbol files.
33222 @node Custom Debug Info
33223 @section Custom Debug Info
33224 @cindex custom JIT debug info
33225 @cindex JIT debug info reader
33227 Generating debug information in platform-native file formats (like ELF
33228 or COFF) may be an overkill for JIT compilers; especially if all the
33229 debug info is used for is displaying a meaningful backtrace. The
33230 issue can be resolved by having the JIT writers decide on a debug info
33231 format and also provide a reader that parses the debug info generated
33232 by the JIT compiler. This section gives a brief overview on writing
33233 such a parser. More specific details can be found in the source file
33234 @file{gdb/jit-reader.in}, which is also installed as a header at
33235 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33237 The reader is implemented as a shared object (so this functionality is
33238 not available on platforms which don't allow loading shared objects at
33239 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33240 @code{jit-reader-unload} are provided, to be used to load and unload
33241 the readers from a preconfigured directory. Once loaded, the shared
33242 object is used the parse the debug information emitted by the JIT
33246 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33247 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33250 @node Using JIT Debug Info Readers
33251 @subsection Using JIT Debug Info Readers
33252 @kindex jit-reader-load
33253 @kindex jit-reader-unload
33255 Readers can be loaded and unloaded using the @code{jit-reader-load}
33256 and @code{jit-reader-unload} commands.
33259 @item jit-reader-load @var{reader-name}
33260 Load the JIT reader named @var{reader-name}. On a UNIX system, this
33261 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
33262 @var{libdir} is the system library directory, usually
33263 @file{/usr/local/lib}. Only one reader can be active at a time;
33264 trying to load a second reader when one is already loaded will result
33265 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
33266 first unloading the current one using @code{jit-reader-load} and then
33267 invoking @code{jit-reader-load}.
33269 @item jit-reader-unload
33270 Unload the currently loaded JIT reader.
33274 @node Writing JIT Debug Info Readers
33275 @subsection Writing JIT Debug Info Readers
33276 @cindex writing JIT debug info readers
33278 As mentioned, a reader is essentially a shared object conforming to a
33279 certain ABI. This ABI is described in @file{jit-reader.h}.
33281 @file{jit-reader.h} defines the structures, macros and functions
33282 required to write a reader. It is installed (along with
33283 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33284 the system include directory.
33286 Readers need to be released under a GPL compatible license. A reader
33287 can be declared as released under such a license by placing the macro
33288 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33290 The entry point for readers is the symbol @code{gdb_init_reader},
33291 which is expected to be a function with the prototype
33293 @findex gdb_init_reader
33295 extern struct gdb_reader_funcs *gdb_init_reader (void);
33298 @cindex @code{struct gdb_reader_funcs}
33300 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33301 functions. These functions are executed to read the debug info
33302 generated by the JIT compiler (@code{read}), to unwind stack frames
33303 (@code{unwind}) and to create canonical frame IDs
33304 (@code{get_Frame_id}). It also has a callback that is called when the
33305 reader is being unloaded (@code{destroy}). The struct looks like this
33308 struct gdb_reader_funcs
33310 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33311 int reader_version;
33313 /* For use by the reader. */
33316 gdb_read_debug_info *read;
33317 gdb_unwind_frame *unwind;
33318 gdb_get_frame_id *get_frame_id;
33319 gdb_destroy_reader *destroy;
33323 @cindex @code{struct gdb_symbol_callbacks}
33324 @cindex @code{struct gdb_unwind_callbacks}
33326 The callbacks are provided with another set of callbacks by
33327 @value{GDBN} to do their job. For @code{read}, these callbacks are
33328 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33329 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33330 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33331 files and new symbol tables inside those object files. @code{struct
33332 gdb_unwind_callbacks} has callbacks to read registers off the current
33333 frame and to write out the values of the registers in the previous
33334 frame. Both have a callback (@code{target_read}) to read bytes off the
33335 target's address space.
33337 @node In-Process Agent
33338 @chapter In-Process Agent
33339 @cindex debugging agent
33340 The traditional debugging model is conceptually low-speed, but works fine,
33341 because most bugs can be reproduced in debugging-mode execution. However,
33342 as multi-core or many-core processors are becoming mainstream, and
33343 multi-threaded programs become more and more popular, there should be more
33344 and more bugs that only manifest themselves at normal-mode execution, for
33345 example, thread races, because debugger's interference with the program's
33346 timing may conceal the bugs. On the other hand, in some applications,
33347 it is not feasible for the debugger to interrupt the program's execution
33348 long enough for the developer to learn anything helpful about its behavior.
33349 If the program's correctness depends on its real-time behavior, delays
33350 introduced by a debugger might cause the program to fail, even when the
33351 code itself is correct. It is useful to be able to observe the program's
33352 behavior without interrupting it.
33354 Therefore, traditional debugging model is too intrusive to reproduce
33355 some bugs. In order to reduce the interference with the program, we can
33356 reduce the number of operations performed by debugger. The
33357 @dfn{In-Process Agent}, a shared library, is running within the same
33358 process with inferior, and is able to perform some debugging operations
33359 itself. As a result, debugger is only involved when necessary, and
33360 performance of debugging can be improved accordingly. Note that
33361 interference with program can be reduced but can't be removed completely,
33362 because the in-process agent will still stop or slow down the program.
33364 The in-process agent can interpret and execute Agent Expressions
33365 (@pxref{Agent Expressions}) during performing debugging operations. The
33366 agent expressions can be used for different purposes, such as collecting
33367 data in tracepoints, and condition evaluation in breakpoints.
33369 @anchor{Control Agent}
33370 You can control whether the in-process agent is used as an aid for
33371 debugging with the following commands:
33374 @kindex set agent on
33376 Causes the in-process agent to perform some operations on behalf of the
33377 debugger. Just which operations requested by the user will be done
33378 by the in-process agent depends on the its capabilities. For example,
33379 if you request to evaluate breakpoint conditions in the in-process agent,
33380 and the in-process agent has such capability as well, then breakpoint
33381 conditions will be evaluated in the in-process agent.
33383 @kindex set agent off
33384 @item set agent off
33385 Disables execution of debugging operations by the in-process agent. All
33386 of the operations will be performed by @value{GDBN}.
33390 Display the current setting of execution of debugging operations by
33391 the in-process agent.
33395 @chapter Reporting Bugs in @value{GDBN}
33396 @cindex bugs in @value{GDBN}
33397 @cindex reporting bugs in @value{GDBN}
33399 Your bug reports play an essential role in making @value{GDBN} reliable.
33401 Reporting a bug may help you by bringing a solution to your problem, or it
33402 may not. But in any case the principal function of a bug report is to help
33403 the entire community by making the next version of @value{GDBN} work better. Bug
33404 reports are your contribution to the maintenance of @value{GDBN}.
33406 In order for a bug report to serve its purpose, you must include the
33407 information that enables us to fix the bug.
33410 * Bug Criteria:: Have you found a bug?
33411 * Bug Reporting:: How to report bugs
33415 @section Have You Found a Bug?
33416 @cindex bug criteria
33418 If you are not sure whether you have found a bug, here are some guidelines:
33421 @cindex fatal signal
33422 @cindex debugger crash
33423 @cindex crash of debugger
33425 If the debugger gets a fatal signal, for any input whatever, that is a
33426 @value{GDBN} bug. Reliable debuggers never crash.
33428 @cindex error on valid input
33430 If @value{GDBN} produces an error message for valid input, that is a
33431 bug. (Note that if you're cross debugging, the problem may also be
33432 somewhere in the connection to the target.)
33434 @cindex invalid input
33436 If @value{GDBN} does not produce an error message for invalid input,
33437 that is a bug. However, you should note that your idea of
33438 ``invalid input'' might be our idea of ``an extension'' or ``support
33439 for traditional practice''.
33442 If you are an experienced user of debugging tools, your suggestions
33443 for improvement of @value{GDBN} are welcome in any case.
33446 @node Bug Reporting
33447 @section How to Report Bugs
33448 @cindex bug reports
33449 @cindex @value{GDBN} bugs, reporting
33451 A number of companies and individuals offer support for @sc{gnu} products.
33452 If you obtained @value{GDBN} from a support organization, we recommend you
33453 contact that organization first.
33455 You can find contact information for many support companies and
33456 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33458 @c should add a web page ref...
33461 @ifset BUGURL_DEFAULT
33462 In any event, we also recommend that you submit bug reports for
33463 @value{GDBN}. The preferred method is to submit them directly using
33464 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33465 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33468 @strong{Do not send bug reports to @samp{info-gdb}, or to
33469 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33470 not want to receive bug reports. Those that do have arranged to receive
33473 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33474 serves as a repeater. The mailing list and the newsgroup carry exactly
33475 the same messages. Often people think of posting bug reports to the
33476 newsgroup instead of mailing them. This appears to work, but it has one
33477 problem which can be crucial: a newsgroup posting often lacks a mail
33478 path back to the sender. Thus, if we need to ask for more information,
33479 we may be unable to reach you. For this reason, it is better to send
33480 bug reports to the mailing list.
33482 @ifclear BUGURL_DEFAULT
33483 In any event, we also recommend that you submit bug reports for
33484 @value{GDBN} to @value{BUGURL}.
33488 The fundamental principle of reporting bugs usefully is this:
33489 @strong{report all the facts}. If you are not sure whether to state a
33490 fact or leave it out, state it!
33492 Often people omit facts because they think they know what causes the
33493 problem and assume that some details do not matter. Thus, you might
33494 assume that the name of the variable you use in an example does not matter.
33495 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33496 stray memory reference which happens to fetch from the location where that
33497 name is stored in memory; perhaps, if the name were different, the contents
33498 of that location would fool the debugger into doing the right thing despite
33499 the bug. Play it safe and give a specific, complete example. That is the
33500 easiest thing for you to do, and the most helpful.
33502 Keep in mind that the purpose of a bug report is to enable us to fix the
33503 bug. It may be that the bug has been reported previously, but neither
33504 you nor we can know that unless your bug report is complete and
33507 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33508 bell?'' Those bug reports are useless, and we urge everyone to
33509 @emph{refuse to respond to them} except to chide the sender to report
33512 To enable us to fix the bug, you should include all these things:
33516 The version of @value{GDBN}. @value{GDBN} announces it if you start
33517 with no arguments; you can also print it at any time using @code{show
33520 Without this, we will not know whether there is any point in looking for
33521 the bug in the current version of @value{GDBN}.
33524 The type of machine you are using, and the operating system name and
33528 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33529 ``@value{GCC}--2.8.1''.
33532 What compiler (and its version) was used to compile the program you are
33533 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33534 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33535 to get this information; for other compilers, see the documentation for
33539 The command arguments you gave the compiler to compile your example and
33540 observe the bug. For example, did you use @samp{-O}? To guarantee
33541 you will not omit something important, list them all. A copy of the
33542 Makefile (or the output from make) is sufficient.
33544 If we were to try to guess the arguments, we would probably guess wrong
33545 and then we might not encounter the bug.
33548 A complete input script, and all necessary source files, that will
33552 A description of what behavior you observe that you believe is
33553 incorrect. For example, ``It gets a fatal signal.''
33555 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33556 will certainly notice it. But if the bug is incorrect output, we might
33557 not notice unless it is glaringly wrong. You might as well not give us
33558 a chance to make a mistake.
33560 Even if the problem you experience is a fatal signal, you should still
33561 say so explicitly. Suppose something strange is going on, such as, your
33562 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33563 the C library on your system. (This has happened!) Your copy might
33564 crash and ours would not. If you told us to expect a crash, then when
33565 ours fails to crash, we would know that the bug was not happening for
33566 us. If you had not told us to expect a crash, then we would not be able
33567 to draw any conclusion from our observations.
33570 @cindex recording a session script
33571 To collect all this information, you can use a session recording program
33572 such as @command{script}, which is available on many Unix systems.
33573 Just run your @value{GDBN} session inside @command{script} and then
33574 include the @file{typescript} file with your bug report.
33576 Another way to record a @value{GDBN} session is to run @value{GDBN}
33577 inside Emacs and then save the entire buffer to a file.
33580 If you wish to suggest changes to the @value{GDBN} source, send us context
33581 diffs. If you even discuss something in the @value{GDBN} source, refer to
33582 it by context, not by line number.
33584 The line numbers in our development sources will not match those in your
33585 sources. Your line numbers would convey no useful information to us.
33589 Here are some things that are not necessary:
33593 A description of the envelope of the bug.
33595 Often people who encounter a bug spend a lot of time investigating
33596 which changes to the input file will make the bug go away and which
33597 changes will not affect it.
33599 This is often time consuming and not very useful, because the way we
33600 will find the bug is by running a single example under the debugger
33601 with breakpoints, not by pure deduction from a series of examples.
33602 We recommend that you save your time for something else.
33604 Of course, if you can find a simpler example to report @emph{instead}
33605 of the original one, that is a convenience for us. Errors in the
33606 output will be easier to spot, running under the debugger will take
33607 less time, and so on.
33609 However, simplification is not vital; if you do not want to do this,
33610 report the bug anyway and send us the entire test case you used.
33613 A patch for the bug.
33615 A patch for the bug does help us if it is a good one. But do not omit
33616 the necessary information, such as the test case, on the assumption that
33617 a patch is all we need. We might see problems with your patch and decide
33618 to fix the problem another way, or we might not understand it at all.
33620 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33621 construct an example that will make the program follow a certain path
33622 through the code. If you do not send us the example, we will not be able
33623 to construct one, so we will not be able to verify that the bug is fixed.
33625 And if we cannot understand what bug you are trying to fix, or why your
33626 patch should be an improvement, we will not install it. A test case will
33627 help us to understand.
33630 A guess about what the bug is or what it depends on.
33632 Such guesses are usually wrong. Even we cannot guess right about such
33633 things without first using the debugger to find the facts.
33636 @c The readline documentation is distributed with the readline code
33637 @c and consists of the two following files:
33640 @c Use -I with makeinfo to point to the appropriate directory,
33641 @c environment var TEXINPUTS with TeX.
33642 @ifclear SYSTEM_READLINE
33643 @include rluser.texi
33644 @include hsuser.texi
33648 @appendix In Memoriam
33650 The @value{GDBN} project mourns the loss of the following long-time
33655 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33656 to Free Software in general. Outside of @value{GDBN}, he was known in
33657 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33659 @item Michael Snyder
33660 Michael was one of the Global Maintainers of the @value{GDBN} project,
33661 with contributions recorded as early as 1996, until 2011. In addition
33662 to his day to day participation, he was a large driving force behind
33663 adding Reverse Debugging to @value{GDBN}.
33666 Beyond their technical contributions to the project, they were also
33667 enjoyable members of the Free Software Community. We will miss them.
33669 @node Formatting Documentation
33670 @appendix Formatting Documentation
33672 @cindex @value{GDBN} reference card
33673 @cindex reference card
33674 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33675 for printing with PostScript or Ghostscript, in the @file{gdb}
33676 subdirectory of the main source directory@footnote{In
33677 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33678 release.}. If you can use PostScript or Ghostscript with your printer,
33679 you can print the reference card immediately with @file{refcard.ps}.
33681 The release also includes the source for the reference card. You
33682 can format it, using @TeX{}, by typing:
33688 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33689 mode on US ``letter'' size paper;
33690 that is, on a sheet 11 inches wide by 8.5 inches
33691 high. You will need to specify this form of printing as an option to
33692 your @sc{dvi} output program.
33694 @cindex documentation
33696 All the documentation for @value{GDBN} comes as part of the machine-readable
33697 distribution. The documentation is written in Texinfo format, which is
33698 a documentation system that uses a single source file to produce both
33699 on-line information and a printed manual. You can use one of the Info
33700 formatting commands to create the on-line version of the documentation
33701 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33703 @value{GDBN} includes an already formatted copy of the on-line Info
33704 version of this manual in the @file{gdb} subdirectory. The main Info
33705 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33706 subordinate files matching @samp{gdb.info*} in the same directory. If
33707 necessary, you can print out these files, or read them with any editor;
33708 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33709 Emacs or the standalone @code{info} program, available as part of the
33710 @sc{gnu} Texinfo distribution.
33712 If you want to format these Info files yourself, you need one of the
33713 Info formatting programs, such as @code{texinfo-format-buffer} or
33716 If you have @code{makeinfo} installed, and are in the top level
33717 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33718 version @value{GDBVN}), you can make the Info file by typing:
33725 If you want to typeset and print copies of this manual, you need @TeX{},
33726 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33727 Texinfo definitions file.
33729 @TeX{} is a typesetting program; it does not print files directly, but
33730 produces output files called @sc{dvi} files. To print a typeset
33731 document, you need a program to print @sc{dvi} files. If your system
33732 has @TeX{} installed, chances are it has such a program. The precise
33733 command to use depends on your system; @kbd{lpr -d} is common; another
33734 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33735 require a file name without any extension or a @samp{.dvi} extension.
33737 @TeX{} also requires a macro definitions file called
33738 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33739 written in Texinfo format. On its own, @TeX{} cannot either read or
33740 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33741 and is located in the @file{gdb-@var{version-number}/texinfo}
33744 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33745 typeset and print this manual. First switch to the @file{gdb}
33746 subdirectory of the main source directory (for example, to
33747 @file{gdb-@value{GDBVN}/gdb}) and type:
33753 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33755 @node Installing GDB
33756 @appendix Installing @value{GDBN}
33757 @cindex installation
33760 * Requirements:: Requirements for building @value{GDBN}
33761 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33762 * Separate Objdir:: Compiling @value{GDBN} in another directory
33763 * Config Names:: Specifying names for hosts and targets
33764 * Configure Options:: Summary of options for configure
33765 * System-wide configuration:: Having a system-wide init file
33769 @section Requirements for Building @value{GDBN}
33770 @cindex building @value{GDBN}, requirements for
33772 Building @value{GDBN} requires various tools and packages to be available.
33773 Other packages will be used only if they are found.
33775 @heading Tools/Packages Necessary for Building @value{GDBN}
33777 @item ISO C90 compiler
33778 @value{GDBN} is written in ISO C90. It should be buildable with any
33779 working C90 compiler, e.g.@: GCC.
33783 @heading Tools/Packages Optional for Building @value{GDBN}
33787 @value{GDBN} can use the Expat XML parsing library. This library may be
33788 included with your operating system distribution; if it is not, you
33789 can get the latest version from @url{http://expat.sourceforge.net}.
33790 The @file{configure} script will search for this library in several
33791 standard locations; if it is installed in an unusual path, you can
33792 use the @option{--with-libexpat-prefix} option to specify its location.
33798 Remote protocol memory maps (@pxref{Memory Map Format})
33800 Target descriptions (@pxref{Target Descriptions})
33802 Remote shared library lists (@xref{Library List Format},
33803 or alternatively @pxref{Library List Format for SVR4 Targets})
33805 MS-Windows shared libraries (@pxref{Shared Libraries})
33807 Traceframe info (@pxref{Traceframe Info Format})
33811 @cindex compressed debug sections
33812 @value{GDBN} will use the @samp{zlib} library, if available, to read
33813 compressed debug sections. Some linkers, such as GNU gold, are capable
33814 of producing binaries with compressed debug sections. If @value{GDBN}
33815 is compiled with @samp{zlib}, it will be able to read the debug
33816 information in such binaries.
33818 The @samp{zlib} library is likely included with your operating system
33819 distribution; if it is not, you can get the latest version from
33820 @url{http://zlib.net}.
33823 @value{GDBN}'s features related to character sets (@pxref{Character
33824 Sets}) require a functioning @code{iconv} implementation. If you are
33825 on a GNU system, then this is provided by the GNU C Library. Some
33826 other systems also provide a working @code{iconv}.
33828 If @value{GDBN} is using the @code{iconv} program which is installed
33829 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33830 This is done with @option{--with-iconv-bin} which specifies the
33831 directory that contains the @code{iconv} program.
33833 On systems without @code{iconv}, you can install GNU Libiconv. If you
33834 have previously installed Libiconv, you can use the
33835 @option{--with-libiconv-prefix} option to configure.
33837 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33838 arrange to build Libiconv if a directory named @file{libiconv} appears
33839 in the top-most source directory. If Libiconv is built this way, and
33840 if the operating system does not provide a suitable @code{iconv}
33841 implementation, then the just-built library will automatically be used
33842 by @value{GDBN}. One easy way to set this up is to download GNU
33843 Libiconv, unpack it, and then rename the directory holding the
33844 Libiconv source code to @samp{libiconv}.
33847 @node Running Configure
33848 @section Invoking the @value{GDBN} @file{configure} Script
33849 @cindex configuring @value{GDBN}
33850 @value{GDBN} comes with a @file{configure} script that automates the process
33851 of preparing @value{GDBN} for installation; you can then use @code{make} to
33852 build the @code{gdb} program.
33854 @c irrelevant in info file; it's as current as the code it lives with.
33855 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33856 look at the @file{README} file in the sources; we may have improved the
33857 installation procedures since publishing this manual.}
33860 The @value{GDBN} distribution includes all the source code you need for
33861 @value{GDBN} in a single directory, whose name is usually composed by
33862 appending the version number to @samp{gdb}.
33864 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33865 @file{gdb-@value{GDBVN}} directory. That directory contains:
33868 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33869 script for configuring @value{GDBN} and all its supporting libraries
33871 @item gdb-@value{GDBVN}/gdb
33872 the source specific to @value{GDBN} itself
33874 @item gdb-@value{GDBVN}/bfd
33875 source for the Binary File Descriptor library
33877 @item gdb-@value{GDBVN}/include
33878 @sc{gnu} include files
33880 @item gdb-@value{GDBVN}/libiberty
33881 source for the @samp{-liberty} free software library
33883 @item gdb-@value{GDBVN}/opcodes
33884 source for the library of opcode tables and disassemblers
33886 @item gdb-@value{GDBVN}/readline
33887 source for the @sc{gnu} command-line interface
33889 @item gdb-@value{GDBVN}/glob
33890 source for the @sc{gnu} filename pattern-matching subroutine
33892 @item gdb-@value{GDBVN}/mmalloc
33893 source for the @sc{gnu} memory-mapped malloc package
33896 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33897 from the @file{gdb-@var{version-number}} source directory, which in
33898 this example is the @file{gdb-@value{GDBVN}} directory.
33900 First switch to the @file{gdb-@var{version-number}} source directory
33901 if you are not already in it; then run @file{configure}. Pass the
33902 identifier for the platform on which @value{GDBN} will run as an
33908 cd gdb-@value{GDBVN}
33909 ./configure @var{host}
33914 where @var{host} is an identifier such as @samp{sun4} or
33915 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33916 (You can often leave off @var{host}; @file{configure} tries to guess the
33917 correct value by examining your system.)
33919 Running @samp{configure @var{host}} and then running @code{make} builds the
33920 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33921 libraries, then @code{gdb} itself. The configured source files, and the
33922 binaries, are left in the corresponding source directories.
33925 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33926 system does not recognize this automatically when you run a different
33927 shell, you may need to run @code{sh} on it explicitly:
33930 sh configure @var{host}
33933 If you run @file{configure} from a directory that contains source
33934 directories for multiple libraries or programs, such as the
33935 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33937 creates configuration files for every directory level underneath (unless
33938 you tell it not to, with the @samp{--norecursion} option).
33940 You should run the @file{configure} script from the top directory in the
33941 source tree, the @file{gdb-@var{version-number}} directory. If you run
33942 @file{configure} from one of the subdirectories, you will configure only
33943 that subdirectory. That is usually not what you want. In particular,
33944 if you run the first @file{configure} from the @file{gdb} subdirectory
33945 of the @file{gdb-@var{version-number}} directory, you will omit the
33946 configuration of @file{bfd}, @file{readline}, and other sibling
33947 directories of the @file{gdb} subdirectory. This leads to build errors
33948 about missing include files such as @file{bfd/bfd.h}.
33950 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33951 However, you should make sure that the shell on your path (named by
33952 the @samp{SHELL} environment variable) is publicly readable. Remember
33953 that @value{GDBN} uses the shell to start your program---some systems refuse to
33954 let @value{GDBN} debug child processes whose programs are not readable.
33956 @node Separate Objdir
33957 @section Compiling @value{GDBN} in Another Directory
33959 If you want to run @value{GDBN} versions for several host or target machines,
33960 you need a different @code{gdb} compiled for each combination of
33961 host and target. @file{configure} is designed to make this easy by
33962 allowing you to generate each configuration in a separate subdirectory,
33963 rather than in the source directory. If your @code{make} program
33964 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33965 @code{make} in each of these directories builds the @code{gdb}
33966 program specified there.
33968 To build @code{gdb} in a separate directory, run @file{configure}
33969 with the @samp{--srcdir} option to specify where to find the source.
33970 (You also need to specify a path to find @file{configure}
33971 itself from your working directory. If the path to @file{configure}
33972 would be the same as the argument to @samp{--srcdir}, you can leave out
33973 the @samp{--srcdir} option; it is assumed.)
33975 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33976 separate directory for a Sun 4 like this:
33980 cd gdb-@value{GDBVN}
33983 ../gdb-@value{GDBVN}/configure sun4
33988 When @file{configure} builds a configuration using a remote source
33989 directory, it creates a tree for the binaries with the same structure
33990 (and using the same names) as the tree under the source directory. In
33991 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33992 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33993 @file{gdb-sun4/gdb}.
33995 Make sure that your path to the @file{configure} script has just one
33996 instance of @file{gdb} in it. If your path to @file{configure} looks
33997 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33998 one subdirectory of @value{GDBN}, not the whole package. This leads to
33999 build errors about missing include files such as @file{bfd/bfd.h}.
34001 One popular reason to build several @value{GDBN} configurations in separate
34002 directories is to configure @value{GDBN} for cross-compiling (where
34003 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34004 programs that run on another machine---the @dfn{target}).
34005 You specify a cross-debugging target by
34006 giving the @samp{--target=@var{target}} option to @file{configure}.
34008 When you run @code{make} to build a program or library, you must run
34009 it in a configured directory---whatever directory you were in when you
34010 called @file{configure} (or one of its subdirectories).
34012 The @code{Makefile} that @file{configure} generates in each source
34013 directory also runs recursively. If you type @code{make} in a source
34014 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34015 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34016 will build all the required libraries, and then build GDB.
34018 When you have multiple hosts or targets configured in separate
34019 directories, you can run @code{make} on them in parallel (for example,
34020 if they are NFS-mounted on each of the hosts); they will not interfere
34024 @section Specifying Names for Hosts and Targets
34026 The specifications used for hosts and targets in the @file{configure}
34027 script are based on a three-part naming scheme, but some short predefined
34028 aliases are also supported. The full naming scheme encodes three pieces
34029 of information in the following pattern:
34032 @var{architecture}-@var{vendor}-@var{os}
34035 For example, you can use the alias @code{sun4} as a @var{host} argument,
34036 or as the value for @var{target} in a @code{--target=@var{target}}
34037 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34039 The @file{configure} script accompanying @value{GDBN} does not provide
34040 any query facility to list all supported host and target names or
34041 aliases. @file{configure} calls the Bourne shell script
34042 @code{config.sub} to map abbreviations to full names; you can read the
34043 script, if you wish, or you can use it to test your guesses on
34044 abbreviations---for example:
34047 % sh config.sub i386-linux
34049 % sh config.sub alpha-linux
34050 alpha-unknown-linux-gnu
34051 % sh config.sub hp9k700
34053 % sh config.sub sun4
34054 sparc-sun-sunos4.1.1
34055 % sh config.sub sun3
34056 m68k-sun-sunos4.1.1
34057 % sh config.sub i986v
34058 Invalid configuration `i986v': machine `i986v' not recognized
34062 @code{config.sub} is also distributed in the @value{GDBN} source
34063 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34065 @node Configure Options
34066 @section @file{configure} Options
34068 Here is a summary of the @file{configure} options and arguments that
34069 are most often useful for building @value{GDBN}. @file{configure} also has
34070 several other options not listed here. @inforef{What Configure
34071 Does,,configure.info}, for a full explanation of @file{configure}.
34074 configure @r{[}--help@r{]}
34075 @r{[}--prefix=@var{dir}@r{]}
34076 @r{[}--exec-prefix=@var{dir}@r{]}
34077 @r{[}--srcdir=@var{dirname}@r{]}
34078 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34079 @r{[}--target=@var{target}@r{]}
34084 You may introduce options with a single @samp{-} rather than
34085 @samp{--} if you prefer; but you may abbreviate option names if you use
34090 Display a quick summary of how to invoke @file{configure}.
34092 @item --prefix=@var{dir}
34093 Configure the source to install programs and files under directory
34096 @item --exec-prefix=@var{dir}
34097 Configure the source to install programs under directory
34100 @c avoid splitting the warning from the explanation:
34102 @item --srcdir=@var{dirname}
34103 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34104 @code{make} that implements the @code{VPATH} feature.}@*
34105 Use this option to make configurations in directories separate from the
34106 @value{GDBN} source directories. Among other things, you can use this to
34107 build (or maintain) several configurations simultaneously, in separate
34108 directories. @file{configure} writes configuration-specific files in
34109 the current directory, but arranges for them to use the source in the
34110 directory @var{dirname}. @file{configure} creates directories under
34111 the working directory in parallel to the source directories below
34114 @item --norecursion
34115 Configure only the directory level where @file{configure} is executed; do not
34116 propagate configuration to subdirectories.
34118 @item --target=@var{target}
34119 Configure @value{GDBN} for cross-debugging programs running on the specified
34120 @var{target}. Without this option, @value{GDBN} is configured to debug
34121 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34123 There is no convenient way to generate a list of all available targets.
34125 @item @var{host} @dots{}
34126 Configure @value{GDBN} to run on the specified @var{host}.
34128 There is no convenient way to generate a list of all available hosts.
34131 There are many other options available as well, but they are generally
34132 needed for special purposes only.
34134 @node System-wide configuration
34135 @section System-wide configuration and settings
34136 @cindex system-wide init file
34138 @value{GDBN} can be configured to have a system-wide init file;
34139 this file will be read and executed at startup (@pxref{Startup, , What
34140 @value{GDBN} does during startup}).
34142 Here is the corresponding configure option:
34145 @item --with-system-gdbinit=@var{file}
34146 Specify that the default location of the system-wide init file is
34150 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34151 it may be subject to relocation. Two possible cases:
34155 If the default location of this init file contains @file{$prefix},
34156 it will be subject to relocation. Suppose that the configure options
34157 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34158 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34159 init file is looked for as @file{$install/etc/gdbinit} instead of
34160 @file{$prefix/etc/gdbinit}.
34163 By contrast, if the default location does not contain the prefix,
34164 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34165 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34166 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34167 wherever @value{GDBN} is installed.
34170 @node Maintenance Commands
34171 @appendix Maintenance Commands
34172 @cindex maintenance commands
34173 @cindex internal commands
34175 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34176 includes a number of commands intended for @value{GDBN} developers,
34177 that are not documented elsewhere in this manual. These commands are
34178 provided here for reference. (For commands that turn on debugging
34179 messages, see @ref{Debugging Output}.)
34182 @kindex maint agent
34183 @kindex maint agent-eval
34184 @item maint agent @var{expression}
34185 @itemx maint agent-eval @var{expression}
34186 Translate the given @var{expression} into remote agent bytecodes.
34187 This command is useful for debugging the Agent Expression mechanism
34188 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34189 expression useful for data collection, such as by tracepoints, while
34190 @samp{maint agent-eval} produces an expression that evaluates directly
34191 to a result. For instance, a collection expression for @code{globa +
34192 globb} will include bytecodes to record four bytes of memory at each
34193 of the addresses of @code{globa} and @code{globb}, while discarding
34194 the result of the addition, while an evaluation expression will do the
34195 addition and return the sum.
34197 @kindex maint info breakpoints
34198 @item @anchor{maint info breakpoints}maint info breakpoints
34199 Using the same format as @samp{info breakpoints}, display both the
34200 breakpoints you've set explicitly, and those @value{GDBN} is using for
34201 internal purposes. Internal breakpoints are shown with negative
34202 breakpoint numbers. The type column identifies what kind of breakpoint
34207 Normal, explicitly set breakpoint.
34210 Normal, explicitly set watchpoint.
34213 Internal breakpoint, used to handle correctly stepping through
34214 @code{longjmp} calls.
34216 @item longjmp resume
34217 Internal breakpoint at the target of a @code{longjmp}.
34220 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34223 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34226 Shared library events.
34230 @kindex set displaced-stepping
34231 @kindex show displaced-stepping
34232 @cindex displaced stepping support
34233 @cindex out-of-line single-stepping
34234 @item set displaced-stepping
34235 @itemx show displaced-stepping
34236 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34237 if the target supports it. Displaced stepping is a way to single-step
34238 over breakpoints without removing them from the inferior, by executing
34239 an out-of-line copy of the instruction that was originally at the
34240 breakpoint location. It is also known as out-of-line single-stepping.
34243 @item set displaced-stepping on
34244 If the target architecture supports it, @value{GDBN} will use
34245 displaced stepping to step over breakpoints.
34247 @item set displaced-stepping off
34248 @value{GDBN} will not use displaced stepping to step over breakpoints,
34249 even if such is supported by the target architecture.
34251 @cindex non-stop mode, and @samp{set displaced-stepping}
34252 @item set displaced-stepping auto
34253 This is the default mode. @value{GDBN} will use displaced stepping
34254 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34255 architecture supports displaced stepping.
34258 @kindex maint check-symtabs
34259 @item maint check-symtabs
34260 Check the consistency of psymtabs and symtabs.
34262 @kindex maint cplus first_component
34263 @item maint cplus first_component @var{name}
34264 Print the first C@t{++} class/namespace component of @var{name}.
34266 @kindex maint cplus namespace
34267 @item maint cplus namespace
34268 Print the list of possible C@t{++} namespaces.
34270 @kindex maint demangle
34271 @item maint demangle @var{name}
34272 Demangle a C@t{++} or Objective-C mangled @var{name}.
34274 @kindex maint deprecate
34275 @kindex maint undeprecate
34276 @cindex deprecated commands
34277 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34278 @itemx maint undeprecate @var{command}
34279 Deprecate or undeprecate the named @var{command}. Deprecated commands
34280 cause @value{GDBN} to issue a warning when you use them. The optional
34281 argument @var{replacement} says which newer command should be used in
34282 favor of the deprecated one; if it is given, @value{GDBN} will mention
34283 the replacement as part of the warning.
34285 @kindex maint dump-me
34286 @item maint dump-me
34287 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34288 Cause a fatal signal in the debugger and force it to dump its core.
34289 This is supported only on systems which support aborting a program
34290 with the @code{SIGQUIT} signal.
34292 @kindex maint internal-error
34293 @kindex maint internal-warning
34294 @item maint internal-error @r{[}@var{message-text}@r{]}
34295 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34296 Cause @value{GDBN} to call the internal function @code{internal_error}
34297 or @code{internal_warning} and hence behave as though an internal error
34298 or internal warning has been detected. In addition to reporting the
34299 internal problem, these functions give the user the opportunity to
34300 either quit @value{GDBN} or create a core file of the current
34301 @value{GDBN} session.
34303 These commands take an optional parameter @var{message-text} that is
34304 used as the text of the error or warning message.
34306 Here's an example of using @code{internal-error}:
34309 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34310 @dots{}/maint.c:121: internal-error: testing, 1, 2
34311 A problem internal to GDB has been detected. Further
34312 debugging may prove unreliable.
34313 Quit this debugging session? (y or n) @kbd{n}
34314 Create a core file? (y or n) @kbd{n}
34318 @cindex @value{GDBN} internal error
34319 @cindex internal errors, control of @value{GDBN} behavior
34321 @kindex maint set internal-error
34322 @kindex maint show internal-error
34323 @kindex maint set internal-warning
34324 @kindex maint show internal-warning
34325 @item maint set internal-error @var{action} [ask|yes|no]
34326 @itemx maint show internal-error @var{action}
34327 @itemx maint set internal-warning @var{action} [ask|yes|no]
34328 @itemx maint show internal-warning @var{action}
34329 When @value{GDBN} reports an internal problem (error or warning) it
34330 gives the user the opportunity to both quit @value{GDBN} and create a
34331 core file of the current @value{GDBN} session. These commands let you
34332 override the default behaviour for each particular @var{action},
34333 described in the table below.
34337 You can specify that @value{GDBN} should always (yes) or never (no)
34338 quit. The default is to ask the user what to do.
34341 You can specify that @value{GDBN} should always (yes) or never (no)
34342 create a core file. The default is to ask the user what to do.
34345 @kindex maint packet
34346 @item maint packet @var{text}
34347 If @value{GDBN} is talking to an inferior via the serial protocol,
34348 then this command sends the string @var{text} to the inferior, and
34349 displays the response packet. @value{GDBN} supplies the initial
34350 @samp{$} character, the terminating @samp{#} character, and the
34353 @kindex maint print architecture
34354 @item maint print architecture @r{[}@var{file}@r{]}
34355 Print the entire architecture configuration. The optional argument
34356 @var{file} names the file where the output goes.
34358 @kindex maint print c-tdesc
34359 @item maint print c-tdesc
34360 Print the current target description (@pxref{Target Descriptions}) as
34361 a C source file. The created source file can be used in @value{GDBN}
34362 when an XML parser is not available to parse the description.
34364 @kindex maint print dummy-frames
34365 @item maint print dummy-frames
34366 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34369 (@value{GDBP}) @kbd{b add}
34371 (@value{GDBP}) @kbd{print add(2,3)}
34372 Breakpoint 2, add (a=2, b=3) at @dots{}
34374 The program being debugged stopped while in a function called from GDB.
34376 (@value{GDBP}) @kbd{maint print dummy-frames}
34377 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
34378 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
34379 call_lo=0x01014000 call_hi=0x01014001
34383 Takes an optional file parameter.
34385 @kindex maint print registers
34386 @kindex maint print raw-registers
34387 @kindex maint print cooked-registers
34388 @kindex maint print register-groups
34389 @kindex maint print remote-registers
34390 @item maint print registers @r{[}@var{file}@r{]}
34391 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34392 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34393 @itemx maint print register-groups @r{[}@var{file}@r{]}
34394 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34395 Print @value{GDBN}'s internal register data structures.
34397 The command @code{maint print raw-registers} includes the contents of
34398 the raw register cache; the command @code{maint print
34399 cooked-registers} includes the (cooked) value of all registers,
34400 including registers which aren't available on the target nor visible
34401 to user; the command @code{maint print register-groups} includes the
34402 groups that each register is a member of; and the command @code{maint
34403 print remote-registers} includes the remote target's register numbers
34404 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
34405 @value{GDBN} Internals}.
34407 These commands take an optional parameter, a file name to which to
34408 write the information.
34410 @kindex maint print reggroups
34411 @item maint print reggroups @r{[}@var{file}@r{]}
34412 Print @value{GDBN}'s internal register group data structures. The
34413 optional argument @var{file} tells to what file to write the
34416 The register groups info looks like this:
34419 (@value{GDBP}) @kbd{maint print reggroups}
34432 This command forces @value{GDBN} to flush its internal register cache.
34434 @kindex maint print objfiles
34435 @cindex info for known object files
34436 @item maint print objfiles
34437 Print a dump of all known object files. For each object file, this
34438 command prints its name, address in memory, and all of its psymtabs
34441 @kindex maint print section-scripts
34442 @cindex info for known .debug_gdb_scripts-loaded scripts
34443 @item maint print section-scripts [@var{regexp}]
34444 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34445 If @var{regexp} is specified, only print scripts loaded by object files
34446 matching @var{regexp}.
34447 For each script, this command prints its name as specified in the objfile,
34448 and the full path if known.
34449 @xref{dotdebug_gdb_scripts section}.
34451 @kindex maint print statistics
34452 @cindex bcache statistics
34453 @item maint print statistics
34454 This command prints, for each object file in the program, various data
34455 about that object file followed by the byte cache (@dfn{bcache})
34456 statistics for the object file. The objfile data includes the number
34457 of minimal, partial, full, and stabs symbols, the number of types
34458 defined by the objfile, the number of as yet unexpanded psym tables,
34459 the number of line tables and string tables, and the amount of memory
34460 used by the various tables. The bcache statistics include the counts,
34461 sizes, and counts of duplicates of all and unique objects, max,
34462 average, and median entry size, total memory used and its overhead and
34463 savings, and various measures of the hash table size and chain
34466 @kindex maint print target-stack
34467 @cindex target stack description
34468 @item maint print target-stack
34469 A @dfn{target} is an interface between the debugger and a particular
34470 kind of file or process. Targets can be stacked in @dfn{strata},
34471 so that more than one target can potentially respond to a request.
34472 In particular, memory accesses will walk down the stack of targets
34473 until they find a target that is interested in handling that particular
34476 This command prints a short description of each layer that was pushed on
34477 the @dfn{target stack}, starting from the top layer down to the bottom one.
34479 @kindex maint print type
34480 @cindex type chain of a data type
34481 @item maint print type @var{expr}
34482 Print the type chain for a type specified by @var{expr}. The argument
34483 can be either a type name or a symbol. If it is a symbol, the type of
34484 that symbol is described. The type chain produced by this command is
34485 a recursive definition of the data type as stored in @value{GDBN}'s
34486 data structures, including its flags and contained types.
34488 @kindex maint set dwarf2 always-disassemble
34489 @kindex maint show dwarf2 always-disassemble
34490 @item maint set dwarf2 always-disassemble
34491 @item maint show dwarf2 always-disassemble
34492 Control the behavior of @code{info address} when using DWARF debugging
34495 The default is @code{off}, which means that @value{GDBN} should try to
34496 describe a variable's location in an easily readable format. When
34497 @code{on}, @value{GDBN} will instead display the DWARF location
34498 expression in an assembly-like format. Note that some locations are
34499 too complex for @value{GDBN} to describe simply; in this case you will
34500 always see the disassembly form.
34502 Here is an example of the resulting disassembly:
34505 (gdb) info addr argc
34506 Symbol "argc" is a complex DWARF expression:
34510 For more information on these expressions, see
34511 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34513 @kindex maint set dwarf2 max-cache-age
34514 @kindex maint show dwarf2 max-cache-age
34515 @item maint set dwarf2 max-cache-age
34516 @itemx maint show dwarf2 max-cache-age
34517 Control the DWARF 2 compilation unit cache.
34519 @cindex DWARF 2 compilation units cache
34520 In object files with inter-compilation-unit references, such as those
34521 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34522 reader needs to frequently refer to previously read compilation units.
34523 This setting controls how long a compilation unit will remain in the
34524 cache if it is not referenced. A higher limit means that cached
34525 compilation units will be stored in memory longer, and more total
34526 memory will be used. Setting it to zero disables caching, which will
34527 slow down @value{GDBN} startup, but reduce memory consumption.
34529 @kindex maint set profile
34530 @kindex maint show profile
34531 @cindex profiling GDB
34532 @item maint set profile
34533 @itemx maint show profile
34534 Control profiling of @value{GDBN}.
34536 Profiling will be disabled until you use the @samp{maint set profile}
34537 command to enable it. When you enable profiling, the system will begin
34538 collecting timing and execution count data; when you disable profiling or
34539 exit @value{GDBN}, the results will be written to a log file. Remember that
34540 if you use profiling, @value{GDBN} will overwrite the profiling log file
34541 (often called @file{gmon.out}). If you have a record of important profiling
34542 data in a @file{gmon.out} file, be sure to move it to a safe location.
34544 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34545 compiled with the @samp{-pg} compiler option.
34547 @kindex maint set show-debug-regs
34548 @kindex maint show show-debug-regs
34549 @cindex hardware debug registers
34550 @item maint set show-debug-regs
34551 @itemx maint show show-debug-regs
34552 Control whether to show variables that mirror the hardware debug
34553 registers. Use @code{ON} to enable, @code{OFF} to disable. If
34554 enabled, the debug registers values are shown when @value{GDBN} inserts or
34555 removes a hardware breakpoint or watchpoint, and when the inferior
34556 triggers a hardware-assisted breakpoint or watchpoint.
34558 @kindex maint set show-all-tib
34559 @kindex maint show show-all-tib
34560 @item maint set show-all-tib
34561 @itemx maint show show-all-tib
34562 Control whether to show all non zero areas within a 1k block starting
34563 at thread local base, when using the @samp{info w32 thread-information-block}
34566 @kindex maint space
34567 @cindex memory used by commands
34569 Control whether to display memory usage for each command. If set to a
34570 nonzero value, @value{GDBN} will display how much memory each command
34571 took, following the command's own output. This can also be requested
34572 by invoking @value{GDBN} with the @option{--statistics} command-line
34573 switch (@pxref{Mode Options}).
34576 @cindex time of command execution
34578 Control whether to display the execution time of @value{GDBN} for each command.
34579 If set to a nonzero value, @value{GDBN} will display how much time it
34580 took to execute each command, following the command's own output.
34581 Both CPU time and wallclock time are printed.
34582 Printing both is useful when trying to determine whether the cost is
34583 CPU or, e.g., disk/network, latency.
34584 Note that the CPU time printed is for @value{GDBN} only, it does not include
34585 the execution time of the inferior because there's no mechanism currently
34586 to compute how much time was spent by @value{GDBN} and how much time was
34587 spent by the program been debugged.
34588 This can also be requested by invoking @value{GDBN} with the
34589 @option{--statistics} command-line switch (@pxref{Mode Options}).
34591 @kindex maint translate-address
34592 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34593 Find the symbol stored at the location specified by the address
34594 @var{addr} and an optional section name @var{section}. If found,
34595 @value{GDBN} prints the name of the closest symbol and an offset from
34596 the symbol's location to the specified address. This is similar to
34597 the @code{info address} command (@pxref{Symbols}), except that this
34598 command also allows to find symbols in other sections.
34600 If section was not specified, the section in which the symbol was found
34601 is also printed. For dynamically linked executables, the name of
34602 executable or shared library containing the symbol is printed as well.
34606 The following command is useful for non-interactive invocations of
34607 @value{GDBN}, such as in the test suite.
34610 @item set watchdog @var{nsec}
34611 @kindex set watchdog
34612 @cindex watchdog timer
34613 @cindex timeout for commands
34614 Set the maximum number of seconds @value{GDBN} will wait for the
34615 target operation to finish. If this time expires, @value{GDBN}
34616 reports and error and the command is aborted.
34618 @item show watchdog
34619 Show the current setting of the target wait timeout.
34622 @node Remote Protocol
34623 @appendix @value{GDBN} Remote Serial Protocol
34628 * Stop Reply Packets::
34629 * General Query Packets::
34630 * Architecture-Specific Protocol Details::
34631 * Tracepoint Packets::
34632 * Host I/O Packets::
34634 * Notification Packets::
34635 * Remote Non-Stop::
34636 * Packet Acknowledgment::
34638 * File-I/O Remote Protocol Extension::
34639 * Library List Format::
34640 * Library List Format for SVR4 Targets::
34641 * Memory Map Format::
34642 * Thread List Format::
34643 * Traceframe Info Format::
34649 There may be occasions when you need to know something about the
34650 protocol---for example, if there is only one serial port to your target
34651 machine, you might want your program to do something special if it
34652 recognizes a packet meant for @value{GDBN}.
34654 In the examples below, @samp{->} and @samp{<-} are used to indicate
34655 transmitted and received data, respectively.
34657 @cindex protocol, @value{GDBN} remote serial
34658 @cindex serial protocol, @value{GDBN} remote
34659 @cindex remote serial protocol
34660 All @value{GDBN} commands and responses (other than acknowledgments
34661 and notifications, see @ref{Notification Packets}) are sent as a
34662 @var{packet}. A @var{packet} is introduced with the character
34663 @samp{$}, the actual @var{packet-data}, and the terminating character
34664 @samp{#} followed by a two-digit @var{checksum}:
34667 @code{$}@var{packet-data}@code{#}@var{checksum}
34671 @cindex checksum, for @value{GDBN} remote
34673 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34674 characters between the leading @samp{$} and the trailing @samp{#} (an
34675 eight bit unsigned checksum).
34677 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34678 specification also included an optional two-digit @var{sequence-id}:
34681 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34684 @cindex sequence-id, for @value{GDBN} remote
34686 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34687 has never output @var{sequence-id}s. Stubs that handle packets added
34688 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34690 When either the host or the target machine receives a packet, the first
34691 response expected is an acknowledgment: either @samp{+} (to indicate
34692 the package was received correctly) or @samp{-} (to request
34696 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34701 The @samp{+}/@samp{-} acknowledgments can be disabled
34702 once a connection is established.
34703 @xref{Packet Acknowledgment}, for details.
34705 The host (@value{GDBN}) sends @var{command}s, and the target (the
34706 debugging stub incorporated in your program) sends a @var{response}. In
34707 the case of step and continue @var{command}s, the response is only sent
34708 when the operation has completed, and the target has again stopped all
34709 threads in all attached processes. This is the default all-stop mode
34710 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34711 execution mode; see @ref{Remote Non-Stop}, for details.
34713 @var{packet-data} consists of a sequence of characters with the
34714 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34717 @cindex remote protocol, field separator
34718 Fields within the packet should be separated using @samp{,} @samp{;} or
34719 @samp{:}. Except where otherwise noted all numbers are represented in
34720 @sc{hex} with leading zeros suppressed.
34722 Implementors should note that prior to @value{GDBN} 5.0, the character
34723 @samp{:} could not appear as the third character in a packet (as it
34724 would potentially conflict with the @var{sequence-id}).
34726 @cindex remote protocol, binary data
34727 @anchor{Binary Data}
34728 Binary data in most packets is encoded either as two hexadecimal
34729 digits per byte of binary data. This allowed the traditional remote
34730 protocol to work over connections which were only seven-bit clean.
34731 Some packets designed more recently assume an eight-bit clean
34732 connection, and use a more efficient encoding to send and receive
34735 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34736 as an escape character. Any escaped byte is transmitted as the escape
34737 character followed by the original character XORed with @code{0x20}.
34738 For example, the byte @code{0x7d} would be transmitted as the two
34739 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34740 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34741 @samp{@}}) must always be escaped. Responses sent by the stub
34742 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34743 is not interpreted as the start of a run-length encoded sequence
34746 Response @var{data} can be run-length encoded to save space.
34747 Run-length encoding replaces runs of identical characters with one
34748 instance of the repeated character, followed by a @samp{*} and a
34749 repeat count. The repeat count is itself sent encoded, to avoid
34750 binary characters in @var{data}: a value of @var{n} is sent as
34751 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34752 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34753 code 32) for a repeat count of 3. (This is because run-length
34754 encoding starts to win for counts 3 or more.) Thus, for example,
34755 @samp{0* } is a run-length encoding of ``0000'': the space character
34756 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34759 The printable characters @samp{#} and @samp{$} or with a numeric value
34760 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34761 seven repeats (@samp{$}) can be expanded using a repeat count of only
34762 five (@samp{"}). For example, @samp{00000000} can be encoded as
34765 The error response returned for some packets includes a two character
34766 error number. That number is not well defined.
34768 @cindex empty response, for unsupported packets
34769 For any @var{command} not supported by the stub, an empty response
34770 (@samp{$#00}) should be returned. That way it is possible to extend the
34771 protocol. A newer @value{GDBN} can tell if a packet is supported based
34774 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34775 commands for register access, and the @samp{m} and @samp{M} commands
34776 for memory access. Stubs that only control single-threaded targets
34777 can implement run control with the @samp{c} (continue), and @samp{s}
34778 (step) commands. Stubs that support multi-threading targets should
34779 support the @samp{vCont} command. All other commands are optional.
34784 The following table provides a complete list of all currently defined
34785 @var{command}s and their corresponding response @var{data}.
34786 @xref{File-I/O Remote Protocol Extension}, for details about the File
34787 I/O extension of the remote protocol.
34789 Each packet's description has a template showing the packet's overall
34790 syntax, followed by an explanation of the packet's meaning. We
34791 include spaces in some of the templates for clarity; these are not
34792 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34793 separate its components. For example, a template like @samp{foo
34794 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34795 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34796 @var{baz}. @value{GDBN} does not transmit a space character between the
34797 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34800 @cindex @var{thread-id}, in remote protocol
34801 @anchor{thread-id syntax}
34802 Several packets and replies include a @var{thread-id} field to identify
34803 a thread. Normally these are positive numbers with a target-specific
34804 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34805 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34808 In addition, the remote protocol supports a multiprocess feature in
34809 which the @var{thread-id} syntax is extended to optionally include both
34810 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34811 The @var{pid} (process) and @var{tid} (thread) components each have the
34812 format described above: a positive number with target-specific
34813 interpretation formatted as a big-endian hex string, literal @samp{-1}
34814 to indicate all processes or threads (respectively), or @samp{0} to
34815 indicate an arbitrary process or thread. Specifying just a process, as
34816 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34817 error to specify all processes but a specific thread, such as
34818 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34819 for those packets and replies explicitly documented to include a process
34820 ID, rather than a @var{thread-id}.
34822 The multiprocess @var{thread-id} syntax extensions are only used if both
34823 @value{GDBN} and the stub report support for the @samp{multiprocess}
34824 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34827 Note that all packet forms beginning with an upper- or lower-case
34828 letter, other than those described here, are reserved for future use.
34830 Here are the packet descriptions.
34835 @cindex @samp{!} packet
34836 @anchor{extended mode}
34837 Enable extended mode. In extended mode, the remote server is made
34838 persistent. The @samp{R} packet is used to restart the program being
34844 The remote target both supports and has enabled extended mode.
34848 @cindex @samp{?} packet
34849 Indicate the reason the target halted. The reply is the same as for
34850 step and continue. This packet has a special interpretation when the
34851 target is in non-stop mode; see @ref{Remote Non-Stop}.
34854 @xref{Stop Reply Packets}, for the reply specifications.
34856 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34857 @cindex @samp{A} packet
34858 Initialized @code{argv[]} array passed into program. @var{arglen}
34859 specifies the number of bytes in the hex encoded byte stream
34860 @var{arg}. See @code{gdbserver} for more details.
34865 The arguments were set.
34871 @cindex @samp{b} packet
34872 (Don't use this packet; its behavior is not well-defined.)
34873 Change the serial line speed to @var{baud}.
34875 JTC: @emph{When does the transport layer state change? When it's
34876 received, or after the ACK is transmitted. In either case, there are
34877 problems if the command or the acknowledgment packet is dropped.}
34879 Stan: @emph{If people really wanted to add something like this, and get
34880 it working for the first time, they ought to modify ser-unix.c to send
34881 some kind of out-of-band message to a specially-setup stub and have the
34882 switch happen "in between" packets, so that from remote protocol's point
34883 of view, nothing actually happened.}
34885 @item B @var{addr},@var{mode}
34886 @cindex @samp{B} packet
34887 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34888 breakpoint at @var{addr}.
34890 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34891 (@pxref{insert breakpoint or watchpoint packet}).
34893 @cindex @samp{bc} packet
34896 Backward continue. Execute the target system in reverse. No parameter.
34897 @xref{Reverse Execution}, for more information.
34900 @xref{Stop Reply Packets}, for the reply specifications.
34902 @cindex @samp{bs} packet
34905 Backward single step. Execute one instruction in reverse. No parameter.
34906 @xref{Reverse Execution}, for more information.
34909 @xref{Stop Reply Packets}, for the reply specifications.
34911 @item c @r{[}@var{addr}@r{]}
34912 @cindex @samp{c} packet
34913 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
34914 resume at current address.
34916 This packet is deprecated for multi-threading support. @xref{vCont
34920 @xref{Stop Reply Packets}, for the reply specifications.
34922 @item C @var{sig}@r{[};@var{addr}@r{]}
34923 @cindex @samp{C} packet
34924 Continue with signal @var{sig} (hex signal number). If
34925 @samp{;@var{addr}} is omitted, resume at same address.
34927 This packet is deprecated for multi-threading support. @xref{vCont
34931 @xref{Stop Reply Packets}, for the reply specifications.
34934 @cindex @samp{d} packet
34937 Don't use this packet; instead, define a general set packet
34938 (@pxref{General Query Packets}).
34942 @cindex @samp{D} packet
34943 The first form of the packet is used to detach @value{GDBN} from the
34944 remote system. It is sent to the remote target
34945 before @value{GDBN} disconnects via the @code{detach} command.
34947 The second form, including a process ID, is used when multiprocess
34948 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34949 detach only a specific process. The @var{pid} is specified as a
34950 big-endian hex string.
34960 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34961 @cindex @samp{F} packet
34962 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34963 This is part of the File-I/O protocol extension. @xref{File-I/O
34964 Remote Protocol Extension}, for the specification.
34967 @anchor{read registers packet}
34968 @cindex @samp{g} packet
34969 Read general registers.
34973 @item @var{XX@dots{}}
34974 Each byte of register data is described by two hex digits. The bytes
34975 with the register are transmitted in target byte order. The size of
34976 each register and their position within the @samp{g} packet are
34977 determined by the @value{GDBN} internal gdbarch functions
34978 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34979 specification of several standard @samp{g} packets is specified below.
34981 When reading registers from a trace frame (@pxref{Analyze Collected
34982 Data,,Using the Collected Data}), the stub may also return a string of
34983 literal @samp{x}'s in place of the register data digits, to indicate
34984 that the corresponding register has not been collected, thus its value
34985 is unavailable. For example, for an architecture with 4 registers of
34986 4 bytes each, the following reply indicates to @value{GDBN} that
34987 registers 0 and 2 have not been collected, while registers 1 and 3
34988 have been collected, and both have zero value:
34992 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34999 @item G @var{XX@dots{}}
35000 @cindex @samp{G} packet
35001 Write general registers. @xref{read registers packet}, for a
35002 description of the @var{XX@dots{}} data.
35012 @item H @var{op} @var{thread-id}
35013 @cindex @samp{H} packet
35014 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35015 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
35016 it should be @samp{c} for step and continue operations (note that this
35017 is deprecated, supporting the @samp{vCont} command is a better
35018 option), @samp{g} for other operations. The thread designator
35019 @var{thread-id} has the format and interpretation described in
35020 @ref{thread-id syntax}.
35031 @c 'H': How restrictive (or permissive) is the thread model. If a
35032 @c thread is selected and stopped, are other threads allowed
35033 @c to continue to execute? As I mentioned above, I think the
35034 @c semantics of each command when a thread is selected must be
35035 @c described. For example:
35037 @c 'g': If the stub supports threads and a specific thread is
35038 @c selected, returns the register block from that thread;
35039 @c otherwise returns current registers.
35041 @c 'G' If the stub supports threads and a specific thread is
35042 @c selected, sets the registers of the register block of
35043 @c that thread; otherwise sets current registers.
35045 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35046 @anchor{cycle step packet}
35047 @cindex @samp{i} packet
35048 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35049 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35050 step starting at that address.
35053 @cindex @samp{I} packet
35054 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35058 @cindex @samp{k} packet
35061 FIXME: @emph{There is no description of how to operate when a specific
35062 thread context has been selected (i.e.@: does 'k' kill only that
35065 @item m @var{addr},@var{length}
35066 @cindex @samp{m} packet
35067 Read @var{length} bytes of memory starting at address @var{addr}.
35068 Note that @var{addr} may not be aligned to any particular boundary.
35070 The stub need not use any particular size or alignment when gathering
35071 data from memory for the response; even if @var{addr} is word-aligned
35072 and @var{length} is a multiple of the word size, the stub is free to
35073 use byte accesses, or not. For this reason, this packet may not be
35074 suitable for accessing memory-mapped I/O devices.
35075 @cindex alignment of remote memory accesses
35076 @cindex size of remote memory accesses
35077 @cindex memory, alignment and size of remote accesses
35081 @item @var{XX@dots{}}
35082 Memory contents; each byte is transmitted as a two-digit hexadecimal
35083 number. The reply may contain fewer bytes than requested if the
35084 server was able to read only part of the region of memory.
35089 @item M @var{addr},@var{length}:@var{XX@dots{}}
35090 @cindex @samp{M} packet
35091 Write @var{length} bytes of memory starting at address @var{addr}.
35092 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
35093 hexadecimal number.
35100 for an error (this includes the case where only part of the data was
35105 @cindex @samp{p} packet
35106 Read the value of register @var{n}; @var{n} is in hex.
35107 @xref{read registers packet}, for a description of how the returned
35108 register value is encoded.
35112 @item @var{XX@dots{}}
35113 the register's value
35117 Indicating an unrecognized @var{query}.
35120 @item P @var{n@dots{}}=@var{r@dots{}}
35121 @anchor{write register packet}
35122 @cindex @samp{P} packet
35123 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35124 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35125 digits for each byte in the register (target byte order).
35135 @item q @var{name} @var{params}@dots{}
35136 @itemx Q @var{name} @var{params}@dots{}
35137 @cindex @samp{q} packet
35138 @cindex @samp{Q} packet
35139 General query (@samp{q}) and set (@samp{Q}). These packets are
35140 described fully in @ref{General Query Packets}.
35143 @cindex @samp{r} packet
35144 Reset the entire system.
35146 Don't use this packet; use the @samp{R} packet instead.
35149 @cindex @samp{R} packet
35150 Restart the program being debugged. @var{XX}, while needed, is ignored.
35151 This packet is only available in extended mode (@pxref{extended mode}).
35153 The @samp{R} packet has no reply.
35155 @item s @r{[}@var{addr}@r{]}
35156 @cindex @samp{s} packet
35157 Single step. @var{addr} is the address at which to resume. If
35158 @var{addr} is omitted, resume at same address.
35160 This packet is deprecated for multi-threading support. @xref{vCont
35164 @xref{Stop Reply Packets}, for the reply specifications.
35166 @item S @var{sig}@r{[};@var{addr}@r{]}
35167 @anchor{step with signal packet}
35168 @cindex @samp{S} packet
35169 Step with signal. This is analogous to the @samp{C} packet, but
35170 requests a single-step, rather than a normal resumption of execution.
35172 This packet is deprecated for multi-threading support. @xref{vCont
35176 @xref{Stop Reply Packets}, for the reply specifications.
35178 @item t @var{addr}:@var{PP},@var{MM}
35179 @cindex @samp{t} packet
35180 Search backwards starting at address @var{addr} for a match with pattern
35181 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
35182 @var{addr} must be at least 3 digits.
35184 @item T @var{thread-id}
35185 @cindex @samp{T} packet
35186 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35191 thread is still alive
35197 Packets starting with @samp{v} are identified by a multi-letter name,
35198 up to the first @samp{;} or @samp{?} (or the end of the packet).
35200 @item vAttach;@var{pid}
35201 @cindex @samp{vAttach} packet
35202 Attach to a new process with the specified process ID @var{pid}.
35203 The process ID is a
35204 hexadecimal integer identifying the process. In all-stop mode, all
35205 threads in the attached process are stopped; in non-stop mode, it may be
35206 attached without being stopped if that is supported by the target.
35208 @c In non-stop mode, on a successful vAttach, the stub should set the
35209 @c current thread to a thread of the newly-attached process. After
35210 @c attaching, GDB queries for the attached process's thread ID with qC.
35211 @c Also note that, from a user perspective, whether or not the
35212 @c target is stopped on attach in non-stop mode depends on whether you
35213 @c use the foreground or background version of the attach command, not
35214 @c on what vAttach does; GDB does the right thing with respect to either
35215 @c stopping or restarting threads.
35217 This packet is only available in extended mode (@pxref{extended mode}).
35223 @item @r{Any stop packet}
35224 for success in all-stop mode (@pxref{Stop Reply Packets})
35226 for success in non-stop mode (@pxref{Remote Non-Stop})
35229 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35230 @cindex @samp{vCont} packet
35231 @anchor{vCont packet}
35232 Resume the inferior, specifying different actions for each thread.
35233 If an action is specified with no @var{thread-id}, then it is applied to any
35234 threads that don't have a specific action specified; if no default action is
35235 specified then other threads should remain stopped in all-stop mode and
35236 in their current state in non-stop mode.
35237 Specifying multiple
35238 default actions is an error; specifying no actions is also an error.
35239 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35241 Currently supported actions are:
35247 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35251 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35256 The optional argument @var{addr} normally associated with the
35257 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35258 not supported in @samp{vCont}.
35260 The @samp{t} action is only relevant in non-stop mode
35261 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35262 A stop reply should be generated for any affected thread not already stopped.
35263 When a thread is stopped by means of a @samp{t} action,
35264 the corresponding stop reply should indicate that the thread has stopped with
35265 signal @samp{0}, regardless of whether the target uses some other signal
35266 as an implementation detail.
35268 The stub must support @samp{vCont} if it reports support for
35269 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35270 this case @samp{vCont} actions can be specified to apply to all threads
35271 in a process by using the @samp{p@var{pid}.-1} form of the
35275 @xref{Stop Reply Packets}, for the reply specifications.
35278 @cindex @samp{vCont?} packet
35279 Request a list of actions supported by the @samp{vCont} packet.
35283 @item vCont@r{[};@var{action}@dots{}@r{]}
35284 The @samp{vCont} packet is supported. Each @var{action} is a supported
35285 command in the @samp{vCont} packet.
35287 The @samp{vCont} packet is not supported.
35290 @item vFile:@var{operation}:@var{parameter}@dots{}
35291 @cindex @samp{vFile} packet
35292 Perform a file operation on the target system. For details,
35293 see @ref{Host I/O Packets}.
35295 @item vFlashErase:@var{addr},@var{length}
35296 @cindex @samp{vFlashErase} packet
35297 Direct the stub to erase @var{length} bytes of flash starting at
35298 @var{addr}. The region may enclose any number of flash blocks, but
35299 its start and end must fall on block boundaries, as indicated by the
35300 flash block size appearing in the memory map (@pxref{Memory Map
35301 Format}). @value{GDBN} groups flash memory programming operations
35302 together, and sends a @samp{vFlashDone} request after each group; the
35303 stub is allowed to delay erase operation until the @samp{vFlashDone}
35304 packet is received.
35314 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35315 @cindex @samp{vFlashWrite} packet
35316 Direct the stub to write data to flash address @var{addr}. The data
35317 is passed in binary form using the same encoding as for the @samp{X}
35318 packet (@pxref{Binary Data}). The memory ranges specified by
35319 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35320 not overlap, and must appear in order of increasing addresses
35321 (although @samp{vFlashErase} packets for higher addresses may already
35322 have been received; the ordering is guaranteed only between
35323 @samp{vFlashWrite} packets). If a packet writes to an address that was
35324 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35325 target-specific method, the results are unpredictable.
35333 for vFlashWrite addressing non-flash memory
35339 @cindex @samp{vFlashDone} packet
35340 Indicate to the stub that flash programming operation is finished.
35341 The stub is permitted to delay or batch the effects of a group of
35342 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35343 @samp{vFlashDone} packet is received. The contents of the affected
35344 regions of flash memory are unpredictable until the @samp{vFlashDone}
35345 request is completed.
35347 @item vKill;@var{pid}
35348 @cindex @samp{vKill} packet
35349 Kill the process with the specified process ID. @var{pid} is a
35350 hexadecimal integer identifying the process. This packet is used in
35351 preference to @samp{k} when multiprocess protocol extensions are
35352 supported; see @ref{multiprocess extensions}.
35362 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35363 @cindex @samp{vRun} packet
35364 Run the program @var{filename}, passing it each @var{argument} on its
35365 command line. The file and arguments are hex-encoded strings. If
35366 @var{filename} is an empty string, the stub may use a default program
35367 (e.g.@: the last program run). The program is created in the stopped
35370 @c FIXME: What about non-stop mode?
35372 This packet is only available in extended mode (@pxref{extended mode}).
35378 @item @r{Any stop packet}
35379 for success (@pxref{Stop Reply Packets})
35383 @anchor{vStopped packet}
35384 @cindex @samp{vStopped} packet
35386 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
35387 reply and prompt for the stub to report another one.
35391 @item @r{Any stop packet}
35392 if there is another unreported stop event (@pxref{Stop Reply Packets})
35394 if there are no unreported stop events
35397 @item X @var{addr},@var{length}:@var{XX@dots{}}
35399 @cindex @samp{X} packet
35400 Write data to memory, where the data is transmitted in binary.
35401 @var{addr} is address, @var{length} is number of bytes,
35402 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35412 @item z @var{type},@var{addr},@var{kind}
35413 @itemx Z @var{type},@var{addr},@var{kind}
35414 @anchor{insert breakpoint or watchpoint packet}
35415 @cindex @samp{z} packet
35416 @cindex @samp{Z} packets
35417 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35418 watchpoint starting at address @var{address} of kind @var{kind}.
35420 Each breakpoint and watchpoint packet @var{type} is documented
35423 @emph{Implementation notes: A remote target shall return an empty string
35424 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35425 remote target shall support either both or neither of a given
35426 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35427 avoid potential problems with duplicate packets, the operations should
35428 be implemented in an idempotent way.}
35430 @item z0,@var{addr},@var{kind}
35431 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35432 @cindex @samp{z0} packet
35433 @cindex @samp{Z0} packet
35434 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35435 @var{addr} of type @var{kind}.
35437 A memory breakpoint is implemented by replacing the instruction at
35438 @var{addr} with a software breakpoint or trap instruction. The
35439 @var{kind} is target-specific and typically indicates the size of
35440 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35441 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35442 architectures have additional meanings for @var{kind};
35443 @var{cond_list} is an optional list of conditional expressions in bytecode
35444 form that should be evaluated on the target's side. These are the
35445 conditions that should be taken into consideration when deciding if
35446 the breakpoint trigger should be reported back to @var{GDBN}.
35448 The @var{cond_list} parameter is comprised of a series of expressions,
35449 concatenated without separators. Each expression has the following form:
35453 @item X @var{len},@var{expr}
35454 @var{len} is the length of the bytecode expression and @var{expr} is the
35455 actual conditional expression in bytecode form.
35459 see @ref{Architecture-Specific Protocol Details}.
35461 @emph{Implementation note: It is possible for a target to copy or move
35462 code that contains memory breakpoints (e.g., when implementing
35463 overlays). The behavior of this packet, in the presence of such a
35464 target, is not defined.}
35476 @item z1,@var{addr},@var{kind}
35477 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35478 @cindex @samp{z1} packet
35479 @cindex @samp{Z1} packet
35480 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35481 address @var{addr}.
35483 A hardware breakpoint is implemented using a mechanism that is not
35484 dependant on being able to modify the target's memory. @var{kind}
35485 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35487 @emph{Implementation note: A hardware breakpoint is not affected by code
35500 @item z2,@var{addr},@var{kind}
35501 @itemx Z2,@var{addr},@var{kind}
35502 @cindex @samp{z2} packet
35503 @cindex @samp{Z2} packet
35504 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35505 @var{kind} is interpreted as the number of bytes to watch.
35517 @item z3,@var{addr},@var{kind}
35518 @itemx Z3,@var{addr},@var{kind}
35519 @cindex @samp{z3} packet
35520 @cindex @samp{Z3} packet
35521 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35522 @var{kind} is interpreted as the number of bytes to watch.
35534 @item z4,@var{addr},@var{kind}
35535 @itemx Z4,@var{addr},@var{kind}
35536 @cindex @samp{z4} packet
35537 @cindex @samp{Z4} packet
35538 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35539 @var{kind} is interpreted as the number of bytes to watch.
35553 @node Stop Reply Packets
35554 @section Stop Reply Packets
35555 @cindex stop reply packets
35557 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35558 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35559 receive any of the below as a reply. Except for @samp{?}
35560 and @samp{vStopped}, that reply is only returned
35561 when the target halts. In the below the exact meaning of @dfn{signal
35562 number} is defined by the header @file{include/gdb/signals.h} in the
35563 @value{GDBN} source code.
35565 As in the description of request packets, we include spaces in the
35566 reply templates for clarity; these are not part of the reply packet's
35567 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35573 The program received signal number @var{AA} (a two-digit hexadecimal
35574 number). This is equivalent to a @samp{T} response with no
35575 @var{n}:@var{r} pairs.
35577 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35578 @cindex @samp{T} packet reply
35579 The program received signal number @var{AA} (a two-digit hexadecimal
35580 number). This is equivalent to an @samp{S} response, except that the
35581 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35582 and other information directly in the stop reply packet, reducing
35583 round-trip latency. Single-step and breakpoint traps are reported
35584 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35588 If @var{n} is a hexadecimal number, it is a register number, and the
35589 corresponding @var{r} gives that register's value. @var{r} is a
35590 series of bytes in target byte order, with each byte given by a
35591 two-digit hex number.
35594 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35595 the stopped thread, as specified in @ref{thread-id syntax}.
35598 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35599 the core on which the stop event was detected.
35602 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35603 specific event that stopped the target. The currently defined stop
35604 reasons are listed below. @var{aa} should be @samp{05}, the trap
35605 signal. At most one stop reason should be present.
35608 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35609 and go on to the next; this allows us to extend the protocol in the
35613 The currently defined stop reasons are:
35619 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35622 @cindex shared library events, remote reply
35624 The packet indicates that the loaded libraries have changed.
35625 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35626 list of loaded libraries. @var{r} is ignored.
35628 @cindex replay log events, remote reply
35630 The packet indicates that the target cannot continue replaying
35631 logged execution events, because it has reached the end (or the
35632 beginning when executing backward) of the log. The value of @var{r}
35633 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35634 for more information.
35638 @itemx W @var{AA} ; process:@var{pid}
35639 The process exited, and @var{AA} is the exit status. This is only
35640 applicable to certain targets.
35642 The second form of the response, including the process ID of the exited
35643 process, can be used only when @value{GDBN} has reported support for
35644 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35645 The @var{pid} is formatted as a big-endian hex string.
35648 @itemx X @var{AA} ; process:@var{pid}
35649 The process terminated with signal @var{AA}.
35651 The second form of the response, including the process ID of the
35652 terminated process, can be used only when @value{GDBN} has reported
35653 support for multiprocess protocol extensions; see @ref{multiprocess
35654 extensions}. The @var{pid} is formatted as a big-endian hex string.
35656 @item O @var{XX}@dots{}
35657 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35658 written as the program's console output. This can happen at any time
35659 while the program is running and the debugger should continue to wait
35660 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35662 @item F @var{call-id},@var{parameter}@dots{}
35663 @var{call-id} is the identifier which says which host system call should
35664 be called. This is just the name of the function. Translation into the
35665 correct system call is only applicable as it's defined in @value{GDBN}.
35666 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35669 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35670 this very system call.
35672 The target replies with this packet when it expects @value{GDBN} to
35673 call a host system call on behalf of the target. @value{GDBN} replies
35674 with an appropriate @samp{F} packet and keeps up waiting for the next
35675 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35676 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35677 Protocol Extension}, for more details.
35681 @node General Query Packets
35682 @section General Query Packets
35683 @cindex remote query requests
35685 Packets starting with @samp{q} are @dfn{general query packets};
35686 packets starting with @samp{Q} are @dfn{general set packets}. General
35687 query and set packets are a semi-unified form for retrieving and
35688 sending information to and from the stub.
35690 The initial letter of a query or set packet is followed by a name
35691 indicating what sort of thing the packet applies to. For example,
35692 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35693 definitions with the stub. These packet names follow some
35698 The name must not contain commas, colons or semicolons.
35700 Most @value{GDBN} query and set packets have a leading upper case
35703 The names of custom vendor packets should use a company prefix, in
35704 lower case, followed by a period. For example, packets designed at
35705 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35706 foos) or @samp{Qacme.bar} (for setting bars).
35709 The name of a query or set packet should be separated from any
35710 parameters by a @samp{:}; the parameters themselves should be
35711 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35712 full packet name, and check for a separator or the end of the packet,
35713 in case two packet names share a common prefix. New packets should not begin
35714 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35715 packets predate these conventions, and have arguments without any terminator
35716 for the packet name; we suspect they are in widespread use in places that
35717 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35718 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35721 Like the descriptions of the other packets, each description here
35722 has a template showing the packet's overall syntax, followed by an
35723 explanation of the packet's meaning. We include spaces in some of the
35724 templates for clarity; these are not part of the packet's syntax. No
35725 @value{GDBN} packet uses spaces to separate its components.
35727 Here are the currently defined query and set packets:
35733 Turn on or off the agent as a helper to perform some debugging operations
35734 delegated from @value{GDBN} (@pxref{Control Agent}).
35736 @item QAllow:@var{op}:@var{val}@dots{}
35737 @cindex @samp{QAllow} packet
35738 Specify which operations @value{GDBN} expects to request of the
35739 target, as a semicolon-separated list of operation name and value
35740 pairs. Possible values for @var{op} include @samp{WriteReg},
35741 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35742 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35743 indicating that @value{GDBN} will not request the operation, or 1,
35744 indicating that it may. (The target can then use this to set up its
35745 own internals optimally, for instance if the debugger never expects to
35746 insert breakpoints, it may not need to install its own trap handler.)
35749 @cindex current thread, remote request
35750 @cindex @samp{qC} packet
35751 Return the current thread ID.
35755 @item QC @var{thread-id}
35756 Where @var{thread-id} is a thread ID as documented in
35757 @ref{thread-id syntax}.
35758 @item @r{(anything else)}
35759 Any other reply implies the old thread ID.
35762 @item qCRC:@var{addr},@var{length}
35763 @cindex CRC of memory block, remote request
35764 @cindex @samp{qCRC} packet
35765 Compute the CRC checksum of a block of memory using CRC-32 defined in
35766 IEEE 802.3. The CRC is computed byte at a time, taking the most
35767 significant bit of each byte first. The initial pattern code
35768 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35770 @emph{Note:} This is the same CRC used in validating separate debug
35771 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35772 Files}). However the algorithm is slightly different. When validating
35773 separate debug files, the CRC is computed taking the @emph{least}
35774 significant bit of each byte first, and the final result is inverted to
35775 detect trailing zeros.
35780 An error (such as memory fault)
35781 @item C @var{crc32}
35782 The specified memory region's checksum is @var{crc32}.
35785 @item QDisableRandomization:@var{value}
35786 @cindex disable address space randomization, remote request
35787 @cindex @samp{QDisableRandomization} packet
35788 Some target operating systems will randomize the virtual address space
35789 of the inferior process as a security feature, but provide a feature
35790 to disable such randomization, e.g.@: to allow for a more deterministic
35791 debugging experience. On such systems, this packet with a @var{value}
35792 of 1 directs the target to disable address space randomization for
35793 processes subsequently started via @samp{vRun} packets, while a packet
35794 with a @var{value} of 0 tells the target to enable address space
35797 This packet is only available in extended mode (@pxref{extended mode}).
35802 The request succeeded.
35805 An error occurred. @var{nn} are hex digits.
35808 An empty reply indicates that @samp{QDisableRandomization} is not supported
35812 This packet is not probed by default; the remote stub must request it,
35813 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35814 This should only be done on targets that actually support disabling
35815 address space randomization.
35818 @itemx qsThreadInfo
35819 @cindex list active threads, remote request
35820 @cindex @samp{qfThreadInfo} packet
35821 @cindex @samp{qsThreadInfo} packet
35822 Obtain a list of all active thread IDs from the target (OS). Since there
35823 may be too many active threads to fit into one reply packet, this query
35824 works iteratively: it may require more than one query/reply sequence to
35825 obtain the entire list of threads. The first query of the sequence will
35826 be the @samp{qfThreadInfo} query; subsequent queries in the
35827 sequence will be the @samp{qsThreadInfo} query.
35829 NOTE: This packet replaces the @samp{qL} query (see below).
35833 @item m @var{thread-id}
35835 @item m @var{thread-id},@var{thread-id}@dots{}
35836 a comma-separated list of thread IDs
35838 (lower case letter @samp{L}) denotes end of list.
35841 In response to each query, the target will reply with a list of one or
35842 more thread IDs, separated by commas.
35843 @value{GDBN} will respond to each reply with a request for more thread
35844 ids (using the @samp{qs} form of the query), until the target responds
35845 with @samp{l} (lower-case ell, for @dfn{last}).
35846 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35849 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35850 @cindex get thread-local storage address, remote request
35851 @cindex @samp{qGetTLSAddr} packet
35852 Fetch the address associated with thread local storage specified
35853 by @var{thread-id}, @var{offset}, and @var{lm}.
35855 @var{thread-id} is the thread ID associated with the
35856 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35858 @var{offset} is the (big endian, hex encoded) offset associated with the
35859 thread local variable. (This offset is obtained from the debug
35860 information associated with the variable.)
35862 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35863 load module associated with the thread local storage. For example,
35864 a @sc{gnu}/Linux system will pass the link map address of the shared
35865 object associated with the thread local storage under consideration.
35866 Other operating environments may choose to represent the load module
35867 differently, so the precise meaning of this parameter will vary.
35871 @item @var{XX}@dots{}
35872 Hex encoded (big endian) bytes representing the address of the thread
35873 local storage requested.
35876 An error occurred. @var{nn} are hex digits.
35879 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35882 @item qGetTIBAddr:@var{thread-id}
35883 @cindex get thread information block address
35884 @cindex @samp{qGetTIBAddr} packet
35885 Fetch address of the Windows OS specific Thread Information Block.
35887 @var{thread-id} is the thread ID associated with the thread.
35891 @item @var{XX}@dots{}
35892 Hex encoded (big endian) bytes representing the linear address of the
35893 thread information block.
35896 An error occured. This means that either the thread was not found, or the
35897 address could not be retrieved.
35900 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35903 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35904 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35905 digit) is one to indicate the first query and zero to indicate a
35906 subsequent query; @var{threadcount} (two hex digits) is the maximum
35907 number of threads the response packet can contain; and @var{nextthread}
35908 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35909 returned in the response as @var{argthread}.
35911 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35915 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35916 Where: @var{count} (two hex digits) is the number of threads being
35917 returned; @var{done} (one hex digit) is zero to indicate more threads
35918 and one indicates no further threads; @var{argthreadid} (eight hex
35919 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35920 is a sequence of thread IDs from the target. @var{threadid} (eight hex
35921 digits). See @code{remote.c:parse_threadlist_response()}.
35925 @cindex section offsets, remote request
35926 @cindex @samp{qOffsets} packet
35927 Get section offsets that the target used when relocating the downloaded
35932 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35933 Relocate the @code{Text} section by @var{xxx} from its original address.
35934 Relocate the @code{Data} section by @var{yyy} from its original address.
35935 If the object file format provides segment information (e.g.@: @sc{elf}
35936 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35937 segments by the supplied offsets.
35939 @emph{Note: while a @code{Bss} offset may be included in the response,
35940 @value{GDBN} ignores this and instead applies the @code{Data} offset
35941 to the @code{Bss} section.}
35943 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35944 Relocate the first segment of the object file, which conventionally
35945 contains program code, to a starting address of @var{xxx}. If
35946 @samp{DataSeg} is specified, relocate the second segment, which
35947 conventionally contains modifiable data, to a starting address of
35948 @var{yyy}. @value{GDBN} will report an error if the object file
35949 does not contain segment information, or does not contain at least
35950 as many segments as mentioned in the reply. Extra segments are
35951 kept at fixed offsets relative to the last relocated segment.
35954 @item qP @var{mode} @var{thread-id}
35955 @cindex thread information, remote request
35956 @cindex @samp{qP} packet
35957 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35958 encoded 32 bit mode; @var{thread-id} is a thread ID
35959 (@pxref{thread-id syntax}).
35961 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35964 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35968 @cindex non-stop mode, remote request
35969 @cindex @samp{QNonStop} packet
35971 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35972 @xref{Remote Non-Stop}, for more information.
35977 The request succeeded.
35980 An error occurred. @var{nn} are hex digits.
35983 An empty reply indicates that @samp{QNonStop} is not supported by
35987 This packet is not probed by default; the remote stub must request it,
35988 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35989 Use of this packet is controlled by the @code{set non-stop} command;
35990 @pxref{Non-Stop Mode}.
35992 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35993 @cindex pass signals to inferior, remote request
35994 @cindex @samp{QPassSignals} packet
35995 @anchor{QPassSignals}
35996 Each listed @var{signal} should be passed directly to the inferior process.
35997 Signals are numbered identically to continue packets and stop replies
35998 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35999 strictly greater than the previous item. These signals do not need to stop
36000 the inferior, or be reported to @value{GDBN}. All other signals should be
36001 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36002 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36003 new list. This packet improves performance when using @samp{handle
36004 @var{signal} nostop noprint pass}.
36009 The request succeeded.
36012 An error occurred. @var{nn} are hex digits.
36015 An empty reply indicates that @samp{QPassSignals} is not supported by
36019 Use of this packet is controlled by the @code{set remote pass-signals}
36020 command (@pxref{Remote Configuration, set remote pass-signals}).
36021 This packet is not probed by default; the remote stub must request it,
36022 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36024 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36025 @cindex signals the inferior may see, remote request
36026 @cindex @samp{QProgramSignals} packet
36027 @anchor{QProgramSignals}
36028 Each listed @var{signal} may be delivered to the inferior process.
36029 Others should be silently discarded.
36031 In some cases, the remote stub may need to decide whether to deliver a
36032 signal to the program or not without @value{GDBN} involvement. One
36033 example of that is while detaching --- the program's threads may have
36034 stopped for signals that haven't yet had a chance of being reported to
36035 @value{GDBN}, and so the remote stub can use the signal list specified
36036 by this packet to know whether to deliver or ignore those pending
36039 This does not influence whether to deliver a signal as requested by a
36040 resumption packet (@pxref{vCont packet}).
36042 Signals are numbered identically to continue packets and stop replies
36043 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36044 strictly greater than the previous item. Multiple
36045 @samp{QProgramSignals} packets do not combine; any earlier
36046 @samp{QProgramSignals} list is completely replaced by the new list.
36051 The request succeeded.
36054 An error occurred. @var{nn} are hex digits.
36057 An empty reply indicates that @samp{QProgramSignals} is not supported
36061 Use of this packet is controlled by the @code{set remote program-signals}
36062 command (@pxref{Remote Configuration, set remote program-signals}).
36063 This packet is not probed by default; the remote stub must request it,
36064 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36066 @item qRcmd,@var{command}
36067 @cindex execute remote command, remote request
36068 @cindex @samp{qRcmd} packet
36069 @var{command} (hex encoded) is passed to the local interpreter for
36070 execution. Invalid commands should be reported using the output
36071 string. Before the final result packet, the target may also respond
36072 with a number of intermediate @samp{O@var{output}} console output
36073 packets. @emph{Implementors should note that providing access to a
36074 stubs's interpreter may have security implications}.
36079 A command response with no output.
36081 A command response with the hex encoded output string @var{OUTPUT}.
36083 Indicate a badly formed request.
36085 An empty reply indicates that @samp{qRcmd} is not recognized.
36088 (Note that the @code{qRcmd} packet's name is separated from the
36089 command by a @samp{,}, not a @samp{:}, contrary to the naming
36090 conventions above. Please don't use this packet as a model for new
36093 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36094 @cindex searching memory, in remote debugging
36095 @cindex @samp{qSearch:memory} packet
36096 @anchor{qSearch memory}
36097 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36098 @var{address} and @var{length} are encoded in hex.
36099 @var{search-pattern} is a sequence of bytes, hex encoded.
36104 The pattern was not found.
36106 The pattern was found at @var{address}.
36108 A badly formed request or an error was encountered while searching memory.
36110 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36113 @item QStartNoAckMode
36114 @cindex @samp{QStartNoAckMode} packet
36115 @anchor{QStartNoAckMode}
36116 Request that the remote stub disable the normal @samp{+}/@samp{-}
36117 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36122 The stub has switched to no-acknowledgment mode.
36123 @value{GDBN} acknowledges this reponse,
36124 but neither the stub nor @value{GDBN} shall send or expect further
36125 @samp{+}/@samp{-} acknowledgments in the current connection.
36127 An empty reply indicates that the stub does not support no-acknowledgment mode.
36130 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36131 @cindex supported packets, remote query
36132 @cindex features of the remote protocol
36133 @cindex @samp{qSupported} packet
36134 @anchor{qSupported}
36135 Tell the remote stub about features supported by @value{GDBN}, and
36136 query the stub for features it supports. This packet allows
36137 @value{GDBN} and the remote stub to take advantage of each others'
36138 features. @samp{qSupported} also consolidates multiple feature probes
36139 at startup, to improve @value{GDBN} performance---a single larger
36140 packet performs better than multiple smaller probe packets on
36141 high-latency links. Some features may enable behavior which must not
36142 be on by default, e.g.@: because it would confuse older clients or
36143 stubs. Other features may describe packets which could be
36144 automatically probed for, but are not. These features must be
36145 reported before @value{GDBN} will use them. This ``default
36146 unsupported'' behavior is not appropriate for all packets, but it
36147 helps to keep the initial connection time under control with new
36148 versions of @value{GDBN} which support increasing numbers of packets.
36152 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36153 The stub supports or does not support each returned @var{stubfeature},
36154 depending on the form of each @var{stubfeature} (see below for the
36157 An empty reply indicates that @samp{qSupported} is not recognized,
36158 or that no features needed to be reported to @value{GDBN}.
36161 The allowed forms for each feature (either a @var{gdbfeature} in the
36162 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36166 @item @var{name}=@var{value}
36167 The remote protocol feature @var{name} is supported, and associated
36168 with the specified @var{value}. The format of @var{value} depends
36169 on the feature, but it must not include a semicolon.
36171 The remote protocol feature @var{name} is supported, and does not
36172 need an associated value.
36174 The remote protocol feature @var{name} is not supported.
36176 The remote protocol feature @var{name} may be supported, and
36177 @value{GDBN} should auto-detect support in some other way when it is
36178 needed. This form will not be used for @var{gdbfeature} notifications,
36179 but may be used for @var{stubfeature} responses.
36182 Whenever the stub receives a @samp{qSupported} request, the
36183 supplied set of @value{GDBN} features should override any previous
36184 request. This allows @value{GDBN} to put the stub in a known
36185 state, even if the stub had previously been communicating with
36186 a different version of @value{GDBN}.
36188 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36193 This feature indicates whether @value{GDBN} supports multiprocess
36194 extensions to the remote protocol. @value{GDBN} does not use such
36195 extensions unless the stub also reports that it supports them by
36196 including @samp{multiprocess+} in its @samp{qSupported} reply.
36197 @xref{multiprocess extensions}, for details.
36200 This feature indicates that @value{GDBN} supports the XML target
36201 description. If the stub sees @samp{xmlRegisters=} with target
36202 specific strings separated by a comma, it will report register
36206 This feature indicates whether @value{GDBN} supports the
36207 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36208 instruction reply packet}).
36211 Stubs should ignore any unknown values for
36212 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36213 packet supports receiving packets of unlimited length (earlier
36214 versions of @value{GDBN} may reject overly long responses). Additional values
36215 for @var{gdbfeature} may be defined in the future to let the stub take
36216 advantage of new features in @value{GDBN}, e.g.@: incompatible
36217 improvements in the remote protocol---the @samp{multiprocess} feature is
36218 an example of such a feature. The stub's reply should be independent
36219 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36220 describes all the features it supports, and then the stub replies with
36221 all the features it supports.
36223 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36224 responses, as long as each response uses one of the standard forms.
36226 Some features are flags. A stub which supports a flag feature
36227 should respond with a @samp{+} form response. Other features
36228 require values, and the stub should respond with an @samp{=}
36231 Each feature has a default value, which @value{GDBN} will use if
36232 @samp{qSupported} is not available or if the feature is not mentioned
36233 in the @samp{qSupported} response. The default values are fixed; a
36234 stub is free to omit any feature responses that match the defaults.
36236 Not all features can be probed, but for those which can, the probing
36237 mechanism is useful: in some cases, a stub's internal
36238 architecture may not allow the protocol layer to know some information
36239 about the underlying target in advance. This is especially common in
36240 stubs which may be configured for multiple targets.
36242 These are the currently defined stub features and their properties:
36244 @multitable @columnfractions 0.35 0.2 0.12 0.2
36245 @c NOTE: The first row should be @headitem, but we do not yet require
36246 @c a new enough version of Texinfo (4.7) to use @headitem.
36248 @tab Value Required
36252 @item @samp{PacketSize}
36257 @item @samp{qXfer:auxv:read}
36262 @item @samp{qXfer:features:read}
36267 @item @samp{qXfer:libraries:read}
36272 @item @samp{qXfer:memory-map:read}
36277 @item @samp{qXfer:sdata:read}
36282 @item @samp{qXfer:spu:read}
36287 @item @samp{qXfer:spu:write}
36292 @item @samp{qXfer:siginfo:read}
36297 @item @samp{qXfer:siginfo:write}
36302 @item @samp{qXfer:threads:read}
36307 @item @samp{qXfer:traceframe-info:read}
36312 @item @samp{qXfer:uib:read}
36317 @item @samp{qXfer:fdpic:read}
36322 @item @samp{QNonStop}
36327 @item @samp{QPassSignals}
36332 @item @samp{QStartNoAckMode}
36337 @item @samp{multiprocess}
36342 @item @samp{ConditionalBreakpoints}
36347 @item @samp{ConditionalTracepoints}
36352 @item @samp{ReverseContinue}
36357 @item @samp{ReverseStep}
36362 @item @samp{TracepointSource}
36367 @item @samp{QAgent}
36372 @item @samp{QAllow}
36377 @item @samp{QDisableRandomization}
36382 @item @samp{EnableDisableTracepoints}
36387 @item @samp{tracenz}
36394 These are the currently defined stub features, in more detail:
36397 @cindex packet size, remote protocol
36398 @item PacketSize=@var{bytes}
36399 The remote stub can accept packets up to at least @var{bytes} in
36400 length. @value{GDBN} will send packets up to this size for bulk
36401 transfers, and will never send larger packets. This is a limit on the
36402 data characters in the packet, including the frame and checksum.
36403 There is no trailing NUL byte in a remote protocol packet; if the stub
36404 stores packets in a NUL-terminated format, it should allow an extra
36405 byte in its buffer for the NUL. If this stub feature is not supported,
36406 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36408 @item qXfer:auxv:read
36409 The remote stub understands the @samp{qXfer:auxv:read} packet
36410 (@pxref{qXfer auxiliary vector read}).
36412 @item qXfer:features:read
36413 The remote stub understands the @samp{qXfer:features:read} packet
36414 (@pxref{qXfer target description read}).
36416 @item qXfer:libraries:read
36417 The remote stub understands the @samp{qXfer:libraries:read} packet
36418 (@pxref{qXfer library list read}).
36420 @item qXfer:libraries-svr4:read
36421 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36422 (@pxref{qXfer svr4 library list read}).
36424 @item qXfer:memory-map:read
36425 The remote stub understands the @samp{qXfer:memory-map:read} packet
36426 (@pxref{qXfer memory map read}).
36428 @item qXfer:sdata:read
36429 The remote stub understands the @samp{qXfer:sdata:read} packet
36430 (@pxref{qXfer sdata read}).
36432 @item qXfer:spu:read
36433 The remote stub understands the @samp{qXfer:spu:read} packet
36434 (@pxref{qXfer spu read}).
36436 @item qXfer:spu:write
36437 The remote stub understands the @samp{qXfer:spu:write} packet
36438 (@pxref{qXfer spu write}).
36440 @item qXfer:siginfo:read
36441 The remote stub understands the @samp{qXfer:siginfo:read} packet
36442 (@pxref{qXfer siginfo read}).
36444 @item qXfer:siginfo:write
36445 The remote stub understands the @samp{qXfer:siginfo:write} packet
36446 (@pxref{qXfer siginfo write}).
36448 @item qXfer:threads:read
36449 The remote stub understands the @samp{qXfer:threads:read} packet
36450 (@pxref{qXfer threads read}).
36452 @item qXfer:traceframe-info:read
36453 The remote stub understands the @samp{qXfer:traceframe-info:read}
36454 packet (@pxref{qXfer traceframe info read}).
36456 @item qXfer:uib:read
36457 The remote stub understands the @samp{qXfer:uib:read}
36458 packet (@pxref{qXfer unwind info block}).
36460 @item qXfer:fdpic:read
36461 The remote stub understands the @samp{qXfer:fdpic:read}
36462 packet (@pxref{qXfer fdpic loadmap read}).
36465 The remote stub understands the @samp{QNonStop} packet
36466 (@pxref{QNonStop}).
36469 The remote stub understands the @samp{QPassSignals} packet
36470 (@pxref{QPassSignals}).
36472 @item QStartNoAckMode
36473 The remote stub understands the @samp{QStartNoAckMode} packet and
36474 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36477 @anchor{multiprocess extensions}
36478 @cindex multiprocess extensions, in remote protocol
36479 The remote stub understands the multiprocess extensions to the remote
36480 protocol syntax. The multiprocess extensions affect the syntax of
36481 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36482 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36483 replies. Note that reporting this feature indicates support for the
36484 syntactic extensions only, not that the stub necessarily supports
36485 debugging of more than one process at a time. The stub must not use
36486 multiprocess extensions in packet replies unless @value{GDBN} has also
36487 indicated it supports them in its @samp{qSupported} request.
36489 @item qXfer:osdata:read
36490 The remote stub understands the @samp{qXfer:osdata:read} packet
36491 ((@pxref{qXfer osdata read}).
36493 @item ConditionalBreakpoints
36494 The target accepts and implements evaluation of conditional expressions
36495 defined for breakpoints. The target will only report breakpoint triggers
36496 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36498 @item ConditionalTracepoints
36499 The remote stub accepts and implements conditional expressions defined
36500 for tracepoints (@pxref{Tracepoint Conditions}).
36502 @item ReverseContinue
36503 The remote stub accepts and implements the reverse continue packet
36507 The remote stub accepts and implements the reverse step packet
36510 @item TracepointSource
36511 The remote stub understands the @samp{QTDPsrc} packet that supplies
36512 the source form of tracepoint definitions.
36515 The remote stub understands the @samp{QAgent} packet.
36518 The remote stub understands the @samp{QAllow} packet.
36520 @item QDisableRandomization
36521 The remote stub understands the @samp{QDisableRandomization} packet.
36523 @item StaticTracepoint
36524 @cindex static tracepoints, in remote protocol
36525 The remote stub supports static tracepoints.
36527 @item InstallInTrace
36528 @anchor{install tracepoint in tracing}
36529 The remote stub supports installing tracepoint in tracing.
36531 @item EnableDisableTracepoints
36532 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36533 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36534 to be enabled and disabled while a trace experiment is running.
36537 @cindex string tracing, in remote protocol
36538 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36539 See @ref{Bytecode Descriptions} for details about the bytecode.
36544 @cindex symbol lookup, remote request
36545 @cindex @samp{qSymbol} packet
36546 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36547 requests. Accept requests from the target for the values of symbols.
36552 The target does not need to look up any (more) symbols.
36553 @item qSymbol:@var{sym_name}
36554 The target requests the value of symbol @var{sym_name} (hex encoded).
36555 @value{GDBN} may provide the value by using the
36556 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36560 @item qSymbol:@var{sym_value}:@var{sym_name}
36561 Set the value of @var{sym_name} to @var{sym_value}.
36563 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36564 target has previously requested.
36566 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36567 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36573 The target does not need to look up any (more) symbols.
36574 @item qSymbol:@var{sym_name}
36575 The target requests the value of a new symbol @var{sym_name} (hex
36576 encoded). @value{GDBN} will continue to supply the values of symbols
36577 (if available), until the target ceases to request them.
36582 @item QTDisconnected
36589 @itemx qTMinFTPILen
36591 @xref{Tracepoint Packets}.
36593 @item qThreadExtraInfo,@var{thread-id}
36594 @cindex thread attributes info, remote request
36595 @cindex @samp{qThreadExtraInfo} packet
36596 Obtain a printable string description of a thread's attributes from
36597 the target OS. @var{thread-id} is a thread ID;
36598 see @ref{thread-id syntax}. This
36599 string may contain anything that the target OS thinks is interesting
36600 for @value{GDBN} to tell the user about the thread. The string is
36601 displayed in @value{GDBN}'s @code{info threads} display. Some
36602 examples of possible thread extra info strings are @samp{Runnable}, or
36603 @samp{Blocked on Mutex}.
36607 @item @var{XX}@dots{}
36608 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36609 comprising the printable string containing the extra information about
36610 the thread's attributes.
36613 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36614 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36615 conventions above. Please don't use this packet as a model for new
36634 @xref{Tracepoint Packets}.
36636 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36637 @cindex read special object, remote request
36638 @cindex @samp{qXfer} packet
36639 @anchor{qXfer read}
36640 Read uninterpreted bytes from the target's special data area
36641 identified by the keyword @var{object}. Request @var{length} bytes
36642 starting at @var{offset} bytes into the data. The content and
36643 encoding of @var{annex} is specific to @var{object}; it can supply
36644 additional details about what data to access.
36646 Here are the specific requests of this form defined so far. All
36647 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36648 formats, listed below.
36651 @item qXfer:auxv:read::@var{offset},@var{length}
36652 @anchor{qXfer auxiliary vector read}
36653 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36654 auxiliary vector}. Note @var{annex} must be empty.
36656 This packet is not probed by default; the remote stub must request it,
36657 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36659 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36660 @anchor{qXfer target description read}
36661 Access the @dfn{target description}. @xref{Target Descriptions}. The
36662 annex specifies which XML document to access. The main description is
36663 always loaded from the @samp{target.xml} annex.
36665 This packet is not probed by default; the remote stub must request it,
36666 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36668 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36669 @anchor{qXfer library list read}
36670 Access the target's list of loaded libraries. @xref{Library List Format}.
36671 The annex part of the generic @samp{qXfer} packet must be empty
36672 (@pxref{qXfer read}).
36674 Targets which maintain a list of libraries in the program's memory do
36675 not need to implement this packet; it is designed for platforms where
36676 the operating system manages the list of loaded libraries.
36678 This packet is not probed by default; the remote stub must request it,
36679 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36681 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36682 @anchor{qXfer svr4 library list read}
36683 Access the target's list of loaded libraries when the target is an SVR4
36684 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36685 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36687 This packet is optional for better performance on SVR4 targets.
36688 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36690 This packet is not probed by default; the remote stub must request it,
36691 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36693 @item qXfer:memory-map:read::@var{offset},@var{length}
36694 @anchor{qXfer memory map read}
36695 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36696 annex part of the generic @samp{qXfer} packet must be empty
36697 (@pxref{qXfer read}).
36699 This packet is not probed by default; the remote stub must request it,
36700 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36702 @item qXfer:sdata:read::@var{offset},@var{length}
36703 @anchor{qXfer sdata read}
36705 Read contents of the extra collected static tracepoint marker
36706 information. The annex part of the generic @samp{qXfer} packet must
36707 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36710 This packet is not probed by default; the remote stub must request it,
36711 by supplying an appropriate @samp{qSupported} response
36712 (@pxref{qSupported}).
36714 @item qXfer:siginfo:read::@var{offset},@var{length}
36715 @anchor{qXfer siginfo read}
36716 Read contents of the extra signal information on the target
36717 system. The annex part of the generic @samp{qXfer} packet must be
36718 empty (@pxref{qXfer read}).
36720 This packet is not probed by default; the remote stub must request it,
36721 by supplying an appropriate @samp{qSupported} response
36722 (@pxref{qSupported}).
36724 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36725 @anchor{qXfer spu read}
36726 Read contents of an @code{spufs} file on the target system. The
36727 annex specifies which file to read; it must be of the form
36728 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36729 in the target process, and @var{name} identifes the @code{spufs} file
36730 in that context to be accessed.
36732 This packet is not probed by default; the remote stub must request it,
36733 by supplying an appropriate @samp{qSupported} response
36734 (@pxref{qSupported}).
36736 @item qXfer:threads:read::@var{offset},@var{length}
36737 @anchor{qXfer threads read}
36738 Access the list of threads on target. @xref{Thread List Format}. The
36739 annex part of the generic @samp{qXfer} packet must be empty
36740 (@pxref{qXfer read}).
36742 This packet is not probed by default; the remote stub must request it,
36743 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36745 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36746 @anchor{qXfer traceframe info read}
36748 Return a description of the current traceframe's contents.
36749 @xref{Traceframe Info Format}. The annex part of the generic
36750 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36752 This packet is not probed by default; the remote stub must request it,
36753 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36755 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36756 @anchor{qXfer unwind info block}
36758 Return the unwind information block for @var{pc}. This packet is used
36759 on OpenVMS/ia64 to ask the kernel unwind information.
36761 This packet is not probed by default.
36763 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36764 @anchor{qXfer fdpic loadmap read}
36765 Read contents of @code{loadmap}s on the target system. The
36766 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36767 executable @code{loadmap} or interpreter @code{loadmap} to read.
36769 This packet is not probed by default; the remote stub must request it,
36770 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36772 @item qXfer:osdata:read::@var{offset},@var{length}
36773 @anchor{qXfer osdata read}
36774 Access the target's @dfn{operating system information}.
36775 @xref{Operating System Information}.
36782 Data @var{data} (@pxref{Binary Data}) has been read from the
36783 target. There may be more data at a higher address (although
36784 it is permitted to return @samp{m} even for the last valid
36785 block of data, as long as at least one byte of data was read).
36786 @var{data} may have fewer bytes than the @var{length} in the
36790 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36791 There is no more data to be read. @var{data} may have fewer bytes
36792 than the @var{length} in the request.
36795 The @var{offset} in the request is at the end of the data.
36796 There is no more data to be read.
36799 The request was malformed, or @var{annex} was invalid.
36802 The offset was invalid, or there was an error encountered reading the data.
36803 @var{nn} is a hex-encoded @code{errno} value.
36806 An empty reply indicates the @var{object} string was not recognized by
36807 the stub, or that the object does not support reading.
36810 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36811 @cindex write data into object, remote request
36812 @anchor{qXfer write}
36813 Write uninterpreted bytes into the target's special data area
36814 identified by the keyword @var{object}, starting at @var{offset} bytes
36815 into the data. @var{data}@dots{} is the binary-encoded data
36816 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
36817 is specific to @var{object}; it can supply additional details about what data
36820 Here are the specific requests of this form defined so far. All
36821 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36822 formats, listed below.
36825 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36826 @anchor{qXfer siginfo write}
36827 Write @var{data} to the extra signal information on the target system.
36828 The annex part of the generic @samp{qXfer} packet must be
36829 empty (@pxref{qXfer write}).
36831 This packet is not probed by default; the remote stub must request it,
36832 by supplying an appropriate @samp{qSupported} response
36833 (@pxref{qSupported}).
36835 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36836 @anchor{qXfer spu write}
36837 Write @var{data} to an @code{spufs} file on the target system. The
36838 annex specifies which file to write; it must be of the form
36839 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36840 in the target process, and @var{name} identifes the @code{spufs} file
36841 in that context to be accessed.
36843 This packet is not probed by default; the remote stub must request it,
36844 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36850 @var{nn} (hex encoded) is the number of bytes written.
36851 This may be fewer bytes than supplied in the request.
36854 The request was malformed, or @var{annex} was invalid.
36857 The offset was invalid, or there was an error encountered writing the data.
36858 @var{nn} is a hex-encoded @code{errno} value.
36861 An empty reply indicates the @var{object} string was not
36862 recognized by the stub, or that the object does not support writing.
36865 @item qXfer:@var{object}:@var{operation}:@dots{}
36866 Requests of this form may be added in the future. When a stub does
36867 not recognize the @var{object} keyword, or its support for
36868 @var{object} does not recognize the @var{operation} keyword, the stub
36869 must respond with an empty packet.
36871 @item qAttached:@var{pid}
36872 @cindex query attached, remote request
36873 @cindex @samp{qAttached} packet
36874 Return an indication of whether the remote server attached to an
36875 existing process or created a new process. When the multiprocess
36876 protocol extensions are supported (@pxref{multiprocess extensions}),
36877 @var{pid} is an integer in hexadecimal format identifying the target
36878 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36879 the query packet will be simplified as @samp{qAttached}.
36881 This query is used, for example, to know whether the remote process
36882 should be detached or killed when a @value{GDBN} session is ended with
36883 the @code{quit} command.
36888 The remote server attached to an existing process.
36890 The remote server created a new process.
36892 A badly formed request or an error was encountered.
36897 @node Architecture-Specific Protocol Details
36898 @section Architecture-Specific Protocol Details
36900 This section describes how the remote protocol is applied to specific
36901 target architectures. Also see @ref{Standard Target Features}, for
36902 details of XML target descriptions for each architecture.
36905 * ARM-Specific Protocol Details::
36906 * MIPS-Specific Protocol Details::
36909 @node ARM-Specific Protocol Details
36910 @subsection @acronym{ARM}-specific Protocol Details
36913 * ARM Breakpoint Kinds::
36916 @node ARM Breakpoint Kinds
36917 @subsubsection @acronym{ARM} Breakpoint Kinds
36918 @cindex breakpoint kinds, @acronym{ARM}
36920 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36925 16-bit Thumb mode breakpoint.
36928 32-bit Thumb mode (Thumb-2) breakpoint.
36931 32-bit @acronym{ARM} mode breakpoint.
36935 @node MIPS-Specific Protocol Details
36936 @subsection @acronym{MIPS}-specific Protocol Details
36939 * MIPS Register packet Format::
36940 * MIPS Breakpoint Kinds::
36943 @node MIPS Register packet Format
36944 @subsubsection @acronym{MIPS} Register Packet Format
36945 @cindex register packet format, @acronym{MIPS}
36947 The following @code{g}/@code{G} packets have previously been defined.
36948 In the below, some thirty-two bit registers are transferred as
36949 sixty-four bits. Those registers should be zero/sign extended (which?)
36950 to fill the space allocated. Register bytes are transferred in target
36951 byte order. The two nibbles within a register byte are transferred
36952 most-significant -- least-significant.
36957 All registers are transferred as thirty-two bit quantities in the order:
36958 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36959 registers; fsr; fir; fp.
36962 All registers are transferred as sixty-four bit quantities (including
36963 thirty-two bit registers such as @code{sr}). The ordering is the same
36968 @node MIPS Breakpoint Kinds
36969 @subsubsection @acronym{MIPS} Breakpoint Kinds
36970 @cindex breakpoint kinds, @acronym{MIPS}
36972 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36977 16-bit @acronym{MIPS16} mode breakpoint.
36980 16-bit @acronym{microMIPS} mode breakpoint.
36983 32-bit standard @acronym{MIPS} mode breakpoint.
36986 32-bit @acronym{microMIPS} mode breakpoint.
36990 @node Tracepoint Packets
36991 @section Tracepoint Packets
36992 @cindex tracepoint packets
36993 @cindex packets, tracepoint
36995 Here we describe the packets @value{GDBN} uses to implement
36996 tracepoints (@pxref{Tracepoints}).
37000 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37001 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37002 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37003 the tracepoint is disabled. @var{step} is the tracepoint's step
37004 count, and @var{pass} is its pass count. If an @samp{F} is present,
37005 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37006 the number of bytes that the target should copy elsewhere to make room
37007 for the tracepoint. If an @samp{X} is present, it introduces a
37008 tracepoint condition, which consists of a hexadecimal length, followed
37009 by a comma and hex-encoded bytes, in a manner similar to action
37010 encodings as described below. If the trailing @samp{-} is present,
37011 further @samp{QTDP} packets will follow to specify this tracepoint's
37017 The packet was understood and carried out.
37019 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37021 The packet was not recognized.
37024 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37025 Define actions to be taken when a tracepoint is hit. @var{n} and
37026 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37027 this tracepoint. This packet may only be sent immediately after
37028 another @samp{QTDP} packet that ended with a @samp{-}. If the
37029 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37030 specifying more actions for this tracepoint.
37032 In the series of action packets for a given tracepoint, at most one
37033 can have an @samp{S} before its first @var{action}. If such a packet
37034 is sent, it and the following packets define ``while-stepping''
37035 actions. Any prior packets define ordinary actions --- that is, those
37036 taken when the tracepoint is first hit. If no action packet has an
37037 @samp{S}, then all the packets in the series specify ordinary
37038 tracepoint actions.
37040 The @samp{@var{action}@dots{}} portion of the packet is a series of
37041 actions, concatenated without separators. Each action has one of the
37047 Collect the registers whose bits are set in @var{mask}. @var{mask} is
37048 a hexadecimal number whose @var{i}'th bit is set if register number
37049 @var{i} should be collected. (The least significant bit is numbered
37050 zero.) Note that @var{mask} may be any number of digits long; it may
37051 not fit in a 32-bit word.
37053 @item M @var{basereg},@var{offset},@var{len}
37054 Collect @var{len} bytes of memory starting at the address in register
37055 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37056 @samp{-1}, then the range has a fixed address: @var{offset} is the
37057 address of the lowest byte to collect. The @var{basereg},
37058 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37059 values (the @samp{-1} value for @var{basereg} is a special case).
37061 @item X @var{len},@var{expr}
37062 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37063 it directs. @var{expr} is an agent expression, as described in
37064 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37065 two-digit hex number in the packet; @var{len} is the number of bytes
37066 in the expression (and thus one-half the number of hex digits in the
37071 Any number of actions may be packed together in a single @samp{QTDP}
37072 packet, as long as the packet does not exceed the maximum packet
37073 length (400 bytes, for many stubs). There may be only one @samp{R}
37074 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37075 actions. Any registers referred to by @samp{M} and @samp{X} actions
37076 must be collected by a preceding @samp{R} action. (The
37077 ``while-stepping'' actions are treated as if they were attached to a
37078 separate tracepoint, as far as these restrictions are concerned.)
37083 The packet was understood and carried out.
37085 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37087 The packet was not recognized.
37090 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37091 @cindex @samp{QTDPsrc} packet
37092 Specify a source string of tracepoint @var{n} at address @var{addr}.
37093 This is useful to get accurate reproduction of the tracepoints
37094 originally downloaded at the beginning of the trace run. @var{type}
37095 is the name of the tracepoint part, such as @samp{cond} for the
37096 tracepoint's conditional expression (see below for a list of types), while
37097 @var{bytes} is the string, encoded in hexadecimal.
37099 @var{start} is the offset of the @var{bytes} within the overall source
37100 string, while @var{slen} is the total length of the source string.
37101 This is intended for handling source strings that are longer than will
37102 fit in a single packet.
37103 @c Add detailed example when this info is moved into a dedicated
37104 @c tracepoint descriptions section.
37106 The available string types are @samp{at} for the location,
37107 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37108 @value{GDBN} sends a separate packet for each command in the action
37109 list, in the same order in which the commands are stored in the list.
37111 The target does not need to do anything with source strings except
37112 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37115 Although this packet is optional, and @value{GDBN} will only send it
37116 if the target replies with @samp{TracepointSource} @xref{General
37117 Query Packets}, it makes both disconnected tracing and trace files
37118 much easier to use. Otherwise the user must be careful that the
37119 tracepoints in effect while looking at trace frames are identical to
37120 the ones in effect during the trace run; even a small discrepancy
37121 could cause @samp{tdump} not to work, or a particular trace frame not
37124 @item QTDV:@var{n}:@var{value}
37125 @cindex define trace state variable, remote request
37126 @cindex @samp{QTDV} packet
37127 Create a new trace state variable, number @var{n}, with an initial
37128 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37129 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37130 the option of not using this packet for initial values of zero; the
37131 target should simply create the trace state variables as they are
37132 mentioned in expressions.
37134 @item QTFrame:@var{n}
37135 Select the @var{n}'th tracepoint frame from the buffer, and use the
37136 register and memory contents recorded there to answer subsequent
37137 request packets from @value{GDBN}.
37139 A successful reply from the stub indicates that the stub has found the
37140 requested frame. The response is a series of parts, concatenated
37141 without separators, describing the frame we selected. Each part has
37142 one of the following forms:
37146 The selected frame is number @var{n} in the trace frame buffer;
37147 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37148 was no frame matching the criteria in the request packet.
37151 The selected trace frame records a hit of tracepoint number @var{t};
37152 @var{t} is a hexadecimal number.
37156 @item QTFrame:pc:@var{addr}
37157 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37158 currently selected frame whose PC is @var{addr};
37159 @var{addr} is a hexadecimal number.
37161 @item QTFrame:tdp:@var{t}
37162 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37163 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37164 is a hexadecimal number.
37166 @item QTFrame:range:@var{start}:@var{end}
37167 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37168 currently selected frame whose PC is between @var{start} (inclusive)
37169 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37172 @item QTFrame:outside:@var{start}:@var{end}
37173 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37174 frame @emph{outside} the given range of addresses (exclusive).
37177 This packet requests the minimum length of instruction at which a fast
37178 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37179 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37180 it depends on the target system being able to create trampolines in
37181 the first 64K of memory, which might or might not be possible for that
37182 system. So the reply to this packet will be 4 if it is able to
37189 The minimum instruction length is currently unknown.
37191 The minimum instruction length is @var{length}, where @var{length} is greater
37192 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
37193 that a fast tracepoint may be placed on any instruction regardless of size.
37195 An error has occurred.
37197 An empty reply indicates that the request is not supported by the stub.
37201 Begin the tracepoint experiment. Begin collecting data from
37202 tracepoint hits in the trace frame buffer. This packet supports the
37203 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37204 instruction reply packet}).
37207 End the tracepoint experiment. Stop collecting trace frames.
37209 @item QTEnable:@var{n}:@var{addr}
37211 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37212 experiment. If the tracepoint was previously disabled, then collection
37213 of data from it will resume.
37215 @item QTDisable:@var{n}:@var{addr}
37217 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37218 experiment. No more data will be collected from the tracepoint unless
37219 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37222 Clear the table of tracepoints, and empty the trace frame buffer.
37224 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37225 Establish the given ranges of memory as ``transparent''. The stub
37226 will answer requests for these ranges from memory's current contents,
37227 if they were not collected as part of the tracepoint hit.
37229 @value{GDBN} uses this to mark read-only regions of memory, like those
37230 containing program code. Since these areas never change, they should
37231 still have the same contents they did when the tracepoint was hit, so
37232 there's no reason for the stub to refuse to provide their contents.
37234 @item QTDisconnected:@var{value}
37235 Set the choice to what to do with the tracing run when @value{GDBN}
37236 disconnects from the target. A @var{value} of 1 directs the target to
37237 continue the tracing run, while 0 tells the target to stop tracing if
37238 @value{GDBN} is no longer in the picture.
37241 Ask the stub if there is a trace experiment running right now.
37243 The reply has the form:
37247 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37248 @var{running} is a single digit @code{1} if the trace is presently
37249 running, or @code{0} if not. It is followed by semicolon-separated
37250 optional fields that an agent may use to report additional status.
37254 If the trace is not running, the agent may report any of several
37255 explanations as one of the optional fields:
37260 No trace has been run yet.
37262 @item tstop[:@var{text}]:0
37263 The trace was stopped by a user-originated stop command. The optional
37264 @var{text} field is a user-supplied string supplied as part of the
37265 stop command (for instance, an explanation of why the trace was
37266 stopped manually). It is hex-encoded.
37269 The trace stopped because the trace buffer filled up.
37271 @item tdisconnected:0
37272 The trace stopped because @value{GDBN} disconnected from the target.
37274 @item tpasscount:@var{tpnum}
37275 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37277 @item terror:@var{text}:@var{tpnum}
37278 The trace stopped because tracepoint @var{tpnum} had an error. The
37279 string @var{text} is available to describe the nature of the error
37280 (for instance, a divide by zero in the condition expression).
37281 @var{text} is hex encoded.
37284 The trace stopped for some other reason.
37288 Additional optional fields supply statistical and other information.
37289 Although not required, they are extremely useful for users monitoring
37290 the progress of a trace run. If a trace has stopped, and these
37291 numbers are reported, they must reflect the state of the just-stopped
37296 @item tframes:@var{n}
37297 The number of trace frames in the buffer.
37299 @item tcreated:@var{n}
37300 The total number of trace frames created during the run. This may
37301 be larger than the trace frame count, if the buffer is circular.
37303 @item tsize:@var{n}
37304 The total size of the trace buffer, in bytes.
37306 @item tfree:@var{n}
37307 The number of bytes still unused in the buffer.
37309 @item circular:@var{n}
37310 The value of the circular trace buffer flag. @code{1} means that the
37311 trace buffer is circular and old trace frames will be discarded if
37312 necessary to make room, @code{0} means that the trace buffer is linear
37315 @item disconn:@var{n}
37316 The value of the disconnected tracing flag. @code{1} means that
37317 tracing will continue after @value{GDBN} disconnects, @code{0} means
37318 that the trace run will stop.
37322 @item qTP:@var{tp}:@var{addr}
37323 @cindex tracepoint status, remote request
37324 @cindex @samp{qTP} packet
37325 Ask the stub for the current state of tracepoint number @var{tp} at
37326 address @var{addr}.
37330 @item V@var{hits}:@var{usage}
37331 The tracepoint has been hit @var{hits} times so far during the trace
37332 run, and accounts for @var{usage} in the trace buffer. Note that
37333 @code{while-stepping} steps are not counted as separate hits, but the
37334 steps' space consumption is added into the usage number.
37338 @item qTV:@var{var}
37339 @cindex trace state variable value, remote request
37340 @cindex @samp{qTV} packet
37341 Ask the stub for the value of the trace state variable number @var{var}.
37346 The value of the variable is @var{value}. This will be the current
37347 value of the variable if the user is examining a running target, or a
37348 saved value if the variable was collected in the trace frame that the
37349 user is looking at. Note that multiple requests may result in
37350 different reply values, such as when requesting values while the
37351 program is running.
37354 The value of the variable is unknown. This would occur, for example,
37355 if the user is examining a trace frame in which the requested variable
37361 These packets request data about tracepoints that are being used by
37362 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37363 of data, and multiple @code{qTsP} to get additional pieces. Replies
37364 to these packets generally take the form of the @code{QTDP} packets
37365 that define tracepoints. (FIXME add detailed syntax)
37369 These packets request data about trace state variables that are on the
37370 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37371 and multiple @code{qTsV} to get additional variables. Replies to
37372 these packets follow the syntax of the @code{QTDV} packets that define
37373 trace state variables.
37377 These packets request data about static tracepoint markers that exist
37378 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37379 first piece of data, and multiple @code{qTsSTM} to get additional
37380 pieces. Replies to these packets take the following form:
37384 @item m @var{address}:@var{id}:@var{extra}
37386 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37387 a comma-separated list of markers
37389 (lower case letter @samp{L}) denotes end of list.
37391 An error occurred. @var{nn} are hex digits.
37393 An empty reply indicates that the request is not supported by the
37397 @var{address} is encoded in hex.
37398 @var{id} and @var{extra} are strings encoded in hex.
37400 In response to each query, the target will reply with a list of one or
37401 more markers, separated by commas. @value{GDBN} will respond to each
37402 reply with a request for more markers (using the @samp{qs} form of the
37403 query), until the target responds with @samp{l} (lower-case ell, for
37406 @item qTSTMat:@var{address}
37407 This packets requests data about static tracepoint markers in the
37408 target program at @var{address}. Replies to this packet follow the
37409 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37410 tracepoint markers.
37412 @item QTSave:@var{filename}
37413 This packet directs the target to save trace data to the file name
37414 @var{filename} in the target's filesystem. @var{filename} is encoded
37415 as a hex string; the interpretation of the file name (relative vs
37416 absolute, wild cards, etc) is up to the target.
37418 @item qTBuffer:@var{offset},@var{len}
37419 Return up to @var{len} bytes of the current contents of trace buffer,
37420 starting at @var{offset}. The trace buffer is treated as if it were
37421 a contiguous collection of traceframes, as per the trace file format.
37422 The reply consists as many hex-encoded bytes as the target can deliver
37423 in a packet; it is not an error to return fewer than were asked for.
37424 A reply consisting of just @code{l} indicates that no bytes are
37427 @item QTBuffer:circular:@var{value}
37428 This packet directs the target to use a circular trace buffer if
37429 @var{value} is 1, or a linear buffer if the value is 0.
37431 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37432 This packet adds optional textual notes to the trace run. Allowable
37433 types include @code{user}, @code{notes}, and @code{tstop}, the
37434 @var{text} fields are arbitrary strings, hex-encoded.
37438 @subsection Relocate instruction reply packet
37439 When installing fast tracepoints in memory, the target may need to
37440 relocate the instruction currently at the tracepoint address to a
37441 different address in memory. For most instructions, a simple copy is
37442 enough, but, for example, call instructions that implicitly push the
37443 return address on the stack, and relative branches or other
37444 PC-relative instructions require offset adjustment, so that the effect
37445 of executing the instruction at a different address is the same as if
37446 it had executed in the original location.
37448 In response to several of the tracepoint packets, the target may also
37449 respond with a number of intermediate @samp{qRelocInsn} request
37450 packets before the final result packet, to have @value{GDBN} handle
37451 this relocation operation. If a packet supports this mechanism, its
37452 documentation will explicitly say so. See for example the above
37453 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37454 format of the request is:
37457 @item qRelocInsn:@var{from};@var{to}
37459 This requests @value{GDBN} to copy instruction at address @var{from}
37460 to address @var{to}, possibly adjusted so that executing the
37461 instruction at @var{to} has the same effect as executing it at
37462 @var{from}. @value{GDBN} writes the adjusted instruction to target
37463 memory starting at @var{to}.
37468 @item qRelocInsn:@var{adjusted_size}
37469 Informs the stub the relocation is complete. @var{adjusted_size} is
37470 the length in bytes of resulting relocated instruction sequence.
37472 A badly formed request was detected, or an error was encountered while
37473 relocating the instruction.
37476 @node Host I/O Packets
37477 @section Host I/O Packets
37478 @cindex Host I/O, remote protocol
37479 @cindex file transfer, remote protocol
37481 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37482 operations on the far side of a remote link. For example, Host I/O is
37483 used to upload and download files to a remote target with its own
37484 filesystem. Host I/O uses the same constant values and data structure
37485 layout as the target-initiated File-I/O protocol. However, the
37486 Host I/O packets are structured differently. The target-initiated
37487 protocol relies on target memory to store parameters and buffers.
37488 Host I/O requests are initiated by @value{GDBN}, and the
37489 target's memory is not involved. @xref{File-I/O Remote Protocol
37490 Extension}, for more details on the target-initiated protocol.
37492 The Host I/O request packets all encode a single operation along with
37493 its arguments. They have this format:
37497 @item vFile:@var{operation}: @var{parameter}@dots{}
37498 @var{operation} is the name of the particular request; the target
37499 should compare the entire packet name up to the second colon when checking
37500 for a supported operation. The format of @var{parameter} depends on
37501 the operation. Numbers are always passed in hexadecimal. Negative
37502 numbers have an explicit minus sign (i.e.@: two's complement is not
37503 used). Strings (e.g.@: filenames) are encoded as a series of
37504 hexadecimal bytes. The last argument to a system call may be a
37505 buffer of escaped binary data (@pxref{Binary Data}).
37509 The valid responses to Host I/O packets are:
37513 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37514 @var{result} is the integer value returned by this operation, usually
37515 non-negative for success and -1 for errors. If an error has occured,
37516 @var{errno} will be included in the result. @var{errno} will have a
37517 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37518 operations which return data, @var{attachment} supplies the data as a
37519 binary buffer. Binary buffers in response packets are escaped in the
37520 normal way (@pxref{Binary Data}). See the individual packet
37521 documentation for the interpretation of @var{result} and
37525 An empty response indicates that this operation is not recognized.
37529 These are the supported Host I/O operations:
37532 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
37533 Open a file at @var{pathname} and return a file descriptor for it, or
37534 return -1 if an error occurs. @var{pathname} is a string,
37535 @var{flags} is an integer indicating a mask of open flags
37536 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37537 of mode bits to use if the file is created (@pxref{mode_t Values}).
37538 @xref{open}, for details of the open flags and mode values.
37540 @item vFile:close: @var{fd}
37541 Close the open file corresponding to @var{fd} and return 0, or
37542 -1 if an error occurs.
37544 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37545 Read data from the open file corresponding to @var{fd}. Up to
37546 @var{count} bytes will be read from the file, starting at @var{offset}
37547 relative to the start of the file. The target may read fewer bytes;
37548 common reasons include packet size limits and an end-of-file
37549 condition. The number of bytes read is returned. Zero should only be
37550 returned for a successful read at the end of the file, or if
37551 @var{count} was zero.
37553 The data read should be returned as a binary attachment on success.
37554 If zero bytes were read, the response should include an empty binary
37555 attachment (i.e.@: a trailing semicolon). The return value is the
37556 number of target bytes read; the binary attachment may be longer if
37557 some characters were escaped.
37559 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37560 Write @var{data} (a binary buffer) to the open file corresponding
37561 to @var{fd}. Start the write at @var{offset} from the start of the
37562 file. Unlike many @code{write} system calls, there is no
37563 separate @var{count} argument; the length of @var{data} in the
37564 packet is used. @samp{vFile:write} returns the number of bytes written,
37565 which may be shorter than the length of @var{data}, or -1 if an
37568 @item vFile:unlink: @var{pathname}
37569 Delete the file at @var{pathname} on the target. Return 0,
37570 or -1 if an error occurs. @var{pathname} is a string.
37572 @item vFile:readlink: @var{filename}
37573 Read value of symbolic link @var{filename} on the target. Return
37574 the number of bytes read, or -1 if an error occurs.
37576 The data read should be returned as a binary attachment on success.
37577 If zero bytes were read, the response should include an empty binary
37578 attachment (i.e.@: a trailing semicolon). The return value is the
37579 number of target bytes read; the binary attachment may be longer if
37580 some characters were escaped.
37585 @section Interrupts
37586 @cindex interrupts (remote protocol)
37588 When a program on the remote target is running, @value{GDBN} may
37589 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37590 a @code{BREAK} followed by @code{g},
37591 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37593 The precise meaning of @code{BREAK} is defined by the transport
37594 mechanism and may, in fact, be undefined. @value{GDBN} does not
37595 currently define a @code{BREAK} mechanism for any of the network
37596 interfaces except for TCP, in which case @value{GDBN} sends the
37597 @code{telnet} BREAK sequence.
37599 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37600 transport mechanisms. It is represented by sending the single byte
37601 @code{0x03} without any of the usual packet overhead described in
37602 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37603 transmitted as part of a packet, it is considered to be packet data
37604 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37605 (@pxref{X packet}), used for binary downloads, may include an unescaped
37606 @code{0x03} as part of its packet.
37608 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37609 When Linux kernel receives this sequence from serial port,
37610 it stops execution and connects to gdb.
37612 Stubs are not required to recognize these interrupt mechanisms and the
37613 precise meaning associated with receipt of the interrupt is
37614 implementation defined. If the target supports debugging of multiple
37615 threads and/or processes, it should attempt to interrupt all
37616 currently-executing threads and processes.
37617 If the stub is successful at interrupting the
37618 running program, it should send one of the stop
37619 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37620 of successfully stopping the program in all-stop mode, and a stop reply
37621 for each stopped thread in non-stop mode.
37622 Interrupts received while the
37623 program is stopped are discarded.
37625 @node Notification Packets
37626 @section Notification Packets
37627 @cindex notification packets
37628 @cindex packets, notification
37630 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37631 packets that require no acknowledgment. Both the GDB and the stub
37632 may send notifications (although the only notifications defined at
37633 present are sent by the stub). Notifications carry information
37634 without incurring the round-trip latency of an acknowledgment, and so
37635 are useful for low-impact communications where occasional packet loss
37638 A notification packet has the form @samp{% @var{data} #
37639 @var{checksum}}, where @var{data} is the content of the notification,
37640 and @var{checksum} is a checksum of @var{data}, computed and formatted
37641 as for ordinary @value{GDBN} packets. A notification's @var{data}
37642 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37643 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37644 to acknowledge the notification's receipt or to report its corruption.
37646 Every notification's @var{data} begins with a name, which contains no
37647 colon characters, followed by a colon character.
37649 Recipients should silently ignore corrupted notifications and
37650 notifications they do not understand. Recipients should restart
37651 timeout periods on receipt of a well-formed notification, whether or
37652 not they understand it.
37654 Senders should only send the notifications described here when this
37655 protocol description specifies that they are permitted. In the
37656 future, we may extend the protocol to permit existing notifications in
37657 new contexts; this rule helps older senders avoid confusing newer
37660 (Older versions of @value{GDBN} ignore bytes received until they see
37661 the @samp{$} byte that begins an ordinary packet, so new stubs may
37662 transmit notifications without fear of confusing older clients. There
37663 are no notifications defined for @value{GDBN} to send at the moment, but we
37664 assume that most older stubs would ignore them, as well.)
37666 The following notification packets from the stub to @value{GDBN} are
37670 @item Stop: @var{reply}
37671 Report an asynchronous stop event in non-stop mode.
37672 The @var{reply} has the form of a stop reply, as
37673 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37674 for information on how these notifications are acknowledged by
37678 @node Remote Non-Stop
37679 @section Remote Protocol Support for Non-Stop Mode
37681 @value{GDBN}'s remote protocol supports non-stop debugging of
37682 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37683 supports non-stop mode, it should report that to @value{GDBN} by including
37684 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37686 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37687 establishing a new connection with the stub. Entering non-stop mode
37688 does not alter the state of any currently-running threads, but targets
37689 must stop all threads in any already-attached processes when entering
37690 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37691 probe the target state after a mode change.
37693 In non-stop mode, when an attached process encounters an event that
37694 would otherwise be reported with a stop reply, it uses the
37695 asynchronous notification mechanism (@pxref{Notification Packets}) to
37696 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37697 in all processes are stopped when a stop reply is sent, in non-stop
37698 mode only the thread reporting the stop event is stopped. That is,
37699 when reporting a @samp{S} or @samp{T} response to indicate completion
37700 of a step operation, hitting a breakpoint, or a fault, only the
37701 affected thread is stopped; any other still-running threads continue
37702 to run. When reporting a @samp{W} or @samp{X} response, all running
37703 threads belonging to other attached processes continue to run.
37705 Only one stop reply notification at a time may be pending; if
37706 additional stop events occur before @value{GDBN} has acknowledged the
37707 previous notification, they must be queued by the stub for later
37708 synchronous transmission in response to @samp{vStopped} packets from
37709 @value{GDBN}. Because the notification mechanism is unreliable,
37710 the stub is permitted to resend a stop reply notification
37711 if it believes @value{GDBN} may not have received it. @value{GDBN}
37712 ignores additional stop reply notifications received before it has
37713 finished processing a previous notification and the stub has completed
37714 sending any queued stop events.
37716 Otherwise, @value{GDBN} must be prepared to receive a stop reply
37717 notification at any time. Specifically, they may appear when
37718 @value{GDBN} is not otherwise reading input from the stub, or when
37719 @value{GDBN} is expecting to read a normal synchronous response or a
37720 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37721 Notification packets are distinct from any other communication from
37722 the stub so there is no ambiguity.
37724 After receiving a stop reply notification, @value{GDBN} shall
37725 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
37726 as a regular, synchronous request to the stub. Such acknowledgment
37727 is not required to happen immediately, as @value{GDBN} is permitted to
37728 send other, unrelated packets to the stub first, which the stub should
37731 Upon receiving a @samp{vStopped} packet, if the stub has other queued
37732 stop events to report to @value{GDBN}, it shall respond by sending a
37733 normal stop reply response. @value{GDBN} shall then send another
37734 @samp{vStopped} packet to solicit further responses; again, it is
37735 permitted to send other, unrelated packets as well which the stub
37736 should process normally.
37738 If the stub receives a @samp{vStopped} packet and there are no
37739 additional stop events to report, the stub shall return an @samp{OK}
37740 response. At this point, if further stop events occur, the stub shall
37741 send a new stop reply notification, @value{GDBN} shall accept the
37742 notification, and the process shall be repeated.
37744 In non-stop mode, the target shall respond to the @samp{?} packet as
37745 follows. First, any incomplete stop reply notification/@samp{vStopped}
37746 sequence in progress is abandoned. The target must begin a new
37747 sequence reporting stop events for all stopped threads, whether or not
37748 it has previously reported those events to @value{GDBN}. The first
37749 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37750 subsequent stop replies are sent as responses to @samp{vStopped} packets
37751 using the mechanism described above. The target must not send
37752 asynchronous stop reply notifications until the sequence is complete.
37753 If all threads are running when the target receives the @samp{?} packet,
37754 or if the target is not attached to any process, it shall respond
37757 @node Packet Acknowledgment
37758 @section Packet Acknowledgment
37760 @cindex acknowledgment, for @value{GDBN} remote
37761 @cindex packet acknowledgment, for @value{GDBN} remote
37762 By default, when either the host or the target machine receives a packet,
37763 the first response expected is an acknowledgment: either @samp{+} (to indicate
37764 the package was received correctly) or @samp{-} (to request retransmission).
37765 This mechanism allows the @value{GDBN} remote protocol to operate over
37766 unreliable transport mechanisms, such as a serial line.
37768 In cases where the transport mechanism is itself reliable (such as a pipe or
37769 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37770 It may be desirable to disable them in that case to reduce communication
37771 overhead, or for other reasons. This can be accomplished by means of the
37772 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37774 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37775 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37776 and response format still includes the normal checksum, as described in
37777 @ref{Overview}, but the checksum may be ignored by the receiver.
37779 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37780 no-acknowledgment mode, it should report that to @value{GDBN}
37781 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37782 @pxref{qSupported}.
37783 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37784 disabled via the @code{set remote noack-packet off} command
37785 (@pxref{Remote Configuration}),
37786 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37787 Only then may the stub actually turn off packet acknowledgments.
37788 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37789 response, which can be safely ignored by the stub.
37791 Note that @code{set remote noack-packet} command only affects negotiation
37792 between @value{GDBN} and the stub when subsequent connections are made;
37793 it does not affect the protocol acknowledgment state for any current
37795 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37796 new connection is established,
37797 there is also no protocol request to re-enable the acknowledgments
37798 for the current connection, once disabled.
37803 Example sequence of a target being re-started. Notice how the restart
37804 does not get any direct output:
37809 @emph{target restarts}
37812 <- @code{T001:1234123412341234}
37816 Example sequence of a target being stepped by a single instruction:
37819 -> @code{G1445@dots{}}
37824 <- @code{T001:1234123412341234}
37828 <- @code{1455@dots{}}
37832 @node File-I/O Remote Protocol Extension
37833 @section File-I/O Remote Protocol Extension
37834 @cindex File-I/O remote protocol extension
37837 * File-I/O Overview::
37838 * Protocol Basics::
37839 * The F Request Packet::
37840 * The F Reply Packet::
37841 * The Ctrl-C Message::
37843 * List of Supported Calls::
37844 * Protocol-specific Representation of Datatypes::
37846 * File-I/O Examples::
37849 @node File-I/O Overview
37850 @subsection File-I/O Overview
37851 @cindex file-i/o overview
37853 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37854 target to use the host's file system and console I/O to perform various
37855 system calls. System calls on the target system are translated into a
37856 remote protocol packet to the host system, which then performs the needed
37857 actions and returns a response packet to the target system.
37858 This simulates file system operations even on targets that lack file systems.
37860 The protocol is defined to be independent of both the host and target systems.
37861 It uses its own internal representation of datatypes and values. Both
37862 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37863 translating the system-dependent value representations into the internal
37864 protocol representations when data is transmitted.
37866 The communication is synchronous. A system call is possible only when
37867 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37868 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37869 the target is stopped to allow deterministic access to the target's
37870 memory. Therefore File-I/O is not interruptible by target signals. On
37871 the other hand, it is possible to interrupt File-I/O by a user interrupt
37872 (@samp{Ctrl-C}) within @value{GDBN}.
37874 The target's request to perform a host system call does not finish
37875 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37876 after finishing the system call, the target returns to continuing the
37877 previous activity (continue, step). No additional continue or step
37878 request from @value{GDBN} is required.
37881 (@value{GDBP}) continue
37882 <- target requests 'system call X'
37883 target is stopped, @value{GDBN} executes system call
37884 -> @value{GDBN} returns result
37885 ... target continues, @value{GDBN} returns to wait for the target
37886 <- target hits breakpoint and sends a Txx packet
37889 The protocol only supports I/O on the console and to regular files on
37890 the host file system. Character or block special devices, pipes,
37891 named pipes, sockets or any other communication method on the host
37892 system are not supported by this protocol.
37894 File I/O is not supported in non-stop mode.
37896 @node Protocol Basics
37897 @subsection Protocol Basics
37898 @cindex protocol basics, file-i/o
37900 The File-I/O protocol uses the @code{F} packet as the request as well
37901 as reply packet. Since a File-I/O system call can only occur when
37902 @value{GDBN} is waiting for a response from the continuing or stepping target,
37903 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37904 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37905 This @code{F} packet contains all information needed to allow @value{GDBN}
37906 to call the appropriate host system call:
37910 A unique identifier for the requested system call.
37913 All parameters to the system call. Pointers are given as addresses
37914 in the target memory address space. Pointers to strings are given as
37915 pointer/length pair. Numerical values are given as they are.
37916 Numerical control flags are given in a protocol-specific representation.
37920 At this point, @value{GDBN} has to perform the following actions.
37924 If the parameters include pointer values to data needed as input to a
37925 system call, @value{GDBN} requests this data from the target with a
37926 standard @code{m} packet request. This additional communication has to be
37927 expected by the target implementation and is handled as any other @code{m}
37931 @value{GDBN} translates all value from protocol representation to host
37932 representation as needed. Datatypes are coerced into the host types.
37935 @value{GDBN} calls the system call.
37938 It then coerces datatypes back to protocol representation.
37941 If the system call is expected to return data in buffer space specified
37942 by pointer parameters to the call, the data is transmitted to the
37943 target using a @code{M} or @code{X} packet. This packet has to be expected
37944 by the target implementation and is handled as any other @code{M} or @code{X}
37949 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37950 necessary information for the target to continue. This at least contains
37957 @code{errno}, if has been changed by the system call.
37964 After having done the needed type and value coercion, the target continues
37965 the latest continue or step action.
37967 @node The F Request Packet
37968 @subsection The @code{F} Request Packet
37969 @cindex file-i/o request packet
37970 @cindex @code{F} request packet
37972 The @code{F} request packet has the following format:
37975 @item F@var{call-id},@var{parameter@dots{}}
37977 @var{call-id} is the identifier to indicate the host system call to be called.
37978 This is just the name of the function.
37980 @var{parameter@dots{}} are the parameters to the system call.
37981 Parameters are hexadecimal integer values, either the actual values in case
37982 of scalar datatypes, pointers to target buffer space in case of compound
37983 datatypes and unspecified memory areas, or pointer/length pairs in case
37984 of string parameters. These are appended to the @var{call-id} as a
37985 comma-delimited list. All values are transmitted in ASCII
37986 string representation, pointer/length pairs separated by a slash.
37992 @node The F Reply Packet
37993 @subsection The @code{F} Reply Packet
37994 @cindex file-i/o reply packet
37995 @cindex @code{F} reply packet
37997 The @code{F} reply packet has the following format:
38001 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38003 @var{retcode} is the return code of the system call as hexadecimal value.
38005 @var{errno} is the @code{errno} set by the call, in protocol-specific
38007 This parameter can be omitted if the call was successful.
38009 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38010 case, @var{errno} must be sent as well, even if the call was successful.
38011 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38018 or, if the call was interrupted before the host call has been performed:
38025 assuming 4 is the protocol-specific representation of @code{EINTR}.
38030 @node The Ctrl-C Message
38031 @subsection The @samp{Ctrl-C} Message
38032 @cindex ctrl-c message, in file-i/o protocol
38034 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38035 reply packet (@pxref{The F Reply Packet}),
38036 the target should behave as if it had
38037 gotten a break message. The meaning for the target is ``system call
38038 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38039 (as with a break message) and return to @value{GDBN} with a @code{T02}
38042 It's important for the target to know in which
38043 state the system call was interrupted. There are two possible cases:
38047 The system call hasn't been performed on the host yet.
38050 The system call on the host has been finished.
38054 These two states can be distinguished by the target by the value of the
38055 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38056 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38057 on POSIX systems. In any other case, the target may presume that the
38058 system call has been finished --- successfully or not --- and should behave
38059 as if the break message arrived right after the system call.
38061 @value{GDBN} must behave reliably. If the system call has not been called
38062 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38063 @code{errno} in the packet. If the system call on the host has been finished
38064 before the user requests a break, the full action must be finished by
38065 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38066 The @code{F} packet may only be sent when either nothing has happened
38067 or the full action has been completed.
38070 @subsection Console I/O
38071 @cindex console i/o as part of file-i/o
38073 By default and if not explicitly closed by the target system, the file
38074 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38075 on the @value{GDBN} console is handled as any other file output operation
38076 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38077 by @value{GDBN} so that after the target read request from file descriptor
38078 0 all following typing is buffered until either one of the following
38083 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38085 system call is treated as finished.
38088 The user presses @key{RET}. This is treated as end of input with a trailing
38092 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38093 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38097 If the user has typed more characters than fit in the buffer given to
38098 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38099 either another @code{read(0, @dots{})} is requested by the target, or debugging
38100 is stopped at the user's request.
38103 @node List of Supported Calls
38104 @subsection List of Supported Calls
38105 @cindex list of supported file-i/o calls
38122 @unnumberedsubsubsec open
38123 @cindex open, file-i/o system call
38128 int open(const char *pathname, int flags);
38129 int open(const char *pathname, int flags, mode_t mode);
38133 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38136 @var{flags} is the bitwise @code{OR} of the following values:
38140 If the file does not exist it will be created. The host
38141 rules apply as far as file ownership and time stamps
38145 When used with @code{O_CREAT}, if the file already exists it is
38146 an error and open() fails.
38149 If the file already exists and the open mode allows
38150 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38151 truncated to zero length.
38154 The file is opened in append mode.
38157 The file is opened for reading only.
38160 The file is opened for writing only.
38163 The file is opened for reading and writing.
38167 Other bits are silently ignored.
38171 @var{mode} is the bitwise @code{OR} of the following values:
38175 User has read permission.
38178 User has write permission.
38181 Group has read permission.
38184 Group has write permission.
38187 Others have read permission.
38190 Others have write permission.
38194 Other bits are silently ignored.
38197 @item Return value:
38198 @code{open} returns the new file descriptor or -1 if an error
38205 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38208 @var{pathname} refers to a directory.
38211 The requested access is not allowed.
38214 @var{pathname} was too long.
38217 A directory component in @var{pathname} does not exist.
38220 @var{pathname} refers to a device, pipe, named pipe or socket.
38223 @var{pathname} refers to a file on a read-only filesystem and
38224 write access was requested.
38227 @var{pathname} is an invalid pointer value.
38230 No space on device to create the file.
38233 The process already has the maximum number of files open.
38236 The limit on the total number of files open on the system
38240 The call was interrupted by the user.
38246 @unnumberedsubsubsec close
38247 @cindex close, file-i/o system call
38256 @samp{Fclose,@var{fd}}
38258 @item Return value:
38259 @code{close} returns zero on success, or -1 if an error occurred.
38265 @var{fd} isn't a valid open file descriptor.
38268 The call was interrupted by the user.
38274 @unnumberedsubsubsec read
38275 @cindex read, file-i/o system call
38280 int read(int fd, void *buf, unsigned int count);
38284 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38286 @item Return value:
38287 On success, the number of bytes read is returned.
38288 Zero indicates end of file. If count is zero, read
38289 returns zero as well. On error, -1 is returned.
38295 @var{fd} is not a valid file descriptor or is not open for
38299 @var{bufptr} is an invalid pointer value.
38302 The call was interrupted by the user.
38308 @unnumberedsubsubsec write
38309 @cindex write, file-i/o system call
38314 int write(int fd, const void *buf, unsigned int count);
38318 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38320 @item Return value:
38321 On success, the number of bytes written are returned.
38322 Zero indicates nothing was written. On error, -1
38329 @var{fd} is not a valid file descriptor or is not open for
38333 @var{bufptr} is an invalid pointer value.
38336 An attempt was made to write a file that exceeds the
38337 host-specific maximum file size allowed.
38340 No space on device to write the data.
38343 The call was interrupted by the user.
38349 @unnumberedsubsubsec lseek
38350 @cindex lseek, file-i/o system call
38355 long lseek (int fd, long offset, int flag);
38359 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38361 @var{flag} is one of:
38365 The offset is set to @var{offset} bytes.
38368 The offset is set to its current location plus @var{offset}
38372 The offset is set to the size of the file plus @var{offset}
38376 @item Return value:
38377 On success, the resulting unsigned offset in bytes from
38378 the beginning of the file is returned. Otherwise, a
38379 value of -1 is returned.
38385 @var{fd} is not a valid open file descriptor.
38388 @var{fd} is associated with the @value{GDBN} console.
38391 @var{flag} is not a proper value.
38394 The call was interrupted by the user.
38400 @unnumberedsubsubsec rename
38401 @cindex rename, file-i/o system call
38406 int rename(const char *oldpath, const char *newpath);
38410 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38412 @item Return value:
38413 On success, zero is returned. On error, -1 is returned.
38419 @var{newpath} is an existing directory, but @var{oldpath} is not a
38423 @var{newpath} is a non-empty directory.
38426 @var{oldpath} or @var{newpath} is a directory that is in use by some
38430 An attempt was made to make a directory a subdirectory
38434 A component used as a directory in @var{oldpath} or new
38435 path is not a directory. Or @var{oldpath} is a directory
38436 and @var{newpath} exists but is not a directory.
38439 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38442 No access to the file or the path of the file.
38446 @var{oldpath} or @var{newpath} was too long.
38449 A directory component in @var{oldpath} or @var{newpath} does not exist.
38452 The file is on a read-only filesystem.
38455 The device containing the file has no room for the new
38459 The call was interrupted by the user.
38465 @unnumberedsubsubsec unlink
38466 @cindex unlink, file-i/o system call
38471 int unlink(const char *pathname);
38475 @samp{Funlink,@var{pathnameptr}/@var{len}}
38477 @item Return value:
38478 On success, zero is returned. On error, -1 is returned.
38484 No access to the file or the path of the file.
38487 The system does not allow unlinking of directories.
38490 The file @var{pathname} cannot be unlinked because it's
38491 being used by another process.
38494 @var{pathnameptr} is an invalid pointer value.
38497 @var{pathname} was too long.
38500 A directory component in @var{pathname} does not exist.
38503 A component of the path is not a directory.
38506 The file is on a read-only filesystem.
38509 The call was interrupted by the user.
38515 @unnumberedsubsubsec stat/fstat
38516 @cindex fstat, file-i/o system call
38517 @cindex stat, file-i/o system call
38522 int stat(const char *pathname, struct stat *buf);
38523 int fstat(int fd, struct stat *buf);
38527 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38528 @samp{Ffstat,@var{fd},@var{bufptr}}
38530 @item Return value:
38531 On success, zero is returned. On error, -1 is returned.
38537 @var{fd} is not a valid open file.
38540 A directory component in @var{pathname} does not exist or the
38541 path is an empty string.
38544 A component of the path is not a directory.
38547 @var{pathnameptr} is an invalid pointer value.
38550 No access to the file or the path of the file.
38553 @var{pathname} was too long.
38556 The call was interrupted by the user.
38562 @unnumberedsubsubsec gettimeofday
38563 @cindex gettimeofday, file-i/o system call
38568 int gettimeofday(struct timeval *tv, void *tz);
38572 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38574 @item Return value:
38575 On success, 0 is returned, -1 otherwise.
38581 @var{tz} is a non-NULL pointer.
38584 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38590 @unnumberedsubsubsec isatty
38591 @cindex isatty, file-i/o system call
38596 int isatty(int fd);
38600 @samp{Fisatty,@var{fd}}
38602 @item Return value:
38603 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38609 The call was interrupted by the user.
38614 Note that the @code{isatty} call is treated as a special case: it returns
38615 1 to the target if the file descriptor is attached
38616 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38617 would require implementing @code{ioctl} and would be more complex than
38622 @unnumberedsubsubsec system
38623 @cindex system, file-i/o system call
38628 int system(const char *command);
38632 @samp{Fsystem,@var{commandptr}/@var{len}}
38634 @item Return value:
38635 If @var{len} is zero, the return value indicates whether a shell is
38636 available. A zero return value indicates a shell is not available.
38637 For non-zero @var{len}, the value returned is -1 on error and the
38638 return status of the command otherwise. Only the exit status of the
38639 command is returned, which is extracted from the host's @code{system}
38640 return value by calling @code{WEXITSTATUS(retval)}. In case
38641 @file{/bin/sh} could not be executed, 127 is returned.
38647 The call was interrupted by the user.
38652 @value{GDBN} takes over the full task of calling the necessary host calls
38653 to perform the @code{system} call. The return value of @code{system} on
38654 the host is simplified before it's returned
38655 to the target. Any termination signal information from the child process
38656 is discarded, and the return value consists
38657 entirely of the exit status of the called command.
38659 Due to security concerns, the @code{system} call is by default refused
38660 by @value{GDBN}. The user has to allow this call explicitly with the
38661 @code{set remote system-call-allowed 1} command.
38664 @item set remote system-call-allowed
38665 @kindex set remote system-call-allowed
38666 Control whether to allow the @code{system} calls in the File I/O
38667 protocol for the remote target. The default is zero (disabled).
38669 @item show remote system-call-allowed
38670 @kindex show remote system-call-allowed
38671 Show whether the @code{system} calls are allowed in the File I/O
38675 @node Protocol-specific Representation of Datatypes
38676 @subsection Protocol-specific Representation of Datatypes
38677 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38680 * Integral Datatypes::
38682 * Memory Transfer::
38687 @node Integral Datatypes
38688 @unnumberedsubsubsec Integral Datatypes
38689 @cindex integral datatypes, in file-i/o protocol
38691 The integral datatypes used in the system calls are @code{int},
38692 @code{unsigned int}, @code{long}, @code{unsigned long},
38693 @code{mode_t}, and @code{time_t}.
38695 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38696 implemented as 32 bit values in this protocol.
38698 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38700 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38701 in @file{limits.h}) to allow range checking on host and target.
38703 @code{time_t} datatypes are defined as seconds since the Epoch.
38705 All integral datatypes transferred as part of a memory read or write of a
38706 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38709 @node Pointer Values
38710 @unnumberedsubsubsec Pointer Values
38711 @cindex pointer values, in file-i/o protocol
38713 Pointers to target data are transmitted as they are. An exception
38714 is made for pointers to buffers for which the length isn't
38715 transmitted as part of the function call, namely strings. Strings
38716 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38723 which is a pointer to data of length 18 bytes at position 0x1aaf.
38724 The length is defined as the full string length in bytes, including
38725 the trailing null byte. For example, the string @code{"hello world"}
38726 at address 0x123456 is transmitted as
38732 @node Memory Transfer
38733 @unnumberedsubsubsec Memory Transfer
38734 @cindex memory transfer, in file-i/o protocol
38736 Structured data which is transferred using a memory read or write (for
38737 example, a @code{struct stat}) is expected to be in a protocol-specific format
38738 with all scalar multibyte datatypes being big endian. Translation to
38739 this representation needs to be done both by the target before the @code{F}
38740 packet is sent, and by @value{GDBN} before
38741 it transfers memory to the target. Transferred pointers to structured
38742 data should point to the already-coerced data at any time.
38746 @unnumberedsubsubsec struct stat
38747 @cindex struct stat, in file-i/o protocol
38749 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38750 is defined as follows:
38754 unsigned int st_dev; /* device */
38755 unsigned int st_ino; /* inode */
38756 mode_t st_mode; /* protection */
38757 unsigned int st_nlink; /* number of hard links */
38758 unsigned int st_uid; /* user ID of owner */
38759 unsigned int st_gid; /* group ID of owner */
38760 unsigned int st_rdev; /* device type (if inode device) */
38761 unsigned long st_size; /* total size, in bytes */
38762 unsigned long st_blksize; /* blocksize for filesystem I/O */
38763 unsigned long st_blocks; /* number of blocks allocated */
38764 time_t st_atime; /* time of last access */
38765 time_t st_mtime; /* time of last modification */
38766 time_t st_ctime; /* time of last change */
38770 The integral datatypes conform to the definitions given in the
38771 appropriate section (see @ref{Integral Datatypes}, for details) so this
38772 structure is of size 64 bytes.
38774 The values of several fields have a restricted meaning and/or
38780 A value of 0 represents a file, 1 the console.
38783 No valid meaning for the target. Transmitted unchanged.
38786 Valid mode bits are described in @ref{Constants}. Any other
38787 bits have currently no meaning for the target.
38792 No valid meaning for the target. Transmitted unchanged.
38797 These values have a host and file system dependent
38798 accuracy. Especially on Windows hosts, the file system may not
38799 support exact timing values.
38802 The target gets a @code{struct stat} of the above representation and is
38803 responsible for coercing it to the target representation before
38806 Note that due to size differences between the host, target, and protocol
38807 representations of @code{struct stat} members, these members could eventually
38808 get truncated on the target.
38810 @node struct timeval
38811 @unnumberedsubsubsec struct timeval
38812 @cindex struct timeval, in file-i/o protocol
38814 The buffer of type @code{struct timeval} used by the File-I/O protocol
38815 is defined as follows:
38819 time_t tv_sec; /* second */
38820 long tv_usec; /* microsecond */
38824 The integral datatypes conform to the definitions given in the
38825 appropriate section (see @ref{Integral Datatypes}, for details) so this
38826 structure is of size 8 bytes.
38829 @subsection Constants
38830 @cindex constants, in file-i/o protocol
38832 The following values are used for the constants inside of the
38833 protocol. @value{GDBN} and target are responsible for translating these
38834 values before and after the call as needed.
38845 @unnumberedsubsubsec Open Flags
38846 @cindex open flags, in file-i/o protocol
38848 All values are given in hexadecimal representation.
38860 @node mode_t Values
38861 @unnumberedsubsubsec mode_t Values
38862 @cindex mode_t values, in file-i/o protocol
38864 All values are given in octal representation.
38881 @unnumberedsubsubsec Errno Values
38882 @cindex errno values, in file-i/o protocol
38884 All values are given in decimal representation.
38909 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38910 any error value not in the list of supported error numbers.
38913 @unnumberedsubsubsec Lseek Flags
38914 @cindex lseek flags, in file-i/o protocol
38923 @unnumberedsubsubsec Limits
38924 @cindex limits, in file-i/o protocol
38926 All values are given in decimal representation.
38929 INT_MIN -2147483648
38931 UINT_MAX 4294967295
38932 LONG_MIN -9223372036854775808
38933 LONG_MAX 9223372036854775807
38934 ULONG_MAX 18446744073709551615
38937 @node File-I/O Examples
38938 @subsection File-I/O Examples
38939 @cindex file-i/o examples
38941 Example sequence of a write call, file descriptor 3, buffer is at target
38942 address 0x1234, 6 bytes should be written:
38945 <- @code{Fwrite,3,1234,6}
38946 @emph{request memory read from target}
38949 @emph{return "6 bytes written"}
38953 Example sequence of a read call, file descriptor 3, buffer is at target
38954 address 0x1234, 6 bytes should be read:
38957 <- @code{Fread,3,1234,6}
38958 @emph{request memory write to target}
38959 -> @code{X1234,6:XXXXXX}
38960 @emph{return "6 bytes read"}
38964 Example sequence of a read call, call fails on the host due to invalid
38965 file descriptor (@code{EBADF}):
38968 <- @code{Fread,3,1234,6}
38972 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38976 <- @code{Fread,3,1234,6}
38981 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38985 <- @code{Fread,3,1234,6}
38986 -> @code{X1234,6:XXXXXX}
38990 @node Library List Format
38991 @section Library List Format
38992 @cindex library list format, remote protocol
38994 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38995 same process as your application to manage libraries. In this case,
38996 @value{GDBN} can use the loader's symbol table and normal memory
38997 operations to maintain a list of shared libraries. On other
38998 platforms, the operating system manages loaded libraries.
38999 @value{GDBN} can not retrieve the list of currently loaded libraries
39000 through memory operations, so it uses the @samp{qXfer:libraries:read}
39001 packet (@pxref{qXfer library list read}) instead. The remote stub
39002 queries the target's operating system and reports which libraries
39005 The @samp{qXfer:libraries:read} packet returns an XML document which
39006 lists loaded libraries and their offsets. Each library has an
39007 associated name and one or more segment or section base addresses,
39008 which report where the library was loaded in memory.
39010 For the common case of libraries that are fully linked binaries, the
39011 library should have a list of segments. If the target supports
39012 dynamic linking of a relocatable object file, its library XML element
39013 should instead include a list of allocated sections. The segment or
39014 section bases are start addresses, not relocation offsets; they do not
39015 depend on the library's link-time base addresses.
39017 @value{GDBN} must be linked with the Expat library to support XML
39018 library lists. @xref{Expat}.
39020 A simple memory map, with one loaded library relocated by a single
39021 offset, looks like this:
39025 <library name="/lib/libc.so.6">
39026 <segment address="0x10000000"/>
39031 Another simple memory map, with one loaded library with three
39032 allocated sections (.text, .data, .bss), looks like this:
39036 <library name="sharedlib.o">
39037 <section address="0x10000000"/>
39038 <section address="0x20000000"/>
39039 <section address="0x30000000"/>
39044 The format of a library list is described by this DTD:
39047 <!-- library-list: Root element with versioning -->
39048 <!ELEMENT library-list (library)*>
39049 <!ATTLIST library-list version CDATA #FIXED "1.0">
39050 <!ELEMENT library (segment*, section*)>
39051 <!ATTLIST library name CDATA #REQUIRED>
39052 <!ELEMENT segment EMPTY>
39053 <!ATTLIST segment address CDATA #REQUIRED>
39054 <!ELEMENT section EMPTY>
39055 <!ATTLIST section address CDATA #REQUIRED>
39058 In addition, segments and section descriptors cannot be mixed within a
39059 single library element, and you must supply at least one segment or
39060 section for each library.
39062 @node Library List Format for SVR4 Targets
39063 @section Library List Format for SVR4 Targets
39064 @cindex library list format, remote protocol
39066 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39067 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39068 shared libraries. Still a special library list provided by this packet is
39069 more efficient for the @value{GDBN} remote protocol.
39071 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39072 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39073 target, the following parameters are reported:
39077 @code{name}, the absolute file name from the @code{l_name} field of
39078 @code{struct link_map}.
39080 @code{lm} with address of @code{struct link_map} used for TLS
39081 (Thread Local Storage) access.
39083 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39084 @code{struct link_map}. For prelinked libraries this is not an absolute
39085 memory address. It is a displacement of absolute memory address against
39086 address the file was prelinked to during the library load.
39088 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39091 Additionally the single @code{main-lm} attribute specifies address of
39092 @code{struct link_map} used for the main executable. This parameter is used
39093 for TLS access and its presence is optional.
39095 @value{GDBN} must be linked with the Expat library to support XML
39096 SVR4 library lists. @xref{Expat}.
39098 A simple memory map, with two loaded libraries (which do not use prelink),
39102 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39103 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39105 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39107 </library-list-svr>
39110 The format of an SVR4 library list is described by this DTD:
39113 <!-- library-list-svr4: Root element with versioning -->
39114 <!ELEMENT library-list-svr4 (library)*>
39115 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39116 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39117 <!ELEMENT library EMPTY>
39118 <!ATTLIST library name CDATA #REQUIRED>
39119 <!ATTLIST library lm CDATA #REQUIRED>
39120 <!ATTLIST library l_addr CDATA #REQUIRED>
39121 <!ATTLIST library l_ld CDATA #REQUIRED>
39124 @node Memory Map Format
39125 @section Memory Map Format
39126 @cindex memory map format
39128 To be able to write into flash memory, @value{GDBN} needs to obtain a
39129 memory map from the target. This section describes the format of the
39132 The memory map is obtained using the @samp{qXfer:memory-map:read}
39133 (@pxref{qXfer memory map read}) packet and is an XML document that
39134 lists memory regions.
39136 @value{GDBN} must be linked with the Expat library to support XML
39137 memory maps. @xref{Expat}.
39139 The top-level structure of the document is shown below:
39142 <?xml version="1.0"?>
39143 <!DOCTYPE memory-map
39144 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39145 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39151 Each region can be either:
39156 A region of RAM starting at @var{addr} and extending for @var{length}
39160 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39165 A region of read-only memory:
39168 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39173 A region of flash memory, with erasure blocks @var{blocksize}
39177 <memory type="flash" start="@var{addr}" length="@var{length}">
39178 <property name="blocksize">@var{blocksize}</property>
39184 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39185 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39186 packets to write to addresses in such ranges.
39188 The formal DTD for memory map format is given below:
39191 <!-- ................................................... -->
39192 <!-- Memory Map XML DTD ................................ -->
39193 <!-- File: memory-map.dtd .............................. -->
39194 <!-- .................................... .............. -->
39195 <!-- memory-map.dtd -->
39196 <!-- memory-map: Root element with versioning -->
39197 <!ELEMENT memory-map (memory | property)>
39198 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39199 <!ELEMENT memory (property)>
39200 <!-- memory: Specifies a memory region,
39201 and its type, or device. -->
39202 <!ATTLIST memory type CDATA #REQUIRED
39203 start CDATA #REQUIRED
39204 length CDATA #REQUIRED
39205 device CDATA #IMPLIED>
39206 <!-- property: Generic attribute tag -->
39207 <!ELEMENT property (#PCDATA | property)*>
39208 <!ATTLIST property name CDATA #REQUIRED>
39211 @node Thread List Format
39212 @section Thread List Format
39213 @cindex thread list format
39215 To efficiently update the list of threads and their attributes,
39216 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39217 (@pxref{qXfer threads read}) and obtains the XML document with
39218 the following structure:
39221 <?xml version="1.0"?>
39223 <thread id="id" core="0">
39224 ... description ...
39229 Each @samp{thread} element must have the @samp{id} attribute that
39230 identifies the thread (@pxref{thread-id syntax}). The
39231 @samp{core} attribute, if present, specifies which processor core
39232 the thread was last executing on. The content of the of @samp{thread}
39233 element is interpreted as human-readable auxilliary information.
39235 @node Traceframe Info Format
39236 @section Traceframe Info Format
39237 @cindex traceframe info format
39239 To be able to know which objects in the inferior can be examined when
39240 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39241 memory ranges, registers and trace state variables that have been
39242 collected in a traceframe.
39244 This list is obtained using the @samp{qXfer:traceframe-info:read}
39245 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39247 @value{GDBN} must be linked with the Expat library to support XML
39248 traceframe info discovery. @xref{Expat}.
39250 The top-level structure of the document is shown below:
39253 <?xml version="1.0"?>
39254 <!DOCTYPE traceframe-info
39255 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39256 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39262 Each traceframe block can be either:
39267 A region of collected memory starting at @var{addr} and extending for
39268 @var{length} bytes from there:
39271 <memory start="@var{addr}" length="@var{length}"/>
39276 The formal DTD for the traceframe info format is given below:
39279 <!ELEMENT traceframe-info (memory)* >
39280 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39282 <!ELEMENT memory EMPTY>
39283 <!ATTLIST memory start CDATA #REQUIRED
39284 length CDATA #REQUIRED>
39287 @include agentexpr.texi
39289 @node Target Descriptions
39290 @appendix Target Descriptions
39291 @cindex target descriptions
39293 One of the challenges of using @value{GDBN} to debug embedded systems
39294 is that there are so many minor variants of each processor
39295 architecture in use. It is common practice for vendors to start with
39296 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39297 and then make changes to adapt it to a particular market niche. Some
39298 architectures have hundreds of variants, available from dozens of
39299 vendors. This leads to a number of problems:
39303 With so many different customized processors, it is difficult for
39304 the @value{GDBN} maintainers to keep up with the changes.
39306 Since individual variants may have short lifetimes or limited
39307 audiences, it may not be worthwhile to carry information about every
39308 variant in the @value{GDBN} source tree.
39310 When @value{GDBN} does support the architecture of the embedded system
39311 at hand, the task of finding the correct architecture name to give the
39312 @command{set architecture} command can be error-prone.
39315 To address these problems, the @value{GDBN} remote protocol allows a
39316 target system to not only identify itself to @value{GDBN}, but to
39317 actually describe its own features. This lets @value{GDBN} support
39318 processor variants it has never seen before --- to the extent that the
39319 descriptions are accurate, and that @value{GDBN} understands them.
39321 @value{GDBN} must be linked with the Expat library to support XML
39322 target descriptions. @xref{Expat}.
39325 * Retrieving Descriptions:: How descriptions are fetched from a target.
39326 * Target Description Format:: The contents of a target description.
39327 * Predefined Target Types:: Standard types available for target
39329 * Standard Target Features:: Features @value{GDBN} knows about.
39332 @node Retrieving Descriptions
39333 @section Retrieving Descriptions
39335 Target descriptions can be read from the target automatically, or
39336 specified by the user manually. The default behavior is to read the
39337 description from the target. @value{GDBN} retrieves it via the remote
39338 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39339 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39340 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39341 XML document, of the form described in @ref{Target Description
39344 Alternatively, you can specify a file to read for the target description.
39345 If a file is set, the target will not be queried. The commands to
39346 specify a file are:
39349 @cindex set tdesc filename
39350 @item set tdesc filename @var{path}
39351 Read the target description from @var{path}.
39353 @cindex unset tdesc filename
39354 @item unset tdesc filename
39355 Do not read the XML target description from a file. @value{GDBN}
39356 will use the description supplied by the current target.
39358 @cindex show tdesc filename
39359 @item show tdesc filename
39360 Show the filename to read for a target description, if any.
39364 @node Target Description Format
39365 @section Target Description Format
39366 @cindex target descriptions, XML format
39368 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39369 document which complies with the Document Type Definition provided in
39370 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39371 means you can use generally available tools like @command{xmllint} to
39372 check that your feature descriptions are well-formed and valid.
39373 However, to help people unfamiliar with XML write descriptions for
39374 their targets, we also describe the grammar here.
39376 Target descriptions can identify the architecture of the remote target
39377 and (for some architectures) provide information about custom register
39378 sets. They can also identify the OS ABI of the remote target.
39379 @value{GDBN} can use this information to autoconfigure for your
39380 target, or to warn you if you connect to an unsupported target.
39382 Here is a simple target description:
39385 <target version="1.0">
39386 <architecture>i386:x86-64</architecture>
39391 This minimal description only says that the target uses
39392 the x86-64 architecture.
39394 A target description has the following overall form, with [ ] marking
39395 optional elements and @dots{} marking repeatable elements. The elements
39396 are explained further below.
39399 <?xml version="1.0"?>
39400 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39401 <target version="1.0">
39402 @r{[}@var{architecture}@r{]}
39403 @r{[}@var{osabi}@r{]}
39404 @r{[}@var{compatible}@r{]}
39405 @r{[}@var{feature}@dots{}@r{]}
39410 The description is generally insensitive to whitespace and line
39411 breaks, under the usual common-sense rules. The XML version
39412 declaration and document type declaration can generally be omitted
39413 (@value{GDBN} does not require them), but specifying them may be
39414 useful for XML validation tools. The @samp{version} attribute for
39415 @samp{<target>} may also be omitted, but we recommend
39416 including it; if future versions of @value{GDBN} use an incompatible
39417 revision of @file{gdb-target.dtd}, they will detect and report
39418 the version mismatch.
39420 @subsection Inclusion
39421 @cindex target descriptions, inclusion
39424 @cindex <xi:include>
39427 It can sometimes be valuable to split a target description up into
39428 several different annexes, either for organizational purposes, or to
39429 share files between different possible target descriptions. You can
39430 divide a description into multiple files by replacing any element of
39431 the target description with an inclusion directive of the form:
39434 <xi:include href="@var{document}"/>
39438 When @value{GDBN} encounters an element of this form, it will retrieve
39439 the named XML @var{document}, and replace the inclusion directive with
39440 the contents of that document. If the current description was read
39441 using @samp{qXfer}, then so will be the included document;
39442 @var{document} will be interpreted as the name of an annex. If the
39443 current description was read from a file, @value{GDBN} will look for
39444 @var{document} as a file in the same directory where it found the
39445 original description.
39447 @subsection Architecture
39448 @cindex <architecture>
39450 An @samp{<architecture>} element has this form:
39453 <architecture>@var{arch}</architecture>
39456 @var{arch} is one of the architectures from the set accepted by
39457 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39460 @cindex @code{<osabi>}
39462 This optional field was introduced in @value{GDBN} version 7.0.
39463 Previous versions of @value{GDBN} ignore it.
39465 An @samp{<osabi>} element has this form:
39468 <osabi>@var{abi-name}</osabi>
39471 @var{abi-name} is an OS ABI name from the same selection accepted by
39472 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39474 @subsection Compatible Architecture
39475 @cindex @code{<compatible>}
39477 This optional field was introduced in @value{GDBN} version 7.0.
39478 Previous versions of @value{GDBN} ignore it.
39480 A @samp{<compatible>} element has this form:
39483 <compatible>@var{arch}</compatible>
39486 @var{arch} is one of the architectures from the set accepted by
39487 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39489 A @samp{<compatible>} element is used to specify that the target
39490 is able to run binaries in some other than the main target architecture
39491 given by the @samp{<architecture>} element. For example, on the
39492 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39493 or @code{powerpc:common64}, but the system is able to run binaries
39494 in the @code{spu} architecture as well. The way to describe this
39495 capability with @samp{<compatible>} is as follows:
39498 <architecture>powerpc:common</architecture>
39499 <compatible>spu</compatible>
39502 @subsection Features
39505 Each @samp{<feature>} describes some logical portion of the target
39506 system. Features are currently used to describe available CPU
39507 registers and the types of their contents. A @samp{<feature>} element
39511 <feature name="@var{name}">
39512 @r{[}@var{type}@dots{}@r{]}
39518 Each feature's name should be unique within the description. The name
39519 of a feature does not matter unless @value{GDBN} has some special
39520 knowledge of the contents of that feature; if it does, the feature
39521 should have its standard name. @xref{Standard Target Features}.
39525 Any register's value is a collection of bits which @value{GDBN} must
39526 interpret. The default interpretation is a two's complement integer,
39527 but other types can be requested by name in the register description.
39528 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39529 Target Types}), and the description can define additional composite types.
39531 Each type element must have an @samp{id} attribute, which gives
39532 a unique (within the containing @samp{<feature>}) name to the type.
39533 Types must be defined before they are used.
39536 Some targets offer vector registers, which can be treated as arrays
39537 of scalar elements. These types are written as @samp{<vector>} elements,
39538 specifying the array element type, @var{type}, and the number of elements,
39542 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39546 If a register's value is usefully viewed in multiple ways, define it
39547 with a union type containing the useful representations. The
39548 @samp{<union>} element contains one or more @samp{<field>} elements,
39549 each of which has a @var{name} and a @var{type}:
39552 <union id="@var{id}">
39553 <field name="@var{name}" type="@var{type}"/>
39559 If a register's value is composed from several separate values, define
39560 it with a structure type. There are two forms of the @samp{<struct>}
39561 element; a @samp{<struct>} element must either contain only bitfields
39562 or contain no bitfields. If the structure contains only bitfields,
39563 its total size in bytes must be specified, each bitfield must have an
39564 explicit start and end, and bitfields are automatically assigned an
39565 integer type. The field's @var{start} should be less than or
39566 equal to its @var{end}, and zero represents the least significant bit.
39569 <struct id="@var{id}" size="@var{size}">
39570 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39575 If the structure contains no bitfields, then each field has an
39576 explicit type, and no implicit padding is added.
39579 <struct id="@var{id}">
39580 <field name="@var{name}" type="@var{type}"/>
39586 If a register's value is a series of single-bit flags, define it with
39587 a flags type. The @samp{<flags>} element has an explicit @var{size}
39588 and contains one or more @samp{<field>} elements. Each field has a
39589 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39593 <flags id="@var{id}" size="@var{size}">
39594 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39599 @subsection Registers
39602 Each register is represented as an element with this form:
39605 <reg name="@var{name}"
39606 bitsize="@var{size}"
39607 @r{[}regnum="@var{num}"@r{]}
39608 @r{[}save-restore="@var{save-restore}"@r{]}
39609 @r{[}type="@var{type}"@r{]}
39610 @r{[}group="@var{group}"@r{]}/>
39614 The components are as follows:
39619 The register's name; it must be unique within the target description.
39622 The register's size, in bits.
39625 The register's number. If omitted, a register's number is one greater
39626 than that of the previous register (either in the current feature or in
39627 a preceding feature); the first register in the target description
39628 defaults to zero. This register number is used to read or write
39629 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39630 packets, and registers appear in the @code{g} and @code{G} packets
39631 in order of increasing register number.
39634 Whether the register should be preserved across inferior function
39635 calls; this must be either @code{yes} or @code{no}. The default is
39636 @code{yes}, which is appropriate for most registers except for
39637 some system control registers; this is not related to the target's
39641 The type of the register. @var{type} may be a predefined type, a type
39642 defined in the current feature, or one of the special types @code{int}
39643 and @code{float}. @code{int} is an integer type of the correct size
39644 for @var{bitsize}, and @code{float} is a floating point type (in the
39645 architecture's normal floating point format) of the correct size for
39646 @var{bitsize}. The default is @code{int}.
39649 The register group to which this register belongs. @var{group} must
39650 be either @code{general}, @code{float}, or @code{vector}. If no
39651 @var{group} is specified, @value{GDBN} will not display the register
39652 in @code{info registers}.
39656 @node Predefined Target Types
39657 @section Predefined Target Types
39658 @cindex target descriptions, predefined types
39660 Type definitions in the self-description can build up composite types
39661 from basic building blocks, but can not define fundamental types. Instead,
39662 standard identifiers are provided by @value{GDBN} for the fundamental
39663 types. The currently supported types are:
39672 Signed integer types holding the specified number of bits.
39679 Unsigned integer types holding the specified number of bits.
39683 Pointers to unspecified code and data. The program counter and
39684 any dedicated return address register may be marked as code
39685 pointers; printing a code pointer converts it into a symbolic
39686 address. The stack pointer and any dedicated address registers
39687 may be marked as data pointers.
39690 Single precision IEEE floating point.
39693 Double precision IEEE floating point.
39696 The 12-byte extended precision format used by ARM FPA registers.
39699 The 10-byte extended precision format used by x87 registers.
39702 32bit @sc{eflags} register used by x86.
39705 32bit @sc{mxcsr} register used by x86.
39709 @node Standard Target Features
39710 @section Standard Target Features
39711 @cindex target descriptions, standard features
39713 A target description must contain either no registers or all the
39714 target's registers. If the description contains no registers, then
39715 @value{GDBN} will assume a default register layout, selected based on
39716 the architecture. If the description contains any registers, the
39717 default layout will not be used; the standard registers must be
39718 described in the target description, in such a way that @value{GDBN}
39719 can recognize them.
39721 This is accomplished by giving specific names to feature elements
39722 which contain standard registers. @value{GDBN} will look for features
39723 with those names and verify that they contain the expected registers;
39724 if any known feature is missing required registers, or if any required
39725 feature is missing, @value{GDBN} will reject the target
39726 description. You can add additional registers to any of the
39727 standard features --- @value{GDBN} will display them just as if
39728 they were added to an unrecognized feature.
39730 This section lists the known features and their expected contents.
39731 Sample XML documents for these features are included in the
39732 @value{GDBN} source tree, in the directory @file{gdb/features}.
39734 Names recognized by @value{GDBN} should include the name of the
39735 company or organization which selected the name, and the overall
39736 architecture to which the feature applies; so e.g.@: the feature
39737 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39739 The names of registers are not case sensitive for the purpose
39740 of recognizing standard features, but @value{GDBN} will only display
39741 registers using the capitalization used in the description.
39748 * PowerPC Features::
39754 @subsection ARM Features
39755 @cindex target descriptions, ARM features
39757 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39759 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39760 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39762 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39763 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39764 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39767 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39768 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39770 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39771 it should contain at least registers @samp{wR0} through @samp{wR15} and
39772 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39773 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39775 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39776 should contain at least registers @samp{d0} through @samp{d15}. If
39777 they are present, @samp{d16} through @samp{d31} should also be included.
39778 @value{GDBN} will synthesize the single-precision registers from
39779 halves of the double-precision registers.
39781 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39782 need to contain registers; it instructs @value{GDBN} to display the
39783 VFP double-precision registers as vectors and to synthesize the
39784 quad-precision registers from pairs of double-precision registers.
39785 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39786 be present and include 32 double-precision registers.
39788 @node i386 Features
39789 @subsection i386 Features
39790 @cindex target descriptions, i386 features
39792 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39793 targets. It should describe the following registers:
39797 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39799 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39801 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39802 @samp{fs}, @samp{gs}
39804 @samp{st0} through @samp{st7}
39806 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39807 @samp{foseg}, @samp{fooff} and @samp{fop}
39810 The register sets may be different, depending on the target.
39812 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39813 describe registers:
39817 @samp{xmm0} through @samp{xmm7} for i386
39819 @samp{xmm0} through @samp{xmm15} for amd64
39824 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39825 @samp{org.gnu.gdb.i386.sse} feature. It should
39826 describe the upper 128 bits of @sc{ymm} registers:
39830 @samp{ymm0h} through @samp{ymm7h} for i386
39832 @samp{ymm0h} through @samp{ymm15h} for amd64
39835 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39836 describe a single register, @samp{orig_eax}.
39838 @node MIPS Features
39839 @subsection @acronym{MIPS} Features
39840 @cindex target descriptions, @acronym{MIPS} features
39842 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39843 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39844 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39847 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39848 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39849 registers. They may be 32-bit or 64-bit depending on the target.
39851 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39852 it may be optional in a future version of @value{GDBN}. It should
39853 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39854 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39856 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39857 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39858 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39859 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39861 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39862 contain a single register, @samp{restart}, which is used by the
39863 Linux kernel to control restartable syscalls.
39865 @node M68K Features
39866 @subsection M68K Features
39867 @cindex target descriptions, M68K features
39870 @item @samp{org.gnu.gdb.m68k.core}
39871 @itemx @samp{org.gnu.gdb.coldfire.core}
39872 @itemx @samp{org.gnu.gdb.fido.core}
39873 One of those features must be always present.
39874 The feature that is present determines which flavor of m68k is
39875 used. The feature that is present should contain registers
39876 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39877 @samp{sp}, @samp{ps} and @samp{pc}.
39879 @item @samp{org.gnu.gdb.coldfire.fp}
39880 This feature is optional. If present, it should contain registers
39881 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39885 @node PowerPC Features
39886 @subsection PowerPC Features
39887 @cindex target descriptions, PowerPC features
39889 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39890 targets. It should contain registers @samp{r0} through @samp{r31},
39891 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39892 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39894 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39895 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39897 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39898 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39901 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39902 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39903 will combine these registers with the floating point registers
39904 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39905 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39906 through @samp{vs63}, the set of vector registers for POWER7.
39908 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39909 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39910 @samp{spefscr}. SPE targets should provide 32-bit registers in
39911 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39912 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39913 these to present registers @samp{ev0} through @samp{ev31} to the
39916 @node TIC6x Features
39917 @subsection TMS320C6x Features
39918 @cindex target descriptions, TIC6x features
39919 @cindex target descriptions, TMS320C6x features
39920 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39921 targets. It should contain registers @samp{A0} through @samp{A15},
39922 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39924 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39925 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39926 through @samp{B31}.
39928 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39929 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39931 @node Operating System Information
39932 @appendix Operating System Information
39933 @cindex operating system information
39939 Users of @value{GDBN} often wish to obtain information about the state of
39940 the operating system running on the target---for example the list of
39941 processes, or the list of open files. This section describes the
39942 mechanism that makes it possible. This mechanism is similar to the
39943 target features mechanism (@pxref{Target Descriptions}), but focuses
39944 on a different aspect of target.
39946 Operating system information is retrived from the target via the
39947 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39948 read}). The object name in the request should be @samp{osdata}, and
39949 the @var{annex} identifies the data to be fetched.
39952 @appendixsection Process list
39953 @cindex operating system information, process list
39955 When requesting the process list, the @var{annex} field in the
39956 @samp{qXfer} request should be @samp{processes}. The returned data is
39957 an XML document. The formal syntax of this document is defined in
39958 @file{gdb/features/osdata.dtd}.
39960 An example document is:
39963 <?xml version="1.0"?>
39964 <!DOCTYPE target SYSTEM "osdata.dtd">
39965 <osdata type="processes">
39967 <column name="pid">1</column>
39968 <column name="user">root</column>
39969 <column name="command">/sbin/init</column>
39970 <column name="cores">1,2,3</column>
39975 Each item should include a column whose name is @samp{pid}. The value
39976 of that column should identify the process on the target. The
39977 @samp{user} and @samp{command} columns are optional, and will be
39978 displayed by @value{GDBN}. The @samp{cores} column, if present,
39979 should contain a comma-separated list of cores that this process
39980 is running on. Target may provide additional columns,
39981 which @value{GDBN} currently ignores.
39983 @node Trace File Format
39984 @appendix Trace File Format
39985 @cindex trace file format
39987 The trace file comes in three parts: a header, a textual description
39988 section, and a trace frame section with binary data.
39990 The header has the form @code{\x7fTRACE0\n}. The first byte is
39991 @code{0x7f} so as to indicate that the file contains binary data,
39992 while the @code{0} is a version number that may have different values
39995 The description section consists of multiple lines of @sc{ascii} text
39996 separated by newline characters (@code{0xa}). The lines may include a
39997 variety of optional descriptive or context-setting information, such
39998 as tracepoint definitions or register set size. @value{GDBN} will
39999 ignore any line that it does not recognize. An empty line marks the end
40002 @c FIXME add some specific types of data
40004 The trace frame section consists of a number of consecutive frames.
40005 Each frame begins with a two-byte tracepoint number, followed by a
40006 four-byte size giving the amount of data in the frame. The data in
40007 the frame consists of a number of blocks, each introduced by a
40008 character indicating its type (at least register, memory, and trace
40009 state variable). The data in this section is raw binary, not a
40010 hexadecimal or other encoding; its endianness matches the target's
40013 @c FIXME bi-arch may require endianness/arch info in description section
40016 @item R @var{bytes}
40017 Register block. The number and ordering of bytes matches that of a
40018 @code{g} packet in the remote protocol. Note that these are the
40019 actual bytes, in target order and @value{GDBN} register order, not a
40020 hexadecimal encoding.
40022 @item M @var{address} @var{length} @var{bytes}...
40023 Memory block. This is a contiguous block of memory, at the 8-byte
40024 address @var{address}, with a 2-byte length @var{length}, followed by
40025 @var{length} bytes.
40027 @item V @var{number} @var{value}
40028 Trace state variable block. This records the 8-byte signed value
40029 @var{value} of trace state variable numbered @var{number}.
40033 Future enhancements of the trace file format may include additional types
40036 @node Index Section Format
40037 @appendix @code{.gdb_index} section format
40038 @cindex .gdb_index section format
40039 @cindex index section format
40041 This section documents the index section that is created by @code{save
40042 gdb-index} (@pxref{Index Files}). The index section is
40043 DWARF-specific; some knowledge of DWARF is assumed in this
40046 The mapped index file format is designed to be directly
40047 @code{mmap}able on any architecture. In most cases, a datum is
40048 represented using a little-endian 32-bit integer value, called an
40049 @code{offset_type}. Big endian machines must byte-swap the values
40050 before using them. Exceptions to this rule are noted. The data is
40051 laid out such that alignment is always respected.
40053 A mapped index consists of several areas, laid out in order.
40057 The file header. This is a sequence of values, of @code{offset_type}
40058 unless otherwise noted:
40062 The version number, currently 6. Versions 1, 2 and 3 are obsolete.
40063 Version 4 uses a different hashing function from versions 5 and 6.
40064 Version 6 includes symbols for inlined functions, whereas versions
40065 4 and 5 do not. @value{GDBN} will only read version 4 and 5 indices
40066 if the @code{--use-deprecated-index-sections} option is used.
40069 The offset, from the start of the file, of the CU list.
40072 The offset, from the start of the file, of the types CU list. Note
40073 that this area can be empty, in which case this offset will be equal
40074 to the next offset.
40077 The offset, from the start of the file, of the address area.
40080 The offset, from the start of the file, of the symbol table.
40083 The offset, from the start of the file, of the constant pool.
40087 The CU list. This is a sequence of pairs of 64-bit little-endian
40088 values, sorted by the CU offset. The first element in each pair is
40089 the offset of a CU in the @code{.debug_info} section. The second
40090 element in each pair is the length of that CU. References to a CU
40091 elsewhere in the map are done using a CU index, which is just the
40092 0-based index into this table. Note that if there are type CUs, then
40093 conceptually CUs and type CUs form a single list for the purposes of
40097 The types CU list. This is a sequence of triplets of 64-bit
40098 little-endian values. In a triplet, the first value is the CU offset,
40099 the second value is the type offset in the CU, and the third value is
40100 the type signature. The types CU list is not sorted.
40103 The address area. The address area consists of a sequence of address
40104 entries. Each address entry has three elements:
40108 The low address. This is a 64-bit little-endian value.
40111 The high address. This is a 64-bit little-endian value. Like
40112 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40115 The CU index. This is an @code{offset_type} value.
40119 The symbol table. This is an open-addressed hash table. The size of
40120 the hash table is always a power of 2.
40122 Each slot in the hash table consists of a pair of @code{offset_type}
40123 values. The first value is the offset of the symbol's name in the
40124 constant pool. The second value is the offset of the CU vector in the
40127 If both values are 0, then this slot in the hash table is empty. This
40128 is ok because while 0 is a valid constant pool index, it cannot be a
40129 valid index for both a string and a CU vector.
40131 The hash value for a table entry is computed by applying an
40132 iterative hash function to the symbol's name. Starting with an
40133 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40134 the string is incorporated into the hash using the formula depending on the
40139 The formula is @code{r = r * 67 + c - 113}.
40141 @item Versions 5 and 6
40142 The formula is @code{r = r * 67 + tolower (c) - 113}.
40145 The terminating @samp{\0} is not incorporated into the hash.
40147 The step size used in the hash table is computed via
40148 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40149 value, and @samp{size} is the size of the hash table. The step size
40150 is used to find the next candidate slot when handling a hash
40153 The names of C@t{++} symbols in the hash table are canonicalized. We
40154 don't currently have a simple description of the canonicalization
40155 algorithm; if you intend to create new index sections, you must read
40159 The constant pool. This is simply a bunch of bytes. It is organized
40160 so that alignment is correct: CU vectors are stored first, followed by
40163 A CU vector in the constant pool is a sequence of @code{offset_type}
40164 values. The first value is the number of CU indices in the vector.
40165 Each subsequent value is the index of a CU in the CU list. This
40166 element in the hash table is used to indicate which CUs define the
40169 A string in the constant pool is zero-terminated.
40174 @node GNU Free Documentation License
40175 @appendix GNU Free Documentation License
40184 % I think something like @colophon should be in texinfo. In the
40186 \long\def\colophon{\hbox to0pt{}\vfill
40187 \centerline{The body of this manual is set in}
40188 \centerline{\fontname\tenrm,}
40189 \centerline{with headings in {\bf\fontname\tenbf}}
40190 \centerline{and examples in {\tt\fontname\tentt}.}
40191 \centerline{{\it\fontname\tenit\/},}
40192 \centerline{{\bf\fontname\tenbf}, and}
40193 \centerline{{\sl\fontname\tensl\/}}
40194 \centerline{are used for emphasis.}\vfill}
40196 % Blame: doc@cygnus.com, 1991.